{"gene":"BOC","run_date":"2026-04-28T17:12:38","timeline":{"discoveries":[{"year":2002,"finding":"BOC forms cis complexes with CDO via both their ectodomains and intracellular domains, and positively regulates myogenic differentiation; a soluble BOC ectodomain fusion protein promotes myogenesis, indicating the intracellular region is dispensable, but a dominant-negative CDO blocks BOC's pro-myogenic effects, placing BOC dependent on CDO for myogenic activity.","method":"Co-immunoprecipitation, soluble fusion protein rescue assay, dominant-negative CDO overexpression, myoblast differentiation assay","journal":"The EMBO journal","confidence":"High","confidence_rationale":"Tier 2 — reciprocal co-IP plus multiple functional readouts (soluble ectodomain, dominant-negative epistasis) in single study","pmids":["11782431"],"is_preprint":false},{"year":2006,"finding":"BOC and CDO bind Sonic Hedgehog (Shh) through a high-affinity interaction with a specific fibronectin repeat, and ectopic expression of BOC promotes Shh-dependent, cell-autonomous ventral cell fates while producing non-cell-autonomous ventral expansion consistent with Shh sequestration; BOC is a target and component of the Hedgehog signaling feedback network.","method":"Binding assays (fibronectin repeat mutants), ectopic expression in neural tube, genetic loss-of-function in mice","journal":"Developmental cell","confidence":"High","confidence_rationale":"Tier 2 — domain-mapping binding assay plus in vivo gain/loss-of-function with defined phenotypic readout","pmids":["16647304"],"is_preprint":false},{"year":2006,"finding":"BOC functions as a receptor for Shh in commissural axon guidance: Boc is expressed by commissural neurons, targeted disruption in mice causes commissural axon misguidance toward the floor plate, and RNAi knockdown of Boc impairs the ability of commissural axons to turn toward an ectopic Shh source in vitro.","method":"In vitro growth-cone turning assay, RNAi knockdown, mouse genetic knockout with axon tracing","journal":"Nature","confidence":"High","confidence_rationale":"Tier 2 — in vitro turning assay plus in vivo knockout with specific axon-guidance phenotype, replicated by two complementary approaches","pmids":["17086203"],"is_preprint":false},{"year":2010,"finding":"BOC (Shh receptor) is enriched in ipsilateral retinal ganglion cells (RGCs); Boc-positive RGC axons retract in vitro in response to Shh and this retraction is lost in Boc mutant RGCs; in vivo, Boc is required for normal segregation of ipsilateral axons at the optic chiasm, and ectopic Boc expression in contralateral RGCs prevents their axons from crossing the chiasm.","method":"In vitro axon retraction assay, Boc mutant mouse analysis, in vivo electroporation of Boc into contralateral RGCs","journal":"The Journal of neuroscience","confidence":"High","confidence_rationale":"Tier 2 — in vitro assay plus in vivo gain- and loss-of-function with specific axon-guidance phenotypes","pmids":["20053908"],"is_preprint":false},{"year":2010,"finding":"X-ray crystal structures of Sonic, Indian, and Desert Hedgehog proteins complexed with active domains of CDO and BOC reveal that all mammalian Hh proteins bind CDO and BOC in the same manner, and that Hh–CDO interactions are weakened at low pH; CDO and BOC use non-orthologous domains compared with Drosophila Ihog.","method":"X-ray crystallography, biochemical binding assays","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 — crystal structures of Hh/BOC complexes with biochemical validation","pmids":["20519495"],"is_preprint":false},{"year":2011,"finding":"GAS1, CDO, and BOC play overlapping and collectively essential roles in Hedgehog-mediated ventral neural patterning; genetic loss-of-function demonstrates an obligatory requirement for these three co-receptors in HH pathway activity in multiple tissues, including early cell fate specification and later motor neuron progenitor maintenance.","method":"Compound mouse genetic knockouts (single, double, triple mutants), neural patterning assays","journal":"Developmental cell","confidence":"High","confidence_rationale":"Tier 2 — multi-allele genetic epistasis across multiple tissues, replicated in companion paper","pmids":["21664576"],"is_preprint":false},{"year":2011,"finding":"Boc (with Cdon and Gas1) forms distinct receptor complexes with Ptch1; in cerebellar granule neuron progenitors, Boc, Cdon, and Gas1 are absolutely required for Hh-dependent proliferation, and a mutated Hh ligand that binds Ptch1 but not Boc/Cdon/Gas1 cannot activate Hh signaling, demonstrating that ligand binding to co-receptors is obligatory for signaling.","method":"Co-immunoprecipitation (Boc–Ptch1 complex), Hh binding mutant ligand, genetic knockout of all three co-receptors in CGNP proliferation assay","journal":"Developmental cell","confidence":"High","confidence_rationale":"Tier 1–2 — reconstitution of receptor complex plus mutant ligand biochemistry plus genetic epistasis","pmids":["21664577"],"is_preprint":false},{"year":2010,"finding":"Boc modifies the holoprosencephaly (HPE) spectrum of Cdo mutant mice: Boc single mutants have no HPE, but Cdo;Boc double mutants display lobar HPE with craniofacial anomalies and defects in Shh target gene expression in the developing forebrain, identifying BOC as a silent HPE modifier gene.","method":"Mouse double knockout genetic epistasis, Shh target gene expression analysis","journal":"Disease models & mechanisms","confidence":"High","confidence_rationale":"Tier 2 — clean double-KO epistasis with defined molecular and morphological phenotype","pmids":["21183473"],"is_preprint":false},{"year":2014,"finding":"BOC associates with Ptch1 and promotes Shh-driven granule cell precursor (GCP) proliferation; mechanistically, Boc, through elevated Shh signaling, promotes high levels of DNA damage mediated by CyclinD1, which increases Ptch1 loss-of-heterozygosity and thereby drives medulloblastoma progression.","method":"Boc genetic knockout in medulloblastoma model, CyclinD1 manipulation, LOH analysis, proliferation assays","journal":"Developmental cell","confidence":"High","confidence_rationale":"Tier 2 — genetic KO with defined molecular mechanism (CyclinD1-mediated DNA damage) and LOH readout","pmids":["25263791"],"is_preprint":false},{"year":2015,"finding":"CDON and BOC utilize distinct molecular mechanisms in HH signal transduction: they have separate extracellular motifs required for HH promotion and distinct membrane attachment requirements, despite displaying functional redundancy in ventral neural patterning.","method":"In vivo gain-of-function (chick spinal cord electroporation) with domain deletion and swap mutants","journal":"Developmental biology","confidence":"Medium","confidence_rationale":"Tier 2 — in vivo structure-function with domain mutants, single lab","pmids":["25848697"],"is_preprint":false},{"year":2016,"finding":"BOC interacts with the non-receptor tyrosine kinase ABL through its putative SH2-binding domain and is phosphorylated in an ABL-dependent manner; BOC–ABL interaction is required for JNK activation and BOC-mediated promotion of neuronal differentiation and neurite outgrowth in P19 cells and cortical neural progenitor cells.","method":"Co-immunoprecipitation (BOC–ABL), ABL-binding defective BOC mutants, JNK activation assay, neurite length measurement in Boc−/− NPCs","journal":"Cellular signalling","confidence":"Medium","confidence_rationale":"Tier 2–3 — co-IP plus domain-mutant rescue plus KO phenotype, single lab","pmids":["27871935"],"is_preprint":false},{"year":2019,"finding":"Shh induces Boc internalization into early endosomes; the endocytic adaptor Numb binds to Boc and is required for Boc internalization, Shh-mediated growth-cone turning in vitro, and commissural axon guidance in vivo. Boc binding to Shh is required for Ptch1 internalization; thus, Boc acts as a Shh-dependent endocytic platform gating Ptch1 internalization and Shh signaling in axon guidance.","method":"Endosome fractionation/live imaging of Boc internalization, Co-IP (Boc–Numb), Numb RNAi knockdown, in vitro growth-cone turning, in vivo commissural axon tracing","journal":"Neuron","confidence":"High","confidence_rationale":"Tier 