{"gene":"PTCH2","run_date":"2026-04-28T19:45:45","timeline":{"discoveries":[{"year":1999,"finding":"PTCH2 encodes a 1203 amino acid putative transmembrane protein highly homologous to PTCH1, localized to chromosome 1p32.1-32.3, comprising 22 coding exons spanning ~15 kb of genomic DNA; truncating mutations identified in medulloblastoma and splice donor site mutations in basal cell carcinoma implicate it as a tumor suppressor.","method":"SSCP mutation analysis, genomic cloning, direct sequencing","journal":"Human molecular genetics","confidence":"Medium","confidence_rationale":"Tier 2 — original cloning and mutation identification with genomic characterization; single study","pmids":["9931336"],"is_preprint":false},{"year":1999,"finding":"PTCH2 undergoes alternative splicing producing multiple mRNA isoforms, including transcripts lacking segments involved in Sonic Hedgehog binding; PTCH2 is a transcriptional target upregulated by HH signaling (negative regulation by PTCH1), linking it to the SHH/PTCH signaling pathway.","method":"cDNA library screening, RACE, BAC sequencing, in situ hybridization, radiation hybrid mapping","journal":"Cancer research","confidence":"Medium","confidence_rationale":"Tier 2 — multiple molecular methods in single study establishing pathway membership and alternative splicing","pmids":["10029063"],"is_preprint":false},{"year":1998,"finding":"Mouse Ptch2 is expressed both in Shh-producing epithelial cells (tooth, hair, whisker) and in adjacent non-producing cells, overlapping but distinct from Ptch1 expression pattern, suggesting distinct roles in Shh signaling during development.","method":"In situ hybridization, chromosomal localization","journal":"Mechanisms of development","confidence":"Low","confidence_rationale":"Tier 3 — localization without direct functional consequence demonstrated","pmids":["9858693"],"is_preprint":false},{"year":2004,"finding":"PTCH2 splice variants localized in the cytoplasm can internalize the N-terminal fragment of Sonic HH (Shh-N); only one PTCH2 variant inhibits SHH-N promoter activity whereas none can inhibit activated SMO-M2 (unlike PTCH1); all PTCH2 isoforms alter SMO localization from cytoplasm to juxtanuclear region upon co-transfection; PTCH2 isoforms physically interact with PTCH1 (confirmed by co-immunoprecipitation); PTCH2 variants and PTCH1 differentially reconstitute SHH- and Desert HH-dependent transcriptional responses in Ptch1-/- cells.","method":"Promoter reporter assays, immunofluorescence localization, co-immunoprecipitation, Ptch1-/- cell reconstitution, Shh-N internalization assay","journal":"The Biochemical journal","confidence":"High","confidence_rationale":"Tier 1-2 — multiple orthogonal functional assays including co-IP, reporter assays, SMO localization, and Ptch1-/- reconstitution in single study","pmids":["14613484"],"is_preprint":false},{"year":2008,"finding":"The PTCH2 missense mutation R719Q (in an extracellular loop) results in loss of PTCH2 inhibitory activity on the SHH signaling pathway and loss of ability to inhibit cell proliferation, demonstrating that this extracellular domain is functionally required for PTCH2 tumor suppressor activity.","method":"GLI1 reporter gene assay, cell growth curve analysis, direct sequencing, restriction enzyme digestion","journal":"Journal of medical genetics","confidence":"Medium","confidence_rationale":"Tier 2 — functional assays with specific mutant showing loss of inhibitory activity; single lab","pmids":["18285427"],"is_preprint":false},{"year":2013,"finding":"PTCH2 functions as a ciliary-localized HH pathway antagonist in vertebrate neural patterning; while dispensable alone, combined loss of PTCH2 and PTCH1 feedback antagonism produces significant expansion of HH-dependent ventral neural progenitors; triple loss of PTCH2, HHIP1, and PTCH1 feedback results in ectopic specification of ventral cell fates throughout the neural tube reflecting constitutive HH pathway activation.","method":"Mouse genetic epistasis (Ptch1, Ptch2, Hhip1 knockout combinations), neural tube patterning analysis, ciliary localization imaging","journal":"Development (Cambridge, England)","confidence":"High","confidence_rationale":"Tier 2 — genetic epistasis with multiple knockout combinations and clear cellular phenotypes; strong evidence from compound mutant analysis","pmids":["23900540"],"is_preprint":false},{"year":2014,"finding":"Ptch2 mediates Shh signaling in the absence of Ptch1: expression of dominant-negative Ptch2 in chick neural tube activates the Shh response; Ptch1-/-;Ptch2-/- cells cannot further activate the Shh response, demonstrating Ptch2 is required for the residual Shh sensitivity in Ptch1-/- cells.","method":"Dominant-negative expression in chick neural tube, Ptch1-/-;Ptch2-/- double-knockout cell analysis, Shh-blocking antibody (5E1) inhibition, fibroblast migration assay","journal":"Development (Cambridge, England)","confidence":"High","confidence_rationale":"Tier 2 — genetic epistasis using double knockouts and dominant-negative constructs with clear mechanistic pathway placement; multiple orthogonal approaches","pmids":["25085974"],"is_preprint":false},{"year":2014,"finding":"Ptch2 is a functional Shh receptor that regulates SMO localization and activity in vitro; Ptch1 and Ptch2 co-operate in regulating cellular responses to Shh in vivo, as loss of Ptch2 exacerbates limb outgrowth defects in limb-specific Ptch1 knockout mutants.","method":"In vitro SMO localization assay, limb-specific Ptch1 knockout combined with Ptch2 knockout, limb bud co-expression analysis","journal":"Developmental biology","confidence":"High","confidence_rationale":"Tier 1-2 — in vitro receptor activity assay combined with in vivo genetic epistasis in compound mutants","pmids":["25448692"],"is_preprint":false},{"year":2016,"finding":"Ptch2 loss in hematopoietic niche cells drives hyperactive noncanonical HH signaling, resulting in reduced production of HSC regulators (Scf, Cxcl12, Jag1) and osteoblast depletion; hematopoietic loss of Ptch2 drives leukocytosis and promotes HSC maintenance; Ptch2-/- mice develop a myeloproliferative neoplasm phenotype demonstrating that Ptch2 regulates both canonical and noncanonical HH signaling in hematopoiesis.","method":"Ptch2-/- mouse model, bone marrow transplantation, flow cytometry, gene expression analysis, HSC functional assays (5-FU treatment, replating)","journal":"The Journal of experimental medicine","confidence":"High","confidence_rationale":"Tier 2 — comprehensive KO mouse study with niche-specific and hematopoietic-specific dissection of function, multiple cellular phenotypes with mechanistic pathway placement","pmids":["26834157"],"is_preprint":false},{"year":2018,"finding":"The sterol-sensing domains (SSDs) of PTCH2 can substitute for those of PTCH1 in chimeric proteins to repress HH