{"gene":"MAG","run_date":"2026-06-10T02:59:50","timeline":{"discoveries":[{"year":2002,"finding":"p75 neurotrophin receptor specifically interacts with NgR (Nogo receptor) and is required as a co-receptor for NgR-mediated inhibitory signaling by MAG, Nogo-66, and OMgp; neurons from p75 knockout mice are no longer responsive to these myelin inhibitors, and a truncated p75 lacking the intracellular domain attenuates inhibitory activity when overexpressed in primary neurons.","method":"Co-immunoprecipitation, knockout neurons, dominant-negative overexpression, neurite outgrowth assay","journal":"Nature","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal interaction demonstrated, genetic KO rescue experiment, dominant-negative functional validation; replicated finding across multiple inhibitors","pmids":["12422217"],"is_preprint":false},{"year":2002,"finding":"Nerve cell surface gangliosides GD1a and GT1b are functional ligands for MAG-mediated inhibition of neurite outgrowth from primary rat cerebellar granule neurons; inhibition is attenuated by neuraminidase treatment, blocking ganglioside biosynthesis, genetic modification of terminal ganglioside structures, or antiganglioside antibodies, and is mimicked by multivalent clustering of GD1a or GT1b.","method":"Neurite outgrowth inhibition assay, neuraminidase treatment, pharmacological biosynthesis inhibition, genetic mouse model (modified ganglioside structures), antiganglioside monoclonal antibodies","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — multiple orthogonal methods (enzymatic, pharmacological, genetic, antibody-mediated) in a single study confirming gangliosides as functional MAG ligands","pmids":["12060784"],"is_preprint":false},{"year":2005,"finding":"MAG binding to cerebellar neurons induces sequential alpha- and gamma-secretase proteolytic cleavage of the p75 neurotrophin receptor in a protein kinase C (PKC)-dependent manner; this cleavage is necessary for both RhoA activation and inhibition of neurite outgrowth.","method":"Biochemical cleavage assay in primary neurons, PKC inhibitors/activators, secretase inhibitors, RhoA activation assay, neurite outgrowth assay","journal":"Neuron","confidence":"High","confidence_rationale":"Tier 1–2 / Moderate — direct biochemical demonstration of regulated intramembrane proteolysis with pharmacological dissection of PKC dependence and functional readouts (RhoA activation, neurite outgrowth)","pmids":["15953414"],"is_preprint":false},{"year":2003,"finding":"MAG is exclusively localized in low-buoyancy Lubrol WX-insoluble lipid raft membrane fractions in brain, primary oligodendrocytes, and MAG-expressing CHO cells; this lipid raft association depends on cellular cholesterol and occurs following terminal glycosylation in the trans-Golgi network. Recombinant MAG specifically interacts with lipid-raft fractions from neurons that contain MAG receptors GT1b and NgR, suggesting a lipid-raft-to-lipid-raft interaction mediates the MAG–neuron signaling interface.","method":"Detergent-resistant membrane fractionation, cholesterol depletion, subcellular fractionation, recombinant MAG binding assay","journal":"Molecular and cellular neurosciences","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple biochemical fractionation approaches in one lab; no reconstitution or structural validation","pmids":["12691736"],"is_preprint":false},{"year":2012,"finding":"LRP1 (LDL receptor-related protein-1) is a high-affinity, sialic-acid-independent endocytic receptor for MAG on neurons; functional inactivation of LRP1 (by receptor-associated protein, RNAi, or gene deletion) significantly reverses MAG- and myelin-mediated inhibition of neurite outgrowth. LRP1 and p75NTR associate in a MAG-dependent manner and MAG-mediated RhoA activation involves both LRP1 and p75NTR. LRP1 complement-like repeat clusters CII and CIV are the MAG-binding domains.","method":"Receptor-associated protein inhibition, RNAi knockdown, genetic deletion (LRP1 knockout), Co-IP, RhoA activation assay, neurite outgrowth assay, Fc-fusion protein binding","journal":"Journal of cell science","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal loss-of-function approaches (pharmacological, RNAi, genetic KO) plus domain-mapping with Fc-fusion proteins, all yielding convergent results","pmids":["23132925"],"is_preprint":false},{"year":1997,"finding":"Soluble MAG (extracellular domain, dMAG), released from myelin and detectable in vivo, potently inhibits axonal regeneration in a dose-dependent manner when presented in solution; this inhibition is completely neutralized by immunodepletion of dMAG or inclusion of a MAG antibody, demonstrating that MAG acts as a true inhibitory molecule (not merely non-permissive) by binding to a specific neuronal receptor and initiating signal transduction.","method":"Soluble chimeric MAG-Fc assay, neurite outgrowth inhibition, immunodepletion, antibody neutralization, growth cone collapse assay","journal":"Molecular and cellular neurosciences","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple functional assays (soluble inhibition, immunodepletion, antibody block) in one lab establishing inhibitory mechanism","pmids":["9361272"],"is_preprint":false},{"year":1999,"finding":"MAG-Fc chimera specifically precipitates several neuronal surface proteins from postnatal cerebellar, DRG, and PC12 neurons in a sialic acid-dependent manner; prominent proteins of ~190 kDa and ~250 kDa are co-precipitated from all three neuron types, and the 190 kDa protein is a sialoglycoprotein. Inhibition by a MAG antibody prevents precipitation, indicating specific receptor interactions.","method":"Chimeric MAG-Fc pulldown from neuronal cell surface proteins, competitive antibody inhibition, desialylation controls","journal":"Journal of neuroscience research","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — pulldown across multiple neuron types with appropriate controls; binding partners not fully identified","pmids":["10494110"],"is_preprint":false},{"year":2008,"finding":"CaMKIV is necessary for neurotrophin-induced phosphorylation of CREB and blockade of MAG-mediated inhibition of axonal growth; pharmacological inhibition or dominant-negative CaMKIV blocks the neurotrophin effect. CaMKIV activation requires calcium flux from intracellular stores and acts in parallel with PKA to overcome MAG inhibition.","method":"Pharmacological inhibition, dominant-negative overexpression, calcium chelation, cAMP/PKA manipulation, neurite outgrowth assay","journal":"Molecular and cellular neurosciences","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — pharmacological and dominant-negative genetic approaches in one lab establishing CaMKIV as a required component of the neurotrophin→CREB→MAG-inhibition-reversal pathway","pmids":["18381242"],"is_preprint":false},{"year":2010,"finding":"MAG and OMgp synergize with Nogo-A to inhibit axonal growth in vivo; myelin lacking only MAG and OMgp is indistinguishable from control in inhibitory activity, but myelin lacking all three inhibitors is less inhibitory than Nogo-A-deficient myelin alone, revealing redundant and synergistic roles. In vivo spinal cord injury studies showed that triple knockout of Nogo-A/MAG/OMgp produces greater axonal growth and locomotor recovery than Nogo-A single knockout.","method":"Genetic knockout mice (single, double, triple mutants), myelin inhibition assay, spinal cord injury model, behavioral assessment, axonal tracing","journal":"The Journal of neuroscience","confidence":"High","confidence_rationale":"Tier 2 / Strong — rigorous genetic epistasis with single, double, and triple knockout animals; in vitro and in vivo convergent results","pmids":["20484625"],"is_preprint":false},{"year":2012,"finding":"CRMP4 mediates MAG-induced inhibition of axonal outgrowth and growth cone collapse; loss of CRMP4 (CRMP4−/− neurons) prevents MAG-induced inhibition and growth cone collapse. CRMP4 is also required for MAG-mediated axonal protection against vincristine-induced degeneration, placing CRMP4 as a downstream effector of MAG/RhoA signaling for both inhibitory and protective functions.","method":"CRMP4 knockout mouse DRG neurons, MAG-induced neurite outgrowth inhibition assay, growth cone collapse assay, vincristine-induced axonal degeneration assay","journal":"Neuroscience letters","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — clean genetic KO with defined cellular phenotypes (inhibition, collapse, degeneration) in one lab","pmids":["22583768"],"is_preprint":false},{"year":2010,"finding":"MAG protects neurons from acute toxic insult (vincristine-induced neurite degeneration) via a ganglioside-mediated signaling pathway involving RhoA activation; protection is reversed by anti-MAG antibody, sialidase treatment, or glycosphingolipid biosynthesis inhibitor, but not by cleavage of NgR (via PI-PLC) or peptide inhibitor of p75NTR. ROCK inhibition also reverses protection, identifying RhoA/ROCK as the protective downstream effector.","method":"Myelin substrate culture, anti-MAG antibody, sialidase, biosynthesis inhibition, PI-PLC treatment, p75NTR inhibitor, ROCK inhibitor, Mag-null myelin","journal":"ACS chemical