2 — multiple orthogonal methods (biochemical, imaging, in vitro, in vivo) establishing mechanistic model","pmids":["31054872"],"is_preprint":false},{"year":2019,"finding":"The Shh receptor Boc is important for myelination: Boc mutant mice exhibit transient decrease in oligodendroglial cell density, delayed myelination, lower myelin basic protein production, reduced callosal axon caliber, and impaired OPC differentiation during myelin repair, and Boc mutant microglia/macrophages show defective morphological transition in vivo.","method":"Boc knockout mouse analysis, immunostaining for oligodendroglial markers, MBP quantification, myelin repair assay","journal":"Development","confidence":"Medium","confidence_rationale":"Tier 2 — clean genetic KO with multiple cellular phenotype readouts, single lab","pmids":["31048318"],"is_preprint":false},{"year":2020,"finding":"Ptch1/Boc and Ptch2/Gas1 form distinct hetero-complexes that mediate Smo de-repression with different kinetics and through distinct modes of Hedgehog ligand reception; Ptch1/Boc complex mediates primordial germ cell migration in mice.","method":"Compound mouse genetic knockouts, co-immunoprecipitation of Ptch1/Boc and Ptch2/Gas1 complexes, PGC migration assays, phospho-Creb/Src signaling analysis","journal":"Nature communications","confidence":"Medium","confidence_rationale":"Tier 2 — co-IP of distinct complexes plus genetic epistasis with defined cellular phenotype, single lab","pmids":["32332736"],"is_preprint":false},{"year":2020,"finding":"BOC acts as a multi-functional regulator of HH signaling during craniofacial development: Boc deletion results in facial widening correlated with increased HH target gene expression, and Boc deletion in a Gas1-null background partially rescues craniofacial defects of Gas1 single mutants, demonstrating tissue-specific HH-promoting or HH-restraining roles for BOC.","method":"Single and compound mouse genetic knockouts, HH target gene expression analysis, craniofacial morphometry","journal":"Development","confidence":"Medium","confidence_rationale":"Tier 2 — clean genetic epistasis across multiple allele combinations with molecular readout, single lab","pmids":["33060130"],"is_preprint":false},{"year":2021,"finding":"A Dispatched (DISP)–BOC/CDON co-receptor complex functions in Shh ligand-producing cells to promote cytoneme occurrence and facilitate ligand delivery; Myosin 10 promotes vesicular transport of Shh in cytonemes and is required for SHH gradient organization in the neural tube.","method":"Co-immunoprecipitation (DISP–BOC complex), Myo10 genetic knockout mouse neural tube analysis, live-cell imaging of cytonemes, rapid signal-response assay","journal":"eLife","confidence":"Medium","confidence_rationale":"Tier 2 — co-IP of novel complex plus in vivo genetic evidence plus live imaging, single lab","pmids":["33570491"],"is_preprint":false},{"year":2015,"finding":"Mice lacking the HH co-receptor BOC display age-related overweight and excess white adipose tissue; cultured Boc−/− mouse embryo fibroblasts show enhanced adipogenesis and reduced HH pathway target gene expression, placing BOC as a positive regulator of HH signaling that inhibits adipogenesis.","method":"Boc knockout mouse adiposity analysis, in vitro adipogenesis assay in MEFs, HH target gene expression","journal":"Diabetes","confidence":"Medium","confidence_rationale":"Tier 2 — genetic KO with defined metabolic/cellular phenotype and molecular pathway readout, single lab","pmids":["25576054"],"is_preprint":false},{"year":2013,"finding":"Shh/Boc signaling is required for sustained generation of ipsilateral-projecting retinal ganglion cells (iRGCs): in Boc−/− mice, the number of Zic2-positive iRGCs is reduced while Islet2/Shh-positive RGCs increase, indicating Boc is required to sustain Zic2 expression likely by regulating Shh signaling levels from neighboring contralateral RGCs.","method":"Boc knockout mouse analysis, immunostaining for Zic2/Islet2 markers, in vivo electroporation of Shh, Zic2, and Boc, retinal projection analysis","journal":"The Journal of neuroscience","confidence":"Medium","confidence_rationale":"Tier 2 — genetic KO plus gain-of-function electroporation with defined molecular phenotype, single lab","pmids":["23678105"],"is_preprint":false},{"year":2005,"finding":"Zebrafish BOC functions as an axon-guidance molecule for dorsoventrally projecting axon tracts: morpholino knockdown of boc causes selective defects in ventrally projecting axons arising from the presumptive telencephalon.","method":"Antisense morpholino knockdown in zebrafish, axon tract immunostaining","journal":"The Journal of comparative neurology","confidence":"Medium","confidence_rationale":"Tier 2 — morpholino loss-of-function with specific axon-guidance phenotype, single lab","pmids":["15776441"],"is_preprint":false},{"year":2017,"finding":"Missense BOC variants identified in holoprosencephaly patients have either loss- or gain-of-function properties in cell-based SHH signaling assays, confirming BOC as a modifier gene whose variant alleles alter SHH pathway activity.","method":"Cell-based SHH signaling assays with patient-derived BOC variant proteins","journal":"Human mutation","confidence":"Medium","confidence_rationale":"Tier 3 — cell-based functional assay for multiple variants, single lab","pmids":["28677295"],"is_preprint":false},{"year":2019,"finding":"A novel BOC-PLAG1 fusion gene was identified in lipoblastoma, in which the constitutively active BOC promoter drives overexpression of PLAG1, establishing a mechanism for PLAG1 activation in this tumor.","method":"5' RACE, RNA sequencing, qRT-PCR","journal":"Biochemical and biophysical research communications","confidence":"Low","confidence_rationale":"Tier 3 — single case molecular characterization, no functional rescue experiment","pmids":["30857637"],"is_preprint":false}],"current_model":"BOC is a transmembrane Ig/fibronectin superfamily co-receptor that binds Hedgehog ligands (Shh, Ihh, Dhh) through a specific fibronectin repeat, forms complexes with Ptch1 and the co-receptors CDON and GAS1 to collectively promote HH pathway activation, mediates Shh-dependent axon guidance by acting as an endocytic platform (via Numb) for Ptch1 internalization, promotes myogenic and neuronal differentiation through CDO-dependent and ABL/JNK-dependent mechanisms respectively, and has tissue-specific roles that can either promote or restrain HH signaling during neural patterning, craniofacial development, myelination, adipogenesis, and retinal ganglion cell specification."},"narrative":{"teleology":[{"year":2002,"claim":"BOC was identified as a partner of CDO that promotes myogenic differentiation, establishing it as a cell-surface molecule with signaling function in cell fate determination—though its ligand was unknown.","evidence":"Co-immunoprecipitation of BOC–CDO, soluble ectodomain fusion protein and dominant-negative CDO epistasis in myoblast differentiation assays","pmids":["11782431"],"confidence":"High","gaps":["No ligand identified for BOC","Mechanism of CDO-dependent signaling unknown","Intracellular signaling pathways downstream of BOC uncharacterized"]},{"year":2005,"claim":"Zebrafish boc knockdown revealed that BOC functions in axon guidance of ventrally projecting tracts, providing the first evidence it acts in neural circuit wiring rather than solely in myogenesis.","evidence":"Antisense morpholino knockdown in zebrafish with axon tract immunostaining","pmids":["15776441"],"confidence":"Medium","gaps":["Morpholino-only approach lacks genetic confirmation","No ligand identified for axon guidance function","Mammalian relevance not yet shown"]},{"year":2006,"claim":"Two landmark studies established that BOC directly binds Sonic Hedgehog through a fibronectin repeat domain and functions both as a Shh-dependent ventral neural patterning co-receptor and as the receptor mediating Shh-guided commissural axon pathfinding—unifying its ligand identity and its roles in patterning and guidance.","evidence":"Domain-mapping binding assays, ectopic expression in neural tube, Boc knockout mice with commissural axon tracing, in vitro