{"gene":"CHL1","run_date":"2026-06-09T22:57:18","timeline":{"discoveries":[{"year":2012,"finding":"CHL1 (the neural cell adhesion molecule close homolog of L1) is cleaved by the protease BACE1 in vivo under physiological conditions. The BACE1 cleavage site on CHL1 was determined by mass spectrometry to be between Gln(1061) and Asp(1062) in the membrane-proximal region.","method":"Quantitative proteomics of neuronal secretome after BACE1 inhibition; genetic BACE1 knockout mice; pharmacological BACE1 inhibition in mice and cell cultures; mass spectrometry for cleavage site mapping","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — multiple orthogonal methods (proteomics, genetic KO, pharmacological inhibition, MS cleavage site mapping), replicated across two independent papers (PMID 22692213, 22988240)","pmids":["22692213","22988240"],"is_preprint":false},{"year":2012,"finding":"BACE1 deficiency in mice produces axon guidance defects (shortened and disorganized infrapyramidal bundle of hippocampal mossy fibers; olfactory sensory neuron projection defects) that are strikingly similar to those in CHL1-deficient mice, establishing that these BACE1-/- phenotypes result from abrogated BACE1 processing of CHL1. BACE1 and CHL1 co-localize in hippocampal mossy fiber terminals, olfactory sensory neuron axons, and growth cones of primary hippocampal neurons.","method":"BACE1 knockout mouse phenotypic analysis; CHL1-/- mouse comparison; immunohistochemistry and co-localization; biochemical processing assays in hippocampus and olfactory bulb","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic epistasis via KO mouse comparison, co-localization, in vivo biochemical substrate validation; replicated across two papers","pmids":["22988240","22692213"],"is_preprint":false},{"year":2004,"finding":"CHL1 ectodomain shedding is performed by the metalloprotease-disintegrin ADAM8, which cleaves a CHL1-Fc fusion protein in vitro at two sites in fibronectin domains II (125 kDa fragment) and V (165 kDa fragment). Cleavage was inhibited by the metalloprotease inhibitor batimastat, was not observed with catalytically inactive ADAM8 (E330Q mutant), and was absent in brain extracts of ADAM8-deficient mice. Soluble CHL1 processed by ADAM8 promoted neurite outgrowth and suppressed neuronal cell death; these effects were not observed with inactive ADAM8, ADAM10, or ADAM17.","method":"In vitro cleavage assay with CHL1-Fc fusion protein; site-directed mutagenesis of ADAM8 active site; ADAM8-deficient mouse brain extracts; cell transfection; co-culture with cerebellar granule neurons; neurite outgrowth and cell death assays","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — in vitro reconstitution with mutagenesis, genetic KO validation in vivo, multiple functional readouts in one rigorous study","pmids":["14761956"],"is_preprint":false},{"year":2006,"finding":"The intracellular domain of CHL1 binds to the clathrin-uncoating ATPase Hsc70. CHL1 functions as a synaptic targeting cue for Hsc70; CHL1 deficiency or disruption of the CHL1/Hsc70 complex reduces Hsc70 targeting to synaptic membranes and vesicles, causes accumulation of abnormally high levels of clathrin-coated synaptic vesicles with reduced ability to release clathrin, and impairs activity-dependent clathrin-coated vesicle generation and FM dye uptake/release, revealing a role for CHL1 in clathrin-dependent synaptic vesicle recycling.","method":"Yeast two-hybrid / binding partner identification; CHL1 gene ablation in mice; biochemical fractionation; electron microscopy; FM dye uptake/release assays in synaptic boutons","journal":"Neuron","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal binding assay, genetic KO with multiple orthogonal functional readouts (fractionation, EM, FM dye assay) in a single rigorous study","pmids":["17178404"],"is_preprint":false},{"year":2007,"finding":"CHL1 recruits ezrin (an ERM family member) to the plasma membrane through a membrane-proximal cytoplasmic motif (RGGKYSV). This CHL1/ERM interaction is required for Sema3A-induced growth cone collapse, CHL1-dependent neurite outgrowth and branching in cortical neurons, haptotactic cell migration, and cellular adhesion to fibronectin.","method":"Cytofluorescence recruitment assay; deletion and point mutagenesis of cytoplasmic domain; Sema3A growth cone collapse assay; neurite outgrowth and branching assay; cell migration and adhesion assay in cortical embryonic neurons","journal":"Journal of neurochemistry","confidence":"High","confidence_rationale":"Tier 2 / Moderate — mutagenesis of specific motif combined with multiple functional assays in a single study; single lab","pmids":["17995939"],"is_preprint":false},{"year":2007,"finding":"CHL1 directly associates with NB-3 (a member of the F3/contactin family) and enhances NB-3 cell surface expression. CHL1 and NB-3 both interact with protein tyrosine phosphatase alpha (PTPα) and regulate its activity. Loss of CHL1, NB-3, or PTPα leads to aberrant/misoriented apical dendrite projections of deep-layer pyramidal neurons in the visual cortex, indicating a CHL1–NB-3–PTPα signaling complex regulates apical dendrite orientation.","method":"Co-immunoprecipitation; cell surface expression assays; PTPα activity assay; CHL1-/-, NB-3-/-, and PTPα-/- mouse analysis; confocal microscopy of cortical neurons","journal":"The EMBO journal","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal co-IP, enzyme activity assay, multiple KO mouse lines with defined cellular phenotype","pmids":["18046458"],"is_preprint":false},{"year":2010,"finding":"CHL1 associates selectively with EphA7 (whereas L1 associates with EphA3, EphA4, and EphA7), as shown by co-immunoprecipitation. L1 and CHL1 cooperate in repellent responses to EphrinA5 for thalamic axon guidance; double CHL1-/-/L1-/y mutant mice show a striking posterior shift of motor thalamic axons to visual cortex not seen in single mutants, demonstrating epistatic cooperation between CHL1 and L1 in thalamocortical targeting.","method":"Co-immunoprecipitation; double-mutant mouse generation and analysis; growth cone collapse assays with EphrinA5; immunofluorescence colocalization","journal":"Cerebral cortex","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal co-IP, genetic epistasis via double KO mice, growth cone functional assay; multiple orthogonal approaches","pmids":["20576928"],"is_preprint":false},{"year":2014,"finding":"CHL1 interacts with vitronectin and plasminogen activator inhibitor-2 (PAI-2) as novel extracellular binding partners. CHL1-induced cerebellar neurite outgrowth and neuronal migration depend on vitronectin-mediated integrin signaling (involving an RGD motif in CHL1) and on PAI-2/uPA/uPA receptor/integrin pathways. At earlier postnatal stages, homophilic CHL1-CHL1 trans-interactions regulate neuronal progenitor differentiation, whereas heterophilic interactions with vitronectin and the plasminogen activator system regulate neuritogenesis and migration at later stages.","method":"Co-immunoprecipitation / colocalization; function-blocking antibodies against vitronectin, PAI-2, uPA, uPA receptor, integrins; CHL1-derived RGD peptide inhibition; cerebellar granule cell migration and neurite outgrowth assays; CHL1-/- mouse comparison","journal":"The Journal of neuroscience","confidence":"High","confidence_rationale":"Tier 2 / Moderate — co-IP, peptide inhibition, antibody blocking, multiple functional assays; single lab but multiple orthogonal methods","pmids":["25355214"],"is_preprint":false},{"year":1999,"finding":"CHL1-Fc fusion protein (extracellular domain of CHL1 fused to human IgG Fc) significantly enhanced survival of cerebellar granule neurons and hippocampal neurons undergoing apoptosis in serum-free culture (~45% increase), both in soluble form and as substrate. Bcl-2 protein levels in cerebellar granule neurons were increased by L1-Fc treatment, implicating Bcl-2 as an intracellular mediator.","method":"Neuronal apoptosis assay in serum-free medium; CHL1-Fc fusion protein treatment; Western blot for Bcl-2 and c-Jun","journal":"Journal of neurobiology","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — defined functional assay with fusion protein, single lab, single method for Bcl-2 downstream pathway","pmids":["10022583"],"is_preprint":false},{"year":2005,"finding":"CHL1-Fc fusion protein promotes survival of purified embryonic motoneurons at picomolar concentrations (similar to L1-Fc). CHL1-induced motoneuron survival is completely inhibited by LY294002 (PI3K inhibitor) and PD98059 (MEK inhibitor), indicating that both PI3K and MEK/ERK pathways are required for CHL1-mediated survival signaling.","method":"Purified motoneuron survival assay; pharmacological inhibition of PI3K (LY294002) and MEK (PD98059); dose-response analysis with CHL1-Fc fusion protein","journal":"Journal of neuroscience research","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — functional assay with defined pharmacological pathway dissection; single lab, single set of