neuroscience","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple pharmacological dissection tools plus Mag-null myelin control in one study; ganglioside pathway and ROCK identified as the protective mechanism","pmids":["20436925"],"is_preprint":false},{"year":2019,"finding":"MAG induces apoptosis in developing cerebellar granule neurons through p75NTR-mediated JNK/cell death signaling pathway; deletion of p75NTR in vivo reduces the number of apoptotic neurons in cerebellar white matter during development. MAG-induced apoptosis also impairs neurite outgrowth, and cell death signaling requires NgR1/p75NTR complex.","method":"p75NTR knockout in vivo, cerebellar neuron apoptosis assay, JNK pathway analysis, neurite outgrowth assay","journal":"Cell death & disease","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vivo genetic KO with defined cellular phenotype (apoptosis, white matter size) plus mechanistic pathway (JNK) identification in one lab","pmids":["31570696"],"is_preprint":false},{"year":2007,"finding":"MUC1 is a counter-receptor for MAG (Siglec-4a) on pancreatic cancer cells; MAG binds pancreatic cells expressing MUC1 in a sialidase-sensitive manner, and MAG physically associates with MUC1. Increased expression of MUC1 or MAG enhances heterotypic adhesion between pancreatic cancer cells and Schwann cells, and specific inhibition of MAG or sialyl-T MUC1 partially blocks this adhesion.","method":"Heterotypic adhesion assay, Co-immunoprecipitation, sialidase sensitivity assay, antibody inhibition, overexpression experiments","journal":"Cancer research","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — Co-IP plus functional adhesion assay with gain- and loss-of-function, two orthogonal methods in one lab","pmids":["17974963"],"is_preprint":false},{"year":2004,"finding":"Progressive and selective loss of MAG protein from brain in mice lacking complex gangliosides (Galgt1-null) occurs with age (60% reduction at 6 months, 70% at 12 months) without reduction of MAG mRNA, indicating that complex gangliosides GD1a and GT1b are required for maintaining MAG protein stability—likely via enhanced stability when MAG on myelin binds its complementary ligands on the axon surface.","method":"Galgt1 gene knockout, Western blot, RT-PCR, age-course analysis","journal":"Glycobiology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — clean genetic KO with protein/mRNA dissociation demonstrating post-transcriptional stabilization mechanism; single lab","pmids":["15175257"],"is_preprint":false},{"year":1995,"finding":"L-MAG is selectively removed from the periaxonal membrane of CNS myelinated fibers by receptor-mediated endocytosis in quaking mice; the cytoplasmic domain of L-MAG contains tyrosine internalization signals at Y35 and Y65, and increased endosomal accumulation of L-MAG is observed in quaking oligodendrocytes. S-MAG remains in periaxonal membranes.","method":"Immunoelectron microscopy, endosome labeling, sequence motif analysis of cytoplasmic domain, developmental time-course comparison","journal":"The Journal of cell biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — immunoelectron microscopy with endosomal markers plus sequence-based identification of tyrosine internalization motifs; single lab","pmids":["8557747"],"is_preprint":false},{"year":1997,"finding":"Mice doubly deficient in MAG and N-CAM develop myelin degeneration approximately 4 weeks earlier than MAG-single-knockout mice, with increased degeneration profiles at 8 weeks; this genetic epistasis shows that N-CAM partially compensates for MAG in the maintenance (but not formation) of axon-myelin integrity in MAG-deficient mice.","method":"Double knockout mouse generation, electron microscopy, single fiber preparation, morphometric analysis","journal":"Cell and tissue research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic epistasis with double-mutant mice establishing compensatory relationship between MAG and N-CAM in myelin maintenance; single lab","pmids":["9011400"],"is_preprint":false},{"year":2013,"finding":"hnRNP A1 regulates alternative splicing of Mag exon 12 by interacting with an element overlapping the 5' splice site of exon 12; this element has reduced affinity for U1 snRNP, and an evolutionarily conserved RNA secondary structure modulates interactions with both hnRNP A1 and U1 snRNP, coordinately controlling the ratio of L-MAG to S-MAG isoforms.","method":"RNA reporter constructs, UV crosslinking/RNA binding assay, splice site mutagenesis, U1 snRNP interaction assay, secondary structure analysis","journal":"RNA (New York, N.Y.)","confidence":"Medium","confidence_rationale":"Tier 1–2 / Moderate — in vitro RNA binding and mutagenesis with reporter constructs establishing mechanistic basis for isoform-specific splicing; single lab","pmids":["23704325"],"is_preprint":false},{"year":2006,"finding":"S-MAG and L-MAG isoforms have distinct subcellular distributions in myelin: in peripheral nerves (where S-MAG is the sole isoform), S-MAG concentrates in periaxonal and abaxonal rings and disc-like structures spanning compact myelin perpendicular to the axon. L-MAG and S-MAG show differential developmental expression in CNS and PNS oligodendrocyte unit phenotypes.","method":"Transgenic mouse expressing GFP-tagged S-MAG, confocal microscopy, electron microscopy, immunolabeling","journal":"Molecular and cellular neurosciences","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct live-imaging/fluorescence localization with GFP-tagged protein in a specifically engineered transgenic mouse; single lab","pmids":["16442810"],"is_preprint":false},{"year":2017,"finding":"GPR37 and MAG form a protein complex when co-expressed in cells; genetic deletion of Gpr37 (but not Gpr37L1) results in markedly decreased MAG protein expression in brain, and Gpr37-knockout mice show dramatically increased myelin loss in the cuprizone demyelination model without loss of oligodendrocyte precursors or mature oligodendrocytes.","method":"Co-immunoprecipitation, Western blot, Gpr37 knockout mouse, cuprizone demyelination model, proteomics","journal":"Neuroscience","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — Co-IP plus genetic KO with functional demyelination phenotype; two methods in one lab","pmids":["28642167"],"is_preprint":false},{"year":2013,"finding":"MAG membrane association is sulfatide-dependent; in mice lacking sulfatide (but retaining galactocerebroside), MAG shows increased susceptibility to detergent extraction from myelin membranes, while other myelin proteins (MOG, MBP, CNPase) are sulfatide-independent for their membrane association.","method":"In situ detergent extraction procedure on spinal cord sections, sulfatide-deficient mouse model, immunolabeling","journal":"Neurochemical research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — defined genetic loss-of-function model with quantitative detergent extraction demonstrating lipid-dependent membrane anchoring; single lab","pmids":["24081651"],"is_preprint":false},{"year":2012,"finding":"MAG plays an essential role in mediating axon-myelin attachment in CMT1A disease; ablating MAG in CMT1A mice (overexpressing human PMP22) results in separation of axons from their myelin sheath, demonstrating that increased MAG expression in CMT1A has a compensatory role in maintaining axonal integrity in the context of PMP22 overexpression.","method":"MAG knockout in CMT1A mouse model (PMP22 overexpressing), electron microscopy, immunohistochemistry, expression analysis","journal":"Neurobiology of disease","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic double-mutant epistasis demonstrating specific adhesion function with electron microscopic readout; single lab","pmids":["22940629"],"is_preprint":false},{"year":2016,"finding":"Homozygous missense mutation p.Arg118His in MAG immunoglobulin domain 1 (a residue critical for sialic acid binding) causes a progressive neurological syndrome in humans with demyelinating leukodystrophy, establishing that the sialic acid-binding activity of MAG's Ig domain 1 is required for normal CNS function in vivo.","method":"Exome sequencing, clinical characterization, structural/functional annotation of MAG sialic acid binding site","journal":"Annals of clinical and translational neurology","confidence":"Low","confidence_rationale":"Tier 3 / Weak — human genetics identifying critical residue; no direct biochemical reconstitution of binding defect in this study; single family","pmids":["27606346"],"is_preprint":false},{"year":2022,"finding":"Three-dimensional FIB-SEM reconstruction of Mag-null mouse CNS shows that MAG-deficient myelin exhibits pathological outfoldings extending up to 10 μm longitudinally along myelinated axons, with complex axonal pathology (including axonal sprouting) underneath outfoldings. Normal-appearing axon/myelin units in Mag-null mice display significantly increased axonal diameters, indicating that MAG is required for maintaining normal axonal diameter and shape.","method":"Focused ion beam-scanning electron microscopy (FIB-SEM), 3D reconstruction, morphometric analysis, Mag-null and Plp-null mouse comparison","journal":"Glia","confidence":"Medium","confidence_rationale":"Tier 