growth-cone turning assay with Boc RNAi","pmids":["16647304","17086203"],"confidence":"High","gaps":["How BOC transduces signal intracellularly unresolved","Relationship between BOC and Ptch1 in receptor complex unknown","Redundancy with CDON and GAS1 not yet genetically dissected"]},{"year":2010,"claim":"Crystal structures of Hedgehog–BOC complexes and functional studies in retinal ganglion cells defined the structural basis of BOC–Hh binding and extended BOC's axon-guidance role to ipsilateral RGC segregation at the optic chiasm, while genetic epistasis with Cdon revealed BOC as a holoprosencephaly modifier.","evidence":"X-ray crystallography of Hh–BOC/CDO complexes, in vitro RGC axon retraction and in vivo gain/loss-of-function at the optic chiasm, Cdo;Boc double-knockout mouse analysis","pmids":["20519495","20053908","21183473"],"confidence":"High","gaps":["No structural information on full receptor complex (BOC–Ptch1–Shh)","Mechanism of intracellular signal transduction from BOC still unknown","Functional distinction between BOC and CDON at molecular level not resolved"]},{"year":2011,"claim":"Compound genetic knockouts demonstrated that BOC, CDON, and GAS1 are collectively obligatory for all Hedgehog pathway activity and form distinct complexes with Ptch1—resolving the longstanding question of whether co-receptors are merely modulatory or essential.","evidence":"Single/double/triple mutant mice with neural patterning readouts; co-immunoprecipitation of BOC–Ptch1 complex; mutant Hh ligand that binds Ptch1 but not co-receptors fails to signal","pmids":["21664576","21664577"],"confidence":"High","gaps":["Molecular mechanism by which co-receptor binding enables Smo de-repression unknown","Tissue-specific deployment of individual co-receptors not fully understood","Structural basis of BOC–Ptch1 interaction unresolved"]},{"year":2013,"claim":"Boc was shown to be required for sustained generation of ipsilateral RGCs through regulation of Zic2 expression, demonstrating that BOC-mediated Shh signaling controls retinal cell fate specification beyond axon guidance.","evidence":"Boc knockout mouse retinal analysis with Zic2/Islet2 immunostaining and in vivo electroporation","pmids":["23678105"],"confidence":"Medium","gaps":["Direct versus indirect regulation of Zic2 by Shh/Boc not resolved","Whether BOC acts cell-autonomously in iRGC fate specification not fully established"]},{"year":2014,"claim":"BOC was found to promote medulloblastoma by amplifying Shh signaling to levels that drive CyclinD1-mediated DNA damage and Ptch1 loss-of-heterozygosity, providing a mechanistic link between co-receptor dosage and tumor progression.","evidence":"Boc knockout in Ptch1+/− medulloblastoma model, CyclinD1 manipulation, LOH analysis","pmids":["25263791"],"confidence":"High","gaps":["Whether BOC also contributes to other Hh-driven cancers untested","Relative contributions of BOC versus CDON/GAS1 to medulloblastoma not dissected"]},{"year":2015,"claim":"Structure-function analysis revealed that CDON and BOC utilize distinct extracellular motifs and membrane-attachment requirements to promote Hh signaling, while Boc knockout mice showed age-related adiposity linked to reduced Hh pathway activity—extending BOC's physiological roles to metabolic regulation.","evidence":"Chick spinal cord electroporation with domain deletion/swap mutants; Boc knockout mouse adiposity and MEF adipogenesis assays","pmids":["25848697","25576054"],"confidence":"Medium","gaps":["Structural determinants of BOC-specific signaling versus CDON not fully mapped","Mechanism by which Hh pathway suppresses adipogenesis downstream of BOC not characterized"]},{"year":2016,"claim":"BOC was shown to interact with ABL kinase through an SH2-binding motif and to require ABL-dependent JNK activation for neuronal differentiation, identifying an intracellular signaling pathway linking BOC to non-canonical Hh outputs.","evidence":"Co-immunoprecipitation of BOC–ABL, ABL-binding-defective BOC mutants, JNK activation assay, neurite outgrowth in Boc−/− neural progenitors","pmids":["27871935"],"confidence":"Medium","gaps":["ABL–BOC interaction not validated by orthogonal methods","Relationship between ABL/JNK pathway and canonical Hh/Smo signaling unclear","In vivo relevance of BOC–ABL axis not tested"]},{"year":2017,"claim":"Identification of BOC missense variants in holoprosencephaly patients with altered signaling properties confirmed BOC as a human disease modifier gene, bridging mouse genetics to clinical relevance.","evidence":"Cell-based SHH signaling assays with patient-derived BOC variants","pmids":["28677295"],"confidence":"Medium","gaps":["No family cosegregation or in vivo rescue for individual variants","Functional consequences of variants on co-receptor complex formation untested"]},{"year":2019,"claim":"The mechanistic basis of BOC in axon guidance was resolved: Shh triggers Numb-dependent BOC internalization into early endosomes, which is required for Ptch1 endocytosis and downstream signaling in growth-cone turning—establishing BOC as an endocytic platform rather than a passive ligand-binding partner.","evidence":"Endosome fractionation, live imaging of BOC internalization, Co-IP of BOC–Numb, Numb RNAi, in vitro turning assay, in vivo commissural axon tracing","pmids":["31054872"],"confidence":"High","gaps":["Whether Numb-dependent internalization operates in non-neuronal Hh signaling contexts unknown","Endosomal signaling events downstream of BOC/Ptch1 internalization uncharacterized"]},{"year":2019,"claim":"Boc was found to be required for normal myelination timing and oligodendrocyte precursor differentiation, extending its roles to glial biology.","evidence":"Boc knockout mouse analysis with oligodendroglial markers, MBP quantification, myelin repair assay","pmids":["31048318"],"confidence":"Medium","gaps":["Cell-autonomous versus non-cell-autonomous role of Boc in OPCs not resolved","Whether Hh signaling mediates all myelination effects of Boc unclear"]},{"year":2020,"claim":"Distinct Ptch1/Boc and Ptch2/Gas1 hetero-complexes were identified with different signaling kinetics, and BOC was shown to have tissue-specific restraining roles on Hh signaling during craniofacial development—resolving the paradox of opposing BOC phenotypes across tissues.","evidence":"Co-IP of Ptch1/Boc versus Ptch2/Gas1 complexes, compound mouse knockouts, PGC migration assays, craniofacial morphometry with Hh target gene analysis","pmids":["32332736","33060130"],"confidence":"Medium","gaps":["Molecular basis of tissue-specific promoting versus restraining functions not resolved","Structural basis for selective Ptch1/Boc versus Ptch2/Gas1 complex formation unknown"]},{"year":2021,"claim":"A DISP–BOC complex was identified in Shh-producing cells that promotes cytoneme formation and ligand delivery, revealing a previously unrecognized role for BOC in signal-sending rather than signal-receiving cells.","evidence":"Co-IP of DISP–BOC, live-cell imaging of cytonemes, Myo10 knockout mouse neural tube analysis","pmids":["33570491"],"confidence":"Medium","gaps":["Whether BOC functions equivalently in all Hh-producing cell types unknown","Mechanism by which DISP–BOC promotes cytoneme formation unresolved","Independence from BOC's role in receiving cells not fully tested"]},{"year":null,"claim":"Key open questions include: the structural basis of full BOC–Ptch1–Shh receptor complexes, the molecular determinants of tissue-specific promoting versus restraining roles, the relationship between canonical (Smo-dependent) and non-canonical (ABL/JNK) signaling downstream of BOC, and whether the DISP–BOC axis in signal-sending cells is separable from co-receptor function in receiving cells.","evidence":"","pmids":[],"confidence":"Low","gaps":["No full-length BOC–Ptch1 structural model","Tissue-specific regulatory logic not decoded","Non-canonical vs canonical signaling integration unclear"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0060089","term_label":"molecular transducer activity","supporting_discovery_ids":[1,2,3,6]},{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[6,11,13]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[0,1,6,11]},{"term_id":"GO:0005768","term_label":"endosome","supporting_discovery_ids":[11]},{"term_id":"GO:0005576","term_label":"extracellular