experiments","pmids":["15880726"],"is_preprint":false},{"year":2007,"finding":"CHL1 is localized to apical Bergmann glial (BG) fibers and stellate cells during cerebellar development. In CHL1-/- mice, stellate axons deviate from BG fibers and show aberrant branching and orientation; synapse formation between aberrant stellate axons and Purkinje dendrites is reduced and cannot be maintained, leading to progressive atrophy of axon terminals. This establishes CHL1 as a molecular signal on BG fibers that organizes GABAergic stellate axon arbors and directs their dendritic innervation.","method":"GFP BAC transgenic reporter mice; CHL1-/- mouse analysis; immunofluorescence localization; electron microscopy of synapses; confocal microscopy of axon morphology","journal":"PLoS biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic KO with multiple quantitative morphological readouts, direct localization with functional consequence, rigorous single study","pmids":["18447583"],"is_preprint":false},{"year":2007,"finding":"CHL1 upregulation in GFAP-positive reactive astrocytes (glial scar) after spinal cord injury restricts axonal growth and remodeling. This upregulation is induced by basic FGF (bFGF) and is abolished by inhibitors of FGF receptor-dependent ERK, CaMKII, and PI3K signaling pathways. Homophilic CHL1-CHL1 interactions between neurons and astrocytes mediate reduced neurite outgrowth. CHL1-/- mice show improved functional recovery after spinal cord injury compared to wild-type, associated with enhanced monoaminergic reinnervation.","method":"CHL1-/- mouse spinal cord injury model; locomotor rating and video analysis; immunohistochemistry; primary astrocyte cultures with bFGF stimulation; pharmacological inhibitor studies; heterogenotypic neuron-astrocyte cocultures","journal":"The Journal of neuroscience","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic KO functional rescue, defined signaling pathway via pharmacological inhibition, in vitro coculture mechanistic validation; multiple orthogonal approaches","pmids":["17611275"],"is_preprint":false},{"year":2010,"finding":"CHL1 deficiency enhances proliferation and self-renewal of neural progenitor cells (NPCs) and promotes neuronal differentiation. CHL1 negatively regulates NPC proliferation through activation of the ERK1/2 MAPK pathway; pharmacological inhibition of ERK1/2 eliminates the increased proliferation seen in CHL1-/- NPCs.","method":"CHL1-/- mouse brain analysis (BrdU incorporation in SVZ, Tuj1 staining in cortical plate); primary NPC cultures from CHL1-/- and wild-type mice; ERK1/2 MAPK pharmacological inhibition; proliferation and differentiation assays","journal":"Molecular and cellular neurosciences","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic KO with in vivo and in vitro assays, pharmacological pathway validation; single lab, two orthogonal approaches","pmids":["20933598"],"is_preprint":false},{"year":2012,"finding":"Neuritogenesis-promoting ligand-dependent clustering of CHL1 induces palmitoylation and lipid raft-dependent endocytosis of CHL1. βII spectrin was identified as a binding partner of CHL1; partial disruption of the CHL1-βII spectrin complex accompanies CHL1 endocytosis. Mutation of cysteine 1102 within the CHL1 intracellular domain reduces lipid raft association and endocytosis. CHL1-dependent neurite outgrowth requires lipid raft assembly, voltage-dependent Ca2+ channels, and the CHL1 Cys-1102 palmitoylation site.","method":"Co-immunoprecipitation of CHL1 and βII spectrin; lipid raft fractionation; site-directed mutagenesis (C1102); pharmacological disruption of lipid rafts; nifedipine (L-type Ca2+ channel inhibitor) treatment; endocytosis assays; neurite outgrowth assays","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1-2 / Moderate — mutagenesis of specific residue, co-IP, biochemical fractionation, pharmacological inhibition, functional neurite assay; multiple orthogonal methods in a single study","pmids":["23144456"],"is_preprint":false},{"year":2009,"finding":"CHL1 cooperates with PAK1-3 kinases in regulating morphological development of the leading process/apical dendrite of embryonic cortical neurons. Dominant-negative PAK inhibition in CHL1-/- mouse cortex caused extreme branching in the intermediate zone and cortical plate, far exceeding effects in either mutant alone, consistent with CHL1 and PAK1-3 acting in independent but cooperating pathways.","method":"In utero electroporation of dominant-negative PAK1 AID construct into CHL1-/- and wild-type embryos; confocal microscopy of GFP-labeled neurons in slice culture; quantitative morphological analysis","journal":"Neuroscience","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — genetic epistasis via dominant-negative in KO background; single lab, single experimental approach","pmids":["19819308"],"is_preprint":false},{"year":2015,"finding":"CHL1 binds to a peptide stretch in the third intracellular loop of the serotonin 2c (5-HT2c) receptor through its own intracellular domain. CHL1 regulates 5-HT2c receptor phosphorylation and the receptor's association with PTEN and β-arrestin 2. CHL1-deficient mice show 5-HT2c-receptor-related reduction in locomotor activity and reactivity to novelty. CHL1 modulates signaling pathways triggered by constitutively active 5-HT2c receptor isoforms. CHL1 and 5-HT2c receptor co-localize in striatal and hippocampal GABAergic neurons.","method":"Co-immunoprecipitation of CHL1 with 5-HT2c receptor; peptide binding assay; CHL1-/- mouse behavioral analysis; immunofluorescence colocalization; phosphorylation and co-IP assays with PTEN and β-arrestin 2","journal":"Journal of cell science","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — co-IP, genetic KO behavioral phenotype, signaling assays; single lab, multiple orthogonal methods","pmids":["26527397"],"is_preprint":false},{"year":2010,"finding":"CHL1 expression in astrocytes is upregulated via a PI3K/PKCδ/ERK1/2/NF-κB signaling cascade. LPS-induced astrogliosis triggers PKCδ translocation to the membrane, ERK1/2 phosphorylation downstream of PKCδ, and NF-κB nuclear translocation, all of which are required for upregulation of CHL1 protein expression. The NO-guanylate cyclase-cGMP pathway, by contrast, does not mediate this upregulation. LPS-induced CHL1 upregulation in reactive astrocytes inhibits hippocampal neurite outgrowth in coculture.","method":"Primary mouse astrocyte cultures; pharmacological inhibition of PI3K, PKCδ, ERK1/2, NF-κB; PKCδ genetic knockdown; subcellular fractionation; Western blot; neurite outgrowth coculture assay","journal":"Glia","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — pharmacological and genetic dissection of signaling pathway, functional coculture assay; single lab, multiple inhibitors tested","pmids":["19672967"],"is_preprint":false},{"year":2019,"finding":"CHL1 suppresses tumor growth and metastasis in nasopharyngeal carcinoma by directly interacting with Integrin-β1 and linking to Merlin, leading to inactivation of the integrin β1-AKT signaling pathway. CHL1 also induces mesenchymal-epithelial transition (MET) and inactivates RhoA/Rac1/Cdc42 signaling, inhibiting stress fiber, lamellipodia, and filopodia formation.","method":"Co-immunoprecipitation of CHL1 with Integrin-β1 and Merlin; ectopic CHL1 expression in NPC cells; colony formation, cell motility, and invasion assays; Western blot for EMT markers and Rho GTPase pathway; in vivo xenograft experiments","journal":"International journal of biological sciences","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct Co-IP, loss and gain of function assays, pathway analysis; single lab, multiple assays","pmids":["31523184"],"is_preprint":false},{"year":2018,"finding":"CHL1 acts as a tumor suppressor in neuroblastoma: overexpression of CHL1 induces neurite-like outgrowth and markers of neuronal differentiation, inhibits anchorage-independent colony formation, and suppresses tumor xenograft growth. Knockdown of CHL1 activates Rho GTPases, enhances proliferation and migration, and accelerates orthotopic xenograft growth. CHL1 functions through inhibition of MAPK and Akt pathways.","method":"Inducible CHL1 overexpression and knockdown cell models; neurite outgrowth assay; colony formation; Transwell migration; orthotopic xenograft mouse model; Western blot for MAPK/Akt pathway components; Rho GTPase pull-down assay","journal":"Oncotarget","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — bidirectional loss- and gain-of-function with pathway analysis and in vivo validation; single lab","pmids":["29899830"],"is_preprint":false},{"year":2019,"finding":"CHL1 mediates axonal growth promotion of midbrain dopamine (mDA) neurons through trans-heterophilic interactions. The growth-promoting effect of ALCAM substrate on mDA neurons was abolished by neutralizing antibodies against Chl1 (as well as Nrp1 and L1cam), and CHL1 modulates the response of mDA neurites to soluble semaphorins (abolishing Sema3A growth promotion; inducing branching in the presence of Sema3C).","method":"Primary midbrain cultures on ALCAM