signaling, demonstrating SSDs act as generic modules; however, the cytoplasmic domains of PTCH1 are necessary but not sufficient for HH repression, and the two principal luminal domains of PTCH1 and PTCH2 are interchangeable; the N-terminal and C-terminal halves of PTCH1 associate noncovalently to mediate ligand-dependent Hh regulation, whereas analogous PTCH2 regions interact but do not repress the pathway.","method":"Chimeric protein construction, HH pathway reporter assays, co-immunoprecipitation of PTCH1 N- and C-terminal halves, domain-swap mutagenesis","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 — systematic domain-swap mutagenesis with functional reconstitution assays defining specific structural determinants of activity","pmids":["30166346"],"is_preprint":false},{"year":2018,"finding":"C2EIP interacts with PTCH2 at the intracellular membrane, promotes PTCH2 ubiquitination, and thereby activates HH signaling via competitive inhibition of SMO to regulate primordial germ cell generation from embryonic stem cells.","method":"Co-immunoprecipitation (C2EIP-PTCH2 interaction), ubiquitination assay, C2EIP knockout/overexpression, PGC differentiation assay","journal":"Cell death & disease","confidence":"Medium","confidence_rationale":"Tier 2 — co-IP and ubiquitination assay with functional KO/OE phenotype; single lab study","pmids":["29703892"],"is_preprint":false},{"year":2020,"finding":"Ptch2 forms a specific hetero-complex with Gas1 (while Ptch1 partners with Boc) to mediate Smo de-repression with distinct kinetics in primordial germ cell migration; Ptch2-mediated HH signaling induces phosphorylation of Creb and Src proteins in parallel to Gli induction, defining a Ptch2-specific non-canonical signal pathway distinct from Ptch1.","method":"Genetic analysis of primordial germ cell migration in mouse, co-receptor complex characterization, phosphorylation analysis (Creb, Src), Gli induction assays, Ptch1/2 and Gas1/Boc knockout combinations","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 2 — multiple orthogonal genetic and biochemical approaches revealing distinct Ptch2-specific signaling mechanism with strong epistasis data","pmids":["32332736"],"is_preprint":false},{"year":2022,"finding":"PTCH2 overexpression upregulates tumor suppressor PTEN expression, leading to suppression of pro-survival AKT signals in glioma cells, suppressing proliferation and invasion.","method":"PTCH2 overexpression in glioma cell lines (LN229, U87-MG), western blotting for PTEN/AKT, in vitro proliferation/invasion assays, in vivo tumor-bearing mouse survival","journal":"Biochemical and biophysical research communications","confidence":"Medium","confidence_rationale":"Tier 2 — gain-of-function with defined pathway readout (PTEN/AKT); single lab, limited mechanistic depth on how PTCH2 regulates PTEN","pmids":["36027694"],"is_preprint":false},{"year":2022,"finding":"Loss of Ptch2 increases number of putative mesenchymal stem cells in continuously growing incisor, causes increased bone length/volume linked to augmented MSC differentiation potential in bone marrow, and alters skin wound closure, establishing Ptch2 as a regulator of HH signaling in MSC biology and organ regeneration.","method":"Ptch2-/- mouse model, histology, immunostaining, microCT, CFU assay, in vitro differentiation assay, in vivo wound healing assay","journal":"Frontiers in physiology","confidence":"Medium","confidence_rationale":"Tier 2 — KO mouse with multiple tissue phenotypes and in vitro MSC functional assays; single lab study","pmids":["35574464"],"is_preprint":false}],"current_model":"PTCH2 is a 22-exon transmembrane receptor in the Hedgehog signaling pathway that, via its sterol-sensing domains and cytoplasmic regions, binds Sonic/Desert HH ligands, physically interacts with PTCH1, regulates SMO localization and activity, and functions as a ligand-dependent feedback antagonist of HH signaling; it forms a specific hetero-complex with Gas1 (distinct from the Ptch1/Boc complex) and activates a unique non-canonical Ptch2-specific signaling branch (Creb/Src phosphorylation) in addition to canonical Gli-mediated transcription, while its ubiquitination by C2EIP interaction promotes HH pathway activation, and loss of Ptch2 in hematopoietic niches dysregulates HSC regulatory factors and drives myeloproliferative disease."},"narrative":{"teleology":[{"year":1998,"claim":"Identification of mouse Ptch2 with an expression pattern overlapping yet distinct from Ptch1 in HH-producing and adjacent tissues raised the question of whether a second Patched receptor has non-redundant roles in HH signaling.","evidence":"In situ hybridization and chromosomal mapping in mouse embryonic tissues","pmids":["9858693"],"confidence":"Low","gaps":["Expression pattern alone; no functional data demonstrating distinct signaling role","No loss-of-function or gain-of-function experiments performed"]},{"year":1999,"claim":"Cloning of human PTCH2, mapping to 1p32, and identification of truncating mutations in medulloblastoma and splice-site mutations in BCC established PTCH2 as a candidate tumor suppressor in the HH pathway, while discovery of alternative splicing affecting SHH-binding regions and transcriptional upregulation by HH signaling placed it as a pathway feedback component.","evidence":"Genomic cloning, SSCP mutation analysis, cDNA library screening, RACE, in situ hybridization","pmids":["9931336","10029063"],"confidence":"Medium","gaps":["No direct demonstration of tumor suppressor function in cell-based or animal models","Functional consequences of individual splice isoforms not determined"]},{"year":2004,"claim":"Functional dissection revealed that PTCH2 internalizes SHH-N, physically interacts with PTCH1, and redirects SMO from the cytoplasm to a juxtanuclear compartment, but unlike PTCH1 cannot inhibit constitutively active SMO-M2, establishing that PTCH2 regulates SMO through a mechanism partially distinct from PTCH1.","evidence":"Co-immunoprecipitation, immunofluorescence, SHH-N internalization assay, promoter reporter assays, Ptch1−/− cell reconstitution","pmids":["14613484"],"confidence":"High","gaps":["Mechanism by which PTCH2 alters SMO localization not resolved","Whether PTCH2–PTCH1 interaction is required for SMO regulation unclear"]},{"year":2008,"claim":"The missense mutation R719Q in an extracellular loop abolished PTCH2 inhibitory activity on HH signaling and cell proliferation, pinpointing a critical functional residue for tumor suppressor activity.","evidence":"GLI1 reporter assay and cell growth curve analysis with R719Q mutant","pmids":["18285427"],"confidence":"Medium","gaps":["No structural basis for why R719Q disrupts function","Single mutant study; other extracellular loop residues not systematically tested"]},{"year":2013,"claim":"Mouse genetic epistasis with PTCH1 and HHIP1 demonstrated