region","supporting_discovery_ids":[0,1]}],"pathway":[{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[1,5,6,8,14]},{"term_id":"R-HSA-1266738","term_label":"Developmental Biology","supporting_discovery_ids":[2,3,5,7,14]},{"term_id":"R-HSA-112316","term_label":"Neuronal System","supporting_discovery_ids":[2,3,10,11,17]}],"complexes":["Ptch1/Boc co-receptor complex","CDON-BOC complex","DISP-BOC complex"],"partners":["CDON","PTCH1","SHH","GAS1","NUMB","ABL1","DISP1"],"other_free_text":[]},"mechanistic_narrative":"BOC is a transmembrane co-receptor of the Ig/fibronectin superfamily that binds all three mammalian Hedgehog ligands through a specific fibronectin repeat domain and, together with the functionally overlapping co-receptors CDON and GAS1, forms obligatory complexes with Patched1 to transduce Hedgehog signaling in multiple developmental contexts [PMID:16647304, PMID:21664577, PMID:20519495]. These co-receptor complexes are collectively essential for Hedgehog-dependent ventral neural patterning, cerebellar granule neuron progenitor proliferation, craniofacial morphogenesis, myelination, adipogenesis suppression, and primordial germ cell migration, with BOC exerting tissue-specific promoting or restraining effects on pathway output [PMID:21664576, PMID:33060130, PMID:31048318, PMID:25576054, PMID:32332736]. In axon guidance, BOC functions as a direct Shh receptor on commissural and retinal ganglion cell neurons: Shh binding triggers Numb-dependent BOC internalization into early endosomes, which gates Ptch1 endocytosis and couples ligand reception to growth-cone turning and axon trajectory decisions at the optic chiasm [PMID:17086203, PMID:20053908, PMID:31054872]. Missense BOC variants with altered Shh signaling activity have been identified in holoprosencephaly patients, and compound Boc;Cdon loss in mice produces holoprosencephaly-spectrum defects, establishing BOC as a modifier of this disorder [PMID:28677295, PMID:11782431]."},"prefetch_data":{"uniprot":{"accession":"Q9BWV1","full_name":"Brother of CDO","aliases":[],"length_aa":1114,"mass_kda":121.1,"function":"Component of a cell-surface receptor complex that mediates cell-cell interactions between muscle precursor cells. 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N-Boc-α-amino Acids from Carbon Dioxide by Electrochemical Carboxylation of N-Boc-α-aminosulfones.","date":"2021","source":"The Journal of organic chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/34550701","citation_count":16,"is_preprint":false},{"pmid":"35447911","id":"PMC_35447911","title":"5-O-(N-Boc-l-Alanine)-Renieramycin T Induces Cancer Stem Cell Apoptosis via Targeting Akt Signaling.","date":"2022","source":"Marine drugs","url":"https://pubmed.ncbi.nlm.nih.gov/35447911","citation_count":15,"is_preprint":false},{"pmid":"32376009","id":"PMC_32376009","title":"Palladium-mediated Suzuki-Miyaura Cross-Coupling Reaction of Potassium Boc-protected aminomethyltrifluoroborate with DNA-Conjugated aryl bromides for DNA-Encoded chemical library synthesis.","date":"2020","source":"Biochemical and biophysical research communications","url":"https://pubmed.ncbi.nlm.nih.gov/32376009","citation_count":15,"is_preprint":false},{"pmid":"25576054","id":"PMC_25576054","title":"Overweight in mice and enhanced adipogenesis in vitro are associated with lack of the hedgehog coreceptor boc.","date":"2015","source":"Diabetes","url":"https://pubmed.ncbi.nlm.nih.gov/25576054","citation_count":15,"is_preprint":false},{"pmid":"1701321","id":"PMC_1701321","title":"Correlation between phospholipid breakdown, intracellular calcium mobilization and enzyme secretion in rat pancreatic acini treated with Boc-[Nle28, Nle31]-CCK-7 and JMV180, two cholecystokinin analogues.","date":"1990","source":"Cellular signalling","url":"https://pubmed.ncbi.nlm.nih.gov/1701321","citation_count":15,"is_preprint":false},{"pmid":"34355694","id":"PMC_34355694","title":"Glypicans define unique roles for the Hedgehog co-receptors boi and ihog in cytoneme-mediated gradient formation.","date":"2021","source":"eLife","url":"https://pubmed.ncbi.nlm.nih.gov/34355694","citation_count":14,"is_preprint":false},{"pmid":"7837233","id":"PMC_7837233","title":"CCK-A receptor selective antagonists derived from the CCK-A receptor selective tetrapeptide agonist Boc-Trp-Lys(Tac)-Asp-MePhe-NH2 (A-71623).","date":"1995","source":"Journal of medicinal chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/7837233","citation_count":14,"is_preprint":false},{"pmid":"32003299","id":"PMC_32003299","title":"Drug-interactive mPEG-b-PLA-Phe(Boc) micelles enhance the tolerance and anti-tumor efficacy of docetaxel.","date":"2020","source":"Drug delivery","url":"https://pubmed.ncbi.nlm.nih.gov/32003299","citation_count":14,"is_preprint":false},{"pmid":"17205168","id":"PMC_17205168","title":"Mixed-sequence pyrrolidine-amide oligonucleotide mimics: Boc(Z) synthesis and DNA/RNA binding properties.","date":"2006","source":"Organic & biomolecular chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/17205168","citation_count":14,"is_preprint":false},{"pmid":"23154411","id":"PMC_23154411","title":"The Drosophila WIF1 homolog Shifted maintains glypican-independent Hedgehog signaling and interacts with the Hedgehog co-receptors Ihog and Boi.","date":"2012","source":"Development (Cambridge, England)","url":"https://pubmed.ncbi.nlm.nih.gov/23154411","citation_count":13,"is_preprint":false},{"pmid":"36344442","id":"PMC_36344442","title":"Chemical Synthesis of Proteins with Base-Labile Posttranslational Modifications Enabled by a Boc-SPPS Based General Strategy Towards Peptide C-Terminal Salicylaldehyde Esters.","date":"2022","source":"Angewandte Chemie (International ed. in English)","url":"https://pubmed.ncbi.nlm.nih.gov/36344442","citation_count":13,"is_preprint":false},{"pmid":"26713104","id":"PMC_26713104","title":"Rapid Synthesis of Boc-2',6'-dimethyl-l-tyrosine and Derivatives and Incorporation into Opioid Peptidomimetics.","date":"2015","source":"ACS medicinal chemistry letters","url":"https://pubmed.ncbi.nlm.nih.gov/26713104","citation_count":13,"is_preprint":false},{"pmid":"21600982","id":"PMC_21600982","title":"Anti-thyroid cancer properties of a novel isoflavone derivative, 7-(O)-carboxymethyl daidzein conjugated to N-t-Boc-hexylenediamine in vitro and in vivo.","date":"2011","source":"The Journal of steroid biochemistry and molecular biology","url":"https://pubmed.ncbi.nlm.nih.gov/21600982","citation_count":13,"is_preprint":false},{"pmid":"1579566","id":"PMC_1579566","title":"Helix packing of leucine-rich peptides: a parallel leucine ladder in the structure of Boc-Aib-Leu-Aib-Aib-Leu-Leu-Leu-Aib-Leu-Aib-OMe.","date":"1992","source":"Proteins","url":"https://pubmed.ncbi.nlm.nih.gov/1579566","citation_count":13,"is_preprint":false},{"pmid":"15959592","id":"PMC_15959592","title":"Dynamic kinetic resolution of N-Boc-2-lithiopyrrolidine.","date":"2005","source":"Chemical communications (Cambridge, England)","url":"https://pubmed.ncbi.nlm.nih.gov/15959592","citation_count":13,"is_preprint":false},{"pmid":"34203581","id":"PMC_34203581","title":"Differential Expression of BOC, SPOCK2, and GJD3 Is Associated with Brain Metastasis of ER-Negative Breast Cancers.","date":"2021","source":"Cancers","url":"https://pubmed.ncbi.nlm.nih.gov/34203581","citation_count":12,"is_preprint":false},{"pmid":"32152757","id":"PMC_32152757","title":"D-Peptide analogues of Boc-Phe-Leu-Phe-Leu-Phe-COOH induce neovascularization via endothelial N-formyl peptide receptor 3.","date":"2020","source":"Angiogenesis","url":"https://pubmed.ncbi.nlm.nih.gov/32152757","citation_count":12,"is_preprint":false},{"pmid":"12720294","id":"PMC_12720294","title":"Overexpression of the immunoglobulin superfamily members CDO and BOC enhances differentiation of the human rhabdomyosarcoma cell line RD.","date":"2003","source":"Molecular carcinogenesis","url":"https://pubmed.ncbi.nlm.nih.gov/12720294","citation_count":12,"is_preprint":false},{"pmid":"33456769","id":"PMC_33456769","title":"Mild