{"gene":"MAP1B","run_date":"2026-06-10T02:59:50","timeline":{"discoveries":[{"year":1989,"finding":"The microtubule-binding domain of MAP1B was mapped to a highly basic region containing repeated KKEE/KKEVI motifs; this region copurifies with microtubules in vitro and mediates microtubule interaction in vivo in transfected cells. A separate 12-repeat region does not bind microtubules. The MAP1B microtubule-binding domain is structurally unrelated to those of MAP2, tau, or kinesin.","method":"Cell-free translation of subcloned fragments + microtubule cosedimentation cycles in vitro; full-length and deletion constructs transfected into cultured cells with immunofluorescence readout","journal":"The Journal of Cell Biology","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro reconstitution with defined fragments plus in vivo deletion-construct validation, multiple orthogonal methods in a single rigorous study","pmids":["2480963"],"is_preprint":false},{"year":1991,"finding":"MAP1B is encoded as a polyprotein: the heavy chain and light chain 1 (LC1) are translated from the same mRNA within the same open reading frame and generated by proteolytic processing. LC1 binds near the heavy-chain N-terminus and together they form a complex microtubule-binding domain.","method":"Amino acid sequencing of heavy-chain fragment, epitope mapping, Northern and Southern blotting; co-purification of heavy chain and LC1","journal":"Neuron","confidence":"High","confidence_rationale":"Tier 1 / Strong — direct protein sequencing, epitope mapping, and molecular cloning demonstrating polyprotein origin with multiple orthogonal approaches","pmids":["1712602"],"is_preprint":false},{"year":1994,"finding":"Light chain 3 (LC3) is a subunit of both MAP1A and MAP1B complexes; purified recombinant LC3 associates with microtubules assembled in the presence of brain MAPs and with microtubules assembled from purified tubulin, demonstrating a direct microtubule-binding activity.","method":"cDNA sequencing, microtubule cosedimentation assays with recombinant LC3, immunoprecipitation, Western blot","journal":"The Journal of Biological Chemistry","confidence":"High","confidence_rationale":"Tier 1 / Moderate — reconstitution of recombinant LC3 binding to microtubules plus biochemical subunit identification; single lab but multiple orthogonal methods","pmids":["7908909"],"is_preprint":false},{"year":1988,"finding":"MAP1B is phosphorylated in vitro by a casein kinase II (CK2)-like activity present in developing neuroblastoma cells; phosphopeptide maps of brain MAP1B phosphorylated by purified CK2 are identical to those of in vivo phosphorylated neuroblastoma MAP1B, identifying CK2 as a principal kinase acting on MAP1B during neurite outgrowth.","method":"In vitro kinase assay with purified CK2 and other kinases; phosphopeptide mapping; immunoprecipitation; microtubule cosedimentation","journal":"The Journal of Cell Biology","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro kinase assay with purified enzyme plus phosphopeptide fingerprinting and in vivo correlation; multiple orthogonal methods single lab","pmids":["3164313"],"is_preprint":false},{"year":1992,"finding":"Expression of MAP1B in fibroblasts stabilizes microtubules against depolymerizing reagents and increases alpha-tubulin acetylation, demonstrating that MAP1B promotes microtubule stability in vivo, though without the extensive microtubule bundling induced by MAP2 or tau.","method":"cDNA transfection into COS/HeLa/3T3 cells; nocodazole resistance assay; immunofluorescence for acetylated tubulin","journal":"Journal of Cell Science","confidence":"High","confidence_rationale":"Tier 2 / Strong — clean gain-of-function in heterologous cells with two orthogonal phenotypic readouts (drug resistance and tubulin modification); replicated across multiple cell types","pmids":["1487506"],"is_preprint":false},{"year":1998,"finding":"The MAP1B light chain (LC1), in the absence of the heavy chain, induces formation of nocodazole- and taxol-resistant stable microtubules; the heavy chain inhibits LC1 activity. LC1 contains a C-terminal actin filament-binding domain, and LC1 can dimerize/oligomerize. Heavy chain–light chain interaction domains were localized by coimmunoprecipitation of epitope-tagged fragments.","method":"Transient transfection in COS cells; immunofluorescence; nocodazole/taxol resistance assay; coimmunoprecipitation of epitope-tagged fragments; actin cosedimentation","journal":"The Journal of Cell Biology","confidence":"High","confidence_rationale":"Tier 1–2 / Moderate — multiple functional assays (drug resistance, actin binding, co-IP domain mapping) in a single study; single lab but orthogonal methods","pmids":["9813091"],"is_preprint":false},{"year":1999,"finding":"MAP1B specifically interacts with the GABA(C) receptor rho1 subunit (but not GABA(A) subunits), co-localizes with GABA(C) receptors at bipolar cell axon terminals in the retina, and redistributes rho1 upon co-expression in COS cells, suggesting MAP1B anchors GABA(C) receptors at postsynaptic sites.","method":"Yeast two-hybrid (interaction discovery), co-immunoprecipitation, immunofluorescence co-localization in retinal slices, heterologous co-expression redistribution assay in COS cells","journal":"Nature","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal binding confirmed by Y2H + co-IP + in vivo co-localization + cell-redistribution assay; multiple orthogonal methods","pmids":["9892354"],"is_preprint":false},{"year":2000,"finding":"Twelve amino acids at the C-terminus of the large intracellular loop of rho1 (and rho2) are sufficient for interaction with MAP1B; disrupting the MAP1B–rho1 interaction in bipolar cells in retinal slices decreased the EC50 of GABA(C) receptors, doubling current at low GABA concentrations without affecting maximum current, demonstrating that cytoskeletal anchoring by MAP1B modulates GABA(C) receptor sensitivity.","method":"Deletion/mutagenesis mapping of rho1 interaction domain; patch-clamp electrophysiology of retinal bipolar cells in slices after disruption of MAP1B–rho interaction","journal":"The Journal of Neuroscience","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — domain-mapping mutagenesis combined with functional electrophysiology in native tissue; rigorous mechanistic follow-up of a prior discovery","pmids":["11102469"],"is_preprint":false},{"year":1998,"finding":"GSK-3β directly phosphorylates MAP1B in vitro; in cerebellar granule neurons, WNT-7a and lithium (a GSK-3β inhibitor) induce loss of the phosphorylated form of MAP1B (MAP1B-P) from axonal processes before axonal remodelling is visible, identifying MAP1B as a downstream target of the WNT–GSK-3β pathway in axonal remodelling.","method":"In vitro phosphorylation assay with purified GSK-3β and MAP1B; immunostaining of granule neurons treated with lithium or WNT-7a; time-course imaging of axonal morphology","journal":"Journal of Cell Science","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro kinase assay demonstrating direct phosphorylation plus in vivo cellular phenotype correlation; two orthogonal approaches","pmids":["9570753"],"is_preprint":false},{"year":2005,"finding":"GSK-3β phosphorylates MAP1B at Ser1260 and Thr1265 in vitro and in vivo; phospho-specific antibodies show that GSK-3β-phosphorylated MAP1B is restricted to growing axons (distal gradient) in developing rat embryos. Site-directed mutation (Ser1260Val or Thr1265Val, or both) in full-length MAP1B alters microtubule dynamics in transfected cells, establishing these sites as a molecular switch regulating microtubule stability in growing axons.","method":"Site-directed mutagenesis of recombinant MAP1B; in vitro GSK-3β kinase assay; phospho-specific antibody generation; immunostaining of developing nervous system; heterologous cell transfection with MT dynamics assay","journal":"Journal of Cell Science","confidence":"High","confidence_rationale":"Tier 1 / Strong — mutagenesis + in vitro kinase assay + phospho-specific antibody validation + in vivo localization + functional rescue; multiple orthogonal methods","pmids":["15731007"],"is_preprint":false},{"year":2005,"finding":"Gigaxonin (GAN protein) binds MAP1B light chain (LC) through its C-terminal kelch repeat domain; gigaxonin overexpression leads to enhanced proteasome-dependent degradation of MAP1B-LC; GAN-null neurons accumulate MAP1B-LC; MAP1B overexpression causes neuronal death similar to GAN-null neurons, while MAP1B knockdown improves GAN-null neuron survival, identifying gigaxonin as a ubiquitin scaffolding protein controlling MAP1B-LC degradation and neuronal survival.","method":"Pull-down, co-immunoprecipitation; overexpression in neurons; proteasome inhibitor experiments; GAN knockout mouse neurons; MAP1B siRNA knockdown; cell viability assay","journal":"Nature","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — direct protein interaction + proteasome inhibitor rescue + KO mouse phenotype + RNAi rescue; multiple orthogonal methods replicated across models","pmids":["16227972"],"is_preprint":false},{"year":2000,"finding":"MAP1B null mice (complete null allele) are viable but selectively lack the corpus callosum due to misguided cortical axons, and have reduced/thinner myelinated axons in peripheral nerves with decreased nerve conduction velocity, demonstrating an essential role for MAP1B in axon guidance and CNS/PNS development.","method":"Gene targeting (complete null allele), histology, electrophysiological nerve conduction velocity measurement, immunohistochemistry","journal":"The Journal of Cell Biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — complete genetic knockout with multiple defined phenotypic readouts (anatomical + electrophysiological); resolves earlier conflicting knockout results","pmids":["11121433"],"is_preprint":false},{"year":2000,"finding":"Tau and MAP1B cooperate synergistically in axonal elongation and neuronal migration: double-knockout (tau−/−map1b−/−) mice show much more severe defects (inhibited axonal elongation in hippocampal neurons, delayed neuronal migration in cerebellar neurons) than single knockouts, demonstrating functional redundancy between the two MAPs.","method":"Double-knockout mouse generation; primary hippocampal and cerebellar neuron cultures from knockout mice; morphological analysis of axon elongation and migration","journal":"The Journal of Cell Biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic epistasis via double KO with single-KO comparison; replicated across two neuronal populations","pmids":["10973990"],"is_preprint":false},{"year":2004,"finding":"Netrin-1 regulates mode I MAP1B phosphorylation (activating GSK-3 and CDK5) both in vivo and in vitro; MAP1B-deficient neurons show reduced chemoattractive response to Netrin-1 in vitro, and map1b mutant mice display severe axonal tract abnormalities similar to netrin-1-deficient mice, placing MAP1B as a downstream effector in Netrin-1 signaling for axon guidance and neuronal migration.","method":"In vitro phosphorylation assays; Netrin-1 treatment of wild-type and map1b-null neurons; chemoattraction assay; analysis of map1b and netrin-1 mutant mouse brain anatomy","journal":"Current Biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic epistasis (double mutant phenocopies), in vitro signaling assays, in vivo anatomy; multiple orthogonal methods across two papers (same year)","pmids":["15186740"],"is_preprint":false},{"year":2004,"finding":"Reelin induces mode I MAP1B phosphorylation through GSK-3 and CDK5 activation, with mDab1 participating in the signaling cascade; map1b-deficient mice have abnormal cortical layering consistent with a failure of neuronal migration, placing MAP1B downstream of Reelin signaling.","method":"In vitro and in vivo phosphorylation assays after Reelin treatment; analysis of map1b-null mouse brain lamination; mDab1 involvement tested biochemically","journal":"Cerebral Cortex","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vitro kinase assays + KO mouse anatomy; single lab, partial mechanistic detail on mDab1 involvement","pmids":["15590913"],"is_preprint":false},{"year":2005,"finding":"The MAPK pathway (not the PI3K pathway) links NGF/TrkA receptor engagement to GSK-3β activation, which then phosphorylates MAP1B to regulate microtubule dynamics and axon growth rate; pharmacological inhibition of MAPK prevents GSK-3β activation and MAP1B phosphorylation and reduces neurite growth, while PI3K inhibition does not.","method":"Pharmacological inhibitor studies (MAPK and PI3K inhibitors) in PC12 cells and sympathetic neurons; in vitro kinase assay; GSK-3β activation assay","journal":"Molecular and Cellular Neurosciences","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — pharmacological epistasis plus in vitro kinase assay; single lab, relies on inhibitor specificity","pmids":["15737742"],"is_preprint":false},{"year":2003,"finding":"NGF activates GSK-3β phosphorylation of MAP1B through TrkA receptors, not through p75NTR; BDNF (which activates p75NTR but not TrkA) does not stimulate this phosphorylation; TrkA-deficient PC12 nnr cells fail to show NGF-dependent MAP1B phosphorylation; TrkA inhibition blocks neurite elongation and MAP1B phosphorylation.","method":"Use of receptor-selective ligands and PC12 nnr cells lacking TrkA; TrkA kinase inhibitor (K252a); in vivo immunostaining for phospho-MAP1B","journal":"Journal of Neurochemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic/pharmacological receptor dissection; single lab, well-controlled negative controls","pmids":["14622124"],"is_preprint":false},{"year":2008,"finding":"DAPK-1 (death-associated protein kinase 1) binds directly to the N-terminal domain of MAP1B (residues 1–126 and a 12-aa motif); amino acid starvation induces a stable endogenous MAP1B–DAPK-1 immune complex; MAP1B is required for DAPK-1-stimulated autophagy and membrane blebbing: MAP1B siRNA attenuates these DAPK-1 activities, and MAP1B overexpression synergizes with DAPK-1 for growth inhibition.","method":"Peptide library selection; immunobinding assays; confocal co-localization; siRNA knockdown; clonogenic growth assay; autophagy and blebbing phenotype assays","journal":"The Journal of Biological Chemistry","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — binding confirmed biochemically + siRNA loss-of-function with multiple phenotypic readouts; single lab","pmids":["18195017"],"is_preprint":false},{"year":2009,"finding":"DYRK1A acts as a priming kinase for GSK-3β phosphorylation of MAP1B; mass spectrometry identified 28 MAP1B phosphorylation sites; DYRK1A-primed GSK-3β sites are distributed throughout the neuron while non-primed GSK-3β sites are restricted to growing axons; DYRK1A knockdown compromises neuritogenesis and alters microtubule stability.","method":"Mass spectrometry phosphosite mapping; phospho-specific antibody panel; kinase inhibitor treatments in embryonic cortical neurons; shRNA knockdown of DYRK1A; EB3 microtubule dynamics imaging","journal":"Journal of Cell Science","confidence":"High","confidence_rationale":"Tier 1–2 / Moderate — mass spec site mapping + phospho-specific antibody validation + RNAi loss-of-function with MT dynamics readout; multiple orthogonal methods","pmids":["19549690"],"is_preprint":false},{"year":1993,"finding":"Protein phosphatase 2A (PP2A) and PP2B (calcineurin) dephosphorylate mode I (proline-directed) MAP1B phosphorylation sites, while mode II (CK2-type) sites are dephosphorylated by PP2A and PP1 but not PP2B; inhibition of PP2A in rat brain slices (okadaic acid) increases MAP1B phosphorylation and inhibits its microtubule-binding activity.","method":"In vitro phosphatase assay with purified PP1, PP2A, PP2B; phosphorylation-state antibodies on rat brain slices treated with okadaic acid or cyclosporin A; microtubule binding assay","journal":"FEBS Letters","confidence":"Medium","confidence_rationale":"Tier 1–2 / Moderate — in vitro phosphatase assay with purified enzymes + cell/tissue pharmacological validation; single lab, multiple phosphatases compared","pmids":["7690334"],"is_preprint":false},{"year":2000,"finding":"PP2A is the major phosphatase regulating MAP1B phosphorylation and microtubule-binding activity in rat brain: okadaic acid (PP2A inhibitor) treatment of brain slices markedly increases MAP1B phosphorylation and inhibits MAP1B microtubule-binding activity; cyclosporin A (PP2B inhibitor) has a lesser effect.","method":"Okadaic acid and cyclosporin A treatment of metabolically active rat brain slices; Western blot with phospho-MAP1B antibodies; immunocytochemistry; microtubule binding assay","journal":"Brain Research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — pharmacological inhibition in native tissue with functional microtubule-binding readout; single lab, relies on inhibitor specificity","pmids":["10640627"],"is_preprint":false},{"year":1996,"finding":"Dephosphorylated MAP1B (but not native phosphorylated MAP1B) binds and cosediments with microfilaments in vitro; the proline-directed kinase (PDPK) phosphorylation site (not the CK2 sites) negatively regulates MAP1B interaction with F-actin.","method":"In vitro alkaline phosphatase dephosphorylation; F-actin cosedimentation assay; dephosphorylation kinetics correlated with F-actin binding","journal":"FEBS Letters","confidence":"Medium","confidence_rationale":"Tier 1 / Weak — in vitro reconstitution with purified protein; single lab, single method type","pmids":["8690071"],"is_preprint":false},{"year":2002,"finding":"MAP1B light chain 1 (LC1) binds microtubules and induces tubulin polymerization via a critical NH2-terminal microtubule-binding domain; LC1 also contains a C-terminal actin-binding domain that directly binds actin filaments; the two MAP1 light chains (LC1 of MAP1B and LC2 of MAP1A) differ in their effects on microtubule bundling and stability despite structural similarity.","method":"In vivo microtubule/actin binding assays in transfected cells; in vitro tubulin polymerization assay; domain deletion analysis; immunofluorescence","journal":"The Journal of Neuroscience","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — functional domain analysis with multiple cellular assays; single lab","pmids":["11896150"],"is_preprint":false},{"year":2007,"finding":"MAP1B heavy chain directly binds actin; co-immunoprecipitation shows actin and tubulin co-precipitate with MAP1B at similar ratios throughout development regardless of phosphorylation state; atomic force microscopy measures MAP1B–actin binding force comparable to MAP1B–tubulin interaction. MAP1B heavy chain thus contains both a microtubule-stabilizing domain and an actin-binding site.","method":"Co-immunoprecipitation from brain tissue; mass spectrometry identification; atomic force microscopy force measurement; electron microscopy; COS-7 cell immunofluorescence","journal":"Brain Research Bulletin","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — co-IP + AFM force measurement + EM; single lab, multiple orthogonal methods","pmids":["17292804"],"is_preprint":false},{"year":2010,"finding":"MAP1B deficiency reduces Rac1 and Cdc42 activity and increases RhoA activity; MAP1B interacts with Tiam1 (a Rac1 GEF); constitutively active Rac1, Cdc42, or Tiam1 rescues axon growth defects in MAP1B-deficient neurons, establishing a MAP1B–Tiam1–Rac1 axis required for microtubule–actin crosstalk during neuronal polarization.","method":"MAP1B-null mouse neurons; Rac1/Cdc42/RhoA activity pull-down assays; co-immunoprecipitation of MAP1B with Tiam1; rescue by constitutively active GTPase constructs; axon outgrowth assay","journal":"Molecular Biology of the Cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — GTPase activity assays + co-IP of interacting protein + genetic rescue with constitutively active constructs; multiple orthogonal methods confirming mechanism","pmids":["20719958"],"is_preprint":false},{"year":2011,"finding":"MAP1B is present in dendritic spines; MAP1B-deficient mice show decreased density of mature dendritic spines, increased filopodia-like protrusions, reduced AMPA receptor-mediated synaptic currents, decreased Rac1 activity, increased RhoA activity, and decreased phospho-cofilin in postsynaptic densities, implicating MAP1B in dendritic spine maturation via actin cytoskeleton regulation.","method":"MAP1B+/- mouse neurons; spine morphology analysis; patch-clamp electrophysiology; Rac1/RhoA activity assays; Western blot of PSD fractions","journal":"The Journal of Biological Chemistry","confidence":"High","confidence_rationale":"Tier 2 / Moderate — KO mouse with multiple cellular/electrophysiological phenotypes + signaling pathway analysis; single lab but orthogonal methods","pmids":["21984824"],"is_preprint":false},{"year":2013,"finding":"MAP1B interacts directly with EB1 and EB3 (+TIP proteins) and sequesters them in the neuronal cytosol; MAP1B overexpression reduces EB binding to microtubule plus-ends, while MAP1B knockdown increases EB-MT association and causes microtubule overstabilization and looping in growth cones, resulting in delayed axon outgrowth.","method":"Co-immunoprecipitation; direct interaction assay; RNAi knockdown; EB3-GFP live imaging of microtubule dynamics; growth cone morphology analysis","journal":"The EMBO Journal","confidence":"High","confidence_rationale":"Tier 2 / Moderate — direct binding shown + RNAi loss-of-function with live MT dynamics imaging and morphological readout; single lab, multiple orthogonal methods","pmids":["23572079"],"is_preprint":false},{"year":2011,"finding":"MAP1B knockdown in embryonic rat cortical neurons decreases microtubule growth speed in the proximal and distal axon shaft (but not in growth cone filopodia) and produces more branched, slower growing axons; expression of MAP1B in MAP1B-naive cells increases microtubule elongation rate, demonstrating that MAP1B enhances microtubule assembly rates.","method":"RNAi knockdown; EB3-GFP live imaging of microtubule polymerization speed; axon morphology analysis; MAP1B expression in heterologous cells","journal":"Molecular and Cellular Neurosciences","confidence":"High","confidence_rationale":"Tier 2 / Moderate — RNAi loss-of-function + gain-of-function in heterologous cells; live imaging quantification of microtubule dynamics; single lab, two complementary approaches","pmids":["22033417"],"is_preprint":false},{"year":2013,"finding":"MAP1B deficiency impairs LTD expression specifically by preventing AMPA receptor endocytosis and spine shrinkage during LTD; this is due to failure of Tiam1 (Rac1 GEF) targeting to synaptic compartments and reduced Rac1 activation; providing additional Rac1 restores LTD and AMPA receptor endocytosis in MAP1B-deficient neurons, establishing a MAP1B–Tiam1–Rac1 relay for synaptic plasticity.","method":"Conditional MAP1B-deficient mouse + shRNA; electrophysiological LTD recording; AMPA receptor endocytosis assay; Tiam1 localization by immunostaining; Rac1 activity assay; rescue with Rac1 expression","journal":"The EMBO Journal","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic + RNAi loss-of-function + electrophysiology + molecular rescue; multiple orthogonal methods confirming pathway","pmids":["23881099"],"is_preprint":false},{"year":2012,"finding":"Dystonin-a2 binds MAP1B in the centrosomal region; loss of this interaction in dt mutant neurons causes altered MAP1B perikaryal localization, microtubule deacetylation and instability, Golgi fragmentation, and impaired anterograde trafficking; restoring MT acetylation (trichostatin A) or MAP1B overexpression rescues these defects.","method":"Dystonin mutant mouse + isoform-specific RNAi; co-immunoprecipitation; immunofluorescence of MAP1B and acetylated tubulin; Golgi morphology; vesicle trafficking assay; rescue experiments","journal":"The Journal of Cell Biology","confidence":"High","confidence_rationale":"Tier 2 / Moderate — co-IP + KO mouse + rescue experiments; multiple phenotypic readouts; single lab, orthogonal methods","pmids":["22412020"],"is_preprint":false},{"year":2012,"finding":"S-nitrosylation of MAP1B light chain 1 (LC1) induces a conformational change that activates LC1 and promotes its ubiquitination by MITOL (mitochondrial ubiquitin ligase); MITOL inhibition results in accumulation of S-nitrosylated LC1, mitochondrial dysfunction, and neuronal cell death, demonstrating that MITOL regulates MAP1B-LC1 through nitrosylation-dependent ubiquitination.","method":"S-nitrosylation assay; MITOL knockdown/overexpression; ubiquitination assay; mitochondrial function assay; neuronal cell death readout; conformational change analysis","journal":"Proceedings of the National Academy of Sciences USA","confidence":"High","confidence_rationale":"Tier 1–2 / Moderate — post-translational modification (S-nitrosylation) linked to ubiquitination by defined E3 ligase; multiple functional readouts; single lab","pmids":["22308378"],"is_preprint":false},{"year":2012,"finding":"Syk protein-tyrosine kinase uses MAP1B as a major substrate to promote microtubule stability in MDA-MB-231 breast cancer cells; MAP1B silencing attenuates Syk-dependent microtubule acetylation and nocodazole resistance, and reverses Syk-induced changes in cell topography/stiffness measured by atomic force microscopy.","method":"Syk expression/silencing; MAP1B siRNA; nocodazole resistance assay; acetylated tubulin immunostaining; multiharmonic AFM nanomechanical mapping","journal":"Biochemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — MAP1B RNAi epistasis downstream of Syk with multiple phenotypic readouts; single lab","pmids":["24914616"],"is_preprint":false},{"year":2012,"finding":"Nav1.6 (SCN8A) voltage-gated sodium channel N-terminus interacts with MAP1B light chain via residues 77–80 (VAVP) of Nav1.6; co-expression of Nav1.6 with Map1b in ND7/23 neuronal cells increases sodium current density 50%; mutation of the Map1b-binding site of Nav1.6 prevents generation of sodium current, demonstrating that MAP1B facilitates Nav1.6 trafficking to the neuronal cell surface.","method":"Yeast two-hybrid screen; co-immunoprecipitation from mouse brain; alanine-scanning mutagenesis; patch-clamp electrophysiology in transfected cells","journal":"The Journal of Biological Chemistry","confidence":"High","confidence_rationale":"Tier 1–2 / Moderate — Y2H + co-IP from native brain + mutagenesis + functional electrophysiology; multiple orthogonal methods in single study","pmids":["22474336"],"is_preprint":false},{"year":2009,"finding":"Nemo-like kinase (NLK) directly phosphorylates MAP1B in vitro; NGF promotes NLK translocation to leading edges of PC12 cells and activates NLK kinase activity; NLK knockdown reduces MAP1B phosphorylation and inhibits NGF-induced F-actin redistribution and neurite outgrowth.","method":"In vitro kinase assay with purified NLK and MAP1B; NLK knockdown; immunofluorescence of F-actin and NLK; neurite outgrowth assay","journal":"Journal of Neurochemistry","confidence":"Medium","confidence_rationale":"Tier 1–2 / Moderate — direct in vitro kinase assay + RNAi loss-of-function with phenotypic readout; single lab","pmids":["19840224"],"is_preprint":false},{"year":2006,"finding":"QKI RNA-binding protein binds the 3'UTR of MAP1B mRNA in oligodendroglia; QKI-deficiency (quakingviable mice) reduces MAP1B mRNA expression; QKI knockdown destabilizes MAP1B mRNA in CG4 cells; forced QKI expression is sufficient to promote MAP1B expression, demonstrating QKI-dependent mRNA stabilization as a post-transcriptional mechanism controlling MAP1B levels specifically in oligodendroglia.","method":"3'UTR binding assay; qv mutant mice analysis; RNAi knockdown of QKI; QKI overexpression; Northern blot / qPCR for MAP1B mRNA stability","journal":"Molecular Biology of the Cell","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple approaches (KO mouse, RNAi, overexpression) converging on same mechanism; single lab","pmids":["16855020"],"is_preprint":false},{"year":2011,"finding":"Staufen 2 (Stau2) knockdown reduces dendritic localization of Map1b mRNA, decreases basal Map1b protein in dendrites, and prevents mGluR/DHPG-induced increases in dendritic Map1b protein; Stau2 is required for mGluR-LTD (but not LTP); mGluR stimulation induces Map1b mRNA dissociation from Stau2/P0-containing granules, demonstrating Stau2 controls Map1b mRNA dendritic distribution and translation for mGluR-LTD.","method":"Stau2 shRNA knockdown; Map1b mRNA FISH; protein immunostaining in dendrites; electrophysiology (LTP, LTD); granule co-localization; DHPG stimulation","journal":"Learning & Memory","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — RNAi + mRNA localization + protein quantification + electrophysiology; single lab, multiple readouts","pmids":["21508097"],"is_preprint":false},{"year":2012,"finding":"In growth cones, a DLK–MKK7–JNK1 MAP kinase module phosphorylates Map1b to regulate microtubule bundling and neurite elongation; MKK7 mRNA localizes to the growth cone and can be locally translated there; disruption of this pathway alters Map1b phosphorylation and microtubule bundling.","method":"Genome-wide mRNA localization screen; MKK7 mRNA FISH in growth cones; phospho-Map1b immunostaining; kinase inhibitor and dominant-negative experiments; neurite elongation assay","journal":"PLoS Biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — pharmacological/genetic epistasis of kinase cascade upstream of MAP1B phosphorylation; single lab","pmids":["23226105"],"is_preprint":false},{"year":2007,"finding":"MAP1B coordinates microtubule and actin cytoskeleton remodeling; MAP1B is required for LPA-induced microtubule backfolding during process retraction in DRG neurons and Schwann cells; MAP1B-deficient cells show actin contraction but fail to execute the subsequent microtubule backfolding step, and MAP1B is required for Schwann cell migration in vitro.","method":"Map1b-null mouse neurons and Schwann cells; LPA stimulation; time-lapse imaging of cytoskeletal rearrangements; migration assay","journal":"Molecular and Cellular Neurosciences","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — KO mouse cells with live imaging of cytoskeletal dynamics; single lab, defined mechanistic