substrate; function-blocking antibodies against CHL1, Nrp1, L1cam; neurite growth and branching assays; semaphorin stimulation experiments","journal":"The Journal of neuroscience","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — antibody neutralization functional assay; single lab, single method per interaction","pmids":["31300520"],"is_preprint":false},{"year":2017,"finding":"CHL1 mediates homophilic CHL1-CHL1 interactions that regulate VM dopaminergic progenitor migration, differentiation, axonal extension, and axonal repulsion (selectively in DA neurons). Both substrate-bound and soluble forms of CHL1 have distinct functional roles in DA neuron development.","method":"Temporal and spatial CHL1 expression mapping in VM; primary VM DA neuron cultures on CHL1 substrates; function-blocking antibodies against CHL1; neurite extension and repulsion assays; DA progenitor migration assays","journal":"Scientific reports","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — functional assays with antibody blocking and substrate, single lab; homophilic interaction inferred from blocking experiments","pmids":["28839197"],"is_preprint":false}],"current_model":"CHL1 (close homolog of L1) is a transmembrane immunoglobulin superfamily cell adhesion molecule that functions in the nervous system through multiple mechanisms: its extracellular domain is shed by ADAM8 and cleaved by BACE1 (at Gln1061-Asp1062) to release bioactive fragments that promote neurite outgrowth and neuronal survival; its intracellular domain binds Hsc70 to target it to synaptic membranes and regulate clathrin-coated synaptic vesicle uncoating and recycling, and recruits ERM proteins via a RGGKYSV motif to mediate Sema3A-induced growth cone collapse and neurite outgrowth; CHL1 engages heterophilic partners including NB-3, PTPα, vitronectin, integrins, PAI-2, Integrin-β1, Merlin, and the 5-HT2c receptor to regulate apical dendrite orientation, neuronal migration, cell survival, and signal transduction; and homophilic CHL1-CHL1 interactions guide stellate axon organization along Bergmann glial fibers and direct dopaminergic axon pathfinding, while reactive-astrocyte upregulation of CHL1 via PI3K/PKCδ/ERK/NF-κB signaling creates a glial scar component that restricts axonal regeneration after injury."},"narrative":{"mechanistic_narrative":"CHL1 (close homolog of L1) is a transmembrane immunoglobulin-superfamily cell adhesion molecule that organizes neuronal migration, axon guidance, dendrite orientation, and synaptic function through both proteolytically released ectodomain fragments and intracellular signaling complexes [PMID:22988240, PMID:22692213, PMID:18447583]. Its extracellular domain is processed by two distinct proteases: ADAM8 sheds the ectodomain in the fibronectin domains, generating soluble fragments that promote neurite outgrowth and suppress neuronal death [PMID:14761956], while BACE1 cleaves CHL1 in vivo between Gln1061 and Asp1062, and loss of this processing reproduces CHL1-null axon guidance defects in hippocampal mossy fibers and olfactory projections, placing CHL1 downstream of BACE1 in axon targeting [PMID:22692213, PMID:22988240]. The intracellular domain couples CHL1 to membrane and cytoskeletal machinery: it binds the clathrin-uncoating ATPase Hsc70 to target it to synapses and drive clathrin-coated synaptic vesicle recycling [PMID:17178404], recruits the ERM protein ezrin via an RGGKYSV motif to mediate Sema3A-induced growth cone collapse and neurite outgrowth [PMID:17995939], and associates with βII spectrin, with ligand-induced clustering triggering Cys1102 palmitoylation and lipid-raft-dependent endocytosis required for neurite outgrowth [PMID:23144456]. CHL1 acts through a network of heterophilic partners—NB-3/PTPα to orient apical dendrites, EphA7 (cooperating with L1) for thalamocortical EphrinA5 responses, vitronectin and the PAI-2/uPA/integrin system for migration and neuritogenesis, and the 5-HT2c receptor to modulate its phosphorylation and behavioral output—as well as homophilic CHL1-CHL1 interactions that organize cerebellar stellate axons along Bergmann glial fibers and guide dopaminergic axon pathfinding [PMID:18046458, PMID:20576928, PMID:25355214, PMID:26527397, PMID:18447583, PMID:28839197]. Survival and proliferative signaling proceed through PI3K and MEK/ERK pathways, with CHL1 negatively regulating neural progenitor proliferation via ERK1/2 [PMID:15880726, PMID:20933598]. After CNS injury, reactive astrocytes upregulate CHL1 through PI3K/PKCδ/ERK/NF-κB signaling, creating a glial-scar component that restricts axonal regeneration [PMID:17611275, PMID:19672967]. In epithelial tumors CHL1 acts as a suppressor, binding Integrin-β1 and Merlin to inactivate integrin-β1/AKT and Rho-family GTPase signaling [PMID:31523184, PMID:29899830].","teleology":[{"year":1999,"claim":"Established that the CHL1 ectodomain is not merely adhesive but actively pro-survival, raising the question of how a cell adhesion molecule signals neuronal survival.","evidence":"CHL1-Fc fusion protein rescue of cerebellar granule and hippocampal neuron apoptosis in serum-free culture, with Bcl-2 induction by Western blot","pmids":["10022583"],"confidence":"Medium","gaps":["Receptor mediating the survival effect not identified","Bcl-2 link is a single-method correlation"]},{"year":2004,"claim":"Identified the protease that converts membrane CHL1 into the bioactive soluble form, defining ADAM8 as the ectodomain sheddase and linking cleavage to outgrowth and survival.","evidence":"In vitro cleavage of CHL1-Fc, ADAM8 active-site mutagenesis, ADAM8-deficient brain extracts, and neurite/cell-death assays with cerebellar neurons","pmids":["14761956"],"confidence":"High","gaps":["Physiological stimulus triggering ADAM8 shedding unknown","Receptor for shed CHL1 fragments not defined"]},{"year":2005,"claim":"Dissected the intracellular signaling required for CHL1-mediated survival, showing dependence on PI3K and MEK/ERK.","evidence":"Picomolar CHL1-Fc rescue of purified motoneurons blocked by LY294002 and PD98059","pmids":["15880726"],"confidence":"Medium","gaps":["Upstream receptor coupling CHL1 to PI3K/ERK not identified","Single pharmacological experiment set"]},{"year":2006,"claim":"Defined an intracellular function for CHL1 by identifying Hsc70 binding, establishing CHL1 as a synaptic targeting cue for clathrin-coated vesicle recycling.","evidence":"Binding-partner identification, CHL1 knockout mice, biochemical fractionation, EM, and FM dye uptake/release at synaptic boutons","pmids":["17178404"],"confidence":"High","gaps":["Structural basis of CHL1-Hsc70 binding not resolved","Regulation of the interaction by activity unclear"]},{"year":2007,"claim":"Mapped CHL1's cytoplasmic signaling to ERM proteins and established the heterophilic and homophilic adhesion partners coordinating dendrite orientation and axon organization.","evidence":"Cytoplasmic-domain mutagenesis defining the RGGKYSV ezrin-recruitment motif with Sema3A/outgrowth assays; co-IP of NB-3 and PTPα with multiple KO mouse lines; Bergmann glial localization with stellate axon analysis in CHL1-/- mice","pmids":["17995939","18046458","18447583"],"confidence":"High","gaps":["How ERM recruitment links to specific cytoskeletal outputs not fully defined","PTPα substrates downstream of the complex unknown"]},{"year":2007,"claim":"Revealed an injury-context role: reactive astrocytes upregulate CHL1 to restrict axon regeneration via homophilic interactions, with consequences for functional recovery.","evidence":"CHL1-/- spinal cord injury model with locomotor scoring, bFGF-stimulated astrocyte cultures with FGFR/ERK/CaMKII/PI3K inhibitors, and neuron-astrocyte cocultures","pmids":["17611275"],"confidence":"High","gaps":["Neuronal receptor mediating growth inhibition not identified beyond homophilic CHL1","Relative contribution of glial scar vs other inhibitors unquantified"]},{"year":2009,"claim":"Showed CHL1 cooperates with PAK1-3 kinases in shaping the leading process/apical dendrite, indicating parallel cooperating cytoskeletal pathways.","evidence":"In utero electroporation of dominant-negative PAK into CHL1-/- cortex with quantitative morphology","pmids":["19819308"],"confidence":"Medium","gaps":["Whether CHL1 and PAK physically interact untested","Single experimental approach"]},{"year":2010,"claim":"Extended CHL1's repertoire to thalamocortical guidance via selective EphA7 association and epistatic cooperation with L1.","evidence":"Co-IP of CHL1 with EphA7 and double CHL1-/-/L1-/y mutant mice with EphrinA5 growth cone collapse assays","pmids":["20576928"],"confidence":"High","gaps":["Functional consequence of CHL1-EphA7 binding on Eph signaling not measured","Mechanism of CHL1/L1 cooperation unresolved"]},{"year":2010,"claim":"Defined CHL1 as a negative regulator of neural progenitor proliferation and the astrocytic signaling cascade controlling its own expression.","evidence":"CHL1-/- NPC proliferation/differentiation assays with ERK1/2 inhibition; astrocyte cultures dissecting PI3K/PKCδ/ERK/NF-κB