deprotection of the N-tert-butyloxycarbonyl (N-Boc) group using oxalyl chloride.","date":"2020","source":"RSC advances","url":"https://pubmed.ncbi.nlm.nih.gov/33456769","citation_count":12,"is_preprint":false},{"pmid":"1375964","id":"PMC_1375964","title":"Development of potent and selective CCK-A receptor agonists from Boc-CCK-4: tetrapeptides containing Lys(N epsilon)-amide residues.","date":"1992","source":"Journal of medicinal chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/1375964","citation_count":12,"is_preprint":false},{"pmid":"17941688","id":"PMC_17941688","title":"Incorporation of the hydrophobic probe N-t-BOC-L-tyrosine tert-butyl ester to red blood cell membranes to study peroxynitrite-dependent reactions.","date":"2007","source":"Chemical research in toxicology","url":"https://pubmed.ncbi.nlm.nih.gov/17941688","citation_count":12,"is_preprint":false},{"pmid":"15280949","id":"PMC_15280949","title":"Highly enantioselective reaction of lithiated N-Boc-thiazolidine: a new chiral formyl anion equivalent.","date":"2004","source":"Organic & biomolecular chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/15280949","citation_count":12,"is_preprint":false},{"pmid":"33710800","id":"PMC_33710800","title":"BOC-PLAG1, a new fusion gene of pleomorphic adenoma: Identified in a fine-needle aspirate by RNA next-generation sequencing.","date":"2021","source":"Diagnostic cytopathology","url":"https://pubmed.ncbi.nlm.nih.gov/33710800","citation_count":11,"is_preprint":false},{"pmid":"22445332","id":"PMC_22445332","title":"Sonic hedgehog, BOC, and synaptic development: new players for an old game.","date":"2012","source":"Neuron","url":"https://pubmed.ncbi.nlm.nih.gov/22445332","citation_count":11,"is_preprint":false},{"pmid":"22799572","id":"PMC_22799572","title":"Growth inhibition of human thyroid carcinoma and goiter cells in vitro by the isoflavone derivative 7-(O)-carboxymethyl daidzein conjugated to N-t-boc-hexylenediamine.","date":"2012","source":"Thyroid : official journal of the American Thyroid Association","url":"https://pubmed.ncbi.nlm.nih.gov/22799572","citation_count":11,"is_preprint":false},{"pmid":"8906884","id":"PMC_8906884","title":"Helix termination and chain reversal: crystal and molecular structure of the alpha, beta-dehydrooctapeptide Boc-Val-DeltaPhe-Phe-Ala-Leu-Ala-DeltaPhe-Leu-OH.","date":"1996","source":"Journal of biomolecular structure & dynamics","url":"https://pubmed.ncbi.nlm.nih.gov/8906884","citation_count":11,"is_preprint":false},{"pmid":"12673890","id":"PMC_12673890","title":"Clinical and immunomodulatory effects of fun-boi, an herbal medicine, on collagen-induced arthritis in vivo.","date":"2003","source":"Clinical and experimental rheumatology","url":"https://pubmed.ncbi.nlm.nih.gov/12673890","citation_count":10,"is_preprint":false},{"pmid":"30487432","id":"PMC_30487432","title":"Characterization of a Carbonyl Reductase from Rhodococcus erythropolis WZ010 and Its Variant Y54F for Asymmetric Synthesis of (S)-N-Boc-3-Hydroxypiperidine.","date":"2018","source":"Molecules (Basel, Switzerland)","url":"https://pubmed.ncbi.nlm.nih.gov/30487432","citation_count":10,"is_preprint":false},{"pmid":"18554537","id":"PMC_18554537","title":"Tyrosine nitration, dimerization, and hydroxylation by peroxynitrite in membranes as studied by the hydrophobic probe N-t-BOC-l-tyrosine tert-butyl ester.","date":"2008","source":"Methods in enzymology","url":"https://pubmed.ncbi.nlm.nih.gov/18554537","citation_count":10,"is_preprint":false},{"pmid":"12493605","id":"PMC_12493605","title":"Effects of intrathecal administration of a cell permeant caspase inhibitor, boc-D-fluoromethylketone (BDFMK), on behavioral deficits following spinal cord ischemia: a dose-response analysis.","date":"2003","source":"Brain research","url":"https://pubmed.ncbi.nlm.nih.gov/12493605","citation_count":10,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":45835,"output_tokens":4748,"usd":0.104362},"stage2":{"model":"claude-opus-4-6","input_tokens":8296,"output_tokens":3795,"usd":0.204533},"total_usd":0.308895,"stage1_batch_id":"msgbatch_01TqNM6p6FsoMBT2jzQTwKBr","stage2_batch_id":"msgbatch_01Ya473eco8sTHbvRymQaU8o","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2002,\n      \"finding\": \"BOC forms cis complexes with CDO via both their ectodomains and intracellular domains, and positively regulates myogenic differentiation; a soluble BOC ectodomain fusion protein promotes myogenesis, indicating the intracellular region is dispensable, but a dominant-negative CDO blocks BOC's pro-myogenic effects, placing BOC dependent on CDO for myogenic activity.\",\n      \"method\": \"Co-immunoprecipitation, soluble fusion protein rescue assay, dominant-negative CDO overexpression, myoblast differentiation assay\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal co-IP plus multiple functional readouts (soluble ectodomain, dominant-negative epistasis) in single study\",\n      \"pmids\": [\"11782431\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"BOC and CDO bind Sonic Hedgehog (Shh) through a high-affinity interaction with a specific fibronectin repeat, and ectopic expression of BOC promotes Shh-dependent, cell-autonomous ventral cell fates while producing non-cell-autonomous ventral expansion consistent with Shh sequestration; BOC is a target and component of the Hedgehog signaling feedback network.\",\n      \"method\": \"Binding assays (fibronectin repeat mutants), ectopic expression in neural tube, genetic loss-of-function in mice\",\n      \"journal\": \"Developmental cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — domain-mapping binding assay plus in vivo gain/loss-of-function with defined phenotypic readout\",\n      \"pmids\": [\"16647304\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"BOC functions as a receptor for Shh in commissural axon guidance: Boc is expressed by commissural neurons, targeted disruption in mice causes commissural axon misguidance toward the floor plate, and RNAi knockdown of Boc impairs the ability of commissural axons to turn toward an ectopic Shh source in vitro.\",\n      \"method\": \"In vitro growth-cone turning assay, RNAi knockdown, mouse genetic knockout with axon tracing\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — in vitro turning assay plus in vivo knockout with specific axon-guidance phenotype, replicated by two complementary approaches\",\n      \"pmids\": [\"17086203\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"BOC (Shh receptor) is enriched in ipsilateral retinal ganglion cells (RGCs); Boc-positive RGC axons retract in vitro in response to Shh and this retraction is lost in Boc mutant RGCs; in vivo, Boc is required for normal segregation of ipsilateral axons at the optic chiasm, and ectopic Boc expression in contralateral RGCs prevents their axons from crossing the chiasm.\",\n      \"method\": \"In vitro axon retraction assay, Boc mutant mouse analysis, in vivo electroporation of Boc into contralateral RGCs\",\n      \"journal\": \"The Journal of neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — in vitro assay plus in vivo gain- and loss-of-function with specific axon-guidance phenotypes\",\n      \"pmids\": [\"20053908\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"X-ray crystal structures of Sonic, Indian, and Desert Hedgehog proteins complexed with active domains of CDO and BOC reveal that all mammalian Hh proteins bind CDO and BOC in the same manner, and that Hh–CDO interactions are weakened at low pH; CDO and BOC use non-orthologous domains compared with Drosophila Ihog.\",\n      \"method\": \"X-ray crystallography, biochemical binding assays\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — crystal structures of Hh/BOC complexes with biochemical validation\",\n      \"pmids\": [\"20519495\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"GAS1, CDO, and BOC play overlapping and collectively essential roles in Hedgehog-mediated ventral neural patterning; genetic loss-of-function demonstrates an obligatory requirement for these three co-receptors in HH pathway activity in multiple tissues, including early cell fate specification and later motor neuron progenitor maintenance.