step","pmids":["17764972"],"is_preprint":false},{"year":2016,"finding":"GSK-3-mediated MAP1B phosphorylation is locally reduced at neurite branching points; MAP1B is required downstream of GSK-3 for branching control, as map1b−/− neurons are not affected by GSK-3 inhibition and re-expression of MAP1B in map1b−/− neurons restores wild-type branching. Phospho-MAP1B preferentially associates with tyrosinated microtubules and its dephosphorylation by GSK-3 inhibition protects both tyrosinated and acetylated MTs from nocodazole depolymerization.","method":"Map1b-null mouse neurons; GSK-3 inhibitor treatments; cDNA rescue transfection; MAP1B-transfected fibroblasts + nocodazole assay; phospho-MAP1B immunostaining at branch points; tyrosinated/acetylated tubulin staining","journal":"Molecular and Cellular Neurosciences","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic epistasis (KO + rescue) + pharmacological inhibition + MT modification analysis; single lab","pmids":["26773468"],"is_preprint":false},{"year":2015,"finding":"FMRP associates with miR-181d, Map1b mRNA, and Calm1 mRNA in axons; miR-181d delivered by FMRP negatively regulates local translation of MAP1B in axons; FMRP deficiency (Fmr1I304N or Fmr1 knockdown) impedes axonal delivery of miR-181d and Map1b mRNA, reducing MAP1B protein in axons; NGF releases Map1b mRNA from FMRP/miR-181d-repressing granules to promote axon elongation.","method":"FMRP co-immunoprecipitation with miR-181d and Map1b mRNA; microfluidic axon isolation; MAP1B protein quantification in axons; NGF stimulation; Fmr1 mutant mice","journal":"Cell Reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — co-IP + axon compartment protein quantification + genetic mouse model; single lab","pmids":["26711345"],"is_preprint":false},{"year":2019,"finding":"In SNCA-A53T (Parkinson's disease) human neurons, mutant α-synuclein fails to complex with PKC, impairing Nrf2 activation; reduced Nrf2 activity on antioxidant response elements (AREs) at the Map1b gene enhancer decreases MAP1B expression; forced MAP1B expression or Nrf2 activation rescues neuritic length/complexity defects in PD neurons.","method":"hPSC-derived A9-type dopaminergic neurons + isogenic controls; ChIP-seq/reporter assay for Nrf2 on Map1b ARE; MAP1B overexpression rescue; Nrf2 pharmaceutical activation; neuritic morphology analysis","journal":"Proceedings of the National Academy of Sciences USA","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Nrf2 binding to Map1b locus shown + genetic rescue; human iPSC model; single lab","pmids":["31235589"],"is_preprint":false},{"year":2016,"finding":"MAP1B-deficient neurons show decreased density of presynaptic terminals, increased proportion of orphan presynaptic terminals, altered synaptic vesicle fusion (FM4-64 assay), and decreased density of synaptic vesicles and dense core vesicles at presynaptic terminals, identifying a presynaptic structural and functional role for MAP1B.","method":"MAP1B KO mouse neurons; immunofluorescence quantification of synaptic terminal density; FM4-64 synaptic vesicle fusion assay; electron microscopy of presynaptic terminals","journal":"Scientific Reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — KO mouse with electron microscopy + functional vesicle release assay; single lab","pmids":["27425640"],"is_preprint":false},{"year":2020,"finding":"MAP1B mutations (c.4198A>G p.S1400G; c.2768T>C p.I923T; c.5512T>C p.F1838L) cause reduced MAP1B levels and deficient MAP1B phosphorylation in patient-derived otic sensory neuron-like cells; these cells exhibit disturbed microtubule dynamics, impaired axonal elongation, and electrophysiological defects, all rescued by CRISPR/Cas9 correction of the MAP1B mutation; Map1b+/- mice show progressive hearing loss with spiral ganglion neuron microtubule phosphorylation defects.","method":"Patient iPSC-derived otic neurons; CRISPR/Cas9 correction; Map1b+/- mouse audiometry; MAP1B phosphorylation Western blot; microtubule dynamics imaging; patch-clamp electrophysiology","journal":"JCI Insight","confidence":"High","confidence_rationale":"Tier 1–2 / Moderate — patient-derived cell model + CRISPR rescue + mouse model + multiple cellular/electrophysiological readouts; comprehensive mechanistic validation","pmids":["33268592"],"is_preprint":false}],"current_model":"MAP1B is a neuronally expressed microtubule-associated phosphoprotein that functions primarily as a regulator of microtubule and actin cytoskeleton dynamics: its basic KKEE/KKEVI-containing domain directly binds microtubules (and its light chain LC1 independently stabilizes microtubules and binds F-actin), while its phosphorylation state—controlled by CK2, GSK-3β (primed by DYRK1A and downstream of TrkA–MAPK and Netrin-1/Reelin signaling), NLK, and reversed by PP2A/PP2B/PP1—acts as a molecular switch toggling microtubule dynamic instability in growing axons; MAP1B also sequesters EB1/3 (+TIPs) in the cytosol to modulate plus-end dynamics, interacts with Tiam1–Rac1 to coordinate actin remodeling required for axon growth, dendritic spine maturation, and LTD-associated AMPA receptor endocytosis, anchors GABA(C) receptors at retinal synapses through rho1 interaction, facilitates Nav1.6 surface trafficking, and is targeted for proteasomal degradation of its light chain by the ubiquitin ligase gigaxonin, whose loss in giant axonal neuropathy causes MAP1B-LC accumulation and neuronal death."},"narrative":{"mechanistic_narrative":"MAP1B is a neuronally enriched microtubule-associated phosphoprotein that integrates microtubule and actin cytoskeletal dynamics to drive axon growth, guidance, neuronal migration, and synaptic plasticity [PMID:11121433, PMID:10973990, PMID:20719958]. It is synthesized as a polyprotein yielding a heavy chain and light chain 1 (LC1) by proteolytic processing, with the heavy chain binding microtubules through a basic KKEE/KKEVI-repeat domain unrelated to those of MAP2 or tau [PMID:2480963, PMID:1712602]; LC1 independently stabilizes microtubules, promotes tubulin polymerization, and carries a C-terminal actin-binding domain [PMID:9813091, PMID:11896150], and the heavy chain itself directly binds actin, making MAP1B a bivalent crosslinker of both cytoskeletal systems [PMID:17292804]. Beyond stabilizing and acetylating microtubules and enhancing their assembly rate [PMID:1487506, PMID:22033417], MAP1B sequesters the +TIP proteins EB1/EB3 in the cytosol to restrain plus-end dynamics and prevent microtubule overstabilization in growth cones [PMID:23572079]. MAP1B activity is governed by a phosphorylation switch: GSK-3β phosphorylates it at Ser1260/Thr1265 (and is primed by DYRK1A) to toggle microtubule dynamic instability selectively in growing axons, with CK2, NLK, and a DLK–MKK7–JNK1 module as additional kinases and PP2A/PP2B/PP1 reversing these modifications to restore microtubule binding [PMID:3164313, PMID:15731007, PMID:19549690, PMID:7690334, PMID:19840224, PMID:23226105]; this GSK-3β input is itself relayed from TrkA–MAPK, Wnt, Netrin-1, and Reelin signaling for axon growth and migration [PMID:9570753, PMID:15186740, PMID:15737742, PMID:14622124]. Through interaction with the Rac1 GEF Tiam1, MAP1B controls a Rac1/Cdc42/RhoA balance required for axon outgrowth, dendritic spine maturation, and LTD-associated AMPA receptor endocytosis [PMID:20719958, PMID:21984824, PMID:23881099]. MAP1B additionally anchors GABA(C) receptors at retinal synapses via the rho1 subunit to tune receptor sensitivity [PMID:9892354, PMID:11102469] and facilitates Nav1.6 surface trafficking [PMID:22474336]. Its LC1 is targeted for ubiquitin-dependent degradation by gigaxonin, whose loss causes MAP1B-LC accumulation and neuronal death in giant axonal neuropathy [PMID:16227972], and MAP1B mutations that reduce protein levels and phosphorylation cause hereditary hearing loss with disturbed microtubule dynamics in sensory neurons [PMID:33268592].","teleology":[{"year":1989,"claim":"Established the structural basis of MAP1B's microtubule binding, defining a novel basic repeat domain distinct from other MAPs.","evidence":"Cell-free translation of subcloned fragments with in vitro microtubule cosedimentation plus transfected-cell deletion analysis","pmids":["2480963"],"confidence":"High","gaps":["No atomic structure of the binding interface","Affinity and stoichiometry of binding not quantified"]},{"year":1991,"claim":"Resolved how MAP1B generates its multi-subunit architecture by showing heavy chain and LC1 arise from one polyprotein.","evidence":"Protein sequencing, epitope mapping, and Northern/Southern blotting with heavy chain–LC1 co-purification","pmids":["1712602"],"confidence":"High","gaps":["Protease responsible for processing not identified","Regulation of processing not addressed"]},{"year":1988,"claim":"Identified CK2 as a principal kinase acting on MAP1B during neurite outgrowth, opening the phosphoregulation question.","evidence":"In vitro kinase assay with purified CK2 plus phosphopeptide mapping against in vivo neuroblastoma MAP1B","pmids":["3164313"],"confidence":"High","gaps":["Specific CK2 sites not mapped","Functional consequence of CK2 phosphorylation not defined here"]},{"year":1992,"claim":"Demonstrated MAP1B is a functional microtubule stabilizer in cells, distinguishing it from the bundling MAPs.","evidence":"Heterologous cDNA transfection with nocodazole resistance and acetylated-tubulin readouts across multiple cell lines","pmids":["1487506"],"confidence":"High","gaps":["Does not separate heavy-chain vs light-chain contributions","Mechanism of acetylation increase unresolved"]},{"year":1998,"claim":"Dissected the light chain as an autonomous stabilizing/actin-binding module under heavy-chain restraint.","evidence":"COS-cell transfection, drug-resistance assays, actin cosedimentation, and co-IP domain mapping of tagged fragments","pmids":["9813091"],"confidence":"High","gaps":["In vivo relevance of LC1 oligomerization unclear","Heavy-chain inhibition mechanism not structurally defined"]},{"year":1994,"claim":"Showed a shared light chain (LC3) confers direct microtubule binding to both MAP1A and MAP1B complexes.","evidence":"cDNA sequencing with recombinant LC3 microtubule cosedimentation and immunoprecipitation","pmids":["7908909"],"confidence":"High","gaps":["Functional distinction of LC3 vs LC1 within MAP1B not addressed","Stoichiometry within the complex unknown"]},{"year":1999,"claim":"Connected MAP1B to receptor anchoring by identifying a specific GABA(C) rho1 interaction at retinal synapses.","evidence":"Yeast two-hybrid, co-IP, retinal co-localization, and COS redistribution assay","pmids":["9892354"],"confidence":"High","gaps":["Did not yet show functional effect on receptor activity"]},{"year":2000,"claim":"Showed cytoskeletal anchoring by MAP1B tunes GABA(C) receptor sensitivity, giving the interaction physiological meaning.","evidence":"rho1 domain-mapping mutagenesis plus patch-clamp of retinal bipolar cells after interaction disruption","pmids":["11102469"],"confidence":"High","gaps":["Mechanism linking anchoring to EC50 shift unresolved"]},{"year":2000,"claim":"Defined MAP1B's essential developmental roles via complete-null mice and revealed redundancy with tau.","evidence":"Gene targeting with histology and nerve conduction measurement; tau/map1b double-knockout epistasis in cultured neurons","pmids":["11121433","10973990"],"confidence":"High","gaps":["Molecular basis of corpus callosum-selective requirement unclear","Extent of redundancy with other MAPs beyond tau not tested"]},{"year":2005,"claim":"Pinpointed GSK-3β phosphosites (Ser1260/Thr1265) as a spatial molecular switch for microtubule dynamics in growing axons.","evidence":"Site-directed mutagenesis, in vitro GSK-3β kinase assay, phospho-specific antibodies, in vivo localization, and MT dynamics in transfected cells","pmids":["15731007"],"confidence":"High","gaps":["How phosphorylation alters MT-binding biophysically not resolved","Interplay with other phosphosites not addressed"]},{"year":2004,"claim":"Placed MAP1B as a downstream effector of Netrin-1 and Reelin axon-guidance/migration signaling via mode I phosphorylation.","evidence":"In vitro phosphorylation assays, mutant-mouse anatomy/phenocopy, and chemoattraction/lamination analyses","pmids":["15186740","15590913"],"confidence":"Medium","gaps":["Direct linkage of GSK-3/CDK5 activation to specific MAP1B sites not mapped","mDab1 role only partially defined"]},{"year":2005,"claim":"Traced the upstream growth-factor route to MAP1B by showing NGF–TrkA–MAPK (not PI3K or p75) drives GSK-3β phosphorylation of MAP1B.","evidence":"Receptor-selective ligands, TrkA-null PC12 cells, K252a inhibition, and pharmacological MAPK/PI3K dissection","pmids":["15737742","14622124"],"confidence":"Medium","gaps":["Relies on inhibitor specificity","Intermediate steps between MAPK and GSK-3β not defined"]},{"year":2005,"claim":"Identified gigaxonin-controlled proteasomal degradation of MAP1B-LC as a determinant of neuronal survival, linking MAP1B to giant axonal neuropathy.","evidence":"Pull-down/co-IP, proteasome inhibition, GAN-null mouse neurons, and MAP1B siRNA rescue of survival","pmids":["16227972"],"confidence":"High","gaps":["Mechanism by which MAP1B-LC excess kills neurons not defined","Ubiquitination sites on MAP1B-LC not mapped"]},{"year":2009,"claim":"Expanded the phosphocode by establishing DYRK1A as a priming kinase generating distinct spatial pools of GSK-3β-phosphorylated MAP1B.","evidence":"Mass spectrometry mapping of 28 sites, phospho-antibody panel, DYRK1A shRNA, and EB3 MT-dynamics imaging","pmids":["19549690"],"confidence":"High","gaps":["Functional consequence of each phosphosite class not individually tested"]},{"year":2009,"claim":"Added NLK as a direct MAP1B kinase coupling NGF signaling to actin redistribution and neurite outgrowth.","evidence":"In vitro kinase assay with purified NLK plus NLK knockdown with F-actin and outgrowth readouts","pmids":["19840224"],"confidence":"Medium","gaps":["NLK target sites on MAP1B not mapped","Single lab"]},{"year":1993,"claim":"Defined the phosphatase arm of the switch, distinguishing PP2A/PP2B/PP1 specificities for mode I vs mode II sites.","evidence":"In vitro phosphatase assays with purified enzymes plus okadaic acid/cyclosporin A treatment of brain slices with MT-binding readout","pmids":["7690334"],"confidence":"Medium","gaps":["In vivo phosphatase targeting/regulation not addressed"]},{"year":2000,"claim":"Established PP2A as the dominant phosphatase controlling MAP1B microtubule-binding activity in brain.","evidence":"Okadaic acid/cyclosporin A treatment of metabolically active brain slices with phospho-MAP1B and MT-binding assays","pmids":["10640627"],"confidence":"Medium","gaps":["Relies on inhibitor specificity","PP2A holoenzyme composition not defined"]},{"year":1996,"claim":"Showed phosphorylation negatively regulates MAP1B–F-actin binding, linking the phosphoswitch to the actin arm.","evidence":"In vitro alkaline-phosphatase dephosphorylation with F-actin cosedimentation","pmids":["8690071"],"confidence":"Medium","gaps":["Single in vitro