1–2 / Moderate — high-resolution 3D ultrastructural analysis with quantitative morphometry in genetic KO; single lab with rigorous method","pmids":["36354016"],"is_preprint":false},{"year":1986,"finding":"MAG is localized by immunoelectron microscopy to axon-Schwann cell apposition, Schmidt-Lanterman incisures, inner and outer mesaxons, and paranodal loops but not in compact myelin or at nodes of Ranvier; it appears after L1 expression ceases during myelination, establishing MAG's specific periaxonal localization distinct from compact myelin proteins like MBP.","method":"Pre- and post-embedding immunoelectron microscopy, developmental time-course","journal":"The Journal of cell biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — direct immunoelectron microscopy with subcellular resolution replicated at multiple developmental time points and in multiple fiber types; foundational localization study","pmids":["2430983"],"is_preprint":false}],"current_model":"MAG (myelin-associated glycoprotein/Siglec-4a) is a type I transmembrane Ig-superfamily protein localized periaxonally in myelin sheaths where it functions bidirectionally: on neurons it inhibits axonal outgrowth and induces growth cone collapse by engaging a receptor complex containing NgR1, p75NTR (which undergoes MAG-triggered PKC-dependent regulated intramembrane proteolysis leading to RhoA activation via CRMP4), and LRP1, with gangliosides GD1a/GT1b serving as functional sialic-acid-bearing neuronal ligands; on oligodendrocytes/Schwann cells it maintains axon–glial contact and long-term axon stability through ganglioside-dependent and sulfatide-dependent membrane interactions, with its two alternatively spliced isoforms (L-MAG and S-MAG, regulated by hnRNP A1 and RNA secondary structure) showing distinct subcellular distributions and the L-MAG isoform subject to tyrosine-motif-directed endocytic removal from periaxonal membranes."},"narrative":{"mechanistic_narrative":"MAG (myelin-associated glycoprotein/Siglec-4a) is a periaxonal Ig-superfamily glycoprotein that couples glial myelin to axons and bidirectionally regulates axon growth, stability, and survival [PMID:2430983, PMID:20484625]. It localizes specifically to axon–glial apposition sites, Schmidt-Lanterman incisures, mesaxons, and paranodal loops but is excluded from compact myelin [PMID:2430983], partitioning into cholesterol-dependent lipid rafts after trans-Golgi glycosylation and engaging neuronal raft fractions containing its receptors [PMID:12691736]. On the neuronal side, MAG—including a soluble shed ectodomain (dMAG)—acts as a true inhibitory ligand that collapses growth cones and blocks neurite outgrowth [PMID:9361272], signaling through a receptor complex of NgR1, the p75 neurotrophin receptor, and the endocytic receptor LRP1, with gangliosides GD1a/GT1b serving as sialic-acid-bearing functional ligands [PMID:12422217, PMID:12060784, PMID:23132925]. MAG binding triggers PKC-dependent regulated intramembrane proteolysis of p75NTR (sequential α- and γ-secretase cleavage) required for RhoA activation, with CRMP4 acting as the downstream effector of both growth inhibition and axon protection [PMID:15953414, PMID:22583768]; the same pathway can drive p75NTR/JNK-dependent apoptosis of developing cerebellar granule neurons [PMID:31570696]. Neurotrophin signaling reverses MAG inhibition via a CaMKIV→CREB arm acting in parallel with PKA [PMID:18381242]. On the glial side, MAG maintains long-term axon–myelin integrity and normal axonal caliber: Mag-null myelin develops pathological outfoldings and enlarged axons [PMID:36354016], and MAG is required for axon–myelin attachment, a role compensated in part by N-CAM and relevant in the CMT1A/PMP22 context [PMID:9011400, PMID:22940629]. MAG membrane anchoring and stability depend on sulfatide and on complex gangliosides, the latter maintaining MAG protein post-transcriptionally [PMID:24081651, PMID:15175257]. Its L-MAG and S-MAG isoforms, generated by hnRNP A1/U1 snRNP-regulated alternative splicing of exon 12, show distinct subcellular distributions, with L-MAG subject to tyrosine-motif-directed endocytosis [PMID:23704325, PMID:16442810, PMID:8557747]. A homozygous p.Arg118His mutation in the sialic-acid-binding Ig domain 1 of MAG causes a human demyelinating leukodystrophy [PMID:27606346].","teleology":[{"year":1986,"claim":"Establishing where MAG resides was the prerequisite to assigning function; immunoEM placed it precisely at axon–glial interfaces and excluded it from compact myelin, defining it as a periaxonal contact molecule distinct from structural myelin proteins.","evidence":"Pre- and post-embedding immunoelectron microscopy across developmental time points","pmids":["2430983"],"confidence":"High","gaps":["Does not identify binding partners on the axon","Functional consequence of periaxonal localization untested"]},{"year":1997,"claim":"It was unclear whether MAG actively signals inhibition or merely fails to support growth; soluble dMAG inhibiting outgrowth, neutralizable by immunodepletion or antibody, established MAG as a true receptor-engaging inhibitory ligand.","evidence":"Soluble MAG-Fc neurite outgrowth and growth cone collapse assays with immunodepletion and antibody block","pmids":["9361272"],"confidence":"Medium","gaps":["Neuronal receptor not identified in this study","Downstream signaling undefined"]},{"year":1999,"claim":"To find the neuronal receptor, MAG-Fc pulldowns identified sialic-acid-dependent neuronal surface sialoglycoproteins (~190/250 kDa), framing MAG as a sialic-acid-binding receptor with defined but unidentified partners.","evidence":"MAG-Fc pulldown across cerebellar, DRG, and PC12 neurons with desialylation and antibody controls","pmids":["10494110"],"confidence":"Medium","gaps":["Co-precipitated proteins not molecularly identified","Direct vs indirect binding not resolved"]},{"year":2002,"claim":"The signaling receptor complex and the sialylated ligand were defined: p75NTR is an obligate co-receptor with NgR, and gangliosides GD1a/GT1b are functional sialic-acid ligands, unifying the receptor and glycan arms of MAG signaling.","evidence":"Co-IP, p75 knockout neurons, dominant-negative p75 (NgR); neuraminidase, ganglioside biosynthesis/genetic modification, antiganglioside antibodies, multivalent clustering","pmids":["12422217","12060784"],"confidence":"High","gaps":["How NgR-glycan and p75 inputs are integrated unresolved","Transmembrane signaling step not yet defined"]},{"year":2003,"claim":"The physical interface of signaling was addressed: MAG partitions into cholesterol-dependent lipid rafts and engages neuronal raft fractions containing GT1b and NgR, framing a raft-to-raft signaling platform.","evidence":"Detergent-resistant membrane fractionation, cholesterol depletion, recombinant MAG raft-binding assay","pmids":["12691736"],"confidence":"Medium","gaps":["No reconstitution or structural validation","Raft requirement for downstream signaling not functionally tested"]},{"year":2005,"claim":"How receptor engagement converts to intracellular signaling was answered: MAG triggers PKC-dependent sequential α/γ-secretase cleavage of p75NTR that is required for RhoA activation and growth inhibition.","evidence":"Biochemical cleavage assay in primary neurons with PKC and secretase inhibitors, RhoA and outgrowth readouts","pmids":["15953414"],"confidence":"High","gaps":["Identity of activating PKC isoform unspecified","Link between cleaved p75 fragment and RhoA GEF unresolved"]},{"year":2008,"claim":"The mechanism of pharmacological reversal of MAG inhibition was clarified: a CaMKIV→CREB arm, dependent on intracellular calcium and parallel to PKA, is required for neurotrophins to overcome MAG inhibition.","evidence":"Pharmacological and dominant-negative CaMKIV, calcium chelation, cAMP/PKA manipulation, outgrowth assays","pmids":["18381242"],"confidence":"Medium","gaps":["Direct CaMKIV substrates in this context not defined","Crosstalk point with RhoA pathway unmapped"]},{"year":2010,"claim":"Two outstanding questions—physiological in vivo relevance and a protective role—were addressed: MAG synergizes with Nogo-A/OMgp to restrict regeneration in vivo, and separately protects axons from toxic degeneration via ganglioside→RhoA/ROCK signaling independent of NgR/p75 cleavage.","evidence":"Single/double/triple knockout mice with spinal cord injury and behavior; myelin-substrate protection assay with sialidase, biosynthesis inhibitor, PI-PLC, p75 peptide, ROCK inhibitor","pmids":["20484625","20436925"],"confidence":"High","gaps":["Why protection bypasses NgR/p75 but inhibition requires them is unresolved","Receptor mediating ganglioside-only protective signaling unidentified"]},{"year":2012,"claim":"The receptor complex and intracellular effector were extended: LRP1 is a high-affinity sialic-acid-independent endocytic MAG receptor associating with p75NTR, and CRMP4 is the shared downstream effector of MAG inhibition, collapse, and protection.","evidence":"RAP/RNAi/LRP1-KO loss of function, domain-mapping Fc-fusion binding, Co-IP, RhoA assay; CRMP4-KO DRG outgrowth, collapse, and vincristine protection assays","pmids":["23132925","22583768"],"confidence":"High","gaps":["Stoichiometry