that PTCH2 is a ciliary-localized feedback antagonist that is dispensable alone but essential in combination for restraining HH-dependent ventral neural progenitor expansion, resolving why single Ptch2 knockouts have mild phenotypes.","evidence":"Compound knockout mice (Ptch1/Ptch2/Hhip1), neural tube patterning analysis, ciliary localization imaging","pmids":["23900540"],"confidence":"High","gaps":["Mechanism of PTCH2 ciliary localization not defined","Whether PTCH2 feedback antagonism operates identically across all HH-responsive tissues unknown"]},{"year":2014,"claim":"Two independent studies established that PTCH2 is a bona fide SHH receptor that mediates residual HH signaling in Ptch1-null cells and cooperates with PTCH1 in vivo for limb outgrowth, resolving the question of whether PTCH2 functions as a true receptor or merely a modulator.","evidence":"Dominant-negative Ptch2 in chick neural tube, Ptch1−/−;Ptch2−/− double-KO cells, limb-specific Ptch1-KO combined with Ptch2-KO, SMO localization assays","pmids":["25085974","25448692"],"confidence":"High","gaps":["Relative affinities of PTCH2 vs PTCH1 for different HH ligands not quantified","Whether PTCH2 mediates cholesterol transport like PTCH1 not addressed"]},{"year":2016,"claim":"Ptch2 knockout mice revealed that PTCH2 regulates the hematopoietic niche through both canonical and noncanonical HH signaling, with loss causing osteoblast depletion, reduced Scf/Cxcl12/Jag1 production, leukocytosis, and myeloproliferative disease, establishing a physiological role beyond development.","evidence":"Ptch2−/− mouse model, bone marrow transplantation, flow cytometry, gene expression analysis, HSC functional assays","pmids":["26834157"],"confidence":"High","gaps":["Molecular identity of the noncanonical HH signaling mechanism downstream of PTCH2 in hematopoietic niche not defined","Whether myeloproliferative phenotype is cell-autonomous or niche-dependent not fully resolved"]},{"year":2018,"claim":"Domain-swap chimeras showed that the sterol-sensing domains of PTCH2 are interchangeable with those of PTCH1 for HH repression, but PTCH1 cytoplasmic domains are uniquely required, explaining the functional divergence between the paralogs at a structural level; separately, C2EIP was identified as a PTCH2-interacting protein that promotes its ubiquitination to activate HH signaling during primordial germ cell differentiation.","evidence":"Chimeric PTCH1/2 proteins with HH reporter assays, co-IP of N/C-terminal halves; C2EIP–PTCH2 co-IP, ubiquitination assay, PGC differentiation in ESCs","pmids":["30166346","29703892"],"confidence":"High","gaps":["Identity of the E3 ubiquitin ligase for PTCH2 not determined","Structural basis for why PTCH2 cytoplasmic domains cannot substitute for PTCH1 unknown","C2EIP–PTCH2 interaction validated by co-IP only; reciprocal and endogenous confirmation limited"]},{"year":2020,"claim":"Discovery that Ptch2 forms a specific complex with Gas1 (not Boc) and activates Creb/Src phosphorylation alongside canonical Gli signaling during primordial germ cell migration defined a non-canonical Ptch2-specific signaling branch, distinguishing it mechanistically from Ptch1.","evidence":"Mouse genetic analysis of PGC migration with Ptch1/2 and Gas1/Boc knockouts, phosphorylation analysis of Creb and Src, Gli induction assays","pmids":["32332736"],"confidence":"High","gaps":["Whether Creb/Src phosphorylation is direct or requires intermediary kinases unknown","Generalizability of Ptch2–Gas1 complex beyond PGC migration not established"]},{"year":2022,"claim":"Ptch2 loss increased mesenchymal stem cells and bone volume, and PTCH2 overexpression upregulated PTEN to suppress AKT signaling in glioma, expanding the functional scope of PTCH2 to stem cell homeostasis and a PTEN/AKT regulatory axis.","evidence":"Ptch2−/− mouse (incisor, bone, wound healing phenotypes); PTCH2 overexpression in glioma lines with PTEN/AKT western blots and xenograft survival","pmids":["35574464","36027694"],"confidence":"Medium","gaps":["Mechanism by which PTCH2 regulates PTEN expression not identified","Whether MSC expansion phenotype is cell-autonomous or niche-mediated not resolved","PTEN regulation could be indirect via canonical HH pathway modulation"]},{"year":null,"claim":"Critical open questions include: the structural basis for PTCH2 function (no cryo-EM or crystal structure), whether PTCH2 transports cholesterol like PTCH1, the identity of kinases mediating Ptch2-specific Creb/Src phosphorylation, and the molecular mechanism by which PTCH2 cytoplasmic domains fail to repress HH signaling when substituted for those of PTCH1.","evidence":"","pmids":[],"confidence":"Low","gaps":["No structural model of PTCH2 available","Cholesterol transport function not tested","Downstream mediators of Ptch2-specific non-canonical signaling uncharacterized"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0060089","term_label":"molecular transducer activity","supporting_discovery_ids":[3,6,7,11]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[3,5,9]}],"localization":[{"term_id":"GO:0005929","term_label":"cilium","supporting_discovery_ids":[5]},{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[3,9]}],"pathway":[{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[3,5,6,7,9,11]},{"term_id":"R-HSA-1266738","term_label":"Developmental Biology","supporting_discovery_ids":[5,7,11]},{"term_id":"R-HSA-1643685","term_label":"Disease","supporting_discovery_ids":[0,4,12]}],"complexes":["Ptch2-Gas1 co-receptor complex"],"partners":["PTCH1","GAS1","SMO","SHH","DHH","C2EIP"],"other_free_text":[]},"mechanistic_narrative":"PTCH2 is a twelve-pass transmembrane receptor in the Hedgehog (HH) signaling pathway that functions as a ligand-dependent feedback antagonist by binding Sonic and Desert Hedgehog ligands, regulating Smoothened (SMO) subcellular localization and activity, and repressing HH target gene transcription through its sterol-sensing domains and cytoplasmic regions [PMID:14613484, PMID:30166346, PMID:25085974]. PTCH2 localizes to primary cilia and cooperates with PTCH1 to attenuate HH signaling during vertebrate neural patterning, limb development, and hematopoiesis, where its loss drives myeloproliferative disease through dysregulation of HSC niche factors including Scf, Cxcl12, and Jag1 [PMID:23900540, PMID:25448692, PMID:26834157]. PTCH2 forms a specific hetero-complex with the co-receptor Gas1 (distinct from the Ptch1–Boc complex) and activates a non-canonical signaling branch involving Creb and Src phosphorylation during primordial germ cell migration [PMID:32332736]. Truncating mutations in PTCH2 have been identified in medulloblastoma and basal cell carcinoma, and the extracellular loop residue R719 is functionally required for its tumor-suppressive inhibition of HH pathway activity [PMID:9931336, PMID:18285427]."