method","Specific PDPK site responsible not pinpointed"]},{"year":2007,"claim":"Confirmed the heavy chain is itself a bivalent actin/microtubule binder, establishing MAP1B as a direct cytoskeletal crosslinker.","evidence":"Brain co-IP, mass spectrometry, atomic force microscopy force measurement, and electron microscopy","pmids":["17292804"],"confidence":"Medium","gaps":["Actin-binding site on heavy chain not mapped","Single lab"]},{"year":2007,"claim":"Demonstrated MAP1B is required for coordinated microtubule–actin remodeling during process retraction and Schwann cell migration.","evidence":"Map1b-null neurons and Schwann cells with LPA stimulation, live cytoskeletal imaging, and migration assays","pmids":["17764972"],"confidence":"Medium","gaps":["Molecular step coupling actin contraction to MT backfolding undefined"]},{"year":2002,"claim":"Refined LC1 domain architecture, separating its N-terminal MT-polymerizing and C-terminal actin-binding activities.","evidence":"Transfected-cell binding assays, in vitro tubulin polymerization, and domain deletion analysis","pmids":["11896150"],"confidence":"Medium","gaps":["Structural basis of LC1 vs LC2 functional divergence unresolved"]},{"year":2008,"claim":"Linked MAP1B to autophagy and cell death by identifying it as a DAPK-1 binding partner required for DAPK-1-driven phenotypes.","evidence":"Peptide-library binding, starvation-induced co-IP, siRNA loss-of-function, and autophagy/blebbing/clonogenic assays","pmids":["18195017"],"confidence":"Medium","gaps":["Whether MAP1B is a DAPK-1 substrate not established","Single lab"]},{"year":2010,"claim":"Defined the MAP1B–Tiam1–Rac1 axis coordinating actin remodeling and microtubule–actin crosstalk for neuronal polarization.","evidence":"MAP1B-null neuron GTPase activity assays, Tiam1 co-IP, and rescue with constitutively active Rac1/Cdc42/Tiam1","pmids":["20719958"],"confidence":"High","gaps":["Direct vs indirect MAP1B–Tiam1 binding interface not mapped"]},{"year":2011,"claim":"Extended MAP1B function to dendritic spine maturation through Rac1/RhoA/cofilin actin regulation.","evidence":"MAP1B+/- neurons with spine morphology, patch-clamp, GTPase assays, and PSD Western blots","pmids":["21984824"],"confidence":"High","gaps":["How MAP1B controls cofilin phosphorylation not mechanistically resolved"]},{"year":2011,"claim":"Quantified MAP1B's contribution to microtubule assembly rate along the axon shaft.","evidence":"RNAi and gain-of-function with EB3-GFP polymerization-speed imaging and axon morphology","pmids":["22033417"],"confidence":"High","gaps":["Molecular mechanism of growth-rate enhancement not defined"]},{"year":2011,"claim":"Established post-transcriptional control of Map1b via Stau2-dependent dendritic mRNA localization required for mGluR-LTD.","evidence":"Stau2 shRNA, Map1b mRNA FISH, dendritic protein quantification, and LTP/LTD electrophysiology","pmids":["21508097"],"confidence":"Medium","gaps":["Translational regulation step downstream of localization not detailed"]},{"year":2012,"claim":"Revealed MAP1B as a major Syk substrate promoting microtubule stability in non-neuronal cancer cells.","evidence":"Syk expression/silencing, MAP1B siRNA epistasis, drug-resistance/acetylation assays, and AFM nanomechanics","pmids":["24914616"],"confidence":"Medium","gaps":["Syk phosphosites on MAP1B not mapped","Single lab"]},{"year":2012,"claim":"Identified MAP1B-LC as a target of S-nitrosylation-dependent ubiquitination by MITOL linking it to mitochondrial integrity.","evidence":"S-nitrosylation and ubiquitination assays, MITOL manipulation, and mitochondrial-function/cell-death readouts","pmids":["22308378"],"confidence":"High","gaps":["Nitrosylated cysteine and ubiquitination sites not mapped","Relationship to gigaxonin pathway unresolved"]},{"year":2012,"claim":"Showed MAP1B facilitates Nav1.6 surface trafficking, broadening its membrane-protein chaperoning role.","evidence":"Yeast two-hybrid, brain co-IP, alanine-scanning of the Nav1.6 N-terminus, and patch-clamp of transfected cells","pmids":["22474336"],"confidence":"High","gaps":["Trafficking mechanism (vs stabilization) not distinguished"]},{"year":2012,"claim":"Connected MAP1B to centrosomal MT organization and Golgi/trafficking integrity via dystonin-a2.","evidence":"Dystonin mutant mice, isoform-specific RNAi, co-IP, and rescue by trichostatin A or MAP1B overexpression","pmids":["22412020"],"confidence":"High","gaps":["Direct vs scaffolded MAP1B–dystonin contact not resolved"]},{"year":2012,"claim":"Added a locally translated DLK–MKK7–JNK1 module phosphorylating Map1b to control growth-cone microtubule bundling.","evidence":"Genome-wide mRNA localization screen, MKK7 FISH, phospho-Map1b staining, and kinase inhibitor/dominant-negative assays","pmids":["23226105"],"confidence":"Medium","gaps":["JNK1 target sites on Map1b not mapped"]},{"year":2013,"claim":"Uncovered MAP1B cytosolic sequestration of EB1/EB3 as a brake on plus-end dynamics governing axon outgrowth.","evidence":"Co-IP, direct binding, RNAi, and EB3-GFP live imaging with growth-cone morphology","pmids":["23572079"],"confidence":"High","gaps":["Binding interface and competition with MT plus-ends not structurally defined"]},{"year":2013,"claim":"Established a MAP1B–Tiam1–Rac1 relay required for AMPA receptor endocytosis during LTD.","evidence":"Conditional MAP1B deletion/shRNA, LTD electrophysiology, endocytosis and Tiam1 localization assays, and Rac1 rescue","pmids":["23881099"],"confidence":"High","gaps":["How MAP1B targets Tiam1 to synapses mechanistically unclear"]},{"year":2016,"claim":"Showed local dephosphorylation of MAP1B at branch points, downstream of GSK-3, controls neurite branching and protects modified microtubules.","evidence":"Map1b-null neurons, GSK-3 inhibition, cDNA rescue, fibroblast nocodazole assays, and tyrosinated/acetylated tubulin staining","pmids":["26773468"],"confidence":"Medium","gaps":["Phosphatase responsible for local dephosphorylation not identified"]},{"year":2016,"claim":"Identified a presynaptic structural/functional role for MAP1B in terminal and vesicle organization.","evidence":"MAP1B KO neurons with terminal-density immunofluorescence, FM4-64 fusion assay, and electron microscopy","pmids":["27425640"],"confidence":"Medium","gaps":["Molecular partners mediating presynaptic role not defined"]},{"year":2006,"claim":"Defined QKI-dependent mRNA stabilization as oligodendroglial post-transcriptional control of MAP1B levels.","evidence":"3'UTR binding, qv mutant mice, QKI knockdown/overexpression, and mRNA-stability measurements","pmids":["16855020"],"confidence":"Medium","gaps":["Functional consequence of MAP1B in oligodendroglia not tested here"]},{"year":2015,"claim":"Revealed FMRP/miR-181d-mediated repression of axonal MAP1B local translation released by NGF.","evidence":"FMRP co-IP with miR-181d/Map1b mRNA, microfluidic axon isolation, axonal protein quantification, and Fmr1 mutant mice","pmids":["26711345"],"confidence":"Medium","gaps":["Direct miR-181d targeting of Map1b 3'UTR not fully validated","Single lab"]},{"year":2019,"claim":"Linked reduced MAP1B expression to Parkinson's-related neuritic defects through Nrf2 transcriptional control at the Map1b enhancer.","evidence":"Isogenic SNCA-A53T iPSC dopaminergic neurons, Nrf2 ChIP/reporter assays, and MAP1B/Nrf2 rescue of morphology","pmids":["31235589"],"confidence":"Medium","gaps":["Causal contribution of MAP1B loss to PD pathology in vivo not established"]},{"year":2020,"claim":"Demonstrated MAP1B mutations cause hereditary hearing loss via reduced levels/phosphorylation and disturbed microtubule dynamics in sensory neurons.","evidence":"Patient iPSC-derived otic neurons with CRISPR correction, Map1b+/- mouse audiometry, and MT-dynamics/electrophysiology readouts","pmids":["33268592"],"confidence":"High","gaps":["How specific missense changes impair phosphorylation not mechanistically resolved"]},{"year":null,"claim":"How the many converging kinase inputs, phosphosites, and binding partners are spatially integrated into a single dynamic regulation of MAP1B at defined subcellular sites remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No structural model of full-length MAP1B or its phosphorylated states","Site-by-site functional decoding of the 28+ phosphosites incomplete","Quantitative integration of competing actin/MT/+TIP/receptor interactions undefined"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0008092","term_label":"cytoskeletal protein binding","supporting_discovery_ids":[0,4,5,22,23,26,27]},{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[6,7,24,32]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[24,26,28]}],"localization":[{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[26]},{"term_id":"GO:0005856","term_label":"cytoskeleton","supporting_discovery_ids":[0,4,23]},{"term_id":"GO:0005815","term_label":"microtubule organizing center","supporting_discovery_ids":[29]}],"pathway":[{"term_id":"R-HSA-1266738","term_label":"Developmental Biology","supporting_discovery_ids":[11,12,13,24,27]},{"term_id":"R-HSA-112316","term_label":"Neuronal System","supporting_discovery_ids":[6,7,25,28,32,41]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[8,13,15,16,24]}],"complexes":["MAP1B heavy chain–light chain (LC1/LC3) complex"],"partners":["EB1","EB3","TIAM1","GAN","DAPK1","MARCHF5","SCN8A","DST"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"P46821","full_name":"Microtubule-associated protein 1B","aliases":[],"length_aa":2468,"mass_kda":270.6,"function":"Facilitates tyrosination of alpha-tubulin in neuronal microtubules (By similarity). Phosphorylated MAP1B is required for proper microtubule dynamics and plays a role in the cytoskeletal changes that accompany neuronal differentiation and neurite extension (PubMed:33268592). Possibly MAP1B binds to at least two tubulin subunits in the polymer, and this bridging of subunits might be involved in nucleating microtubule polymerization and in stabilizing microtubules. Acts as a positive cofactor in DAPK1-mediated autophagic vesicle formation and membrane blebbing","subcellular_location":"Cytoplasm","url":"https://www.uniprot.org/uniprotkb/P46821/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/MAP1B","classification":"Not Classified","n_dependent_lines":0,"n_total_lines":1208,"dependency_fraction":0.0},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[{"gene":"MAP1LC3B","stoichiometry":4.0},{"gene":"DNAJB6","stoichiometry":0.2},{"gene":"KRT18","stoichiometry":0.2},{"gene":"PDCD6","stoichiometry":0.2},{"gene":"STK4","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/search/MAP1B","total_profiled":1310},"omim":[{"mim_id":"619808","title":"DEAFNESS, AUTOSOMAL DOMINANT 83; DFNA83","url":"https://www.omim.org/entry/619808"},{"mim_id":"618918","title":"PERIVENTRICULAR NODULAR HETEROTOPIA 9; PVNH9","url":"https://www.omim.org/entry/618918"},{"mim_id":"611372","title":"SMALL ADP-RIBOSYLATION FACTOR GTPase-ACTIVATING PROTEIN 1; SMAP1","url":"https://www.omim.org/entry/611372"},{"mim_id":"610267","title":"METHIONINE AMINOPEPTIDASE 1D; METAP1D","url":"https://www.omim.org/entry/610267"},{"mim_id":"607465","title":"CODANIN 1; CDAN1","url":"https://www.omim.org/entry/607465"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Cytosol","reliability":"Supported"},{"location":"Equatorial segment","reliability":"Additional"}],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in many","driving_tissues":[{"tissue":"blood vessel","ntpm":83.8},{"tissue":"brain","ntpm":116.7},{"tissue":"retina","ntpm":143.5}],"url":"https://www.proteinatlas.org/search/MAP1B"},"hgnc":{"alias_symbol":["MAP5","PPP1R102"],"prev_symbol":[]},"alphafold":{"accession":"P46821","domains":[{"cath_id":"-","chopping":"34-237","consensus_level":"high","plddt":91.8983,"start":34,"end":237},{"cath_id":"3.60.15.10","chopping":"242-338_347-360_362-397","consensus_level":"medium","plddt":87.7971,"start":242,"end":397}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/P46821","model_url":"https://alphafold.ebi.ac.uk/files/AF-P46821-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-P46821-F1-predicted_aligned_error_v6.png","plddt_mean":45.72},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=MAP1B","jax_strain_url":"https://www.jax.org/strain/search?query=MAP1B"},"sequence":{"accession":"P46821","fasta_url":"https://rest.uniprot.org/uniprotkb/P46821.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/P46821/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/P46821"}},"corpus_meta":[{"pmid":"11733059","id":"PMC_11733059","title":"Drosophila fragile X-related gene regulates the MAP1B homolog Futsch to control synaptic structure and function.","date":"2001","source":"Cell","url":"https://pubmed.ncbi.nlm.nih.gov/11733059","citation_count":547,"is_preprint":false},{"pmid":"10839355","id":"PMC_10839355","title":"Drosophila Futsch/22C10 is a MAP1B-like protein required for dendritic and axonal development.","date":"2000","source":"Neuron","url":"https://pubmed.ncbi.nlm.nih.gov/10839355","citation_count":377,"is_preprint":false},{"pmid":"10973990","id":"PMC_10973990","title":"Defects in axonal elongation and neuronal migration in mice with disrupted tau and map1b genes.","date":"2000","source":"The Journal of cell biology","url":"https://pubmed.ncbi.nlm.nih.gov/10973990","citation_count":331,"is_preprint":false},{"pmid":"2480963","id":"PMC_2480963","title":"The microtubule binding domain of microtubule-associated protein MAP1B contains a repeated sequence motif unrelated to that of MAP2 and tau.","date":"1989","source":"The Journal of cell biology","url":"https://pubmed.ncbi.nlm.nih.gov/2480963","citation_count":297,"is_preprint":false},{"pmid":"1487506","id":"PMC_1487506","title":"Increased microtubule stability and alpha tubulin acetylation in cells transfected with microtubule-associated proteins MAP1B, MAP2 or tau.","date":"1992","source":"Journal of cell science","url":"https://pubmed.ncbi.nlm.nih.gov/1487506","citation_count":292,"is_preprint":false},{"pmid":"9570753","id":"PMC_9570753","title":"Inhibition of GSK-3beta leading to the loss of phosphorylated MAP-1B is an early event in axonal remodelling induced by WNT-7a or lithium.","date":"1998","source":"Journal of cell science","url":"https://pubmed.ncbi.nlm.nih.gov/9570753","citation_count":260,"is_preprint":false},{"pmid":"25053844","id":"PMC_25053844","title":"Activity-associated miRNA are packaged in Map1b-enriched exosomes released from depolarized neurons.","date":"2014","source":"Nucleic acids research","url":"https://pubmed.ncbi.nlm.nih.gov/25053844","citation_count":241,"is_preprint":false},{"pmid":"7908909","id":"PMC_7908909","title":"Molecular characterization of light chain 3. 