of NgR/p75/LRP1/ganglioside complex unknown","How one CRMP4 node bifurcates into inhibition vs protection unresolved"]},{"year":2019,"claim":"A developmental fate decision was assigned to MAG signaling: MAG drives p75NTR-dependent JNK-mediated apoptosis of cerebellar granule neurons, with p75 deletion reducing developmental cell death in vivo.","evidence":"p75NTR-knockout in vivo, cerebellar apoptosis and JNK pathway analysis, outgrowth assays","pmids":["31570696"],"confidence":"Medium","gaps":["Determinants selecting apoptosis vs growth inhibition output undefined","Requirement for LRP1/gangliosides in this death pathway untested"]},{"year":null,"claim":"How a single ligand–receptor system selects among opposing outputs—growth inhibition, axon protection, and apoptosis—and how the NgR/p75/LRP1/ganglioside inputs assemble into a defined signaling complex remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No structural model of the receptor complex","Switch determining inhibitory vs protective vs apoptotic signaling unknown"]},{"year":2007,"claim":"A non-neural function was identified: MAG (Siglec-4a) acts as a counter-receptor for sialyl-T MUC1, mediating sialidase-sensitive heterotypic adhesion between pancreatic cancer cells and Schwann cells.","evidence":"Heterotypic adhesion assay, Co-IP, sialidase sensitivity, antibody inhibition, overexpression","pmids":["17974963"],"confidence":"Medium","gaps":["In vivo relevance to perineural invasion untested","Downstream signaling from MAG–MUC1 adhesion undefined"]},{"year":1986,"claim":"Glial-side maintenance functions and the structural basis of MAG anchoring and isoform control were progressively defined, establishing MAG's role in long-term axon–myelin integrity and caliber.","evidence":"Galgt1-KO ganglioside-dependent protein stability; MAG/N-CAM double KO and CMT1A/MAG-KO epistasis; sulfatide-dependent membrane anchoring; FIB-SEM of Mag-null myelin; hnRNP A1/U1 splicing of exon 12; GFP-S-MAG localization; L-MAG tyrosine-motif endocytosis","pmids":["15175257","9011400","22940629","24081651","36354016","23704325","16442810","8557747"],"confidence":"Medium","gaps":["Molecular link between glial binding and axonal caliber control unclear","Functional division of labor between L-MAG and S-MAG not fully resolved"]},{"year":2016,"claim":"Human relevance of MAG's sialic-acid-binding activity was established: a homozygous p.Arg118His mutation in Ig domain 1 causes a demyelinating leukodystrophy.","evidence":"Exome sequencing, clinical characterization, structural annotation of the sialic-acid binding site","pmids":["27606346"],"confidence":"Low","gaps":["No direct biochemical reconstitution of the binding defect","Single family; genotype–phenotype scope limited"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0098631","term_label":"cell adhesion mediator activity","supporting_discovery_ids":[12,20,23]},{"term_id":"GO:0060089","term_label":"molecular transducer activity","supporting_discovery_ids":[0,5,2]},{"term_id":"GO:0008289","term_label":"lipid binding","supporting_discovery_ids":[1,19,3]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[23,3,17]},{"term_id":"GO:0005768","term_label":"endosome","supporting_discovery_ids":[14,4]}],"pathway":[{"term_id":"R-HSA-1266738","term_label":"Developmental Biology","supporting_discovery_ids":[8,11,22]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[2,4,9]},{"term_id":"R-HSA-5357801","term_label":"Programmed Cell Death","supporting_discovery_ids":[11]}],"complexes":["NgR1–p75NTR–LRP1 MAG receptor complex"],"partners":["NGFR","RTN4R","LRP1","CRMP4","GPR37","MUC1","NCAM1"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"P20916","full_name":"Myelin-associated glycoprotein","aliases":["Siglec-4a"],"length_aa":626,"mass_kda":69.1,"function":"Adhesion molecule that mediates interactions between myelinating cells and neurons by binding to neuronal sialic acid-containing gangliosides and to the glycoproteins RTN4R and RTN4RL2 (By similarity). Not required for initial myelination, but seems to play a role in the maintenance of normal axon myelination. Protects motoneurons against apoptosis, also after injury; protection against apoptosis is probably mediated via interaction with neuronal RTN4R and RTN4RL2. Required to prevent degeneration of myelinated axons in adults; this probably depends on binding to gangliosides on the axon cell membrane (By similarity). Negative regulator of neurite outgrowth; in dorsal root ganglion neurons the inhibition is mediated primarily via binding to neuronal RTN4R or RTN4RL2 and to a lesser degree via binding to neuronal gangliosides. In cerebellar granule cells the inhibition is mediated primarily via binding to neuronal gangliosides. In sensory neurons, inhibition of neurite extension depends only partially on RTN4R, RTN4RL2 and gangliosides. Inhibits axon longitudinal growth (By similarity). Inhibits axon outgrowth by binding to RTN4R (By similarity). Preferentially binds to alpha-2,3-linked sialic acid. 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Gastrointestinal and liver physiology","url":"https://pubmed.ncbi.nlm.nih.gov/27012773","citation_count":20,"is_preprint":false},{"pmid":"35423496","id":"PMC_35423496","title":"Facile multifunctional IOL surface modification via poly(PEGMA-co-GMA) grafting for posterior capsular opacification inhibition.","date":"2021","source":"RSC advances","url":"https://pubmed.ncbi.nlm.nih.gov/35423496","citation_count":20,"is_preprint":false},{"pmid":"31791739","id":"PMC_31791739","title":"Development of Bis-GMA-free biopolymer to avoid estrogenicity.","date":"2019","source":"Dental materials : official publication of the Academy of Dental Materials","url":"https://pubmed.ncbi.nlm.nih.gov/31791739","citation_count":19,"is_preprint":false},{"pmid":"6200494","id":"PMC_6200494","title":"Myelin-associated glycoprotein (MAG) distribution in human central nervous tissue studied immunocytochemically with monoclonal antibody.","date":"1984","source":"Journal of neuroimmunology","url":"https://pubmed.ncbi.nlm.nih.gov/6200494","citation_count":19,"is_preprint":false},{"pmid":"2579092","id":"PMC_2579092","title":"Shared antigen between the myelin-associated glycoprotein (MAG) and a cell line from human T cell leukemia (HSB-2).","date":"1985","source":"Journal of neuroimmunology","url":"https://pubmed.ncbi.nlm.nih.gov/2579092","citation_count":19,"is_preprint":false},{"pmid":"32543782","id":"PMC_32543782","title":"The effects of the dental methacrylates TEGDMA, Bis-GMA, and UDMA on neutrophils in vitro.","date":"2020","source":"Clinical and experimental dental research","url":"https://pubmed.ncbi.nlm.nih.gov/32543782","citation_count":18,"is_preprint":false},{"pmid":"9935167","id":"PMC_9935167","title":"Interleukin-10 gene transfer activates interferon-gamma and the interferon-gamma-inducible genes Gbp-1/Mag-1 and Mig-1 in mammary tumors.","date":"1999","source":"International journal of cancer","url":"https://pubmed.ncbi.nlm.nih.gov/9935167","citation_count":18,"is_preprint":false},{"pmid":"22583768","id":"PMC_22583768","title":"CRMP4 mediates MAG-induced inhibition of axonal outgrowth and protection against Vincristine-induced axonal degeneration.","date":"2012","source":"Neuroscience letters","url":"https://pubmed.ncbi.nlm.nih.gov/22583768","citation_count":18,"is_preprint":false},{"pmid":"2579517","id":"PMC_2579517","title":"Immunocytochemical study of myelin-associated glycoprotein (MAG), basic protein (BP), and glial fibrillary acidic protein (GFAP) in chronic relapsing experimental allergic encephalomyelitis (EAE).","date":"1985","source":"Acta neuropathologica","url":"https://pubmed.ncbi.nlm.nih.gov/2579517","citation_count":18,"is_preprint":false},{"pmid":"26343756","id":"PMC_26343756","title":"N-acetyl cysteine protects human oral keratinocytes from Bis-GMA-induced apoptosis and cell cycle arrest by inhibiting reactive oxygen species-mediated mitochondrial dysfunction and the PI3K/Akt pathway.","date":"2015","source":"Toxicology in vitro : an international journal published in association with BIBRA","url":"https://pubmed.ncbi.nlm.nih.gov/26343756","citation_count":17,"is_preprint":false},{"pmid":"28839126","id":"PMC_28839126","title":"Ancestor of land plants acquired the DNA-3-methyladenine glycosylase (MAG) gene from bacteria through horizontal gene transfer.","date":"2017","source":"Scientific reports","url":"https://pubmed.ncbi.nlm.nih.gov/28839126","citation_count":17,"is_preprint":false},{"pmid":"9749612","id":"PMC_9749612","title":"Correlation between cytomegalovirus infection and IgM anti-MAG/SGPG antibody-associated neuropathy.","date":"1998","source":"Annals of neurology","url":"https://pubmed.ncbi.nlm.nih.gov/9749612","citation_count":16,"is_preprint":false},{"pmid":"32270492","id":"PMC_32270492","title":"Selective inhibition of anti-MAG IgM autoantibody binding to myelin by an antigen-specific glycopolymer.","date":"2020","source":"Journal of neurochemistry","url":"https://pubmed.ncbi.nlm.nih.gov/32270492","citation_count":16,"is_preprint":false},{"pmid":"2484442","id":"PMC_2484442","title":"Myelin-associated glycoprotein (MAG) and rat brain-specific 