\",\n      \"method\": \"Compound mouse genetic knockouts (single, double, triple mutants), neural patterning assays\",\n      \"journal\": \"Developmental cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multi-allele genetic epistasis across multiple tissues, replicated in companion paper\",\n      \"pmids\": [\"21664576\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Boc (with Cdon and Gas1) forms distinct receptor complexes with Ptch1; in cerebellar granule neuron progenitors, Boc, Cdon, and Gas1 are absolutely required for Hh-dependent proliferation, and a mutated Hh ligand that binds Ptch1 but not Boc/Cdon/Gas1 cannot activate Hh signaling, demonstrating that ligand binding to co-receptors is obligatory for signaling.\",\n      \"method\": \"Co-immunoprecipitation (Boc–Ptch1 complex), Hh binding mutant ligand, genetic knockout of all three co-receptors in CGNP proliferation assay\",\n      \"journal\": \"Developmental cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — reconstitution of receptor complex plus mutant ligand biochemistry plus genetic epistasis\",\n      \"pmids\": [\"21664577\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"Boc modifies the holoprosencephaly (HPE) spectrum of Cdo mutant mice: Boc single mutants have no HPE, but Cdo;Boc double mutants display lobar HPE with craniofacial anomalies and defects in Shh target gene expression in the developing forebrain, identifying BOC as a silent HPE modifier gene.\",\n      \"method\": \"Mouse double knockout genetic epistasis, Shh target gene expression analysis\",\n      \"journal\": \"Disease models & mechanisms\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — clean double-KO epistasis with defined molecular and morphological phenotype\",\n      \"pmids\": [\"21183473\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"BOC associates with Ptch1 and promotes Shh-driven granule cell precursor (GCP) proliferation; mechanistically, Boc, through elevated Shh signaling, promotes high levels of DNA damage mediated by CyclinD1, which increases Ptch1 loss-of-heterozygosity and thereby drives medulloblastoma progression.\",\n      \"method\": \"Boc genetic knockout in medulloblastoma model, CyclinD1 manipulation, LOH analysis, proliferation assays\",\n      \"journal\": \"Developmental cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic KO with defined molecular mechanism (CyclinD1-mediated DNA damage) and LOH readout\",\n      \"pmids\": [\"25263791\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"CDON and BOC utilize distinct molecular mechanisms in HH signal transduction: they have separate extracellular motifs required for HH promotion and distinct membrane attachment requirements, despite displaying functional redundancy in ventral neural patterning.\",\n      \"method\": \"In vivo gain-of-function (chick spinal cord electroporation) with domain deletion and swap mutants\",\n      \"journal\": \"Developmental biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — in vivo structure-function with domain mutants, single lab\",\n      \"pmids\": [\"25848697\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"BOC interacts with the non-receptor tyrosine kinase ABL through its putative SH2-binding domain and is phosphorylated in an ABL-dependent manner; BOC–ABL interaction is required for JNK activation and BOC-mediated promotion of neuronal differentiation and neurite outgrowth in P19 cells and cortical neural progenitor cells.\",\n      \"method\": \"Co-immunoprecipitation (BOC–ABL), ABL-binding defective BOC mutants, JNK activation assay, neurite length measurement in Boc−/− NPCs\",\n      \"journal\": \"Cellular signalling\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 — co-IP plus domain-mutant rescue plus KO phenotype, single lab\",\n      \"pmids\": [\"27871935\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Shh induces Boc internalization into early endosomes; the endocytic adaptor Numb binds to Boc and is required for Boc internalization, Shh-mediated growth-cone turning in vitro, and commissural axon guidance in vivo. Boc binding to Shh is required for Ptch1 internalization; thus, Boc acts as a Shh-dependent endocytic platform gating Ptch1 internalization and Shh signaling in axon guidance.\",\n      \"method\": \"Endosome fractionation/live imaging of Boc internalization, Co-IP (Boc–Numb), Numb RNAi knockdown, in vitro growth-cone turning, in vivo commissural axon tracing\",\n      \"journal\": \"Neuron\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal methods (biochemical, imaging, in vitro, in vivo) establishing mechanistic model\",\n      \"pmids\": [\"31054872\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"The Shh receptor Boc is important for myelination: Boc mutant mice exhibit transient decrease in oligodendroglial cell density, delayed myelination, lower myelin basic protein production, reduced callosal axon caliber, and impaired OPC differentiation during myelin repair, and Boc mutant microglia/macrophages show defective morphological transition in vivo.\",\n      \"method\": \"Boc knockout mouse analysis, immunostaining for oligodendroglial markers, MBP quantification, myelin repair assay\",\n      \"journal\": \"Development\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — clean genetic KO with multiple cellular phenotype readouts, single lab\",\n      \"pmids\": [\"31048318\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Ptch1/Boc and Ptch2/Gas1 form distinct hetero-complexes that mediate Smo de-repression with different kinetics and through distinct modes of Hedgehog ligand reception; Ptch1/Boc complex mediates primordial germ cell migration in mice.\",\n      \"method\": \"Compound mouse genetic knockouts, co-immunoprecipitation of Ptch1/Boc and Ptch2/Gas1 complexes, PGC migration assays, phospho-Creb/Src signaling analysis\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — co-IP of distinct complexes plus genetic epistasis with defined cellular phenotype, single lab\",\n      \"pmids\": [\"32332736\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"BOC acts as a multi-functional regulator of HH signaling during craniofacial development: Boc deletion results in facial widening correlated with increased HH target gene expression, and Boc deletion in a Gas1-null background partially rescues craniofacial defects of Gas1 single mutants, demonstrating tissue-specific HH-promoting or HH-restraining roles for BOC.\",\n      \"method\": \"Single and compound mouse genetic knockouts, HH target gene expression analysis, craniofacial morphometry\",\n      \"journal\": \"Development\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — clean genetic epistasis across multiple allele combinations with molecular readout, single lab\",\n      \"pmids\": [\"33060130\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"A Dispatched (DISP)–BOC/CDON co-receptor complex functions in Shh ligand-producing cells to promote cytoneme occurrence and facilitate ligand delivery; Myosin 10 promotes vesicular transport of Shh in cytonemes and is required for SHH gradient organization in the neural tube.\",\n      \"method\": \"Co-immunoprecipitation (DISP–BOC complex), Myo10 genetic knockout mouse neural tube analysis, live-cell imaging of cytonemes, rapid signal-response assay\",\n      \"journal\": \"eLife\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — co-IP of novel complex plus in vivo genetic evidence plus live imaging, single lab\",\n      \"pmids\": [\"33570491\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Mice lacking the HH co-receptor BOC display age-related overweight and excess white adipose tissue; cultured Boc−/− mouse embryo fibroblasts show enhanced adipogenesis and reduced HH pathway target gene expression, placing BOC as a positive regulator of HH signaling that inhibits adipogenesis.