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communications","url":"https://pubmed.ncbi.nlm.nih.gov/30150678","citation_count":33,"is_preprint":false},{"pmid":"19840224","id":"PMC_19840224","title":"Nemo-like kinase is involved in NGF-induced neurite outgrowth via phosphorylating MAP1B and paxillin.","date":"2009","source":"Journal of neurochemistry","url":"https://pubmed.ncbi.nlm.nih.gov/19840224","citation_count":32,"is_preprint":false},{"pmid":"22474336","id":"PMC_22474336","title":"Interaction of voltage-gated sodium channel Nav1.6 (SCN8A) with microtubule-associated protein Map1b.","date":"2012","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/22474336","citation_count":32,"is_preprint":false},{"pmid":"31235589","id":"PMC_31235589","title":"Axonal pathology in hPSC-based models of Parkinson's disease results from loss of Nrf2 transcriptional activity at the Map1b gene locus.","date":"2019","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/31235589","citation_count":31,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":45314,"output_tokens":11715,"usd":0.155834,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":23007,"output_tokens":9137,"usd":0.17173,"stage2_stop_reason":"end_turn"},"total_usd":0.327564,"stage1_batch_id":"msgbatch_01BbTCMyrRPyhtEq6b1MdwCN","stage2_batch_id":"msgbatch_011dEed5bbxYvTAaQWKJevxu","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 1989,\n      \"finding\": \"The microtubule-binding domain of MAP1B was mapped to a highly basic region containing repeated KKEE/KKEVI motifs; this region copurifies with microtubules in vitro and mediates microtubule interaction in vivo in transfected cells. A separate 12-repeat region does not bind microtubules. The MAP1B microtubule-binding domain is structurally unrelated to those of MAP2, tau, or kinesin.\",\n      \"method\": \"Cell-free translation of subcloned fragments + microtubule cosedimentation cycles in vitro; full-length and deletion constructs transfected into cultured cells with immunofluorescence readout\",\n      \"journal\": \"The Journal of Cell Biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro reconstitution with defined fragments plus in vivo deletion-construct validation, multiple orthogonal methods in a single rigorous study\",\n      \"pmids\": [\"2480963\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1991,\n      \"finding\": \"MAP1B is encoded as a polyprotein: the heavy chain and light chain 1 (LC1) are translated from the same mRNA within the same open reading frame and generated by proteolytic processing. LC1 binds near the heavy-chain N-terminus and together they form a complex microtubule-binding domain.\",\n      \"method\": \"Amino acid sequencing of heavy-chain fragment, epitope mapping, Northern and Southern blotting; co-purification of heavy chain and LC1\",\n      \"journal\": \"Neuron\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — direct protein sequencing, epitope mapping, and molecular cloning demonstrating polyprotein origin with multiple orthogonal approaches\",\n      \"pmids\": [\"1712602\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1994,\n      \"finding\": \"Light chain 3 (LC3) is a subunit of both MAP1A and MAP1B complexes; purified recombinant LC3 associates with microtubules assembled in the presence of brain MAPs and with microtubules assembled from purified tubulin, demonstrating a direct microtubule-binding activity.\",\n      \"method\": \"cDNA sequencing, microtubule cosedimentation assays with recombinant LC3, immunoprecipitation, Western blot\",\n      \"journal\": \"The Journal of Biological Chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — reconstitution of recombinant LC3 binding to microtubules plus biochemical subunit identification; single lab but multiple orthogonal methods\",\n      \"pmids\": [\"7908909\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1988,\n      \"finding\": \"MAP1B is phosphorylated in vitro by a casein kinase II (CK2)-like activity present in developing neuroblastoma cells; phosphopeptide maps of brain MAP1B phosphorylated by purified CK2 are identical to those of in vivo phosphorylated neuroblastoma MAP1B, identifying CK2 as a principal kinase acting on MAP1B during neurite outgrowth.\",\n      \"method\": \"In vitro kinase assay with purified CK2 and other kinases; phosphopeptide mapping; immunoprecipitation; microtubule cosedimentation\",\n      \"journal\": \"The Journal of Cell Biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro kinase assay with purified enzyme plus phosphopeptide fingerprinting and in vivo correlation; multiple orthogonal methods single lab\",\n      \"pmids\": [\"3164313\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1992,\n      \"finding\": \"Expression of MAP1B in fibroblasts stabilizes microtubules against depolymerizing reagents and increases alpha-tubulin acetylation, demonstrating that MAP1B promotes microtubule stability in vivo, though without the extensive microtubule bundling induced by MAP2 or tau.\",\n      \"method\": \"cDNA transfection into COS/HeLa/3T3 cells; nocodazole resistance assay; immunofluorescence for acetylated tubulin\",\n      \"journal\": \"Journal of Cell Science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — clean gain-of-function in heterologous cells with two orthogonal phenotypic readouts (drug resistance and tubulin modification); replicated across multiple cell types\",\n      \"pmids\": [\"1487506\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"The MAP1B light chain (LC1), in the absence of the heavy chain, induces formation of nocodazole- and taxol-resistant stable microtubules; the heavy chain inhibits LC1 activity. LC1 contains a C-terminal actin filament-binding domain, and LC1 can dimerize/oligomerize. Heavy chain–light chain interaction domains were localized by coimmunoprecipitation of epitope-tagged fragments.\",\n      \"method\": \"Transient transfection in COS cells; immunofluorescence; nocodazole/taxol resistance assay; coimmunoprecipitation of epitope-tagged fragments; actin cosedimentation\",\n      \"journal\": \"The Journal of Cell Biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — multiple functional assays (drug resistance, actin binding, co-IP domain mapping) in a single study; single lab but orthogonal methods\",\n      \"pmids\": [\"9813091\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"MAP1B specifically interacts with the GABA(C) receptor rho1 subunit (but not GABA(A) subunits), co-localizes with GABA(C) receptors at bipolar cell axon terminals in the retina, and redistributes rho1 upon co-expression in COS cells, suggesting MAP1B anchors GABA(C) receptors at postsynaptic sites.\",\n      \"method\": \"Yeast two-hybrid (interaction discovery), co-immunoprecipitation, immunofluorescence co-localization in retinal slices, heterologous co-expression redistribution assay in COS cells\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal binding confirmed by Y2H + co-IP + in vivo co-localization + cell-redistribution assay; multiple orthogonal methods\",\n      \"pmids\": [\"9892354\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"Twelve amino acids at the C-terminus of the large intracellular loop of rho1 (and rho2) are sufficient for interaction with MAP1B; disrupting the MAP1B–rho1 interaction in bipolar cells in retinal slices decreased the EC50 of GABA(C) receptors, doubling current at low GABA concentrations without affecting maximum current, demonstrating that cytoskeletal anchoring by MAP1B modulates GABA(C) receptor sensitivity.\",\n      \"method\": \"Deletion/mutagenesis mapping of rho1 interaction domain; patch-clamp electrophysiology of retinal bipolar cells in slices after disruption of MAP1B–rho interaction\",\n      \"journal\": \"The Journal of Neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — domain-mapping mutagenesis combined with functional electrophysiology in native tissue; rigorous mechanistic follow-up of a prior discovery\",\n      \"pmids\": [\"11102469\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"GSK-3β directly phosphorylates MAP1B in vitro; in cerebellar granule neurons, WNT-7a and lithium (a GSK-3β inhibitor) induce loss of the phosphorylated form of MAP1B (MAP1B-P) from axonal processes before axonal remodelling is visible, identifying MAP1B as a downstream target of the WNT–GSK-3β pathway in axonal remodelling.\",\n      \"method\": \"In vitro phosphorylation assay with purified GSK-3β and MAP1B; immunostaining of granule neurons treated with lithium or WNT-7a; time-course imaging of axonal morphology\",\n      \"journal\": \"Journal of Cell Science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro kinase assay demonstrating direct phosphorylation plus in vivo cellular phenotype correlation; two orthogonal approaches\",\n      \"pmids\": [\"9570753\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"GSK-3β phosphorylates MAP1B at Ser1260 and Thr1265 in vitro and in vivo; phospho-specific antibodies show that GSK-3β-phosphorylated MAP1B is restricted to growing axons (distal gradient) in developing rat embryos. Site-directed mutation (Ser1260Val or Thr1265Val, or both) in full-length MAP1B alters microtubule dynamics in transfected cells, establishing these sites as a molecular switch regulating microtubule stability in growing axons.\",\n      \"method\": \"Site-directed mutagenesis of recombinant MAP1B; in vitro GSK-3β kinase assay; phospho-specific antibody generation; immunostaining of developing nervous system; heterologous cell transfection with MT dynamics assay\",\n      \"journal\": \"Journal of Cell Science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — mutagenesis + in vitro kinase assay + phospho-specific antibody validation + in vivo localization + functional rescue; multiple orthogonal methods\",\n      \"pmids\": [\"15731007\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"Gigaxonin (GAN protein) binds MAP1B light chain (LC) through its C-terminal kelch repeat domain; gigaxonin overexpression leads to enhanced proteasome-dependent degradation of MAP1B-LC; GAN-null neurons accumulate MAP1B-LC; MAP1B overexpression causes neuronal death similar to GAN-null neurons, while MAP1B knockdown improves GAN-null neuron survival, identifying gigaxonin as a ubiquitin scaffolding protein controlling MAP1B-LC degradation and neuronal survival.\",\n      \"method\": \"Pull-down, co-immunoprecipitation; overexpression in neurons; proteasome inhibitor experiments; GAN knockout mouse neurons; MAP1B siRNA knockdown; cell viability assay\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — direct protein interaction + proteasome inhibitor rescue + KO mouse phenotype + RNAi rescue; multiple orthogonal methods replicated across models\",\n      \"pmids\": [\"16227972\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"MAP1B null mice (complete null allele) are viable but selectively lack the corpus callosum due to misguided cortical axons, and have reduced/thinner myelinated axons in peripheral nerves with decreased nerve conduction velocity, demonstrating an essential role for MAP1B in axon guidance and CNS/PNS development.\",\n      \"method\": \"Gene targeting (complete null allele), histology, electrophysiological nerve conduction velocity measurement, immunohistochemistry\",\n      \"journal\": \"The Journal of Cell Biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — complete genetic knockout with multiple defined phenotypic readouts (anatomical + electrophysiological); resolves earlier conflicting knockout results\",\n      \"pmids\": [\"11121433\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"Tau and MAP1B cooperate synergistically in axonal elongation and neuronal migration: double-knockout (tau−/−map1b−/−) mice show much more severe defects (inhibited axonal elongation in hippocampal neurons, delayed neuronal migration in cerebellar neurons) than single knockouts, demonstrating functional redundancy between the two MAPs.\",\n      \"method\": \"Double-knockout mouse generation; primary hippocampal and cerebellar neuron cultures from knockout mice; morphological analysis of axon elongation and migration\",\n      \"journal\": \"The Journal of Cell Biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic epistasis via double KO with single-KO comparison; replicated across two neuronal populations\",\n      \"pmids\": [\"10973990\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"Netrin-1 regulates mode I MAP1B phosphorylation (activating GSK-3 and CDK5) both in vivo and in vitro; MAP1B-deficient neurons show reduced chemoattractive response to Netrin-1 in vitro, and map1b mutant mice display severe axonal tract abnormalities similar to netrin-1-deficient mice, placing MAP1B as a downstream effector in Netrin-1 signaling for axon guidance and neuronal migration.\",\n      \"method\": \"In vitro phosphorylation assays; Netrin-1 treatment of wild-type and map1b-null neurons; chemoattraction assay; analysis of map1b and netrin-1 mutant mouse brain anatomy\",\n      \"journal\": \"Current Biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic epistasis (double mutant phenocopies), in vitro signaling assays, in vivo anatomy; multiple orthogonal methods across two papers (same year)\",\n      \"pmids\": [\"15186740\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"Reelin induces mode I MAP1B phosphorylation through GSK-3 and CDK5 activation, with mDab1 participating in the signaling cascade; map1b-deficient mice have abnormal cortical layering consistent with a failure of neuronal migration, placing MAP1B downstream of Reelin signaling.\",\n      \"method\": \"In vitro and in vivo phosphorylation assays after Reelin treatment; analysis of map1b-null mouse brain lamination; mDab1 involvement tested biochemically\",\n      \"journal\": \"Cerebral Cortex\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vitro kinase assays + KO mouse anatomy; single lab, partial mechanistic detail on mDab1 involvement\",\n      \"pmids\": [\"15590913\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"The MAPK pathway (not the PI3K pathway) links NGF/TrkA receptor engagement to GSK-3β activation, which then phosphorylates MAP1B to regulate microtubule dynamics and axon growth rate; pharmacological inhibition of MAPK prevents GSK-3β activation and MAP1B phosphorylation and reduces neurite growth, while PI3K inhibition does not.\",\n      \"method\": \"Pharmacological inhibitor studies (MAPK and PI3K inhibitors) in PC12 cells and sympathetic neurons; in vitro kinase assay; GSK-3β activation assay\",\n      \"journal\": \"Molecular and Cellular Neurosciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — pharmacological epistasis plus in vitro kinase assay; single lab, relies on inhibitor specificity\",\n      \"pmids\": [\"15737742\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"NGF activates GSK-3β phosphorylation of MAP1B through TrkA receptors, not through p75NTR; BDNF (which activates p75NTR but not TrkA) does not stimulate this phosphorylation; TrkA-deficient PC12 nnr cells fail to show NGF-dependent MAP1B phosphorylation; TrkA inhibition blocks neurite elongation and MAP1B phosphorylation.