control of CHL1 upregulation","pmids":["20933598","19672967"],"confidence":"Medium","gaps":["How CHL1 engages ERK1/2 in progenitors mechanistically unclear","Transcription factors directly driving the CHL1 gene not identified"]},{"year":2012,"claim":"Identified BACE1 as a second, physiological protease cleaving CHL1 and connected this processing to specific axon guidance phenotypes.","evidence":"Neuronal secretome proteomics, BACE1 KO mice, pharmacological BACE1 inhibition, MS cleavage-site mapping (Gln1061-Asp1062), and phenotypic comparison of BACE1-/- and CHL1-/- mice","pmids":["22692213","22988240"],"confidence":"High","gaps":["Fate and receptor of the BACE1-generated fragment undefined","Relationship between ADAM8 and BACE1 cleavage not reconciled"]},{"year":2012,"claim":"Linked CHL1 ligand-induced clustering to palmitoylation-dependent endocytosis via βII spectrin, providing a trafficking mechanism for outgrowth signaling.","evidence":"Co-IP of CHL1 with βII spectrin, lipid raft fractionation, C1102 mutagenesis, raft disruption, nifedipine treatment, and neurite outgrowth assays","pmids":["23144456"],"confidence":"High","gaps":["Palmitoyltransferase acting on Cys1102 not identified","How endocytosis converts to outgrowth signaling unresolved"]},{"year":2014,"claim":"Resolved stage-specific use of homophilic vs heterophilic adhesion, adding vitronectin and the PAI-2/uPA/integrin system as extracellular partners for migration and neuritogenesis.","evidence":"Co-IP/colocalization, function-blocking antibodies, CHL1 RGD-peptide inhibition, and cerebellar migration/outgrowth assays with CHL1-/- comparison","pmids":["25355214"],"confidence":"High","gaps":["Which integrin heterodimers CHL1 engages not specified","Direct vs indirect vitronectin binding not structurally defined"]},{"year":2015,"claim":"Extended CHL1 to receptor signaling regulation by showing it binds the 5-HT2c receptor and controls its phosphorylation and effector coupling, with behavioral consequences.","evidence":"Co-IP and peptide binding with the 5-HT2c third intracellular loop, CHL1-/- behavior, and phosphorylation/PTEN/β-arrestin 2 assays","pmids":["26527397"],"confidence":"Medium","gaps":["Stoichiometry and structural interface of the interaction unknown","Causal chain from receptor modulation to behavior incomplete"]},{"year":2017,"claim":"Demonstrated cell-type-selective homophilic CHL1 signaling in dopaminergic neuron development, governing migration, extension, and repulsion.","evidence":"VM expression mapping, primary DA neuron cultures on CHL1 substrates, and function-blocking antibody assays","pmids":["28839197"],"confidence":"Medium","gaps":["Homophilic interaction inferred from blocking rather than direct binding","Downstream signaling in DA neurons not defined"]},{"year":2018,"claim":"Established a tumor-suppressor role for CHL1 in neuroblastoma acting through MAPK/Akt and Rho-GTPase inhibition.","evidence":"Inducible overexpression/knockdown, neurite/colony/migration assays, orthotopic xenografts, and pathway Western blots with Rho pull-downs","pmids":["29899830"],"confidence":"Medium","gaps":["Membrane partner transducing the suppressor effect not identified","Single-lab tumor model"]},{"year":2019,"claim":"Identified the Integrin-β1/Merlin axis as the mechanism of CHL1 tumor suppression in epithelial cancer and added CHL1 trans-heterophilic guidance of dopaminergic axons.","evidence":"Co-IP of CHL1 with Integrin-β1 and Merlin plus xenograft and EMT/Rho assays in NPC; ALCAM-substrate mDA cultures with CHL1/Nrp1/L1cam neutralizing antibodies and semaphorin assays","pmids":["31523184","31300520"],"confidence":"Medium","gaps":["Whether the same Integrin-β1/Merlin axis operates in neurons untested","Direct binding partners for the ALCAM/semaphorin responses not biochemically resolved"]},{"year":null,"claim":"The identity of the neuronal receptor(s) transducing signals from shed/soluble CHL1 fragments, and how ADAM8 and BACE1 cleavage events are coordinated, remain unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No receptor identified for ADAM8- or BACE1-released CHL1 ectodomain fragments","Structural basis of most intracellular and extracellular CHL1 interactions undetermined","Integration of the multiple parallel signaling pathways (ERM, Hsc70, spectrin, integrin) into a unified model lacking"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0098631","term_label":"cell adhesion mediator activity","supporting_discovery_ids":[10,20,7,11]},{"term_id":"GO:0060089","term_label":"molecular transducer activity","supporting_discovery_ids":[5,6,15,19]},{"term_id":"GO:0008092","term_label":"cytoskeletal protein binding","supporting_discovery_ids":[4,13]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[3,5,15]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[4,13,5]},{"term_id":"GO:0031410","term_label":"cytoplasmic vesicle","supporting_discovery_ids":[3,13]}],"pathway":[{"term_id":"R-HSA-1266738","term_label":"Developmental Biology","supporting_discovery_ids":[1,10,7,20]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[5,9,17,15]},{"term_id":"R-HSA-5653656","term_label":"Vesicle-mediated transport","supporting_discovery_ids":[3,13]},{"term_id":"R-HSA-112316","term_label":"Neuronal System","supporting_discovery_ids":[3,10,15]},{"term_id":"R-HSA-1643685","term_label":"Disease","supporting_discovery_ids":[17,18]}],"complexes":[],"partners":["BACE1","ADAM8","HSPA8","EZR","NB-3","PTPRA","EPHA7","ITGB1"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q96FC9","full_name":"ATP-dependent DNA helicase DDX11","aliases":["CHL1-related protein 1","hCHLR1","DEAD/H-box protein 11","DNA 5'-3' helicase DDX11","Keratinocyte growth factor-regulated gene 2 protein","KRG-2"],"length_aa":970,"mass_kda":108.3,"function":"DNA-dependent ATPase and ATP-dependent DNA helicase that participates in various functions in genomic stability, including DNA replication, DNA repair and heterochromatin organization as well as in ribosomal RNA synthesis (PubMed:10648783, PubMed:21854770, PubMed:23797032, PubMed:26089203, PubMed:26503245). Its double-stranded DNA helicase activity requires either a minimal 5'-single-stranded tail length of approximately 15 nt (flap substrates) or 10 nt length single-stranded gapped DNA substrates of a partial duplex DNA structure for helicase loading and translocation along DNA in a 5' to 3' direction (PubMed:10648783, PubMed:18499658, PubMed:22102414). The helicase activity is capable of displacing duplex regions up to 100 bp, which can be extended up to 500 bp by the replication protein A (RPA) or the cohesion CTF18-replication factor C (Ctf18-RFC) complex activities (PubMed:18499658). Also shows ATPase- and helicase activities on substrates that mimic key DNA intermediates of replication, repair and homologous recombination reactions, including forked duplex, anti-parallel G-quadruplex and three-stranded D-loop DNA molecules (PubMed:22102414, PubMed:26503245). Plays a role in DNA double-strand break (DSB) repair at the DNA replication fork during DNA replication recovery from DNA damage (PubMed:23797032). Recruited with TIMELESS factor upon DNA-replication stress response at DNA replication fork to preserve replication fork progression, and hence ensure DNA replication fidelity (PubMed:26503245). Also cooperates with TIMELESS factor during DNA replication to regulate proper sister chromatid cohesion and mitotic chromosome segregation (PubMed:17105772, PubMed:18499658, PubMed:20124417, PubMed:23116066, PubMed:23797032). Stimulates 5'-single-stranded DNA flap endonuclease activity of FEN1 in an ATP- and helicase-independent manner; and hence it may contribute in Okazaki fragment processing at DNA replication fork during lagging strand DNA synthesis (PubMed:18499658). Its ability to function at DNA replication fork is modulated by its binding to long non-coding RNA (lncRNA) cohesion regulator non-coding RNA DDX11-AS1/CONCR, which is able to increase both DDX11 ATPase activity and binding to DNA replicating regions (PubMed:27477908). Also plays a role in heterochromatin organization (PubMed:21854770). Involved in rRNA transcription activation through binding to active hypomethylated rDNA gene loci by recruiting UBTF and the RNA polymerase Pol I transcriptional machinery (PubMed:26089203). Plays a role in embryonic development and prevention of aneuploidy (By similarity). Involved in melanoma cell proliferation and survival (PubMed:23116066). Associates with chromatin at DNA replication fork regions (PubMed:27477908). Binds to single- and double-stranded DNAs (PubMed:18499658, PubMed:22102414, PubMed:9013641) (Microbial infection) Required for bovine papillomavirus type 1 regulatory protein E2 loading onto mitotic chromosomes during DNA replication for the viral genome to be maintained and segregated","subcellular_location":"Chromosome","url":"https://www.uniprot.org/uniprotkb/Q96FC9/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/CHL1","classification":"Not