\",\n      \"method\": \"Boc knockout mouse adiposity analysis, in vitro adipogenesis assay in MEFs, HH target gene expression\",\n      \"journal\": \"Diabetes\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — genetic KO with defined metabolic/cellular phenotype and molecular pathway readout, single lab\",\n      \"pmids\": [\"25576054\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Shh/Boc signaling is required for sustained generation of ipsilateral-projecting retinal ganglion cells (iRGCs): in Boc−/− mice, the number of Zic2-positive iRGCs is reduced while Islet2/Shh-positive RGCs increase, indicating Boc is required to sustain Zic2 expression likely by regulating Shh signaling levels from neighboring contralateral RGCs.\",\n      \"method\": \"Boc knockout mouse analysis, immunostaining for Zic2/Islet2 markers, in vivo electroporation of Shh, Zic2, and Boc, retinal projection analysis\",\n      \"journal\": \"The Journal of neuroscience\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — genetic KO plus gain-of-function electroporation with defined molecular phenotype, single lab\",\n      \"pmids\": [\"23678105\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"Zebrafish BOC functions as an axon-guidance molecule for dorsoventrally projecting axon tracts: morpholino knockdown of boc causes selective defects in ventrally projecting axons arising from the presumptive telencephalon.\",\n      \"method\": \"Antisense morpholino knockdown in zebrafish, axon tract immunostaining\",\n      \"journal\": \"The Journal of comparative neurology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — morpholino loss-of-function with specific axon-guidance phenotype, single lab\",\n      \"pmids\": [\"15776441\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Missense BOC variants identified in holoprosencephaly patients have either loss- or gain-of-function properties in cell-based SHH signaling assays, confirming BOC as a modifier gene whose variant alleles alter SHH pathway activity.\",\n      \"method\": \"Cell-based SHH signaling assays with patient-derived BOC variant proteins\",\n      \"journal\": \"Human mutation\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — cell-based functional assay for multiple variants, single lab\",\n      \"pmids\": [\"28677295\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"A novel BOC-PLAG1 fusion gene was identified in lipoblastoma, in which the constitutively active BOC promoter drives overexpression of PLAG1, establishing a mechanism for PLAG1 activation in this tumor.\",\n      \"method\": \"5' RACE, RNA sequencing, qRT-PCR\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 — single case molecular characterization, no functional rescue experiment\",\n      \"pmids\": [\"30857637\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"BOC is a transmembrane Ig/fibronectin superfamily co-receptor that binds Hedgehog ligands (Shh, Ihh, Dhh) through a specific fibronectin repeat, forms complexes with Ptch1 and the co-receptors CDON and GAS1 to collectively promote HH pathway activation, mediates Shh-dependent axon guidance by acting as an endocytic platform (via Numb) for Ptch1 internalization, promotes myogenic and neuronal differentiation through CDO-dependent and ABL/JNK-dependent mechanisms respectively, and has tissue-specific roles that can either promote or restrain HH signaling during neural patterning, craniofacial development, myelination, adipogenesis, and retinal ganglion cell specification.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"BOC is a transmembrane co-receptor of the Ig/fibronectin superfamily that binds all three mammalian Hedgehog ligands through a specific fibronectin repeat domain and, together with the functionally overlapping co-receptors CDON and GAS1, forms obligatory complexes with Patched1 to transduce Hedgehog signaling in multiple developmental contexts [PMID:16647304, PMID:21664577, PMID:20519495]. These co-receptor complexes are collectively essential for Hedgehog-dependent ventral neural patterning, cerebellar granule neuron progenitor proliferation, craniofacial morphogenesis, myelination, adipogenesis suppression, and primordial germ cell migration, with BOC exerting tissue-specific promoting or restraining effects on pathway output [PMID:21664576, PMID:33060130, PMID:31048318, PMID:25576054, PMID:32332736]. In axon guidance, BOC functions as a direct Shh receptor on commissural and retinal ganglion cell neurons: Shh binding triggers Numb-dependent BOC internalization into early endosomes, which gates Ptch1 endocytosis and couples ligand reception to growth-cone turning and axon trajectory decisions at the optic chiasm [PMID:17086203, PMID:20053908, PMID:31054872]. Missense BOC variants with altered Shh signaling activity have been identified in holoprosencephaly patients, and compound Boc;Cdon loss in mice produces holoprosencephaly-spectrum defects, establishing BOC as a modifier of this disorder [PMID:28677295, PMID:11782431].\",\n  \"teleology\": [\n    {\n      \"year\": 2002,\n      \"claim\": \"BOC was identified as a partner of CDO that promotes myogenic differentiation, establishing it as a cell-surface molecule with signaling function in cell fate determination—though its ligand was unknown.\",\n      \"evidence\": \"Co-immunoprecipitation of BOC–CDO, soluble ectodomain fusion protein and dominant-negative CDO epistasis in myoblast differentiation assays\",\n      \"pmids\": [\"11782431\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No ligand identified for BOC\", \"Mechanism of CDO-dependent signaling unknown\", \"Intracellular signaling pathways downstream of BOC uncharacterized\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Zebrafish boc knockdown revealed that BOC functions in axon guidance of ventrally projecting tracts, providing the first evidence it acts in neural circuit wiring rather than solely in myogenesis.\",\n      \"evidence\": \"Antisense morpholino knockdown in zebrafish with axon tract immunostaining\",\n      \"pmids\": [\"15776441\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Morpholino-only approach lacks genetic confirmation\", \"No ligand identified for axon guidance function\", \"Mammalian relevance not yet shown\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Two landmark studies established that BOC directly binds Sonic Hedgehog through a fibronectin repeat domain and functions both as a Shh-dependent ventral neural patterning co-receptor and as the receptor mediating Shh-guided commissural axon pathfinding—unifying its ligand identity and its roles in patterning and guidance.\",\n      \"evidence\": \"Domain-mapping binding assays, ectopic expression in neural tube, Boc knockout mice with commissural axon tracing, in vitro growth-cone turning assay with Boc RNAi\",\n      \"pmids\": [\"16647304\", \"17086203\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How BOC transduces signal intracellularly unresolved\", \"Relationship between BOC and Ptch1 in receptor complex unknown\", \"Redundancy with CDON and GAS1 not yet genetically dissected\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Crystal structures of Hedgehog–BOC complexes and functional studies in retinal ganglion cells defined the structural basis of BOC–Hh binding and extended BOC's axon-guidance role to ipsilateral RGC segregation at the optic chiasm, while genetic epistasis with Cdon revealed BOC as a holoprosencephaly modifier.\",\n      \"evidence\": \"X-ray crystallography of Hh–BOC/CDO complexes, in vitro RGC axon retraction and in vivo gain/loss-of-function at the optic chiasm, Cdo;Boc double-knockout mouse analysis\",\n      \"pmids\": [\"20519495\", \"20053908\", \"21183473\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No structural information on full receptor complex (BOC–Ptch1–Shh)\", \"Mechanism of intracellular signal transduction from BOC still unknown\", \"Functional distinction between BOC and CDON at molecular level not resolved\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Compound genetic knockouts demonstrated that BOC, CDON, and GAS1 are collectively obligatory for all Hedgehog pathway activity and form distinct complexes with Ptch1—resolving the longstanding question of whether co-receptors are merely modulatory or essential.