\",\n      \"method\": \"Use of receptor-selective ligands and PC12 nnr cells lacking TrkA; TrkA kinase inhibitor (K252a); in vivo immunostaining for phospho-MAP1B\",\n      \"journal\": \"Journal of Neurochemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic/pharmacological receptor dissection; single lab, well-controlled negative controls\",\n      \"pmids\": [\"14622124\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"DAPK-1 (death-associated protein kinase 1) binds directly to the N-terminal domain of MAP1B (residues 1–126 and a 12-aa motif); amino acid starvation induces a stable endogenous MAP1B–DAPK-1 immune complex; MAP1B is required for DAPK-1-stimulated autophagy and membrane blebbing: MAP1B siRNA attenuates these DAPK-1 activities, and MAP1B overexpression synergizes with DAPK-1 for growth inhibition.\",\n      \"method\": \"Peptide library selection; immunobinding assays; confocal co-localization; siRNA knockdown; clonogenic growth assay; autophagy and blebbing phenotype assays\",\n      \"journal\": \"The Journal of Biological Chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — binding confirmed biochemically + siRNA loss-of-function with multiple phenotypic readouts; single lab\",\n      \"pmids\": [\"18195017\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"DYRK1A acts as a priming kinase for GSK-3β phosphorylation of MAP1B; mass spectrometry identified 28 MAP1B phosphorylation sites; DYRK1A-primed GSK-3β sites are distributed throughout the neuron while non-primed GSK-3β sites are restricted to growing axons; DYRK1A knockdown compromises neuritogenesis and alters microtubule stability.\",\n      \"method\": \"Mass spectrometry phosphosite mapping; phospho-specific antibody panel; kinase inhibitor treatments in embryonic cortical neurons; shRNA knockdown of DYRK1A; EB3 microtubule dynamics imaging\",\n      \"journal\": \"Journal of Cell Science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — mass spec site mapping + phospho-specific antibody validation + RNAi loss-of-function with MT dynamics readout; multiple orthogonal methods\",\n      \"pmids\": [\"19549690\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1993,\n      \"finding\": \"Protein phosphatase 2A (PP2A) and PP2B (calcineurin) dephosphorylate mode I (proline-directed) MAP1B phosphorylation sites, while mode II (CK2-type) sites are dephosphorylated by PP2A and PP1 but not PP2B; inhibition of PP2A in rat brain slices (okadaic acid) increases MAP1B phosphorylation and inhibits its microtubule-binding activity.\",\n      \"method\": \"In vitro phosphatase assay with purified PP1, PP2A, PP2B; phosphorylation-state antibodies on rat brain slices treated with okadaic acid or cyclosporin A; microtubule binding assay\",\n      \"journal\": \"FEBS Letters\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — in vitro phosphatase assay with purified enzymes + cell/tissue pharmacological validation; single lab, multiple phosphatases compared\",\n      \"pmids\": [\"7690334\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"PP2A is the major phosphatase regulating MAP1B phosphorylation and microtubule-binding activity in rat brain: okadaic acid (PP2A inhibitor) treatment of brain slices markedly increases MAP1B phosphorylation and inhibits MAP1B microtubule-binding activity; cyclosporin A (PP2B inhibitor) has a lesser effect.\",\n      \"method\": \"Okadaic acid and cyclosporin A treatment of metabolically active rat brain slices; Western blot with phospho-MAP1B antibodies; immunocytochemistry; microtubule binding assay\",\n      \"journal\": \"Brain Research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — pharmacological inhibition in native tissue with functional microtubule-binding readout; single lab, relies on inhibitor specificity\",\n      \"pmids\": [\"10640627\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1996,\n      \"finding\": \"Dephosphorylated MAP1B (but not native phosphorylated MAP1B) binds and cosediments with microfilaments in vitro; the proline-directed kinase (PDPK) phosphorylation site (not the CK2 sites) negatively regulates MAP1B interaction with F-actin.\",\n      \"method\": \"In vitro alkaline phosphatase dephosphorylation; F-actin cosedimentation assay; dephosphorylation kinetics correlated with F-actin binding\",\n      \"journal\": \"FEBS Letters\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Weak — in vitro reconstitution with purified protein; single lab, single method type\",\n      \"pmids\": [\"8690071\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"MAP1B light chain 1 (LC1) binds microtubules and induces tubulin polymerization via a critical NH2-terminal microtubule-binding domain; LC1 also contains a C-terminal actin-binding domain that directly binds actin filaments; the two MAP1 light chains (LC1 of MAP1B and LC2 of MAP1A) differ in their effects on microtubule bundling and stability despite structural similarity.\",\n      \"method\": \"In vivo microtubule/actin binding assays in transfected cells; in vitro tubulin polymerization assay; domain deletion analysis; immunofluorescence\",\n      \"journal\": \"The Journal of Neuroscience\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — functional domain analysis with multiple cellular assays; single lab\",\n      \"pmids\": [\"11896150\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"MAP1B heavy chain directly binds actin; co-immunoprecipitation shows actin and tubulin co-precipitate with MAP1B at similar ratios throughout development regardless of phosphorylation state; atomic force microscopy measures MAP1B–actin binding force comparable to MAP1B–tubulin interaction. MAP1B heavy chain thus contains both a microtubule-stabilizing domain and an actin-binding site.\",\n      \"method\": \"Co-immunoprecipitation from brain tissue; mass spectrometry identification; atomic force microscopy force measurement; electron microscopy; COS-7 cell immunofluorescence\",\n      \"journal\": \"Brain Research Bulletin\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — co-IP + AFM force measurement + EM; single lab, multiple orthogonal methods\",\n      \"pmids\": [\"17292804\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"MAP1B deficiency reduces Rac1 and Cdc42 activity and increases RhoA activity; MAP1B interacts with Tiam1 (a Rac1 GEF); constitutively active Rac1, Cdc42, or Tiam1 rescues axon growth defects in MAP1B-deficient neurons, establishing a MAP1B–Tiam1–Rac1 axis required for microtubule–actin crosstalk during neuronal polarization.\",\n      \"method\": \"MAP1B-null mouse neurons; Rac1/Cdc42/RhoA activity pull-down assays; co-immunoprecipitation of MAP1B with Tiam1; rescue by constitutively active GTPase constructs; axon outgrowth assay\",\n      \"journal\": \"Molecular Biology of the Cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — GTPase activity assays + co-IP of interacting protein + genetic rescue with constitutively active constructs; multiple orthogonal methods confirming mechanism\",\n      \"pmids\": [\"20719958\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"MAP1B is present in dendritic spines; MAP1B-deficient mice show decreased density of mature dendritic spines, increased filopodia-like protrusions, reduced AMPA receptor-mediated synaptic currents, decreased Rac1 activity, increased RhoA activity, and decreased phospho-cofilin in postsynaptic densities, implicating MAP1B in dendritic spine maturation via actin cytoskeleton regulation.\",\n      \"method\": \"MAP1B+/- mouse neurons; spine morphology analysis; patch-clamp electrophysiology; Rac1/RhoA activity assays; Western blot of PSD fractions\",\n      \"journal\": \"The Journal of Biological Chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — KO mouse with multiple cellular/electrophysiological phenotypes + signaling pathway analysis; single lab but orthogonal methods\",\n      \"pmids\": [\"21984824\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"MAP1B interacts directly with EB1 and EB3 (+TIP proteins) and sequesters them in the neuronal cytosol; MAP1B overexpression reduces EB binding to microtubule plus-ends, while MAP1B knockdown increases EB-MT association and causes microtubule overstabilization and looping in growth cones, resulting in delayed axon outgrowth.\",\n      \"method\": \"Co-immunoprecipitation; direct interaction assay; RNAi knockdown; EB3-GFP live imaging of microtubule dynamics; growth cone morphology analysis\",\n      \"journal\": \"The EMBO Journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct binding shown + RNAi loss-of-function with live MT dynamics imaging and morphological readout; single lab, multiple orthogonal methods\",\n      \"pmids\": [\"23572079\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"MAP1B knockdown in embryonic rat cortical neurons decreases microtubule growth speed in the proximal and distal axon shaft (but not in growth cone filopodia) and produces more branched, slower growing axons; expression of MAP1B in MAP1B-naive cells increases microtubule elongation rate, demonstrating that MAP1B enhances microtubule assembly rates.\",\n      \"method\": \"RNAi knockdown; EB3-GFP live imaging of microtubule polymerization speed; axon morphology analysis; MAP1B expression in heterologous cells\",\n      \"journal\": \"Molecular and Cellular Neurosciences\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — RNAi loss-of-function + gain-of-function in heterologous cells; live imaging quantification of microtubule dynamics; single lab, two complementary approaches\",\n      \"pmids\": [\"22033417\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"MAP1B deficiency impairs LTD expression specifically by preventing AMPA receptor endocytosis and spine shrinkage during LTD; this is due to failure of Tiam1 (Rac1 GEF) targeting to synaptic compartments and reduced Rac1 activation; providing additional Rac1 restores LTD and AMPA receptor endocytosis in MAP1B-deficient neurons, establishing a MAP1B–Tiam1–Rac1 relay for synaptic plasticity.\",\n      \"method\": \"Conditional MAP1B-deficient mouse + shRNA; electrophysiological LTD recording; AMPA receptor endocytosis assay; Tiam1 localization by immunostaining; Rac1 activity assay; rescue with Rac1 expression\",\n      \"journal\": \"The EMBO Journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic + RNAi loss-of-function + electrophysiology + molecular rescue; multiple orthogonal methods confirming pathway\",\n      \"pmids\": [\"23881099\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"Dystonin-a2 binds MAP1B in the centrosomal region; loss of this interaction in dt mutant neurons causes altered MAP1B perikaryal localization, microtubule deacetylation and instability, Golgi fragmentation, and impaired anterograde trafficking; restoring MT acetylation (trichostatin A) or MAP1B overexpression rescues these defects.\",\n      \"method\": \"Dystonin mutant mouse + isoform-specific RNAi; co-immunoprecipitation; immunofluorescence of MAP1B and acetylated tubulin; Golgi morphology; vesicle trafficking assay; rescue experiments\",\n      \"journal\": \"The Journal of Cell Biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — co-IP + KO mouse + rescue experiments; multiple phenotypic readouts; single lab, orthogonal methods\",\n      \"pmids\": [\"22412020\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"S-nitrosylation of MAP1B light chain 1 (LC1) induces a conformational change that activates LC1 and promotes its ubiquitination by MITOL (mitochondrial ubiquitin ligase); MITOL inhibition results in accumulation of S-nitrosylated LC1, mitochondrial dysfunction, and neuronal cell death, demonstrating that MITOL regulates MAP1B-LC1 through nitrosylation-dependent ubiquitination.\",\n      \"method\": \"S-nitrosylation assay; MITOL knockdown/overexpression; ubiquitination assay; mitochondrial function assay; neuronal cell death readout; conformational change analysis\",\n      \"journal\": \"Proceedings of the National Academy of Sciences USA\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — post-translational modification (S-nitrosylation) linked to ubiquitination by defined E3 ligase; multiple functional readouts; single lab\",\n      \"pmids\": [\"22308378\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"Syk protein-tyrosine kinase uses MAP1B as a major substrate to promote microtubule stability in MDA-MB-231 breast cancer cells; MAP1B silencing attenuates Syk-dependent microtubule acetylation and nocodazole resistance, and reverses Syk-induced changes in cell topography/stiffness measured by atomic force microscopy.\",\n      \"method\": \"Syk expression/silencing; MAP1B siRNA; nocodazole resistance assay; acetylated tubulin immunostaining; multiharmonic AFM nanomechanical mapping\",\n      \"journal\": \"Biochemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — MAP1B RNAi epistasis downstream of Syk with multiple phenotypic readouts; single lab\",\n      \"pmids\": [\"24914616\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"Nav1.6 (SCN8A) voltage-gated sodium channel N-terminus interacts with MAP1B light chain via residues 77–80 (VAVP) of Nav1.6; co-expression of Nav1.6 with Map1b in ND7/23 neuronal cells increases sodium current density 50%; mutation of the Map1b-binding site of Nav1.6 prevents generation of sodium current, demonstrating that MAP1B facilitates Nav1.6 trafficking to the neuronal cell surface.\",\n      \"method\": \"Yeast two-hybrid screen; co-immunoprecipitation from mouse brain; alanine-scanning mutagenesis; patch-clamp electrophysiology in transfected cells\",\n      \"journal\": \"The Journal of Biological Chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — Y2H + co-IP from native brain + mutagenesis + functional electrophysiology; multiple orthogonal methods in single study\",\n      \"pmids\": [\"22474336\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Nemo-like kinase (NLK) directly phosphorylates MAP1B in vitro; NGF promotes NLK translocation to leading edges of PC12 cells and activates NLK kinase activity; NLK knockdown reduces MAP1B phosphorylation and inhibits NGF-induced F-actin redistribution and neurite outgrowth.\",\n      \"method\": \"In vitro kinase assay with purified NLK and MAP1B; NLK knockdown; immunofluorescence of F-actin and NLK; neurite outgrowth assay\",\n      \"journal\": \"Journal of Neurochemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — direct in vitro kinase assay + RNAi loss-of-function with phenotypic readout; single lab\",\n      \"pmids\": [\"19840224\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"QKI RNA-binding protein binds the 3'UTR of MAP1B mRNA in oligodendroglia; QKI-deficiency (quakingviable mice) reduces MAP1B mRNA expression; QKI knockdown destabilizes MAP1B mRNA in CG4 cells; forced QKI expression is sufficient to promote MAP1B expression, demonstrating QKI-dependent mRNA stabilization as a post-transcriptional mechanism controlling MAP1B levels specifically in oligodendroglia.