},"prefetch_data":{"uniprot":{"accession":"Q9Y6C5","full_name":"Protein patched homolog 2","aliases":[],"length_aa":1203,"mass_kda":130.5,"function":"Plays a role in the control of cellular growth (PubMed:18285427). May have a role in epidermal development. May act as a receptor for Sonic hedgehog (SHH)","subcellular_location":"Membrane","url":"https://www.uniprot.org/uniprotkb/Q9Y6C5/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/PTCH2","classification":"Not Classified","n_dependent_lines":28,"n_total_lines":1208,"dependency_fraction":0.023178807947019868},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/PTCH2","total_profiled":1310},"omim":[{"mim_id":"620343","title":"BASAL CELL NEVUS SYNDROME 2; BCNS2","url":"https://www.omim.org/entry/620343"},{"mim_id":"616908","title":"PATCHED DOMAIN-CONTAINING PROTEIN 4; PTCHD4","url":"https://www.omim.org/entry/616908"},{"mim_id":"613545","title":"MACROSTOMIA, ISOLATED","url":"https://www.omim.org/entry/613545"},{"mim_id":"605462","title":"BASAL CELL CARCINOMA, SUSCEPTIBILITY TO, 1; BCC1","url":"https://www.omim.org/entry/605462"},{"mim_id":"603673","title":"PATCHED 2; PTCH2","url":"https://www.omim.org/entry/603673"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Plasma membrane","reliability":"Supported"},{"location":"Nucleoli","reliability":"Additional"}],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in many","driving_tissues":[{"tissue":"parathyroid gland","ntpm":55.6},{"tissue":"salivary gland","ntpm":70.9}],"url":"https://www.proteinatlas.org/search/PTCH2"},"hgnc":{"alias_symbol":["SLC65B2"],"prev_symbol":[]},"alphafold":{"accession":"Q9Y6C5","domains":[{"cath_id":"-","chopping":"109-390","consensus_level":"medium","plddt":87.0541,"start":109,"end":390},{"cath_id":"1.20.1640.10","chopping":"669-707_959-1120","consensus_level":"medium","plddt":90.8052,"start":669,"end":1120},{"cath_id":"-","chopping":"780-903","consensus_level":"medium","plddt":87.2507,"start":780,"end":903}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9Y6C5","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q9Y6C5-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q9Y6C5-F1-predicted_aligned_error_v6.png","plddt_mean":78.88},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=PTCH2","jax_strain_url":"https://www.jax.org/strain/search?query=PTCH2"},"sequence":{"accession":"Q9Y6C5","fasta_url":"https://rest.uniprot.org/uniprotkb/Q9Y6C5.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q9Y6C5/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9Y6C5"}},"corpus_meta":[{"pmid":"9931336","id":"PMC_9931336","title":"Isolation and characterization of human patched 2 (PTCH2), a putative tumour suppressor gene inbasal cell carcinoma and medulloblastoma on chromosome 1p32.","date":"1999","source":"Human molecular genetics","url":"https://pubmed.ncbi.nlm.nih.gov/9931336","citation_count":149,"is_preprint":false},{"pmid":"18285427","id":"PMC_18285427","title":"A missense mutation in PTCH2 underlies dominantly inherited NBCCS in a Chinese family.","date":"2008","source":"Journal of medical genetics","url":"https://pubmed.ncbi.nlm.nih.gov/18285427","citation_count":89,"is_preprint":false},{"pmid":"23900540","id":"PMC_23900540","title":"Essential role for ligand-dependent feedback antagonism of vertebrate hedgehog signaling by PTCH1, PTCH2 and HHIP1 during neural patterning.","date":"2013","source":"Development (Cambridge, England)","url":"https://pubmed.ncbi.nlm.nih.gov/23900540","citation_count":76,"is_preprint":false},{"pmid":"10029063","id":"PMC_10029063","title":"PTCH2, a novel human patched gene, undergoing alternative splicing and up-regulated in basal cell carcinomas.","date":"1999","source":"Cancer research","url":"https://pubmed.ncbi.nlm.nih.gov/10029063","citation_count":64,"is_preprint":false},{"pmid":"14613484","id":"PMC_14613484","title":"Distinct roles of PTCH2 splice variants in Hedgehog signalling.","date":"2004","source":"The Biochemical journal","url":"https://pubmed.ncbi.nlm.nih.gov/14613484","citation_count":62,"is_preprint":false},{"pmid":"9858693","id":"PMC_9858693","title":"Overlapping and non-overlapping Ptch2 expression with Shh during mouse embryogenesis.","date":"1998","source":"Mechanisms of development","url":"https://pubmed.ncbi.nlm.nih.gov/9858693","citation_count":61,"is_preprint":false},{"pmid":"23479190","id":"PMC_23479190","title":"Frameshift mutation in the PTCH2 gene can cause nevoid basal cell carcinoma syndrome.","date":"2013","source":"Familial cancer","url":"https://pubmed.ncbi.nlm.nih.gov/23479190","citation_count":60,"is_preprint":false},{"pmid":"25085974","id":"PMC_25085974","title":"Ptch2 mediates the Shh response in Ptch1-/- cells.","date":"2014","source":"Development (Cambridge, England)","url":"https://pubmed.ncbi.nlm.nih.gov/25085974","citation_count":40,"is_preprint":false},{"pmid":"25448692","id":"PMC_25448692","title":"Ptch2 shares overlapping functions with Ptch1 in Smo regulation and limb development.","date":"2014","source":"Developmental biology","url":"https://pubmed.ncbi.nlm.nih.gov/25448692","citation_count":39,"is_preprint":false},{"pmid":"16707443","id":"PMC_16707443","title":"Lack of Rb and p53 delays cerebellar development and predisposes to large cell anaplastic medulloblastoma through amplification of N-Myc and Ptch2.","date":"2006","source":"Cancer research","url":"https://pubmed.ncbi.nlm.nih.gov/16707443","citation_count":37,"is_preprint":false},{"pmid":"26834157","id":"PMC_26834157","title":"Ptch2 loss drives myeloproliferation and myeloproliferative neoplasm progression.","date":"2016","source":"The Journal of experimental medicine","url":"https://pubmed.ncbi.nlm.nih.gov/26834157","citation_count":35,"is_preprint":false},{"pmid":"30021865","id":"PMC_30021865","title":"Hotspot DAXX, PTCH2 and CYFIP2 mutations in pancreatic neuroendocrine neoplasms.","date":"2019","source":"Endocrine-related cancer","url":"https://pubmed.ncbi.nlm.nih.gov/30021865","citation_count":24,"is_preprint":false},{"pmid":"32332736","id":"PMC_32332736","title":"Ptch2/Gas1 and Ptch1/Boc differentially regulate Hedgehog signalling in murine primordial germ cell migration.","date":"2020","source":"Nature communications","url":"https://pubmed.ncbi.nlm.nih.gov/32332736","citation_count":22,"is_preprint":false},{"pmid":"31233836","id":"PMC_31233836","title":"PDS5B regulates cell proliferation and motility via upregulation of Ptch2 in pancreatic cancer cells.","date":"2019","source":"Cancer 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genome variation","url":"https://pubmed.ncbi.nlm.nih.gov/30820324","citation_count":15,"is_preprint":false},{"pmid":"34170463","id":"PMC_34170463","title":"PTCH2 is not a strong candidate gene for gorlin syndrome predisposition.","date":"2021","source":"Familial