\",\n      \"evidence\": \"Single/double/triple mutant mice with neural patterning readouts; co-immunoprecipitation of BOC–Ptch1 complex; mutant Hh ligand that binds Ptch1 but not co-receptors fails to signal\",\n      \"pmids\": [\"21664576\", \"21664577\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular mechanism by which co-receptor binding enables Smo de-repression unknown\", \"Tissue-specific deployment of individual co-receptors not fully understood\", \"Structural basis of BOC–Ptch1 interaction unresolved\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Boc was shown to be required for sustained generation of ipsilateral RGCs through regulation of Zic2 expression, demonstrating that BOC-mediated Shh signaling controls retinal cell fate specification beyond axon guidance.\",\n      \"evidence\": \"Boc knockout mouse retinal analysis with Zic2/Islet2 immunostaining and in vivo electroporation\",\n      \"pmids\": [\"23678105\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct versus indirect regulation of Zic2 by Shh/Boc not resolved\", \"Whether BOC acts cell-autonomously in iRGC fate specification not fully established\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"BOC was found to promote medulloblastoma by amplifying Shh signaling to levels that drive CyclinD1-mediated DNA damage and Ptch1 loss-of-heterozygosity, providing a mechanistic link between co-receptor dosage and tumor progression.\",\n      \"evidence\": \"Boc knockout in Ptch1+/− medulloblastoma model, CyclinD1 manipulation, LOH analysis\",\n      \"pmids\": [\"25263791\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether BOC also contributes to other Hh-driven cancers untested\", \"Relative contributions of BOC versus CDON/GAS1 to medulloblastoma not dissected\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Structure-function analysis revealed that CDON and BOC utilize distinct extracellular motifs and membrane-attachment requirements to promote Hh signaling, while Boc knockout mice showed age-related adiposity linked to reduced Hh pathway activity—extending BOC's physiological roles to metabolic regulation.\",\n      \"evidence\": \"Chick spinal cord electroporation with domain deletion/swap mutants; Boc knockout mouse adiposity and MEF adipogenesis assays\",\n      \"pmids\": [\"25848697\", \"25576054\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Structural determinants of BOC-specific signaling versus CDON not fully mapped\", \"Mechanism by which Hh pathway suppresses adipogenesis downstream of BOC not characterized\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"BOC was shown to interact with ABL kinase through an SH2-binding motif and to require ABL-dependent JNK activation for neuronal differentiation, identifying an intracellular signaling pathway linking BOC to non-canonical Hh outputs.\",\n      \"evidence\": \"Co-immunoprecipitation of BOC–ABL, ABL-binding-defective BOC mutants, JNK activation assay, neurite outgrowth in Boc−/− neural progenitors\",\n      \"pmids\": [\"27871935\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"ABL–BOC interaction not validated by orthogonal methods\", \"Relationship between ABL/JNK pathway and canonical Hh/Smo signaling unclear\", \"In vivo relevance of BOC–ABL axis not tested\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Identification of BOC missense variants in holoprosencephaly patients with altered signaling properties confirmed BOC as a human disease modifier gene, bridging mouse genetics to clinical relevance.\",\n      \"evidence\": \"Cell-based SHH signaling assays with patient-derived BOC variants\",\n      \"pmids\": [\"28677295\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No family cosegregation or in vivo rescue for individual variants\", \"Functional consequences of variants on co-receptor complex formation untested\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"The mechanistic basis of BOC in axon guidance was resolved: Shh triggers Numb-dependent BOC internalization into early endosomes, which is required for Ptch1 endocytosis and downstream signaling in growth-cone turning—establishing BOC as an endocytic platform rather than a passive ligand-binding partner.\",\n      \"evidence\": \"Endosome fractionation, live imaging of BOC internalization, Co-IP of BOC–Numb, Numb RNAi, in vitro turning assay, in vivo commissural axon tracing\",\n      \"pmids\": [\"31054872\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether Numb-dependent internalization operates in non-neuronal Hh signaling contexts unknown\", \"Endosomal signaling events downstream of BOC/Ptch1 internalization uncharacterized\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Boc was found to be required for normal myelination timing and oligodendrocyte precursor differentiation, extending its roles to glial biology.\",\n      \"evidence\": \"Boc knockout mouse analysis with oligodendroglial markers, MBP quantification, myelin repair assay\",\n      \"pmids\": [\"31048318\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Cell-autonomous versus non-cell-autonomous role of Boc in OPCs not resolved\", \"Whether Hh signaling mediates all myelination effects of Boc unclear\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Distinct Ptch1/Boc and Ptch2/Gas1 hetero-complexes were identified with different signaling kinetics, and BOC was shown to have tissue-specific restraining roles on Hh signaling during craniofacial development—resolving the paradox of opposing BOC phenotypes across tissues.\",\n      \"evidence\": \"Co-IP of Ptch1/Boc versus Ptch2/Gas1 complexes, compound mouse knockouts, PGC migration assays, craniofacial morphometry with Hh target gene analysis\",\n      \"pmids\": [\"32332736\", \"33060130\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Molecular basis of tissue-specific promoting versus restraining functions not resolved\", \"Structural basis for selective Ptch1/Boc versus Ptch2/Gas1 complex formation unknown\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"A DISP–BOC complex was identified in Shh-producing cells that promotes cytoneme formation and ligand delivery, revealing a previously unrecognized role for BOC in signal-sending rather than signal-receiving cells.\",\n      \"evidence\": \"Co-IP of DISP–BOC, live-cell imaging of cytonemes, Myo10 knockout mouse neural tube analysis\",\n      \"pmids\": [\"33570491\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether BOC functions equivalently in all Hh-producing cell types unknown\", \"Mechanism by which DISP–BOC promotes cytoneme formation unresolved\", \"Independence from BOC's role in receiving cells not fully tested\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Key open questions include: the structural basis of full BOC–Ptch1–Shh receptor complexes, the molecular determinants of tissue-specific promoting versus restraining roles, the relationship between canonical (Smo-dependent) and non-canonical (ABL/JNK) signaling downstream of BOC, and whether the DISP–BOC axis in signal-sending cells is separable from co-receptor function in receiving cells.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No full-length BOC–Ptch1 structural model\", \"Tissue-specific regulatory logic not decoded\", \"Non-canonical vs canonical signaling integration unclear\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0060089\", \"supporting_discovery_ids\": [1, 2, 3, 6]},\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [6, 11, 13]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [0, 1, 6, 11]},\n      {\"term_id\": \"GO:0005768\", \"supporting_discovery_ids\": [11]},\n      {\"term_id\": \"GO:0005576\", \"supporting_discovery_ids\": [0, 1]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [1, 5, 6, 8, 14]},\n      {\"term_id\": \"R-HSA-1266738\", \"supporting_discovery_ids\": [2, 3, 5, 7, 14]},\n      {\"term_id\": \"R-HSA-112316\", \"supporting_discovery_ids\": [2, 3, 10, 11, 17]}\n    ],\n    \"complexes\": [\n      \"Ptch1/Boc co-receptor complex\",\n      \"CDON-BOC complex\",\n      \"DISP-BOC complex\"\n    ],\n    \"partners\": [\n      \"CDON\",\n      \"PTCH1\",\n      \"SHH\",\n      \"GAS1\",\n      \"NUMB\",\n      \"ABL1\",\n      \"DISP1\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}