\",\n      \"method\": \"3'UTR binding assay; qv mutant mice analysis; RNAi knockdown of QKI; QKI overexpression; Northern blot / qPCR for MAP1B mRNA stability\",\n      \"journal\": \"Molecular Biology of the Cell\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple approaches (KO mouse, RNAi, overexpression) converging on same mechanism; single lab\",\n      \"pmids\": [\"16855020\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Staufen 2 (Stau2) knockdown reduces dendritic localization of Map1b mRNA, decreases basal Map1b protein in dendrites, and prevents mGluR/DHPG-induced increases in dendritic Map1b protein; Stau2 is required for mGluR-LTD (but not LTP); mGluR stimulation induces Map1b mRNA dissociation from Stau2/P0-containing granules, demonstrating Stau2 controls Map1b mRNA dendritic distribution and translation for mGluR-LTD.\",\n      \"method\": \"Stau2 shRNA knockdown; Map1b mRNA FISH; protein immunostaining in dendrites; electrophysiology (LTP, LTD); granule co-localization; DHPG stimulation\",\n      \"journal\": \"Learning & Memory\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — RNAi + mRNA localization + protein quantification + electrophysiology; single lab, multiple readouts\",\n      \"pmids\": [\"21508097\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"In growth cones, a DLK–MKK7–JNK1 MAP kinase module phosphorylates Map1b to regulate microtubule bundling and neurite elongation; MKK7 mRNA localizes to the growth cone and can be locally translated there; disruption of this pathway alters Map1b phosphorylation and microtubule bundling.\",\n      \"method\": \"Genome-wide mRNA localization screen; MKK7 mRNA FISH in growth cones; phospho-Map1b immunostaining; kinase inhibitor and dominant-negative experiments; neurite elongation assay\",\n      \"journal\": \"PLoS Biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — pharmacological/genetic epistasis of kinase cascade upstream of MAP1B phosphorylation; single lab\",\n      \"pmids\": [\"23226105\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"MAP1B coordinates microtubule and actin cytoskeleton remodeling; MAP1B is required for LPA-induced microtubule backfolding during process retraction in DRG neurons and Schwann cells; MAP1B-deficient cells show actin contraction but fail to execute the subsequent microtubule backfolding step, and MAP1B is required for Schwann cell migration in vitro.\",\n      \"method\": \"Map1b-null mouse neurons and Schwann cells; LPA stimulation; time-lapse imaging of cytoskeletal rearrangements; migration assay\",\n      \"journal\": \"Molecular and Cellular Neurosciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — KO mouse cells with live imaging of cytoskeletal dynamics; single lab, defined mechanistic step\",\n      \"pmids\": [\"17764972\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"GSK-3-mediated MAP1B phosphorylation is locally reduced at neurite branching points; MAP1B is required downstream of GSK-3 for branching control, as map1b−/− neurons are not affected by GSK-3 inhibition and re-expression of MAP1B in map1b−/− neurons restores wild-type branching. Phospho-MAP1B preferentially associates with tyrosinated microtubules and its dephosphorylation by GSK-3 inhibition protects both tyrosinated and acetylated MTs from nocodazole depolymerization.\",\n      \"method\": \"Map1b-null mouse neurons; GSK-3 inhibitor treatments; cDNA rescue transfection; MAP1B-transfected fibroblasts + nocodazole assay; phospho-MAP1B immunostaining at branch points; tyrosinated/acetylated tubulin staining\",\n      \"journal\": \"Molecular and Cellular Neurosciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic epistasis (KO + rescue) + pharmacological inhibition + MT modification analysis; single lab\",\n      \"pmids\": [\"26773468\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"FMRP associates with miR-181d, Map1b mRNA, and Calm1 mRNA in axons; miR-181d delivered by FMRP negatively regulates local translation of MAP1B in axons; FMRP deficiency (Fmr1I304N or Fmr1 knockdown) impedes axonal delivery of miR-181d and Map1b mRNA, reducing MAP1B protein in axons; NGF releases Map1b mRNA from FMRP/miR-181d-repressing granules to promote axon elongation.\",\n      \"method\": \"FMRP co-immunoprecipitation with miR-181d and Map1b mRNA; microfluidic axon isolation; MAP1B protein quantification in axons; NGF stimulation; Fmr1 mutant mice\",\n      \"journal\": \"Cell Reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — co-IP + axon compartment protein quantification + genetic mouse model; single lab\",\n      \"pmids\": [\"26711345\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"In SNCA-A53T (Parkinson's disease) human neurons, mutant α-synuclein fails to complex with PKC, impairing Nrf2 activation; reduced Nrf2 activity on antioxidant response elements (AREs) at the Map1b gene enhancer decreases MAP1B expression; forced MAP1B expression or Nrf2 activation rescues neuritic length/complexity defects in PD neurons.\",\n      \"method\": \"hPSC-derived A9-type dopaminergic neurons + isogenic controls; ChIP-seq/reporter assay for Nrf2 on Map1b ARE; MAP1B overexpression rescue; Nrf2 pharmaceutical activation; neuritic morphology analysis\",\n      \"journal\": \"Proceedings of the National Academy of Sciences USA\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Nrf2 binding to Map1b locus shown + genetic rescue; human iPSC model; single lab\",\n      \"pmids\": [\"31235589\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"MAP1B-deficient neurons show decreased density of presynaptic terminals, increased proportion of orphan presynaptic terminals, altered synaptic vesicle fusion (FM4-64 assay), and decreased density of synaptic vesicles and dense core vesicles at presynaptic terminals, identifying a presynaptic structural and functional role for MAP1B.\",\n      \"method\": \"MAP1B KO mouse neurons; immunofluorescence quantification of synaptic terminal density; FM4-64 synaptic vesicle fusion assay; electron microscopy of presynaptic terminals\",\n      \"journal\": \"Scientific Reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — KO mouse with electron microscopy + functional vesicle release assay; single lab\",\n      \"pmids\": [\"27425640\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"MAP1B mutations (c.4198A>G p.S1400G; c.2768T>C p.I923T; c.5512T>C p.F1838L) cause reduced MAP1B levels and deficient MAP1B phosphorylation in patient-derived otic sensory neuron-like cells; these cells exhibit disturbed microtubule dynamics, impaired axonal elongation, and electrophysiological defects, all rescued by CRISPR/Cas9 correction of the MAP1B mutation; Map1b+/- mice show progressive hearing loss with spiral ganglion neuron microtubule phosphorylation defects.\",\n      \"method\": \"Patient iPSC-derived otic neurons; CRISPR/Cas9 correction; Map1b+/- mouse audiometry; MAP1B phosphorylation Western blot; microtubule dynamics imaging; patch-clamp electrophysiology\",\n      \"journal\": \"JCI Insight\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — patient-derived cell model + CRISPR rescue + mouse model + multiple cellular/electrophysiological readouts; comprehensive mechanistic validation\",\n      \"pmids\": [\"33268592\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"MAP1B is a neuronally expressed microtubule-associated phosphoprotein that functions primarily as a regulator of microtubule and actin cytoskeleton dynamics: its basic KKEE/KKEVI-containing domain directly binds microtubules (and its light chain LC1 independently stabilizes microtubules and binds F-actin), while its phosphorylation state—controlled by CK2, GSK-3β (primed by DYRK1A and downstream of TrkA–MAPK and Netrin-1/Reelin signaling), NLK, and reversed by PP2A/PP2B/PP1—acts as a molecular switch toggling microtubule dynamic instability in growing axons; MAP1B also sequesters EB1/3 (+TIPs) in the cytosol to modulate plus-end dynamics, interacts with Tiam1–Rac1 to coordinate actin remodeling required for axon growth, dendritic spine maturation, and LTD-associated AMPA receptor endocytosis, anchors GABA(C) receptors at retinal synapses through rho1 interaction, facilitates Nav1.6 surface trafficking, and is targeted for proteasomal degradation of its light chain by the ubiquitin ligase gigaxonin, whose loss in giant axonal neuropathy causes MAP1B-LC accumulation and neuronal death.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"MAP1B is a neuronally enriched microtubule-associated phosphoprotein that integrates microtubule and actin cytoskeletal dynamics to drive axon growth, guidance, neuronal migration, and synaptic plasticity [#11, #12, #24]. It is synthesized as a polyprotein yielding a heavy chain and light chain 1 (LC1) by proteolytic processing, with the heavy chain binding microtubules through a basic KKEE/KKEVI-repeat domain unrelated to those of MAP2 or tau [#0, #1]; LC1 independently stabilizes microtubules, promotes tubulin polymerization, and carries a C-terminal actin-binding domain [#5, #22], and the heavy chain itself directly binds actin, making MAP1B a bivalent crosslinker of both cytoskeletal systems [#23]. Beyond stabilizing and acetylating microtubules and enhancing their assembly rate [#4, #27], MAP1B sequesters the +TIP proteins EB1/EB3 in the cytosol to restrain plus-end dynamics and prevent microtubule overstabilization in growth cones [#26]. MAP1B activity is governed by a phosphorylation switch: GSK-3\\u03b2 phosphorylates it at Ser1260/Thr1265 (and is primed by DYRK1A) to toggle microtubule dynamic instability selectively in growing axons, with CK2, NLK, and a DLK\\u2013MKK7\\u2013JNK1 module as additional kinases and PP2A/PP2B/PP1 reversing these modifications to restore microtubule binding [#3, #9, #18, #19, #33, #36]; this GSK-3\\u03b2 input is itself relayed from TrkA\\u2013MAPK, Wnt, Netrin-1, and Reelin signaling for axon growth and migration [#8, #13, #15, #16]. Through interaction with the Rac1 GEF Tiam1, MAP1B controls a Rac1/Cdc42/RhoA balance required for axon outgrowth, dendritic spine maturation, and LTD-associated AMPA receptor endocytosis [#24, #25, #28]. MAP1B additionally anchors GABA(C) receptors at retinal synapses via the rho1 subunit to tune receptor sensitivity [#6, #7] and facilitates Nav1.6 surface trafficking [#32]. Its LC1 is targeted for ubiquitin-dependent degradation by gigaxonin, whose loss causes MAP1B-LC accumulation and neuronal death in giant axonal neuropathy [#10], and MAP1B mutations that reduce protein levels and phosphorylation cause hereditary hearing loss with disturbed microtubule dynamics in sensory neurons [#42].\",\n  \"teleology\": [\n    {\n      \"year\": 1989,\n      \"claim\": \"Established the structural basis of MAP1B's microtubule binding, defining a novel basic repeat domain distinct from other MAPs.\",\n      \"evidence\": \"Cell-free translation of subcloned fragments with in vitro microtubule cosedimentation plus transfected-cell deletion analysis\",\n      \"pmids\": [\"2480963\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No atomic structure of the binding interface\", \"Affinity and stoichiometry of binding not quantified\"]\n    },\n    {\n      \"year\": 1991,\n      \"claim\": \"Resolved how MAP1B generates its multi-subunit architecture by showing heavy chain and LC1 arise from one polyprotein.\",\n      \"evidence\": \"Protein sequencing, epitope mapping, and Northern/Southern blotting with heavy chain\\u2013LC1 co-purification\",\n      \"pmids\": [\"1712602\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Protease responsible for processing not identified\", \"Regulation of processing not addressed\"]\n    },\n    {\n      \"year\": 1988,\n      \"claim\": \"Identified CK2 as a principal kinase acting on MAP1B during neurite outgrowth, opening the phosphoregulation question.\",\n      \"evidence\": \"In vitro kinase assay with purified CK2 plus phosphopeptide mapping against in vivo neuroblastoma MAP1B\",\n      \"pmids\": [\"3164313\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Specific CK2 sites not mapped\", \"Functional consequence of CK2 phosphorylation not defined here\"]\n    },\n    {\n      \"year\": 1992,\n      \"claim\": \"Demonstrated MAP1B is a functional microtubule stabilizer in cells, distinguishing it from the bundling MAPs.\",\n      \"evidence\": \"Heterologous cDNA transfection with nocodazole resistance and acetylated-tubulin readouts across multiple cell lines\",\n      \"pmids\": [\"1487506\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Does not separate heavy-chain vs light-chain contributions\", \"Mechanism of acetylation increase unresolved\"]\n    },\n    {\n      \"year\": 1998,\n      \"claim\": \"Dissected the light chain as an autonomous stabilizing/actin-binding module under heavy-chain restraint.\",\n      \"evidence\": \"COS-cell transfection, drug-resistance assays, actin cosedimentation, and co-IP domain mapping of tagged fragments\",\n      \"pmids\": [\"9813091\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"In vivo relevance of LC1 oligomerization unclear\", \"Heavy-chain inhibition mechanism not structurally defined\"]\n    },\n    {\n      \"year\": 1994,\n      \"claim\": \"Showed a shared light chain (LC3) confers direct microtubule binding to both MAP1A and MAP1B complexes.\",\n      \"evidence\": \"cDNA sequencing with recombinant LC3 microtubule cosedimentation and immunoprecipitation\",\n      \"pmids\": [\"7908909\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Functional distinction of LC3 vs LC1 within MAP1B not addressed\", \"Stoichiometry within the complex unknown\"]\n    },\n    {\n      \"year\": 1999,\n      \"claim\": \"Connected MAP1B to receptor anchoring by identifying a specific GABA(C) rho1 interaction at retinal synapses.\",\n      \"evidence\": \"Yeast two-hybrid, co-IP, retinal co-localization, and COS redistribution assay\",\n      \"pmids\": [\"9892354\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not yet show functional effect on receptor activity\"]\n    },\n    {\n      \"year\": 2000,\n      \"claim\": \"Showed cytoskeletal anchoring by MAP1B tunes GABA(C) receptor sensitivity, giving the interaction physiological meaning.\",\n      \"evidence\": \"rho1 domain-mapping mutagenesis plus patch-clamp of retinal bipolar cells after interaction disruption\",\n      \"pmids\": [\"11102469\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism linking anchoring to EC50 shift unresolved\"]\n    },\n    {\n      \"year\": 2000,\n      \"claim\": \"Defined MAP1B's essential developmental roles via complete-null mice and revealed redundancy with tau.\",\n      \"evidence\": \"Gene targeting with histology and nerve conduction measurement; tau/map1b double-knockout epistasis in cultured neurons\",\n      \"pmids\": [\"11121433\", \"10973990\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular basis of corpus callosum-selective requirement unclear\", \"Extent of redundancy with other MAPs beyond tau not tested\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Pinpointed GSK-3\\u03b2 phosphosites (Ser1260/Thr1265) as a spatial molecular switch for microtubule dynamics in growing axons.