Classified","n_dependent_lines":1,"n_total_lines":1208,"dependency_fraction":0.0008278145695364238},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/CHL1","total_profiled":1310},"omim":[{"mim_id":"613792","title":"CHROMOSOME 3pter-p25 DELETION SYNDROME","url":"https://www.omim.org/entry/613792"},{"mim_id":"607416","title":"CELL ADHESION MOLECULE L1-LIKE; CHL1","url":"https://www.omim.org/entry/607416"},{"mim_id":"601151","title":"DEAD/H-BOX HELICASE 12, PSEUDOGENE; DDX12P","url":"https://www.omim.org/entry/601151"},{"mim_id":"601150","title":"DEAD/H-BOX HELICASE 11; DDX11","url":"https://www.omim.org/entry/601150"},{"mim_id":"600816","title":"HEAT-SHOCK 70-KD PROTEIN 8; HSPA8","url":"https://www.omim.org/entry/600816"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"","locations":[],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in many","driving_tissues":[{"tissue":"brain","ntpm":62.8},{"tissue":"ovary","ntpm":31.9}],"url":"https://www.proteinatlas.org/search/CHL1"},"hgnc":{"alias_symbol":["CALL","L1CAM2","FLJ44930","MGC132578"],"prev_symbol":[]},"alphafold":{"accession":"Q96FC9","domains":[{"cath_id":"1.10.275.40","chopping":"410-519_560-603","consensus_level":"high","plddt":87.1852,"start":410,"end":603},{"cath_id":"3.40.50,3.40.50","chopping":"656-797","consensus_level":"high","plddt":87.7789,"start":656,"end":797}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q96FC9","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q96FC9-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q96FC9-F1-predicted_aligned_error_v6.png","plddt_mean":71.31},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=CHL1","jax_strain_url":"https://www.jax.org/strain/search?query=CHL1"},"sequence":{"accession":"Q96FC9","fasta_url":"https://rest.uniprot.org/uniprotkb/Q96FC9.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q96FC9/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q96FC9"}},"corpus_meta":[{"pmid":"21653522","id":"PMC_21653522","title":"The 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The BACE1 cleavage site on CHL1 was determined by mass spectrometry to be between Gln(1061) and Asp(1062) in the membrane-proximal region.\",\n      \"method\": \"Quantitative proteomics of neuronal secretome after BACE1 inhibition; genetic BACE1 knockout mice; pharmacological BACE1 inhibition in mice and cell cultures; mass spectrometry for cleavage site mapping\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — multiple orthogonal methods (proteomics, genetic KO, pharmacological inhibition, MS cleavage site mapping), replicated across two independent papers (PMID 22692213, 22988240)\",\n      \"pmids\": [\"22692213\", \"22988240\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"BACE1 deficiency in mice produces axon guidance defects (shortened and disorganized infrapyramidal bundle of hippocampal mossy fibers; olfactory sensory neuron projection defects) that are strikingly similar to those in CHL1-deficient mice, establishing that these BACE1-/- phenotypes result from abrogated BACE1 processing of CHL1. BACE1 and CHL1 co-localize in hippocampal mossy fiber terminals, olfactory sensory neuron axons, and growth cones of primary hippocampal neurons.\",\n      \"method\": \"BACE1 knockout mouse phenotypic analysis; CHL1-/- mouse comparison; immunohistochemistry and co-localization; biochemical processing assays in hippocampus and olfactory bulb\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic epistasis via KO mouse comparison, co-localization, in vivo biochemical substrate validation; replicated across two papers\",\n      \"pmids\": [\"22988240\", \"22692213\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"CHL1 ectodomain shedding is performed by the metalloprotease-disintegrin ADAM8, which cleaves a CHL1-Fc fusion protein in vitro at two sites in fibronectin domains II (125 kDa fragment) and V (165 kDa fragment). Cleavage was inhibited by the metalloprotease inhibitor batimastat, was not observed with catalytically inactive ADAM8 (E330Q mutant), and was absent in brain extracts of ADAM8-deficient mice. Soluble CHL1 processed by ADAM8 promoted neurite outgrowth and suppressed neuronal cell death; these effects were not observed with inactive ADAM8, ADAM10, or ADAM17.\",\n      \"method\": \"In vitro cleavage assay with CHL1-Fc fusion protein; site-directed mutagenesis of ADAM8 active site; ADAM8-deficient mouse brain extracts; cell transfection; co-culture with cerebellar granule neurons; neurite outgrowth and cell death assays\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — in vitro reconstitution with mutagenesis, genetic KO validation in vivo, multiple functional readouts in one rigorous study\",\n      \"pmids\": [\"14761956\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"The intracellular domain of CHL1 binds to the clathrin-uncoating ATPase Hsc70. CHL1 functions as a synaptic targeting cue for Hsc70; CHL1 deficiency or disruption of the CHL1/Hsc70 complex reduces Hsc70 targeting to synaptic membranes and vesicles, causes accumulation of abnormally high levels of clathrin-coated synaptic vesicles with reduced ability to release clathrin, and impairs activity-dependent clathrin-coated vesicle generation and FM dye uptake/release, revealing a role for CHL1 in clathrin-dependent synaptic vesicle recycling.\",\n      \"method\": \"Yeast two-hybrid / binding partner identification; CHL1 gene ablation in mice; biochemical fractionation; electron microscopy; FM dye uptake/release assays in synaptic boutons\",\n      \"journal\": \"Neuron\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal binding assay, genetic KO with multiple orthogonal functional readouts (fractionation, EM, FM dye assay) in a single rigorous study\",\n      \"pmids\": [\"17178404\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"CHL1 recruits ezrin (an ERM family member) to the plasma membrane through a membrane-proximal cytoplasmic motif (RGGKYSV). This CHL1/ERM interaction is required for Sema3A-induced growth cone collapse, CHL1-dependent neurite outgrowth and branching in cortical neurons, haptotactic cell migration, and cellular adhesion to fibronectin.\",\n      \"method\": \"Cytofluorescence recruitment assay; deletion and point mutagenesis of cytoplasmic domain; Sema3A growth cone collapse assay; neurite outgrowth and branching assay; cell migration and adhesion assay in cortical embryonic neurons\",\n      \"journal\": \"Journal of neurochemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — mutagenesis of specific motif combined with multiple functional assays in a single study; single lab\",\n      \"pmids\": [\"17995939\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"CHL1 directly associates with NB-3 (a member of the F3/contactin family) and enhances NB-3 cell surface expression. CHL1 and NB-3 both interact with protein tyrosine phosphatase alpha (PTPα) and regulate its activity. Loss of CHL1, NB-3, or PTPα leads to aberrant/misoriented apical dendrite projections of deep-layer pyramidal neurons in the visual cortex, indicating a CHL1–NB-3–PTPα signaling complex regulates apical dendrite orientation.\",\n      \"method\": \"Co-immunoprecipitation; cell surface expression assays; PTPα activity assay; CHL1-/-, NB-3-/-, and PTPα-/- mouse analysis; confocal microscopy of cortical neurons\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal co-IP, enzyme activity assay, multiple KO mouse lines with defined cellular phenotype\",\n      \"pmids\": [\"18046458\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"CHL1 associates selectively with EphA7 (whereas L1 associates with EphA3, EphA4, and EphA7), as shown by co-immunoprecipitation. L1 and CHL1 cooperate in repellent responses to EphrinA5 for thalamic axon guidance; double CHL1-/-/L1-/y mutant mice show a striking posterior shift of motor thalamic axons to visual cortex not seen in single mutants, demonstrating epistatic cooperation between CHL1 and L1 in thalamocortical targeting.\",\n      \"method\": \"Co-immunoprecipitation; double-mutant mouse generation and analysis; growth cone collapse assays with EphrinA5; immunofluorescence colocalization\",\n      \"journal\": \"Cerebral cortex\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal co-IP, genetic epistasis via double KO mice, growth cone functional assay; multiple orthogonal approaches\",\n      \"pmids\": [\"20576928\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"CHL1 interacts with vitronectin and plasminogen activator inhibitor-2 (PAI-2) as novel extracellular binding partners. CHL1-induced cerebellar neurite outgrowth and neuronal migration depend on vitronectin-mediated integrin signaling (involving an RGD motif in CHL1) and on PAI-2/uPA/uPA receptor/integrin pathways. At earlier postnatal stages, homophilic CHL1-CHL1 trans-interactions regulate neuronal progenitor differentiation, whereas heterophilic interactions with vitronectin and the plasminogen activator system regulate neuritogenesis and migration at later stages.