1B236 protein: mapping of epitopes and demonstration of immunological identity.","date":"1989","source":"Journal of molecular neuroscience : MN","url":"https://pubmed.ncbi.nlm.nih.gov/2484442","citation_count":16,"is_preprint":false},{"pmid":"9482208","id":"PMC_9482208","title":"MAG-deficient Schwann cells myelinate dorsal root ganglion neurons in culture.","date":"1998","source":"Glia","url":"https://pubmed.ncbi.nlm.nih.gov/9482208","citation_count":16,"is_preprint":false},{"pmid":"27267749","id":"PMC_27267749","title":"Therapeutic options and management of polyneuropathy associated with anti-MAG antibodies.","date":"2016","source":"Expert review of neurotherapeutics","url":"https://pubmed.ncbi.nlm.nih.gov/27267749","citation_count":15,"is_preprint":false},{"pmid":"31570696","id":"PMC_31570696","title":"MAG induces apoptosis in cerebellar granule neurons through p75NTR demarcating granule layer/white matter boundary.","date":"2019","source":"Cell death & disease","url":"https://pubmed.ncbi.nlm.nih.gov/31570696","citation_count":15,"is_preprint":false},{"pmid":"25113382","id":"PMC_25113382","title":"MAG-EPA and 17,18-EpETE target cytoplasmic signalling pathways to reduce short-term airway hyperresponsiveness.","date":"2014","source":"Pflugers Archiv : European journal of physiology","url":"https://pubmed.ncbi.nlm.nih.gov/25113382","citation_count":15,"is_preprint":false},{"pmid":"30144659","id":"PMC_30144659","title":"Anti-MAG neuropathy: Role of IgM antibodies, the paranodal junction and juxtaparanodal potassium channels.","date":"2018","source":"Clinical neurophysiology : official journal of the International Federation of Clinical Neurophysiology","url":"https://pubmed.ncbi.nlm.nih.gov/30144659","citation_count":15,"is_preprint":false},{"pmid":"23704325","id":"PMC_23704325","title":"hnRNP A1 and secondary structure coordinate alternative splicing of Mag.","date":"2013","source":"RNA (New York, N.Y.)","url":"https://pubmed.ncbi.nlm.nih.gov/23704325","citation_count":15,"is_preprint":false},{"pmid":"36354016","id":"PMC_36354016","title":"Focused ion beam-scanning electron microscopy links pathological myelin outfoldings to axonal changes in mice lacking Plp1 or Mag.","date":"2022","source":"Glia","url":"https://pubmed.ncbi.nlm.nih.gov/36354016","citation_count":15,"is_preprint":false},{"pmid":"24081651","id":"PMC_24081651","title":"Nfasc155H and MAG are specifically susceptible to detergent extraction in the absence of the myelin sphingolipid sulfatide.","date":"2013","source":"Neurochemical research","url":"https://pubmed.ncbi.nlm.nih.gov/24081651","citation_count":14,"is_preprint":false},{"pmid":"27606346","id":"PMC_27606346","title":"Neurologic syndrome associated with homozygous mutation at MAG sialic acid binding site.","date":"2016","source":"Annals of clinical and translational neurology","url":"https://pubmed.ncbi.nlm.nih.gov/27606346","citation_count":14,"is_preprint":false},{"pmid":"21172861","id":"PMC_21172861","title":"B-cell-activating factor in rituximab-treated patients with anti-MAG polyneuropathy.","date":"2010","source":"Journal of neurology, neurosurgery, and psychiatry","url":"https://pubmed.ncbi.nlm.nih.gov/21172861","citation_count":14,"is_preprint":false},{"pmid":"7766685","id":"PMC_7766685","title":"Streptococcal protein MAG--a protein with broad albumin binding specificity.","date":"1995","source":"Biochimica et biophysica acta","url":"https://pubmed.ncbi.nlm.nih.gov/7766685","citation_count":13,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":48672,"output_tokens":6319,"usd":0.1204,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":15398,"output_tokens":4815,"usd":0.098683,"stage2_stop_reason":"end_turn"},"total_usd":0.219083,"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\": 2002,\n      \"finding\": \"p75 neurotrophin receptor specifically interacts with NgR (Nogo receptor) and is required as a co-receptor for NgR-mediated inhibitory signaling by MAG, Nogo-66, and OMgp; neurons from p75 knockout mice are no longer responsive to these myelin inhibitors, and a truncated p75 lacking the intracellular domain attenuates inhibitory activity when overexpressed in primary neurons.\",\n      \"method\": \"Co-immunoprecipitation, knockout neurons, dominant-negative overexpression, neurite outgrowth assay\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal interaction demonstrated, genetic KO rescue experiment, dominant-negative functional validation; replicated finding across multiple inhibitors\",\n      \"pmids\": [\"12422217\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"Nerve cell surface gangliosides GD1a and GT1b are functional ligands for MAG-mediated inhibition of neurite outgrowth from primary rat cerebellar granule neurons; inhibition is attenuated by neuraminidase treatment, blocking ganglioside biosynthesis, genetic modification of terminal ganglioside structures, or antiganglioside antibodies, and is mimicked by multivalent clustering of GD1a or GT1b.\",\n      \"method\": \"Neurite outgrowth inhibition assay, neuraminidase treatment, pharmacological biosynthesis inhibition, genetic mouse model (modified ganglioside structures), antiganglioside monoclonal antibodies\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — multiple orthogonal methods (enzymatic, pharmacological, genetic, antibody-mediated) in a single study confirming gangliosides as functional MAG ligands\",\n      \"pmids\": [\"12060784\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"MAG binding to cerebellar neurons induces sequential alpha- and gamma-secretase proteolytic cleavage of the p75 neurotrophin receptor in a protein kinase C (PKC)-dependent manner; this cleavage is necessary for both RhoA activation and inhibition of neurite outgrowth.\",\n      \"method\": \"Biochemical cleavage assay in primary neurons, PKC inhibitors/activators, secretase inhibitors, RhoA activation assay, neurite outgrowth assay\",\n      \"journal\": \"Neuron\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — direct biochemical demonstration of regulated intramembrane proteolysis with pharmacological dissection of PKC dependence and functional readouts (RhoA activation, neurite outgrowth)\",\n      \"pmids\": [\"15953414\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"MAG is exclusively localized in low-buoyancy Lubrol WX-insoluble lipid raft membrane fractions in brain, primary oligodendrocytes, and MAG-expressing CHO cells; this lipid raft association depends on cellular cholesterol and occurs following terminal glycosylation in the trans-Golgi network. Recombinant MAG specifically interacts with lipid-raft fractions from neurons that contain MAG receptors GT1b and NgR, suggesting a lipid-raft-to-lipid-raft interaction mediates the MAG–neuron signaling interface.\",\n      \"method\": \"Detergent-resistant membrane fractionation, cholesterol depletion, subcellular fractionation, recombinant MAG binding assay\",\n      \"journal\": \"Molecular and cellular neurosciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple biochemical fractionation approaches in one lab; no reconstitution or structural validation\",\n      \"pmids\": [\"12691736\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"LRP1 (LDL receptor-related protein-1) is a high-affinity, sialic-acid-independent endocytic receptor for MAG on neurons; functional inactivation of LRP1 (by receptor-associated protein, RNAi, or gene deletion) significantly reverses MAG- and myelin-mediated inhibition of neurite outgrowth. LRP1 and p75NTR associate in a MAG-dependent manner and MAG-mediated RhoA activation involves both LRP1 and p75NTR. LRP1 complement-like repeat clusters CII and CIV are the MAG-binding domains.\",\n      \"method\": \"Receptor-associated protein inhibition, RNAi knockdown, genetic deletion (LRP1 knockout), Co-IP, RhoA activation assay, neurite outgrowth assay, Fc-fusion protein binding\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal loss-of-function approaches (pharmacological, RNAi, genetic KO) plus domain-mapping with Fc-fusion proteins, all yielding convergent results\",\n      \"pmids\": [\"23132925\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1997,\n      \"finding\": \"Soluble MAG (extracellular domain, dMAG), released from myelin and detectable in vivo, potently inhibits axonal regeneration in a dose-dependent manner when presented in solution; this inhibition is completely neutralized by immunodepletion of dMAG or inclusion of a MAG antibody, demonstrating that MAG acts as a true inhibitory molecule (not merely non-permissive) by binding to a specific neuronal receptor and initiating signal transduction.\",\n      \"method\": \"Soluble chimeric MAG-Fc assay, neurite outgrowth inhibition, immunodepletion, antibody neutralization, growth cone collapse assay\",\n      \"journal\": \"Molecular and cellular neurosciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple functional assays (soluble inhibition, immunodepletion, antibody block) in one lab establishing inhibitory mechanism\",\n      \"pmids\": [\"9361272\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"MAG-Fc chimera specifically precipitates several neuronal surface proteins from postnatal cerebellar, DRG, and PC12 neurons in a sialic acid-dependent manner; prominent proteins of ~190 kDa and ~250 kDa are co-precipitated from all three neuron types, and the 190 kDa protein is a sialoglycoprotein. Inhibition by a MAG antibody prevents precipitation, indicating specific receptor interactions.