cancer","url":"https://pubmed.ncbi.nlm.nih.gov/34170463","citation_count":14,"is_preprint":false},{"pmid":"31945512","id":"PMC_31945512","title":"Gorlin-like phenotype in a patient with a PTCH2 variant of uncertain significance.","date":"2020","source":"European journal of medical genetics","url":"https://pubmed.ncbi.nlm.nih.gov/31945512","citation_count":14,"is_preprint":false},{"pmid":"30166346","id":"PMC_30166346","title":"The protein-specific activities of the transmembrane modules of Ptch1 and Ptch2 are determined by their adjacent protein domains.","date":"2018","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/30166346","citation_count":12,"is_preprint":false},{"pmid":"29703892","id":"PMC_29703892","title":"Interaction of the primordial germ cell-specific protein C2EIP with PTCH2 directs differentiation of embryonic stem cells via HH signaling activation.","date":"2018","source":"Cell death & disease","url":"https://pubmed.ncbi.nlm.nih.gov/29703892","citation_count":11,"is_preprint":false},{"pmid":"34990798","id":"PMC_34990798","title":"Inherited rare and common variants in PTCH1 and PTCH2 contributing to the predisposition to reproductive cancers.","date":"2022","source":"Gene","url":"https://pubmed.ncbi.nlm.nih.gov/34990798","citation_count":8,"is_preprint":false},{"pmid":"18278130","id":"PMC_18278130","title":"[PTCH2 gene alterations in keratocystic odontogenic tumors associated with nevoid basal cell carcinoma syndrome].","date":"2008","source":"Beijing da xue xue bao. Yi xue ban = Journal of Peking University. Health sciences","url":"https://pubmed.ncbi.nlm.nih.gov/18278130","citation_count":6,"is_preprint":false},{"pmid":"34979374","id":"PMC_34979374","title":"Expression pattern of Ptch2 in mouse embryonic maxillofacial development.","date":"2021","source":"Acta histochemica","url":"https://pubmed.ncbi.nlm.nih.gov/34979374","citation_count":4,"is_preprint":false},{"pmid":"12438747","id":"PMC_12438747","title":"Genomic structure and refined chromosomal localization of the mouse Ptch2 gene.","date":"2002","source":"Cytogenetic and genome research","url":"https://pubmed.ncbi.nlm.nih.gov/12438747","citation_count":3,"is_preprint":false},{"pmid":"35574464","id":"PMC_35574464","title":"Ptch2 is a Potential Regulator of Mesenchymal Stem Cells.","date":"2022","source":"Frontiers in physiology","url":"https://pubmed.ncbi.nlm.nih.gov/35574464","citation_count":3,"is_preprint":false},{"pmid":"38360123","id":"PMC_38360123","title":"Identification of rare variants in PTCH2 associated with non-syndromic orofacial clefts.","date":"2024","source":"Gene","url":"https://pubmed.ncbi.nlm.nih.gov/38360123","citation_count":2,"is_preprint":false},{"pmid":"32371876","id":"PMC_32371876","title":"Author Correction: Ptch2/Gas1 and Ptch1/Boc differentially regulate Hedgehog signalling in murine primordial germ cell migration.","date":"2020","source":"Nature communications","url":"https://pubmed.ncbi.nlm.nih.gov/32371876","citation_count":2,"is_preprint":false},{"pmid":"36027694","id":"PMC_36027694","title":"Reduced PTCH2 expression is associated with glioma development through its regulation of the PTEN/AKT signaling pathway.","date":"2022","source":"Biochemical and biophysical research communications","url":"https://pubmed.ncbi.nlm.nih.gov/36027694","citation_count":1,"is_preprint":false},{"pmid":"38354379","id":"PMC_38354379","title":"Gorlin-Like Phenotype in a Young Girl With a De Novo PTCH2 Variant Mutation of Uncertain Significance.","date":"2024","source":"The American Journal of dermatopathology","url":"https://pubmed.ncbi.nlm.nih.gov/38354379","citation_count":1,"is_preprint":false},{"pmid":"41681386","id":"PMC_41681386","title":"Ptch2 Deficiency Triggers Lipoma Formation and Adipogenic Transcriptome Reprogramming in Nile tilapia (Oreochromis niloticus).","date":"2026","source":"Animals : an open access journal from MDPI","url":"https://pubmed.ncbi.nlm.nih.gov/41681386","citation_count":0,"is_preprint":false},{"pmid":"39800815","id":"PMC_39800815","title":"Dual PTCH2 mutation [Ser391*, Leu104Pro]: unveiling a potential new genetic susceptibility factor for glioma development.","date":"2025","source":"Investigational new drugs","url":"https://pubmed.ncbi.nlm.nih.gov/39800815","citation_count":0,"is_preprint":false},{"pmid":"33047712","id":"PMC_33047712","title":"[Exploring parent-of-origin effects for non-syndromic cleft lip with or without cleft palate on PTCH1, PTCH2, SHH, SMO genes in Chinese case-parent trios].","date":"2020","source":"Beijing da xue xue bao. Yi xue ban = Journal of Peking University. Health sciences","url":"https://pubmed.ncbi.nlm.nih.gov/33047712","citation_count":0,"is_preprint":false},{"pmid":null,"id":"bio_10.1101_2025.06.13.659479","title":"Desert Hedgehog mediates stem Leydig cell differentiation through Ptch2/Gli1/Sf1 signaling axis","date":"2025-06-15","source":"bioRxiv","url":"https://doi.org/10.1101/2025.06.13.659479","citation_count":0,"is_preprint":true},{"pmid":null,"id":"bio_10.1101_2024.06.18.599642","title":"Increased Netrin downstream of overactive Hedgehog signaling disrupts optic fissure formation","date":"2024-06-22","source":"bioRxiv","url":"https://doi.org/10.1101/2024.06.18.599642","citation_count":0,"is_preprint":true}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":17366,"output_tokens":3572,"usd":0.052839},"stage2":{"model":"claude-opus-4-6","input_tokens":6951,"output_tokens":3095,"usd":0.168195},"total_usd":0.221034,"stage1_batch_id":"msgbatch_01SUR8NDzVrNmyszWyJeCct7","stage2_batch_id":"msgbatch_01G7Yfutko3cDWzejrwH5AMx","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 1999,\n      \"finding\": \"PTCH2 encodes a 1203 amino acid putative transmembrane protein highly homologous to PTCH1, localized to chromosome 1p32.1-32.3, comprising 22 coding exons spanning ~15 kb of genomic DNA; truncating mutations identified in medulloblastoma and splice donor site mutations in basal cell carcinoma implicate it as a tumor suppressor.\",\n      \"method\": \"SSCP mutation analysis, genomic cloning, direct sequencing\",\n      \"journal\": \"Human molecular genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — original cloning and mutation identification with genomic characterization; single study\",\n      \"pmids\": [\"9931336\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"PTCH2 undergoes alternative splicing producing multiple mRNA isoforms, including transcripts lacking segments involved in Sonic Hedgehog binding; PTCH2 is a transcriptional target upregulated by HH signaling (negative regulation by PTCH1), linking it to the SHH/PTCH signaling pathway.