\",\n      \"method\": \"Co-immunoprecipitation / colocalization; function-blocking antibodies against vitronectin, PAI-2, uPA, uPA receptor, integrins; CHL1-derived RGD peptide inhibition; cerebellar granule cell migration and neurite outgrowth assays; CHL1-/- mouse comparison\",\n      \"journal\": \"The Journal of neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — co-IP, peptide inhibition, antibody blocking, multiple functional assays; single lab but multiple orthogonal methods\",\n      \"pmids\": [\"25355214\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"CHL1-Fc fusion protein (extracellular domain of CHL1 fused to human IgG Fc) significantly enhanced survival of cerebellar granule neurons and hippocampal neurons undergoing apoptosis in serum-free culture (~45% increase), both in soluble form and as substrate. Bcl-2 protein levels in cerebellar granule neurons were increased by L1-Fc treatment, implicating Bcl-2 as an intracellular mediator.\",\n      \"method\": \"Neuronal apoptosis assay in serum-free medium; CHL1-Fc fusion protein treatment; Western blot for Bcl-2 and c-Jun\",\n      \"journal\": \"Journal of neurobiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — defined functional assay with fusion protein, single lab, single method for Bcl-2 downstream pathway\",\n      \"pmids\": [\"10022583\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"CHL1-Fc fusion protein promotes survival of purified embryonic motoneurons at picomolar concentrations (similar to L1-Fc). CHL1-induced motoneuron survival is completely inhibited by LY294002 (PI3K inhibitor) and PD98059 (MEK inhibitor), indicating that both PI3K and MEK/ERK pathways are required for CHL1-mediated survival signaling.\",\n      \"method\": \"Purified motoneuron survival assay; pharmacological inhibition of PI3K (LY294002) and MEK (PD98059); dose-response analysis with CHL1-Fc fusion protein\",\n      \"journal\": \"Journal of neuroscience research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — functional assay with defined pharmacological pathway dissection; single lab, single set of experiments\",\n      \"pmids\": [\"15880726\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"CHL1 is localized to apical Bergmann glial (BG) fibers and stellate cells during cerebellar development. In CHL1-/- mice, stellate axons deviate from BG fibers and show aberrant branching and orientation; synapse formation between aberrant stellate axons and Purkinje dendrites is reduced and cannot be maintained, leading to progressive atrophy of axon terminals. This establishes CHL1 as a molecular signal on BG fibers that organizes GABAergic stellate axon arbors and directs their dendritic innervation.\",\n      \"method\": \"GFP BAC transgenic reporter mice; CHL1-/- mouse analysis; immunofluorescence localization; electron microscopy of synapses; confocal microscopy of axon morphology\",\n      \"journal\": \"PLoS biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic KO with multiple quantitative morphological readouts, direct localization with functional consequence, rigorous single study\",\n      \"pmids\": [\"18447583\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"CHL1 upregulation in GFAP-positive reactive astrocytes (glial scar) after spinal cord injury restricts axonal growth and remodeling. This upregulation is induced by basic FGF (bFGF) and is abolished by inhibitors of FGF receptor-dependent ERK, CaMKII, and PI3K signaling pathways. Homophilic CHL1-CHL1 interactions between neurons and astrocytes mediate reduced neurite outgrowth. CHL1-/- mice show improved functional recovery after spinal cord injury compared to wild-type, associated with enhanced monoaminergic reinnervation.\",\n      \"method\": \"CHL1-/- mouse spinal cord injury model; locomotor rating and video analysis; immunohistochemistry; primary astrocyte cultures with bFGF stimulation; pharmacological inhibitor studies; heterogenotypic neuron-astrocyte cocultures\",\n      \"journal\": \"The Journal of neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic KO functional rescue, defined signaling pathway via pharmacological inhibition, in vitro coculture mechanistic validation; multiple orthogonal approaches\",\n      \"pmids\": [\"17611275\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"CHL1 deficiency enhances proliferation and self-renewal of neural progenitor cells (NPCs) and promotes neuronal differentiation. CHL1 negatively regulates NPC proliferation through activation of the ERK1/2 MAPK pathway; pharmacological inhibition of ERK1/2 eliminates the increased proliferation seen in CHL1-/- NPCs.\",\n      \"method\": \"CHL1-/- mouse brain analysis (BrdU incorporation in SVZ, Tuj1 staining in cortical plate); primary NPC cultures from CHL1-/- and wild-type mice; ERK1/2 MAPK pharmacological inhibition; proliferation and differentiation assays\",\n      \"journal\": \"Molecular and cellular neurosciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic KO with in vivo and in vitro assays, pharmacological pathway validation; single lab, two orthogonal approaches\",\n      \"pmids\": [\"20933598\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"Neuritogenesis-promoting ligand-dependent clustering of CHL1 induces palmitoylation and lipid raft-dependent endocytosis of CHL1. βII spectrin was identified as a binding partner of CHL1; partial disruption of the CHL1-βII spectrin complex accompanies CHL1 endocytosis. Mutation of cysteine 1102 within the CHL1 intracellular domain reduces lipid raft association and endocytosis. CHL1-dependent neurite outgrowth requires lipid raft assembly, voltage-dependent Ca2+ channels, and the CHL1 Cys-1102 palmitoylation site.\",\n      \"method\": \"Co-immunoprecipitation of CHL1 and βII spectrin; lipid raft fractionation; site-directed mutagenesis (C1102); pharmacological disruption of lipid rafts; nifedipine (L-type Ca2+ channel inhibitor) treatment; endocytosis assays; neurite outgrowth assays\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Moderate — mutagenesis of specific residue, co-IP, biochemical fractionation, pharmacological inhibition, functional neurite assay; multiple orthogonal methods in a single study\",\n      \"pmids\": [\"23144456\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"CHL1 cooperates with PAK1-3 kinases in regulating morphological development of the leading process/apical dendrite of embryonic cortical neurons. Dominant-negative PAK inhibition in CHL1-/- mouse cortex caused extreme branching in the intermediate zone and cortical plate, far exceeding effects in either mutant alone, consistent with CHL1 and PAK1-3 acting in independent but cooperating pathways.\",\n      \"method\": \"In utero electroporation of dominant-negative PAK1 AID construct into CHL1-/- and wild-type embryos; confocal microscopy of GFP-labeled neurons in slice culture; quantitative morphological analysis\",\n      \"journal\": \"Neuroscience\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — genetic epistasis via dominant-negative in KO background; single lab, single experimental approach\",\n      \"pmids\": [\"19819308\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"CHL1 binds to a peptide stretch in the third intracellular loop of the serotonin 2c (5-HT2c) receptor through its own intracellular domain. CHL1 regulates 5-HT2c receptor phosphorylation and the receptor's association with PTEN and β-arrestin 2. CHL1-deficient mice show 5-HT2c-receptor-related reduction in locomotor activity and reactivity to novelty. CHL1 modulates signaling pathways triggered by constitutively active 5-HT2c receptor isoforms. CHL1 and 5-HT2c receptor co-localize in striatal and hippocampal GABAergic neurons.\",\n      \"method\": \"Co-immunoprecipitation of CHL1 with 5-HT2c receptor; peptide binding assay; CHL1-/- mouse behavioral analysis; immunofluorescence colocalization; phosphorylation and co-IP assays with PTEN and β-arrestin 2\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — co-IP, genetic KO behavioral phenotype, signaling assays; single lab, multiple orthogonal methods\",\n      \"pmids\": [\"26527397\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"CHL1 expression in astrocytes is upregulated via a PI3K/PKCδ/ERK1/2/NF-κB signaling cascade. LPS-induced astrogliosis triggers PKCδ translocation to the membrane, ERK1/2 phosphorylation downstream of PKCδ, and NF-κB nuclear translocation, all of which are required for upregulation of CHL1 protein expression. The NO-guanylate cyclase-cGMP pathway, by contrast, does not mediate this upregulation. LPS-induced CHL1 upregulation in reactive astrocytes inhibits hippocampal neurite outgrowth in coculture.\",\n      \"method\": \"Primary mouse astrocyte cultures; pharmacological inhibition of PI3K, PKCδ, ERK1/2, NF-κB; PKCδ genetic knockdown; subcellular fractionation; Western blot; neurite outgrowth coculture assay\",\n      \"journal\": \"Glia\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — pharmacological and genetic dissection of signaling pathway, functional coculture assay; single lab, multiple inhibitors tested\",\n      \"pmids\": [\"19672967\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"CHL1 suppresses tumor growth and metastasis in nasopharyngeal carcinoma by directly interacting with Integrin-β1 and linking to Merlin, leading to inactivation of the integrin β1-AKT signaling pathway. CHL1 also induces mesenchymal-epithelial transition (MET) and inactivates RhoA/Rac1/Cdc42 signaling, inhibiting stress fiber, lamellipodia, and filopodia formation.