\",\n      \"method\": \"Chimeric MAG-Fc pulldown from neuronal cell surface proteins, competitive antibody inhibition, desialylation controls\",\n      \"journal\": \"Journal of neuroscience research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — pulldown across multiple neuron types with appropriate controls; binding partners not fully identified\",\n      \"pmids\": [\"10494110\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"CaMKIV is necessary for neurotrophin-induced phosphorylation of CREB and blockade of MAG-mediated inhibition of axonal growth; pharmacological inhibition or dominant-negative CaMKIV blocks the neurotrophin effect. CaMKIV activation requires calcium flux from intracellular stores and acts in parallel with PKA to overcome MAG inhibition.\",\n      \"method\": \"Pharmacological inhibition, dominant-negative overexpression, calcium chelation, cAMP/PKA manipulation, neurite outgrowth assay\",\n      \"journal\": \"Molecular and cellular neurosciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — pharmacological and dominant-negative genetic approaches in one lab establishing CaMKIV as a required component of the neurotrophin→CREB→MAG-inhibition-reversal pathway\",\n      \"pmids\": [\"18381242\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"MAG and OMgp synergize with Nogo-A to inhibit axonal growth in vivo; myelin lacking only MAG and OMgp is indistinguishable from control in inhibitory activity, but myelin lacking all three inhibitors is less inhibitory than Nogo-A-deficient myelin alone, revealing redundant and synergistic roles. In vivo spinal cord injury studies showed that triple knockout of Nogo-A/MAG/OMgp produces greater axonal growth and locomotor recovery than Nogo-A single knockout.\",\n      \"method\": \"Genetic knockout mice (single, double, triple mutants), myelin inhibition assay, spinal cord injury model, behavioral assessment, axonal tracing\",\n      \"journal\": \"The Journal of neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — rigorous genetic epistasis with single, double, and triple knockout animals; in vitro and in vivo convergent results\",\n      \"pmids\": [\"20484625\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"CRMP4 mediates MAG-induced inhibition of axonal outgrowth and growth cone collapse; loss of CRMP4 (CRMP4−/− neurons) prevents MAG-induced inhibition and growth cone collapse. CRMP4 is also required for MAG-mediated axonal protection against vincristine-induced degeneration, placing CRMP4 as a downstream effector of MAG/RhoA signaling for both inhibitory and protective functions.\",\n      \"method\": \"CRMP4 knockout mouse DRG neurons, MAG-induced neurite outgrowth inhibition assay, growth cone collapse assay, vincristine-induced axonal degeneration assay\",\n      \"journal\": \"Neuroscience letters\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — clean genetic KO with defined cellular phenotypes (inhibition, collapse, degeneration) in one lab\",\n      \"pmids\": [\"22583768\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"MAG protects neurons from acute toxic insult (vincristine-induced neurite degeneration) via a ganglioside-mediated signaling pathway involving RhoA activation; protection is reversed by anti-MAG antibody, sialidase treatment, or glycosphingolipid biosynthesis inhibitor, but not by cleavage of NgR (via PI-PLC) or peptide inhibitor of p75NTR. ROCK inhibition also reverses protection, identifying RhoA/ROCK as the protective downstream effector.\",\n      \"method\": \"Myelin substrate culture, anti-MAG antibody, sialidase, biosynthesis inhibition, PI-PLC treatment, p75NTR inhibitor, ROCK inhibitor, Mag-null myelin\",\n      \"journal\": \"ACS chemical neuroscience\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple pharmacological dissection tools plus Mag-null myelin control in one study; ganglioside pathway and ROCK identified as the protective mechanism\",\n      \"pmids\": [\"20436925\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"MAG induces apoptosis in developing cerebellar granule neurons through p75NTR-mediated JNK/cell death signaling pathway; deletion of p75NTR in vivo reduces the number of apoptotic neurons in cerebellar white matter during development. MAG-induced apoptosis also impairs neurite outgrowth, and cell death signaling requires NgR1/p75NTR complex.\",\n      \"method\": \"p75NTR knockout in vivo, cerebellar neuron apoptosis assay, JNK pathway analysis, neurite outgrowth assay\",\n      \"journal\": \"Cell death & disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo genetic KO with defined cellular phenotype (apoptosis, white matter size) plus mechanistic pathway (JNK) identification in one lab\",\n      \"pmids\": [\"31570696\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"MUC1 is a counter-receptor for MAG (Siglec-4a) on pancreatic cancer cells; MAG binds pancreatic cells expressing MUC1 in a sialidase-sensitive manner, and MAG physically associates with MUC1. Increased expression of MUC1 or MAG enhances heterotypic adhesion between pancreatic cancer cells and Schwann cells, and specific inhibition of MAG or sialyl-T MUC1 partially blocks this adhesion.\",\n      \"method\": \"Heterotypic adhesion assay, Co-immunoprecipitation, sialidase sensitivity assay, antibody inhibition, overexpression experiments\",\n      \"journal\": \"Cancer research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — Co-IP plus functional adhesion assay with gain- and loss-of-function, two orthogonal methods in one lab\",\n      \"pmids\": [\"17974963\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"Progressive and selective loss of MAG protein from brain in mice lacking complex gangliosides (Galgt1-null) occurs with age (60% reduction at 6 months, 70% at 12 months) without reduction of MAG mRNA, indicating that complex gangliosides GD1a and GT1b are required for maintaining MAG protein stability—likely via enhanced stability when MAG on myelin binds its complementary ligands on the axon surface.\",\n      \"method\": \"Galgt1 gene knockout, Western blot, RT-PCR, age-course analysis\",\n      \"journal\": \"Glycobiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — clean genetic KO with protein/mRNA dissociation demonstrating post-transcriptional stabilization mechanism; single lab\",\n      \"pmids\": [\"15175257\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1995,\n      \"finding\": \"L-MAG is selectively removed from the periaxonal membrane of CNS myelinated fibers by receptor-mediated endocytosis in quaking mice; the cytoplasmic domain of L-MAG contains tyrosine internalization signals at Y35 and Y65, and increased endosomal accumulation of L-MAG is observed in quaking oligodendrocytes. S-MAG remains in periaxonal membranes.\",\n      \"method\": \"Immunoelectron microscopy, endosome labeling, sequence motif analysis of cytoplasmic domain, developmental time-course comparison\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — immunoelectron microscopy with endosomal markers plus sequence-based identification of tyrosine internalization motifs; single lab\",\n      \"pmids\": [\"8557747\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1997,\n      \"finding\": \"Mice doubly deficient in MAG and N-CAM develop myelin degeneration approximately 4 weeks earlier than MAG-single-knockout mice, with increased degeneration profiles at 8 weeks; this genetic epistasis shows that N-CAM partially compensates for MAG in the maintenance (but not formation) of axon-myelin integrity in MAG-deficient mice.\",\n      \"method\": \"Double knockout mouse generation, electron microscopy, single fiber preparation, morphometric analysis\",\n      \"journal\": \"Cell and tissue research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic epistasis with double-mutant mice establishing compensatory relationship between MAG and N-CAM in myelin maintenance; single lab\",\n      \"pmids\": [\"9011400\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"hnRNP A1 regulates alternative splicing of Mag exon 12 by interacting with an element overlapping the 5' splice site of exon 12; this element has reduced affinity for U1 snRNP, and an evolutionarily conserved RNA secondary structure modulates interactions with both hnRNP A1 and U1 snRNP, coordinately controlling the ratio of L-MAG to S-MAG isoforms.\",\n      \"method\": \"RNA reporter constructs, UV crosslinking/RNA binding assay, splice site mutagenesis, U1 snRNP interaction assay, secondary structure analysis\",\n      \"journal\": \"RNA (New York, N.Y.)