\",\n      \"method\": \"cDNA library screening, RACE, BAC sequencing, in situ hybridization, radiation hybrid mapping\",\n      \"journal\": \"Cancer research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — multiple molecular methods in single study establishing pathway membership and alternative splicing\",\n      \"pmids\": [\"10029063\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"Mouse Ptch2 is expressed both in Shh-producing epithelial cells (tooth, hair, whisker) and in adjacent non-producing cells, overlapping but distinct from Ptch1 expression pattern, suggesting distinct roles in Shh signaling during development.\",\n      \"method\": \"In situ hybridization, chromosomal localization\",\n      \"journal\": \"Mechanisms of development\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 — localization without direct functional consequence demonstrated\",\n      \"pmids\": [\"9858693\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"PTCH2 splice variants localized in the cytoplasm can internalize the N-terminal fragment of Sonic HH (Shh-N); only one PTCH2 variant inhibits SHH-N promoter activity whereas none can inhibit activated SMO-M2 (unlike PTCH1); all PTCH2 isoforms alter SMO localization from cytoplasm to juxtanuclear region upon co-transfection; PTCH2 isoforms physically interact with PTCH1 (confirmed by co-immunoprecipitation); PTCH2 variants and PTCH1 differentially reconstitute SHH- and Desert HH-dependent transcriptional responses in Ptch1-/- cells.\",\n      \"method\": \"Promoter reporter assays, immunofluorescence localization, co-immunoprecipitation, Ptch1-/- cell reconstitution, Shh-N internalization assay\",\n      \"journal\": \"The Biochemical journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — multiple orthogonal functional assays including co-IP, reporter assays, SMO localization, and Ptch1-/- reconstitution in single study\",\n      \"pmids\": [\"14613484\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"The PTCH2 missense mutation R719Q (in an extracellular loop) results in loss of PTCH2 inhibitory activity on the SHH signaling pathway and loss of ability to inhibit cell proliferation, demonstrating that this extracellular domain is functionally required for PTCH2 tumor suppressor activity.\",\n      \"method\": \"GLI1 reporter gene assay, cell growth curve analysis, direct sequencing, restriction enzyme digestion\",\n      \"journal\": \"Journal of medical genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — functional assays with specific mutant showing loss of inhibitory activity; single lab\",\n      \"pmids\": [\"18285427\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"PTCH2 functions as a ciliary-localized HH pathway antagonist in vertebrate neural patterning; while dispensable alone, combined loss of PTCH2 and PTCH1 feedback antagonism produces significant expansion of HH-dependent ventral neural progenitors; triple loss of PTCH2, HHIP1, and PTCH1 feedback results in ectopic specification of ventral cell fates throughout the neural tube reflecting constitutive HH pathway activation.\",\n      \"method\": \"Mouse genetic epistasis (Ptch1, Ptch2, Hhip1 knockout combinations), neural tube patterning analysis, ciliary localization imaging\",\n      \"journal\": \"Development (Cambridge, England)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic epistasis with multiple knockout combinations and clear cellular phenotypes; strong evidence from compound mutant analysis\",\n      \"pmids\": [\"23900540\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Ptch2 mediates Shh signaling in the absence of Ptch1: expression of dominant-negative Ptch2 in chick neural tube activates the Shh response; Ptch1-/-;Ptch2-/- cells cannot further activate the Shh response, demonstrating Ptch2 is required for the residual Shh sensitivity in Ptch1-/- cells.\",\n      \"method\": \"Dominant-negative expression in chick neural tube, Ptch1-/-;Ptch2-/- double-knockout cell analysis, Shh-blocking antibody (5E1) inhibition, fibroblast migration assay\",\n      \"journal\": \"Development (Cambridge, England)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic epistasis using double knockouts and dominant-negative constructs with clear mechanistic pathway placement; multiple orthogonal approaches\",\n      \"pmids\": [\"25085974\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Ptch2 is a functional Shh receptor that regulates SMO localization and activity in vitro; Ptch1 and Ptch2 co-operate in regulating cellular responses to Shh in vivo, as loss of Ptch2 exacerbates limb outgrowth defects in limb-specific Ptch1 knockout mutants.\",\n      \"method\": \"In vitro SMO localization assay, limb-specific Ptch1 knockout combined with Ptch2 knockout, limb bud co-expression analysis\",\n      \"journal\": \"Developmental biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — in vitro receptor activity assay combined with in vivo genetic epistasis in compound mutants\",\n      \"pmids\": [\"25448692\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Ptch2 loss in hematopoietic niche cells drives hyperactive noncanonical HH signaling, resulting in reduced production of HSC regulators (Scf, Cxcl12, Jag1) and osteoblast depletion; hematopoietic loss of Ptch2 drives leukocytosis and promotes HSC maintenance; Ptch2-/- mice develop a myeloproliferative neoplasm phenotype demonstrating that Ptch2 regulates both canonical and noncanonical HH signaling in hematopoiesis.\",\n      \"method\": \"Ptch2-/- mouse model, bone marrow transplantation, flow cytometry, gene expression analysis, HSC functional assays (5-FU treatment, replating)\",\n      \"journal\": \"The Journal of experimental medicine\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — comprehensive KO mouse study with niche-specific and hematopoietic-specific dissection of function, multiple cellular phenotypes with mechanistic pathway placement\",\n      \"pmids\": [\"26834157\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"The sterol-sensing domains (SSDs) of PTCH2 can substitute for those of PTCH1 in chimeric proteins to repress HH signaling, demonstrating SSDs act as generic modules; however, the cytoplasmic domains of PTCH1 are necessary but not sufficient for HH repression, and the two principal luminal domains of PTCH1 and PTCH2 are interchangeable; the N-terminal and C-terminal halves of PTCH1 associate noncovalently to mediate ligand-dependent Hh regulation, whereas analogous PTCH2 regions interact but do not repress the pathway.\",\n      \"method\": \"Chimeric protein construction, HH pathway reporter assays, co-immunoprecipitation of PTCH1 N- and C-terminal halves, domain-swap mutagenesis\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — systematic domain-swap mutagenesis with functional reconstitution assays defining specific structural determinants of activity\",\n      \"pmids\": [\"30166346\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"C2EIP interacts with PTCH2 at the intracellular membrane, promotes PTCH2 ubiquitination, and thereby activates HH signaling via competitive inhibition of SMO to regulate primordial germ cell generation from embryonic stem cells.