\",\n      \"evidence\": \"Site-directed mutagenesis, in vitro GSK-3\\u03b2 kinase assay, phospho-specific antibodies, in vivo localization, and MT dynamics in transfected cells\",\n      \"pmids\": [\"15731007\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How phosphorylation alters MT-binding biophysically not resolved\", \"Interplay with other phosphosites not addressed\"]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"Placed MAP1B as a downstream effector of Netrin-1 and Reelin axon-guidance/migration signaling via mode I phosphorylation.\",\n      \"evidence\": \"In vitro phosphorylation assays, mutant-mouse anatomy/phenocopy, and chemoattraction/lamination analyses\",\n      \"pmids\": [\"15186740\", \"15590913\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct linkage of GSK-3/CDK5 activation to specific MAP1B sites not mapped\", \"mDab1 role only partially defined\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Traced the upstream growth-factor route to MAP1B by showing NGF\\u2013TrkA\\u2013MAPK (not PI3K or p75) drives GSK-3\\u03b2 phosphorylation of MAP1B.\",\n      \"evidence\": \"Receptor-selective ligands, TrkA-null PC12 cells, K252a inhibition, and pharmacological MAPK/PI3K dissection\",\n      \"pmids\": [\"15737742\", \"14622124\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Relies on inhibitor specificity\", \"Intermediate steps between MAPK and GSK-3\\u03b2 not defined\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Identified gigaxonin-controlled proteasomal degradation of MAP1B-LC as a determinant of neuronal survival, linking MAP1B to giant axonal neuropathy.\",\n      \"evidence\": \"Pull-down/co-IP, proteasome inhibition, GAN-null mouse neurons, and MAP1B siRNA rescue of survival\",\n      \"pmids\": [\"16227972\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism by which MAP1B-LC excess kills neurons not defined\", \"Ubiquitination sites on MAP1B-LC not mapped\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Expanded the phosphocode by establishing DYRK1A as a priming kinase generating distinct spatial pools of GSK-3\\u03b2-phosphorylated MAP1B.\",\n      \"evidence\": \"Mass spectrometry mapping of 28 sites, phospho-antibody panel, DYRK1A shRNA, and EB3 MT-dynamics imaging\",\n      \"pmids\": [\"19549690\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Functional consequence of each phosphosite class not individually tested\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Added NLK as a direct MAP1B kinase coupling NGF signaling to actin redistribution and neurite outgrowth.\",\n      \"evidence\": \"In vitro kinase assay with purified NLK plus NLK knockdown with F-actin and outgrowth readouts\",\n      \"pmids\": [\"19840224\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"NLK target sites on MAP1B not mapped\", \"Single lab\"]\n    },\n    {\n      \"year\": 1993,\n      \"claim\": \"Defined the phosphatase arm of the switch, distinguishing PP2A/PP2B/PP1 specificities for mode I vs mode II sites.\",\n      \"evidence\": \"In vitro phosphatase assays with purified enzymes plus okadaic acid/cyclosporin A treatment of brain slices with MT-binding readout\",\n      \"pmids\": [\"7690334\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"In vivo phosphatase targeting/regulation not addressed\"]\n    },\n    {\n      \"year\": 2000,\n      \"claim\": \"Established PP2A as the dominant phosphatase controlling MAP1B microtubule-binding activity in brain.\",\n      \"evidence\": \"Okadaic acid/cyclosporin A treatment of metabolically active brain slices with phospho-MAP1B and MT-binding assays\",\n      \"pmids\": [\"10640627\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Relies on inhibitor specificity\", \"PP2A holoenzyme composition not defined\"]\n    },\n    {\n      \"year\": 1996,\n      \"claim\": \"Showed phosphorylation negatively regulates MAP1B\\u2013F-actin binding, linking the phosphoswitch to the actin arm.\",\n      \"evidence\": \"In vitro alkaline-phosphatase dephosphorylation with F-actin cosedimentation\",\n      \"pmids\": [\"8690071\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single in vitro method\", \"Specific PDPK site responsible not pinpointed\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Confirmed the heavy chain is itself a bivalent actin/microtubule binder, establishing MAP1B as a direct cytoskeletal crosslinker.\",\n      \"evidence\": \"Brain co-IP, mass spectrometry, atomic force microscopy force measurement, and electron microscopy\",\n      \"pmids\": [\"17292804\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Actin-binding site on heavy chain not mapped\", \"Single lab\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Demonstrated MAP1B is required for coordinated microtubule\\u2013actin remodeling during process retraction and Schwann cell migration.\",\n      \"evidence\": \"Map1b-null neurons and Schwann cells with LPA stimulation, live cytoskeletal imaging, and migration assays\",\n      \"pmids\": [\"17764972\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Molecular step coupling actin contraction to MT backfolding undefined\"]\n    },\n    {\n      \"year\": 2002,\n      \"claim\": \"Refined LC1 domain architecture, separating its N-terminal MT-polymerizing and C-terminal actin-binding activities.\",\n      \"evidence\": \"Transfected-cell binding assays, in vitro tubulin polymerization, and domain deletion analysis\",\n      \"pmids\": [\"11896150\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Structural basis of LC1 vs LC2 functional divergence unresolved\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Linked MAP1B to autophagy and cell death by identifying it as a DAPK-1 binding partner required for DAPK-1-driven phenotypes.\",\n      \"evidence\": \"Peptide-library binding, starvation-induced co-IP, siRNA loss-of-function, and autophagy/blebbing/clonogenic assays\",\n      \"pmids\": [\"18195017\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether MAP1B is a DAPK-1 substrate not established\", \"Single lab\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Defined the MAP1B\\u2013Tiam1\\u2013Rac1 axis coordinating actin remodeling and microtubule\\u2013actin crosstalk for neuronal polarization.\",\n      \"evidence\": \"MAP1B-null neuron GTPase activity assays, Tiam1 co-IP, and rescue with constitutively active Rac1/Cdc42/Tiam1\",\n      \"pmids\": [\"20719958\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct vs indirect MAP1B\\u2013Tiam1 binding interface not mapped\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Extended MAP1B function to dendritic spine maturation through Rac1/RhoA/cofilin actin regulation.\",\n      \"evidence\": \"MAP1B+/- neurons with spine morphology, patch-clamp, GTPase assays, and PSD Western blots\",\n      \"pmids\": [\"21984824\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How MAP1B controls cofilin phosphorylation not mechanistically resolved\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Quantified MAP1B's contribution to microtubule assembly rate along the axon shaft.\",\n      \"evidence\": \"RNAi and gain-of-function with EB3-GFP polymerization-speed imaging and axon morphology\",\n      \"pmids\": [\"22033417\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular mechanism of growth-rate enhancement not defined\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Established post-transcriptional control of Map1b via Stau2-dependent dendritic mRNA localization required for mGluR-LTD.\",\n      \"evidence\": \"Stau2 shRNA, Map1b mRNA FISH, dendritic protein quantification, and LTP/LTD electrophysiology\",\n      \"pmids\": [\"21508097\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Translational regulation step downstream of localization not detailed\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Revealed MAP1B as a major Syk substrate promoting microtubule stability in non-neuronal cancer cells.\",\n      \"evidence\": \"Syk expression/silencing, MAP1B siRNA epistasis, drug-resistance/acetylation assays, and AFM nanomechanics\",\n      \"pmids\": [\"24914616\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Syk phosphosites on MAP1B not mapped\", \"Single lab\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Identified MAP1B-LC as a target of S-nitrosylation-dependent ubiquitination by MITOL linking it to mitochondrial integrity.\",\n      \"evidence\": \"S-nitrosylation and ubiquitination assays, MITOL manipulation, and mitochondrial-function/cell-death readouts\",\n      \"pmids\": [\"22308378\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Nitrosylated cysteine and ubiquitination sites not mapped\", \"Relationship to gigaxonin pathway unresolved\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Showed MAP1B facilitates Nav1.6 surface trafficking, broadening its membrane-protein chaperoning role.\",\n      \"evidence\": \"Yeast two-hybrid, brain co-IP, alanine-scanning of the Nav1.6 N-terminus, and patch-clamp of transfected cells\",\n      \"pmids\": [\"22474336\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Trafficking mechanism (vs stabilization) not distinguished\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Connected MAP1B to centrosomal MT organization and Golgi/trafficking integrity via dystonin-a2.\",\n      \"evidence\": \"Dystonin mutant mice, isoform-specific RNAi, co-IP, and rescue by trichostatin A or MAP1B overexpression\",\n      \"pmids\": [\"22412020\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct vs scaffolded MAP1B\\u2013dystonin contact not resolved\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Added a locally translated DLK\\u2013MKK7\\u2013JNK1 module phosphorylating Map1b to control growth-cone microtubule bundling.\",\n      \"evidence\": \"Genome-wide mRNA localization screen, MKK7 FISH, phospho-Map1b staining, and kinase inhibitor/dominant-negative assays\",\n      \"pmids\": [\"23226105\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"JNK1 target sites on Map1b not mapped\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Uncovered MAP1B cytosolic sequestration of EB1/EB3 as a brake on plus-end dynamics governing axon outgrowth.\",\n      \"evidence\": \"Co-IP, direct binding, RNAi, and EB3-GFP live imaging with growth-cone morphology\",\n      \"pmids\": [\"23572079\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Binding interface and competition with MT plus-ends not structurally defined\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Established a MAP1B\\u2013Tiam1\\u2013Rac1 relay required for AMPA receptor endocytosis during LTD.\",\n      \"evidence\": \"Conditional MAP1B deletion/shRNA, LTD electrophysiology, endocytosis and Tiam1 localization assays, and Rac1 rescue\",\n      \"pmids\": [\"23881099\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How MAP1B targets Tiam1 to synapses mechanistically unclear\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Showed local dephosphorylation of MAP1B at branch points, downstream of GSK-3, controls neurite branching and protects modified microtubules.\",\n      \"evidence\": \"Map1b-null neurons, GSK-3 inhibition, cDNA rescue, fibroblast nocodazole assays, and tyrosinated/acetylated tubulin staining\",\n      \"pmids\": [\"26773468\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Phosphatase responsible for local dephosphorylation not identified\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Identified a presynaptic structural/functional role for MAP1B in terminal and vesicle organization.\",\n      \"evidence\": \"MAP1B KO neurons with terminal-density immunofluorescence, FM4-64 fusion assay, and electron microscopy\",\n      \"pmids\": [\"27425640\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Molecular partners mediating presynaptic role not defined\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Defined QKI-dependent mRNA stabilization as oligodendroglial post-transcriptional control of MAP1B levels.\",\n      \"evidence\": \"3'UTR binding, qv mutant mice, QKI knockdown/overexpression, and mRNA-stability measurements\",\n      \"pmids\": [\"16855020\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Functional consequence of MAP1B in oligodendroglia not tested here\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Revealed FMRP/miR-181d-mediated repression of axonal MAP1B local translation released by NGF.\",\n      \"evidence\": \"FMRP co-IP with miR-181d/Map1b mRNA, microfluidic axon isolation, axonal protein quantification, and Fmr1 mutant mice\",\n      \"pmids\": [\"26711345\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct miR-181d targeting of Map1b 3'UTR not fully validated\", \"Single lab\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Linked reduced MAP1B expression to Parkinson's-related neuritic defects through Nrf2 transcriptional control at the Map1b enhancer.\",\n      \"evidence\": \"Isogenic SNCA-A53T iPSC dopaminergic neurons, Nrf2 ChIP/reporter assays, and MAP1B/Nrf2 rescue of morphology\",\n      \"pmids\": [\"31235589\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Causal contribution of MAP1B loss to PD pathology in vivo not established\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Demonstrated MAP1B mutations cause hereditary hearing loss via reduced levels/phosphorylation and disturbed microtubule dynamics in sensory neurons.\",\n      \"evidence\": \"Patient iPSC-derived otic neurons with CRISPR correction, Map1b+/- mouse audiometry, and MT-dynamics/electrophysiology readouts\",\n      \"pmids\": [\"33268592\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How specific missense changes impair phosphorylation not mechanistically resolved\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How the many converging kinase inputs, phosphosites, and binding partners are spatially integrated into a single dynamic regulation of MAP1B at defined subcellular sites remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No structural model of full-length MAP1B or its phosphorylated states\", \"Site-by-site functional decoding of the 28+ phosphosites incomplete\", \"Quantitative integration of competing actin/MT/+TIP/receptor interactions undefined\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0008092\", \"supporting_discovery_ids\": [0, 4, 5, 22, 23, 26, 27]},\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [6, 7, 24, 32]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [24, 26, 28]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [26]},\n      {\"term_id\": \"GO:0005856\", \"supporting_discovery_ids\": [0, 4, 23]},\n      {\"term_id\": \"GO:0005815\", \"supporting_discovery_ids\": [29]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-1266738\", \"supporting_discovery_ids\": [11, 12, 13, 24, 27]},\n      {\"term_id\": \"R-HSA-112316\", \"supporting_discovery_ids\": [6, 7, 25, 28, 32, 41]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [8, 13, 15, 16, 24]}\n    ],\n    \"complexes\": [\"MAP1B heavy chain\\u2013light chain (LC1/LC3) complex\"],\n    \"partners\": [\"EB1\", \"EB3\", \"TIAM1\", \"GAN\", \"DAPK1\", \"MARCHF5\", \"SCN8A\", \"DST\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":7,"faith_total":7,"faith_pct":100.0}}