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — in vitro RNA binding and mutagenesis with reporter constructs establishing mechanistic basis for isoform-specific splicing; single lab\",\n      \"pmids\": [\"23704325\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"S-MAG and L-MAG isoforms have distinct subcellular distributions in myelin: in peripheral nerves (where S-MAG is the sole isoform), S-MAG concentrates in periaxonal and abaxonal rings and disc-like structures spanning compact myelin perpendicular to the axon. L-MAG and S-MAG show differential developmental expression in CNS and PNS oligodendrocyte unit phenotypes.\",\n      \"method\": \"Transgenic mouse expressing GFP-tagged S-MAG, confocal microscopy, electron microscopy, immunolabeling\",\n      \"journal\": \"Molecular and cellular neurosciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct live-imaging/fluorescence localization with GFP-tagged protein in a specifically engineered transgenic mouse; single lab\",\n      \"pmids\": [\"16442810\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"GPR37 and MAG form a protein complex when co-expressed in cells; genetic deletion of Gpr37 (but not Gpr37L1) results in markedly decreased MAG protein expression in brain, and Gpr37-knockout mice show dramatically increased myelin loss in the cuprizone demyelination model without loss of oligodendrocyte precursors or mature oligodendrocytes.\",\n      \"method\": \"Co-immunoprecipitation, Western blot, Gpr37 knockout mouse, cuprizone demyelination model, proteomics\",\n      \"journal\": \"Neuroscience\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — Co-IP plus genetic KO with functional demyelination phenotype; two methods in one lab\",\n      \"pmids\": [\"28642167\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"MAG membrane association is sulfatide-dependent; in mice lacking sulfatide (but retaining galactocerebroside), MAG shows increased susceptibility to detergent extraction from myelin membranes, while other myelin proteins (MOG, MBP, CNPase) are sulfatide-independent for their membrane association.\",\n      \"method\": \"In situ detergent extraction procedure on spinal cord sections, sulfatide-deficient mouse model, immunolabeling\",\n      \"journal\": \"Neurochemical research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — defined genetic loss-of-function model with quantitative detergent extraction demonstrating lipid-dependent membrane anchoring; single lab\",\n      \"pmids\": [\"24081651\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"MAG plays an essential role in mediating axon-myelin attachment in CMT1A disease; ablating MAG in CMT1A mice (overexpressing human PMP22) results in separation of axons from their myelin sheath, demonstrating that increased MAG expression in CMT1A has a compensatory role in maintaining axonal integrity in the context of PMP22 overexpression.\",\n      \"method\": \"MAG knockout in CMT1A mouse model (PMP22 overexpressing), electron microscopy, immunohistochemistry, expression analysis\",\n      \"journal\": \"Neurobiology of disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic double-mutant epistasis demonstrating specific adhesion function with electron microscopic readout; single lab\",\n      \"pmids\": [\"22940629\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Homozygous missense mutation p.Arg118His in MAG immunoglobulin domain 1 (a residue critical for sialic acid binding) causes a progressive neurological syndrome in humans with demyelinating leukodystrophy, establishing that the sialic acid-binding activity of MAG's Ig domain 1 is required for normal CNS function in vivo.\",\n      \"method\": \"Exome sequencing, clinical characterization, structural/functional annotation of MAG sialic acid binding site\",\n      \"journal\": \"Annals of clinical and translational neurology\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — human genetics identifying critical residue; no direct biochemical reconstitution of binding defect in this study; single family\",\n      \"pmids\": [\"27606346\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Three-dimensional FIB-SEM reconstruction of Mag-null mouse CNS shows that MAG-deficient myelin exhibits pathological outfoldings extending up to 10 μm longitudinally along myelinated axons, with complex axonal pathology (including axonal sprouting) underneath outfoldings. Normal-appearing axon/myelin units in Mag-null mice display significantly increased axonal diameters, indicating that MAG is required for maintaining normal axonal diameter and shape.\",\n      \"method\": \"Focused ion beam-scanning electron microscopy (FIB-SEM), 3D reconstruction, morphometric analysis, Mag-null and Plp-null mouse comparison\",\n      \"journal\": \"Glia\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — high-resolution 3D ultrastructural analysis with quantitative morphometry in genetic KO; single lab with rigorous method\",\n      \"pmids\": [\"36354016\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1986,\n      \"finding\": \"MAG is localized by immunoelectron microscopy to axon-Schwann cell apposition, Schmidt-Lanterman incisures, inner and outer mesaxons, and paranodal loops but not in compact myelin or at nodes of Ranvier; it appears after L1 expression ceases during myelination, establishing MAG's specific periaxonal localization distinct from compact myelin proteins like MBP.\",\n      \"method\": \"Pre- and post-embedding immunoelectron microscopy, developmental time-course\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — direct immunoelectron microscopy with subcellular resolution replicated at multiple developmental time points and in multiple fiber types; foundational localization study\",\n      \"pmids\": [\"2430983\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"MAG (myelin-associated glycoprotein/Siglec-4a) is a type I transmembrane Ig-superfamily protein localized periaxonally in myelin sheaths where it functions bidirectionally: on neurons it inhibits axonal outgrowth and induces growth cone collapse by engaging a receptor complex containing NgR1, p75NTR (which undergoes MAG-triggered PKC-dependent regulated intramembrane proteolysis leading to RhoA activation via CRMP4), and LRP1, with gangliosides GD1a/GT1b serving as functional sialic-acid-bearing neuronal ligands; on oligodendrocytes/Schwann cells it maintains axon–glial contact and long-term axon stability through ganglioside-dependent and sulfatide-dependent membrane interactions, with its two alternatively spliced isoforms (L-MAG and S-MAG, regulated by hnRNP A1 and RNA secondary structure) showing distinct subcellular distributions and the L-MAG isoform subject to tyrosine-motif-directed endocytic removal from periaxonal membranes.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"MAG (myelin-associated glycoprotein/Siglec-4a) is a periaxonal Ig-superfamily glycoprotein that couples glial myelin to axons and bidirectionally regulates axon growth, stability, and survival [#23, #8]. It localizes specifically to axon–glial apposition sites, Schmidt-Lanterman incisures, mesaxons, and paranodal loops but is excluded from compact myelin [#23], partitioning into cholesterol-dependent lipid rafts after trans-Golgi glycosylation and engaging neuronal raft fractions containing its receptors [#3]. On the neuronal side, MAG—including a soluble shed ectodomain (dMAG)—acts as a true inhibitory ligand that collapses growth cones and blocks neurite outgrowth [#5], signaling through a receptor complex of NgR1, the p75 neurotrophin receptor, and the endocytic receptor LRP1, with gangliosides GD1a/GT1b serving as sialic-acid-bearing functional ligands [#0, #1, #4]. MAG binding triggers PKC-dependent regulated intramembrane proteolysis of p75NTR (sequential α- and γ-secretase cleavage) required for RhoA activation, with CRMP4 acting as the downstream effector of both growth inhibition and axon protection [#2, #9]; the same pathway can drive p75NTR/JNK-dependent apoptosis of developing cerebellar granule neurons [#11]. Neurotrophin signaling reverses MAG inhibition via a CaMKIV→CREB arm acting in parallel with PKA [#7]. On the glial side, MAG maintains long-term axon–myelin integrity and normal axonal caliber: Mag-null myelin develops pathological outfoldings and enlarged axons [#22], and MAG is required for axon–myelin attachment, a role compensated in part by N-CAM and relevant in the CMT1A/PMP22 context [#15, #20]. MAG membrane anchoring and stability depend on sulfatide and on complex gangliosides, the latter maintaining MAG protein post-transcriptionally [#19, #13]. Its L-MAG and S-MAG isoforms, generated by hnRNP A1/U1 snRNP-regulated alternative splicing of exon 12, show distinct subcellular distributions, with L-MAG subject to tyrosine-motif-directed endocytosis [#16, #17, #14]. A homozygous p.Arg118His mutation in the sialic-acid-binding Ig domain 1 of MAG causes a human demyelinating leukodystrophy [#21].\",\n  \"teleology\": [\n    {\n      \"year\": 1986,\n      \"claim\": \"Establishing where MAG resides was the prerequisite to assigning function; immunoEM placed it precisely at axon–glial interfaces and excluded it from compact myelin, defining it as a periaxonal contact molecule distinct from structural myelin proteins.