\",\n      \"method\": \"Co-immunoprecipitation (C2EIP-PTCH2 interaction), ubiquitination assay, C2EIP knockout/overexpression, PGC differentiation assay\",\n      \"journal\": \"Cell death & disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — co-IP and ubiquitination assay with functional KO/OE phenotype; single lab study\",\n      \"pmids\": [\"29703892\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Ptch2 forms a specific hetero-complex with Gas1 (while Ptch1 partners with Boc) to mediate Smo de-repression with distinct kinetics in primordial germ cell migration; Ptch2-mediated HH signaling induces phosphorylation of Creb and Src proteins in parallel to Gli induction, defining a Ptch2-specific non-canonical signal pathway distinct from Ptch1.\",\n      \"method\": \"Genetic analysis of primordial germ cell migration in mouse, co-receptor complex characterization, phosphorylation analysis (Creb, Src), Gli induction assays, Ptch1/2 and Gas1/Boc knockout combinations\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal genetic and biochemical approaches revealing distinct Ptch2-specific signaling mechanism with strong epistasis data\",\n      \"pmids\": [\"32332736\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"PTCH2 overexpression upregulates tumor suppressor PTEN expression, leading to suppression of pro-survival AKT signals in glioma cells, suppressing proliferation and invasion.\",\n      \"method\": \"PTCH2 overexpression in glioma cell lines (LN229, U87-MG), western blotting for PTEN/AKT, in vitro proliferation/invasion assays, in vivo tumor-bearing mouse survival\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — gain-of-function with defined pathway readout (PTEN/AKT); single lab, limited mechanistic depth on how PTCH2 regulates PTEN\",\n      \"pmids\": [\"36027694\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Loss of Ptch2 increases number of putative mesenchymal stem cells in continuously growing incisor, causes increased bone length/volume linked to augmented MSC differentiation potential in bone marrow, and alters skin wound closure, establishing Ptch2 as a regulator of HH signaling in MSC biology and organ regeneration.\",\n      \"method\": \"Ptch2-/- mouse model, histology, immunostaining, microCT, CFU assay, in vitro differentiation assay, in vivo wound healing assay\",\n      \"journal\": \"Frontiers in physiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — KO mouse with multiple tissue phenotypes and in vitro MSC functional assays; single lab study\",\n      \"pmids\": [\"35574464\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"PTCH2 is a 22-exon transmembrane receptor in the Hedgehog signaling pathway that, via its sterol-sensing domains and cytoplasmic regions, binds Sonic/Desert HH ligands, physically interacts with PTCH1, regulates SMO localization and activity, and functions as a ligand-dependent feedback antagonist of HH signaling; it forms a specific hetero-complex with Gas1 (distinct from the Ptch1/Boc complex) and activates a unique non-canonical Ptch2-specific signaling branch (Creb/Src phosphorylation) in addition to canonical Gli-mediated transcription, while its ubiquitination by C2EIP interaction promotes HH pathway activation, and loss of Ptch2 in hematopoietic niches dysregulates HSC regulatory factors and drives myeloproliferative disease.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"PTCH2 is a twelve-pass transmembrane receptor in the Hedgehog (HH) signaling pathway that functions as a ligand-dependent feedback antagonist by binding Sonic and Desert Hedgehog ligands, regulating Smoothened (SMO) subcellular localization and activity, and repressing HH target gene transcription through its sterol-sensing domains and cytoplasmic regions [PMID:14613484, PMID:30166346, PMID:25085974]. PTCH2 localizes to primary cilia and cooperates with PTCH1 to attenuate HH signaling during vertebrate neural patterning, limb development, and hematopoiesis, where its loss drives myeloproliferative disease through dysregulation of HSC niche factors including Scf, Cxcl12, and Jag1 [PMID:23900540, PMID:25448692, PMID:26834157]. PTCH2 forms a specific hetero-complex with the co-receptor Gas1 (distinct from the Ptch1–Boc complex) and activates a non-canonical signaling branch involving Creb and Src phosphorylation during primordial germ cell migration [PMID:32332736]. Truncating mutations in PTCH2 have been identified in medulloblastoma and basal cell carcinoma, and the extracellular loop residue R719 is functionally required for its tumor-suppressive inhibition of HH pathway activity [PMID:9931336, PMID:18285427].\",\n  \"teleology\": [\n    {\n      \"year\": 1998,\n      \"claim\": \"Identification of mouse Ptch2 with an expression pattern overlapping yet distinct from Ptch1 in HH-producing and adjacent tissues raised the question of whether a second Patched receptor has non-redundant roles in HH signaling.\",\n      \"evidence\": \"In situ hybridization and chromosomal mapping in mouse embryonic tissues\",\n      \"pmids\": [\"9858693\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"Expression pattern alone; no functional data demonstrating distinct signaling role\", \"No loss-of-function or gain-of-function experiments performed\"]\n    },\n    {\n      \"year\": 1999,\n      \"claim\": \"Cloning of human PTCH2, mapping to 1p32, and identification of truncating mutations in medulloblastoma and splice-site mutations in BCC established PTCH2 as a candidate tumor suppressor in the HH pathway, while discovery of alternative splicing affecting SHH-binding regions and transcriptional upregulation by HH signaling placed it as a pathway feedback component.\",\n      \"evidence\": \"Genomic cloning, SSCP mutation analysis, cDNA library screening, RACE, in situ hybridization\",\n      \"pmids\": [\"9931336\", \"10029063\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No direct demonstration of tumor suppressor function in cell-based or animal models\", \"Functional consequences of individual splice isoforms not determined\"]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"Functional dissection revealed that PTCH2 internalizes SHH-N, physically interacts with PTCH1, and redirects SMO from the cytoplasm to a juxtanuclear compartment, but unlike PTCH1 cannot inhibit constitutively active SMO-M2, establishing that PTCH2 regulates SMO through a mechanism partially distinct from PTCH1.\",\n      \"evidence\": \"Co-immunoprecipitation, immunofluorescence, SHH-N internalization assay, promoter reporter assays, Ptch1−/− cell reconstitution\",\n      \"pmids\": [\"14613484\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism by which PTCH2 alters SMO localization not resolved\", \"Whether PTCH2–PTCH1 interaction is required for SMO regulation unclear\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"The missense mutation R719Q in an extracellular loop abolished PTCH2 inhibitory activity on HH signaling and cell proliferation, pinpointing a critical functional residue for tumor suppressor activity.