\",\n      \"method\": \"Co-immunoprecipitation of CHL1 with Integrin-β1 and Merlin; ectopic CHL1 expression in NPC cells; colony formation, cell motility, and invasion assays; Western blot for EMT markers and Rho GTPase pathway; in vivo xenograft experiments\",\n      \"journal\": \"International journal of biological sciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct Co-IP, loss and gain of function assays, pathway analysis; single lab, multiple assays\",\n      \"pmids\": [\"31523184\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"CHL1 acts as a tumor suppressor in neuroblastoma: overexpression of CHL1 induces neurite-like outgrowth and markers of neuronal differentiation, inhibits anchorage-independent colony formation, and suppresses tumor xenograft growth. Knockdown of CHL1 activates Rho GTPases, enhances proliferation and migration, and accelerates orthotopic xenograft growth. CHL1 functions through inhibition of MAPK and Akt pathways.\",\n      \"method\": \"Inducible CHL1 overexpression and knockdown cell models; neurite outgrowth assay; colony formation; Transwell migration; orthotopic xenograft mouse model; Western blot for MAPK/Akt pathway components; Rho GTPase pull-down assay\",\n      \"journal\": \"Oncotarget\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — bidirectional loss- and gain-of-function with pathway analysis and in vivo validation; single lab\",\n      \"pmids\": [\"29899830\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"CHL1 mediates axonal growth promotion of midbrain dopamine (mDA) neurons through trans-heterophilic interactions. The growth-promoting effect of ALCAM substrate on mDA neurons was abolished by neutralizing antibodies against Chl1 (as well as Nrp1 and L1cam), and CHL1 modulates the response of mDA neurites to soluble semaphorins (abolishing Sema3A growth promotion; inducing branching in the presence of Sema3C).\",\n      \"method\": \"Primary midbrain cultures on ALCAM substrate; function-blocking antibodies against CHL1, Nrp1, L1cam; neurite growth and branching assays; semaphorin stimulation experiments\",\n      \"journal\": \"The Journal of neuroscience\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — antibody neutralization functional assay; single lab, single method per interaction\",\n      \"pmids\": [\"31300520\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"CHL1 mediates homophilic CHL1-CHL1 interactions that regulate VM dopaminergic progenitor migration, differentiation, axonal extension, and axonal repulsion (selectively in DA neurons). Both substrate-bound and soluble forms of CHL1 have distinct functional roles in DA neuron development.\",\n      \"method\": \"Temporal and spatial CHL1 expression mapping in VM; primary VM DA neuron cultures on CHL1 substrates; function-blocking antibodies against CHL1; neurite extension and repulsion assays; DA progenitor migration assays\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — functional assays with antibody blocking and substrate, single lab; homophilic interaction inferred from blocking experiments\",\n      \"pmids\": [\"28839197\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"CHL1 (close homolog of L1) is a transmembrane immunoglobulin superfamily cell adhesion molecule that functions in the nervous system through multiple mechanisms: its extracellular domain is shed by ADAM8 and cleaved by BACE1 (at Gln1061-Asp1062) to release bioactive fragments that promote neurite outgrowth and neuronal survival; its intracellular domain binds Hsc70 to target it to synaptic membranes and regulate clathrin-coated synaptic vesicle uncoating and recycling, and recruits ERM proteins via a RGGKYSV motif to mediate Sema3A-induced growth cone collapse and neurite outgrowth; CHL1 engages heterophilic partners including NB-3, PTPα, vitronectin, integrins, PAI-2, Integrin-β1, Merlin, and the 5-HT2c receptor to regulate apical dendrite orientation, neuronal migration, cell survival, and signal transduction; and homophilic CHL1-CHL1 interactions guide stellate axon organization along Bergmann glial fibers and direct dopaminergic axon pathfinding, while reactive-astrocyte upregulation of CHL1 via PI3K/PKCδ/ERK/NF-κB signaling creates a glial scar component that restricts axonal regeneration after injury.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"CHL1 (close homolog of L1) is a transmembrane immunoglobulin-superfamily cell adhesion molecule that organizes neuronal migration, axon guidance, dendrite orientation, and synaptic function through both proteolytically released ectodomain fragments and intracellular signaling complexes [#1, #10]. Its extracellular domain is processed by two distinct proteases: ADAM8 sheds the ectodomain in the fibronectin domains, generating soluble fragments that promote neurite outgrowth and suppress neuronal death [#2], while BACE1 cleaves CHL1 in vivo between Gln1061 and Asp1062, and loss of this processing reproduces CHL1-null axon guidance defects in hippocampal mossy fibers and olfactory projections, placing CHL1 downstream of BACE1 in axon targeting [#0, #1]. The intracellular domain couples CHL1 to membrane and cytoskeletal machinery: it binds the clathrin-uncoating ATPase Hsc70 to target it to synapses and drive clathrin-coated synaptic vesicle recycling [#3], recruits the ERM protein ezrin via an RGGKYSV motif to mediate Sema3A-induced growth cone collapse and neurite outgrowth [#4], and associates with \\u03b2II spectrin, with ligand-induced clustering triggering Cys1102 palmitoylation and lipid-raft-dependent endocytosis required for neurite outgrowth [#13]. CHL1 acts through a network of heterophilic partners\\u2014NB-3/PTP\\u03b1 to orient apical dendrites, EphA7 (cooperating with L1) for thalamocortical EphrinA5 responses, vitronectin and the PAI-2/uPA/integrin system for migration and neuritogenesis, and the 5-HT2c receptor to modulate its phosphorylation and behavioral output\\u2014as well as homophilic CHL1-CHL1 interactions that organize cerebellar stellate axons along Bergmann glial fibers and guide dopaminergic axon pathfinding [#5, #6, #7, #15, #10, #20]. Survival and proliferative signaling proceed through PI3K and MEK/ERK pathways, with CHL1 negatively regulating neural progenitor proliferation via ERK1/2 [#9, #12]. After CNS injury, reactive astrocytes upregulate CHL1 through PI3K/PKC\\u03b4/ERK/NF-\\u03baB signaling, creating a glial-scar component that restricts axonal regeneration [#11, #16]. In epithelial tumors CHL1 acts as a suppressor, binding Integrin-\\u03b21 and Merlin to inactivate integrin-\\u03b21/AKT and Rho-family GTPase signaling [#17, #18].\",\n  \"teleology\": [\n    {\n      \"year\": 1999,\n      \"claim\": \"Established that the CHL1 ectodomain is not merely adhesive but actively pro-survival, raising the question of how a cell adhesion molecule signals neuronal survival.\",\n      \"evidence\": \"CHL1-Fc fusion protein rescue of cerebellar granule and hippocampal neuron apoptosis in serum-free culture, with Bcl-2 induction by Western blot\",\n      \"pmids\": [\"10022583\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Receptor mediating the survival effect not identified\", \"Bcl-2 link is a single-method correlation\"]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"Identified the protease that converts membrane CHL1 into the bioactive soluble form, defining ADAM8 as the ectodomain sheddase and linking cleavage to outgrowth and survival.\",\n      \"evidence\": \"In vitro cleavage of CHL1-Fc, ADAM8 active-site mutagenesis, ADAM8-deficient brain extracts, and neurite/cell-death assays with cerebellar neurons\",\n      \"pmids\": [\"14761956\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Physiological stimulus triggering ADAM8 shedding unknown\", \"Receptor for shed CHL1 fragments not defined\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Dissected the intracellular signaling required for CHL1-mediated survival, showing dependence on PI3K and MEK/ERK.\",\n      \"evidence\": \"Picomolar CHL1-Fc rescue of purified motoneurons blocked by LY294002 and PD98059\",\n      \"pmids\": [\"15880726\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Upstream receptor coupling CHL1 to PI3K/ERK not identified\", \"Single pharmacological experiment set\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Defined an intracellular function for CHL1 by identifying Hsc70 binding, establishing CHL1 as a synaptic targeting cue for clathrin-coated vesicle recycling.