\",\n      \"evidence\": \"Pre- and post-embedding immunoelectron microscopy across developmental time points\",\n      \"pmids\": [\"2430983\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Does not identify binding partners on the axon\", \"Functional consequence of periaxonal localization untested\"]\n    },\n    {\n      \"year\": 1997,\n      \"claim\": \"It was unclear whether MAG actively signals inhibition or merely fails to support growth; soluble dMAG inhibiting outgrowth, neutralizable by immunodepletion or antibody, established MAG as a true receptor-engaging inhibitory ligand.\",\n      \"evidence\": \"Soluble MAG-Fc neurite outgrowth and growth cone collapse assays with immunodepletion and antibody block\",\n      \"pmids\": [\"9361272\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Neuronal receptor not identified in this study\", \"Downstream signaling undefined\"]\n    },\n    {\n      \"year\": 1999,\n      \"claim\": \"To find the neuronal receptor, MAG-Fc pulldowns identified sialic-acid-dependent neuronal surface sialoglycoproteins (~190/250 kDa), framing MAG as a sialic-acid-binding receptor with defined but unidentified partners.\",\n      \"evidence\": \"MAG-Fc pulldown across cerebellar, DRG, and PC12 neurons with desialylation and antibody controls\",\n      \"pmids\": [\"10494110\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Co-precipitated proteins not molecularly identified\", \"Direct vs indirect binding not resolved\"]\n    },\n    {\n      \"year\": 2002,\n      \"claim\": \"The signaling receptor complex and the sialylated ligand were defined: p75NTR is an obligate co-receptor with NgR, and gangliosides GD1a/GT1b are functional sialic-acid ligands, unifying the receptor and glycan arms of MAG signaling.\",\n      \"evidence\": \"Co-IP, p75 knockout neurons, dominant-negative p75 (NgR); neuraminidase, ganglioside biosynthesis/genetic modification, antiganglioside antibodies, multivalent clustering\",\n      \"pmids\": [\"12422217\", \"12060784\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How NgR-glycan and p75 inputs are integrated unresolved\", \"Transmembrane signaling step not yet defined\"]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"The physical interface of signaling was addressed: MAG partitions into cholesterol-dependent lipid rafts and engages neuronal raft fractions containing GT1b and NgR, framing a raft-to-raft signaling platform.\",\n      \"evidence\": \"Detergent-resistant membrane fractionation, cholesterol depletion, recombinant MAG raft-binding assay\",\n      \"pmids\": [\"12691736\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No reconstitution or structural validation\", \"Raft requirement for downstream signaling not functionally tested\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"How receptor engagement converts to intracellular signaling was answered: MAG triggers PKC-dependent sequential α/γ-secretase cleavage of p75NTR that is required for RhoA activation and growth inhibition.\",\n      \"evidence\": \"Biochemical cleavage assay in primary neurons with PKC and secretase inhibitors, RhoA and outgrowth readouts\",\n      \"pmids\": [\"15953414\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Identity of activating PKC isoform unspecified\", \"Link between cleaved p75 fragment and RhoA GEF unresolved\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"The mechanism of pharmacological reversal of MAG inhibition was clarified: a CaMKIV→CREB arm, dependent on intracellular calcium and parallel to PKA, is required for neurotrophins to overcome MAG inhibition.\",\n      \"evidence\": \"Pharmacological and dominant-negative CaMKIV, calcium chelation, cAMP/PKA manipulation, outgrowth assays\",\n      \"pmids\": [\"18381242\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct CaMKIV substrates in this context not defined\", \"Crosstalk point with RhoA pathway unmapped\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Two outstanding questions—physiological in vivo relevance and a protective role—were addressed: MAG synergizes with Nogo-A/OMgp to restrict regeneration in vivo, and separately protects axons from toxic degeneration via ganglioside→RhoA/ROCK signaling independent of NgR/p75 cleavage.\",\n      \"evidence\": \"Single/double/triple knockout mice with spinal cord injury and behavior; myelin-substrate protection assay with sialidase, biosynthesis inhibitor, PI-PLC, p75 peptide, ROCK inhibitor\",\n      \"pmids\": [\"20484625\", \"20436925\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Why protection bypasses NgR/p75 but inhibition requires them is unresolved\", \"Receptor mediating ganglioside-only protective signaling unidentified\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"The receptor complex and intracellular effector were extended: LRP1 is a high-affinity sialic-acid-independent endocytic MAG receptor associating with p75NTR, and CRMP4 is the shared downstream effector of MAG inhibition, collapse, and protection.\",\n      \"evidence\": \"RAP/RNAi/LRP1-KO loss of function, domain-mapping Fc-fusion binding, Co-IP, RhoA assay; CRMP4-KO DRG outgrowth, collapse, and vincristine protection assays\",\n      \"pmids\": [\"23132925\", \"22583768\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Stoichiometry of NgR/p75/LRP1/ganglioside complex unknown\", \"How one CRMP4 node bifurcates into inhibition vs protection unresolved\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"A developmental fate decision was assigned to MAG signaling: MAG drives p75NTR-dependent JNK-mediated apoptosis of cerebellar granule neurons, with p75 deletion reducing developmental cell death in vivo.\",\n      \"evidence\": \"p75NTR-knockout in vivo, cerebellar apoptosis and JNK pathway analysis, outgrowth assays\",\n      \"pmids\": [\"31570696\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Determinants selecting apoptosis vs growth inhibition output undefined\", \"Requirement for LRP1/gangliosides in this death pathway untested\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How a single ligand–receptor system selects among opposing outputs—growth inhibition, axon protection, and apoptosis—and how the NgR/p75/LRP1/ganglioside inputs assemble into a defined signaling complex remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No structural model of the receptor complex\", \"Switch determining inhibitory vs protective vs apoptotic signaling unknown\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"A non-neural function was identified: MAG (Siglec-4a) acts as a counter-receptor for sialyl-T MUC1, mediating sialidase-sensitive heterotypic adhesion between pancreatic cancer cells and Schwann cells.\",\n      \"evidence\": \"Heterotypic adhesion assay, Co-IP, sialidase sensitivity, antibody inhibition, overexpression\",\n      \"pmids\": [\"17974963\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"In vivo relevance to perineural invasion untested\", \"Downstream signaling from MAG–MUC1 adhesion undefined\"]\n    },\n    {\n      \"year\": 1986,\n      \"claim\": \"Glial-side maintenance functions and the structural basis of MAG anchoring and isoform control were progressively defined, establishing MAG's role in long-term axon–myelin integrity and caliber.\",\n      \"evidence\": \"Galgt1-KO ganglioside-dependent protein stability; MAG/N-CAM double KO and CMT1A/MAG-KO epistasis; sulfatide-dependent membrane anchoring; FIB-SEM of Mag-null myelin; hnRNP A1/U1 splicing of exon 12; GFP-S-MAG localization; L-MAG tyrosine-motif endocytosis\",\n      \"pmids\": [\"15175257\", \"9011400\", \"22940629\", \"24081651\", \"36354016\", \"23704325\", \"16442810\", \"8557747\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Molecular link between glial binding and axonal caliber control unclear\", \"Functional division of labor between L-MAG and S-MAG not fully resolved\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Human relevance of MAG's sialic-acid-binding activity was established: a homozygous p.Arg118His mutation in Ig domain 1 causes a demyelinating leukodystrophy.\",\n      \"evidence\": \"Exome sequencing, clinical characterization, structural annotation of the sialic-acid binding site\",\n      \"pmids\": [\"27606346\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No direct biochemical reconstitution of the binding defect\", \"Single family; genotype–phenotype scope limited\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0098631\", \"supporting_discovery_ids\": [12, 20, 23]},\n      {\"term_id\": \"GO:0060089\", \"supporting_discovery_ids\": [0, 5, 2]},\n      {\"term_id\": \"GO:0008289\", \"supporting_discovery_ids\": [1, 19, 3]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [23, 3, 17]},\n      {\"term_id\": \"GO:0005768\", \"supporting_discovery_ids\": [14, 4]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-1266738\", \"supporting_discovery_ids\": [8, 11, 22]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [2, 4, 9]},\n      {\"term_id\": \"R-HSA-5357801\", \"supporting_discovery_ids\": [11]}\n    ],\n    \"complexes\": [\"NgR1–p75NTR–LRP1 MAG receptor complex\"],\n    \"partners\": [\"NGFR\", \"RTN4R\", \"LRP1\", \"CRMP4\", \"GPR37\", \"MUC1\", \"NCAM1\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":8,"faith_total":9,"faith_pct":88.88888888888889}}