\",\n      \"evidence\": \"GLI1 reporter assay and cell growth curve analysis with R719Q mutant\",\n      \"pmids\": [\"18285427\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No structural basis for why R719Q disrupts function\", \"Single mutant study; other extracellular loop residues not systematically tested\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Mouse genetic epistasis with PTCH1 and HHIP1 demonstrated that PTCH2 is a ciliary-localized feedback antagonist that is dispensable alone but essential in combination for restraining HH-dependent ventral neural progenitor expansion, resolving why single Ptch2 knockouts have mild phenotypes.\",\n      \"evidence\": \"Compound knockout mice (Ptch1/Ptch2/Hhip1), neural tube patterning analysis, ciliary localization imaging\",\n      \"pmids\": [\"23900540\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism of PTCH2 ciliary localization not defined\", \"Whether PTCH2 feedback antagonism operates identically across all HH-responsive tissues unknown\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Two independent studies established that PTCH2 is a bona fide SHH receptor that mediates residual HH signaling in Ptch1-null cells and cooperates with PTCH1 in vivo for limb outgrowth, resolving the question of whether PTCH2 functions as a true receptor or merely a modulator.\",\n      \"evidence\": \"Dominant-negative Ptch2 in chick neural tube, Ptch1−/−;Ptch2−/− double-KO cells, limb-specific Ptch1-KO combined with Ptch2-KO, SMO localization assays\",\n      \"pmids\": [\"25085974\", \"25448692\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Relative affinities of PTCH2 vs PTCH1 for different HH ligands not quantified\", \"Whether PTCH2 mediates cholesterol transport like PTCH1 not addressed\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Ptch2 knockout mice revealed that PTCH2 regulates the hematopoietic niche through both canonical and noncanonical HH signaling, with loss causing osteoblast depletion, reduced Scf/Cxcl12/Jag1 production, leukocytosis, and myeloproliferative disease, establishing a physiological role beyond development.\",\n      \"evidence\": \"Ptch2−/− mouse model, bone marrow transplantation, flow cytometry, gene expression analysis, HSC functional assays\",\n      \"pmids\": [\"26834157\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular identity of the noncanonical HH signaling mechanism downstream of PTCH2 in hematopoietic niche not defined\", \"Whether myeloproliferative phenotype is cell-autonomous or niche-dependent not fully resolved\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Domain-swap chimeras showed that the sterol-sensing domains of PTCH2 are interchangeable with those of PTCH1 for HH repression, but PTCH1 cytoplasmic domains are uniquely required, explaining the functional divergence between the paralogs at a structural level; separately, C2EIP was identified as a PTCH2-interacting protein that promotes its ubiquitination to activate HH signaling during primordial germ cell differentiation.\",\n      \"evidence\": \"Chimeric PTCH1/2 proteins with HH reporter assays, co-IP of N/C-terminal halves; C2EIP–PTCH2 co-IP, ubiquitination assay, PGC differentiation in ESCs\",\n      \"pmids\": [\"30166346\", \"29703892\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Identity of the E3 ubiquitin ligase for PTCH2 not determined\", \"Structural basis for why PTCH2 cytoplasmic domains cannot substitute for PTCH1 unknown\", \"C2EIP–PTCH2 interaction validated by co-IP only; reciprocal and endogenous confirmation limited\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Discovery that Ptch2 forms a specific complex with Gas1 (not Boc) and activates Creb/Src phosphorylation alongside canonical Gli signaling during primordial germ cell migration defined a non-canonical Ptch2-specific signaling branch, distinguishing it mechanistically from Ptch1.\",\n      \"evidence\": \"Mouse genetic analysis of PGC migration with Ptch1/2 and Gas1/Boc knockouts, phosphorylation analysis of Creb and Src, Gli induction assays\",\n      \"pmids\": [\"32332736\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether Creb/Src phosphorylation is direct or requires intermediary kinases unknown\", \"Generalizability of Ptch2–Gas1 complex beyond PGC migration not established\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Ptch2 loss increased mesenchymal stem cells and bone volume, and PTCH2 overexpression upregulated PTEN to suppress AKT signaling in glioma, expanding the functional scope of PTCH2 to stem cell homeostasis and a PTEN/AKT regulatory axis.\",\n      \"evidence\": \"Ptch2−/− mouse (incisor, bone, wound healing phenotypes); PTCH2 overexpression in glioma lines with PTEN/AKT western blots and xenograft survival\",\n      \"pmids\": [\"35574464\", \"36027694\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism by which PTCH2 regulates PTEN expression not identified\", \"Whether MSC expansion phenotype is cell-autonomous or niche-mediated not resolved\", \"PTEN regulation could be indirect via canonical HH pathway modulation\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Critical open questions include: the structural basis for PTCH2 function (no cryo-EM or crystal structure), whether PTCH2 transports cholesterol like PTCH1, the identity of kinases mediating Ptch2-specific Creb/Src phosphorylation, and the molecular mechanism by which PTCH2 cytoplasmic domains fail to repress HH signaling when substituted for those of PTCH1.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No structural model of PTCH2 available\", \"Cholesterol transport function not tested\", \"Downstream mediators of Ptch2-specific non-canonical signaling uncharacterized\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0060089\", \"supporting_discovery_ids\": [3, 6, 7, 11]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [3, 5, 9]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005929\", \"supporting_discovery_ids\": [5]},\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [3, 9]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [3, 5, 6, 7, 9, 11]},\n      {\"term_id\": \"R-HSA-1266738\", \"supporting_discovery_ids\": [5, 7, 11]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [0, 4, 12]}\n    ],\n    \"complexes\": [\n      \"Ptch2-Gas1 co-receptor complex\"\n    ],\n    \"partners\": [\n      \"PTCH1\",\n      \"GAS1\",\n      \"SMO\",\n      \"SHH\",\n      \"DHH\",\n      \"C2EIP\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}