\",\n      \"evidence\": \"Binding-partner identification, CHL1 knockout mice, biochemical fractionation, EM, and FM dye uptake/release at synaptic boutons\",\n      \"pmids\": [\"17178404\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of CHL1-Hsc70 binding not resolved\", \"Regulation of the interaction by activity unclear\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Mapped CHL1's cytoplasmic signaling to ERM proteins and established the heterophilic and homophilic adhesion partners coordinating dendrite orientation and axon organization.\",\n      \"evidence\": \"Cytoplasmic-domain mutagenesis defining the RGGKYSV ezrin-recruitment motif with Sema3A/outgrowth assays; co-IP of NB-3 and PTP\\u03b1 with multiple KO mouse lines; Bergmann glial localization with stellate axon analysis in CHL1-/- mice\",\n      \"pmids\": [\"17995939\", \"18046458\", \"18447583\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How ERM recruitment links to specific cytoskeletal outputs not fully defined\", \"PTP\\u03b1 substrates downstream of the complex unknown\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Revealed an injury-context role: reactive astrocytes upregulate CHL1 to restrict axon regeneration via homophilic interactions, with consequences for functional recovery.\",\n      \"evidence\": \"CHL1-/- spinal cord injury model with locomotor scoring, bFGF-stimulated astrocyte cultures with FGFR/ERK/CaMKII/PI3K inhibitors, and neuron-astrocyte cocultures\",\n      \"pmids\": [\"17611275\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Neuronal receptor mediating growth inhibition not identified beyond homophilic CHL1\", \"Relative contribution of glial scar vs other inhibitors unquantified\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Showed CHL1 cooperates with PAK1-3 kinases in shaping the leading process/apical dendrite, indicating parallel cooperating cytoskeletal pathways.\",\n      \"evidence\": \"In utero electroporation of dominant-negative PAK into CHL1-/- cortex with quantitative morphology\",\n      \"pmids\": [\"19819308\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether CHL1 and PAK physically interact untested\", \"Single experimental approach\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Extended CHL1's repertoire to thalamocortical guidance via selective EphA7 association and epistatic cooperation with L1.\",\n      \"evidence\": \"Co-IP of CHL1 with EphA7 and double CHL1-/-/L1-/y mutant mice with EphrinA5 growth cone collapse assays\",\n      \"pmids\": [\"20576928\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Functional consequence of CHL1-EphA7 binding on Eph signaling not measured\", \"Mechanism of CHL1/L1 cooperation unresolved\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Defined CHL1 as a negative regulator of neural progenitor proliferation and the astrocytic signaling cascade controlling its own expression.\",\n      \"evidence\": \"CHL1-/- NPC proliferation/differentiation assays with ERK1/2 inhibition; astrocyte cultures dissecting PI3K/PKC\\u03b4/ERK/NF-\\u03baB control of CHL1 upregulation\",\n      \"pmids\": [\"20933598\", \"19672967\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"How CHL1 engages ERK1/2 in progenitors mechanistically unclear\", \"Transcription factors directly driving the CHL1 gene not identified\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Identified BACE1 as a second, physiological protease cleaving CHL1 and connected this processing to specific axon guidance phenotypes.\",\n      \"evidence\": \"Neuronal secretome proteomics, BACE1 KO mice, pharmacological BACE1 inhibition, MS cleavage-site mapping (Gln1061-Asp1062), and phenotypic comparison of BACE1-/- and CHL1-/- mice\",\n      \"pmids\": [\"22692213\", \"22988240\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Fate and receptor of the BACE1-generated fragment undefined\", \"Relationship between ADAM8 and BACE1 cleavage not reconciled\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Linked CHL1 ligand-induced clustering to palmitoylation-dependent endocytosis via \\u03b2II spectrin, providing a trafficking mechanism for outgrowth signaling.\",\n      \"evidence\": \"Co-IP of CHL1 with \\u03b2II spectrin, lipid raft fractionation, C1102 mutagenesis, raft disruption, nifedipine treatment, and neurite outgrowth assays\",\n      \"pmids\": [\"23144456\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Palmitoyltransferase acting on Cys1102 not identified\", \"How endocytosis converts to outgrowth signaling unresolved\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Resolved stage-specific use of homophilic vs heterophilic adhesion, adding vitronectin and the PAI-2/uPA/integrin system as extracellular partners for migration and neuritogenesis.\",\n      \"evidence\": \"Co-IP/colocalization, function-blocking antibodies, CHL1 RGD-peptide inhibition, and cerebellar migration/outgrowth assays with CHL1-/- comparison\",\n      \"pmids\": [\"25355214\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Which integrin heterodimers CHL1 engages not specified\", \"Direct vs indirect vitronectin binding not structurally defined\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Extended CHL1 to receptor signaling regulation by showing it binds the 5-HT2c receptor and controls its phosphorylation and effector coupling, with behavioral consequences.\",\n      \"evidence\": \"Co-IP and peptide binding with the 5-HT2c third intracellular loop, CHL1-/- behavior, and phosphorylation/PTEN/\\u03b2-arrestin 2 assays\",\n      \"pmids\": [\"26527397\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Stoichiometry and structural interface of the interaction unknown\", \"Causal chain from receptor modulation to behavior incomplete\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Demonstrated cell-type-selective homophilic CHL1 signaling in dopaminergic neuron development, governing migration, extension, and repulsion.\",\n      \"evidence\": \"VM expression mapping, primary DA neuron cultures on CHL1 substrates, and function-blocking antibody assays\",\n      \"pmids\": [\"28839197\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Homophilic interaction inferred from blocking rather than direct binding\", \"Downstream signaling in DA neurons not defined\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Established a tumor-suppressor role for CHL1 in neuroblastoma acting through MAPK/Akt and Rho-GTPase inhibition.\",\n      \"evidence\": \"Inducible overexpression/knockdown, neurite/colony/migration assays, orthotopic xenografts, and pathway Western blots with Rho pull-downs\",\n      \"pmids\": [\"29899830\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Membrane partner transducing the suppressor effect not identified\", \"Single-lab tumor model\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Identified the Integrin-\\u03b21/Merlin axis as the mechanism of CHL1 tumor suppression in epithelial cancer and added CHL1 trans-heterophilic guidance of dopaminergic axons.\",\n      \"evidence\": \"Co-IP of CHL1 with Integrin-\\u03b21 and Merlin plus xenograft and EMT/Rho assays in NPC; ALCAM-substrate mDA cultures with CHL1/Nrp1/L1cam neutralizing antibodies and semaphorin assays\",\n      \"pmids\": [\"31523184\", \"31300520\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether the same Integrin-\\u03b21/Merlin axis operates in neurons untested\", \"Direct binding partners for the ALCAM/semaphorin responses not biochemically resolved\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"The identity of the neuronal receptor(s) transducing signals from shed/soluble CHL1 fragments, and how ADAM8 and BACE1 cleavage events are coordinated, remain unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No receptor identified for ADAM8- or BACE1-released CHL1 ectodomain fragments\", \"Structural basis of most intracellular and extracellular CHL1 interactions undetermined\", \"Integration of the multiple parallel signaling pathways (ERM, Hsc70, spectrin, integrin) into a unified model lacking\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0098631\", \"supporting_discovery_ids\": [10, 20, 7, 11]},\n      {\"term_id\": \"GO:0060089\", \"supporting_discovery_ids\": [5, 6, 15, 19]},\n      {\"term_id\": \"GO:0008092\", \"supporting_discovery_ids\": [4, 13]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [3, 5, 15]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [4, 13, 5]},\n      {\"term_id\": \"GO:0031410\", \"supporting_discovery_ids\": [3, 13]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-1266738\", \"supporting_discovery_ids\": [1, 10, 7, 20]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [5, 9, 17, 15]},\n      {\"term_id\": \"R-HSA-5653656\", \"supporting_discovery_ids\": [3, 13]},\n      {\"term_id\": \"R-HSA-112316\", \"supporting_discovery_ids\": [3, 10, 15]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [17, 18]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"BACE1\", \"ADAM8\", \"HSPA8\", \"EZR\", \"NB-3\", \"PTPRA\", \"EPHA7\", \"ITGB1\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"tie","faith_supported":7,"faith_total":7,"faith_pct":100.0}}