{"gene":"OPHN1","run_date":"2026-06-10T05:19:53","timeline":{"discoveries":[{"year":2003,"finding":"OPHN1 is a novel F-actin-binding protein; its RhoGAP domain inhibits Rho pathways and regulates the actin cytoskeleton in vivo, while its amino-terminal domain negatively controls RhoGAP activity through an intramolecular inhibitory mechanism. OPHN1 colocalizes with actin at the tip of growing neurites, and the F-actin interaction is mediated by a novel carboxyl-terminal domain.","method":"Overexpression in fibroblasts; co-localization studies; domain deletion/overexpression analysis; in vivo actin cytoskeleton assays","journal":"Molecular and cellular neurosciences","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple cellular assays (overexpression, co-localization, domain analysis) in a single lab establishing RhoGAP activity and autoinhibitory mechanism","pmids":["12932438"],"is_preprint":false},{"year":2009,"finding":"OPHN1 forms a complex with endophilin A1 (a membrane curvature-generating protein) at presynaptic sites, and both this interaction and OPHN1's Rho-GAP activity are required for OPHN1's role in controlling the kinetic efficiency of synaptic vesicle endocytosis at hippocampal synapses. OPHN1 knockdown impairs the SV cycling/endocytosis rate.","method":"Co-immunoprecipitation; shRNA knockdown in hippocampal neurons; live fluorescence imaging of SV cycling (FM dye assays); epistasis with endophilin A1","journal":"Current biology : CB","confidence":"High","confidence_rationale":"Tier 2 / Moderate — reciprocal Co-IP identifying complex, shRNA loss-of-function with defined endocytosis phenotype, and domain-specific rescue in neurons","pmids":["19481455"],"is_preprint":false},{"year":2011,"finding":"mGluR1 activation induces rapid dendritic synthesis of OPHN1 (independent of FMRP), and this newly synthesized OPHN1 mediates mGluR-LTD and persistent decreases in surface AMPARs via interactions with endophilin A2/3. Separately, OPHN1's role in basal synaptic strength requires its Rho-GAP activity and interaction with Homer1b/c, distinguishing two mechanistically distinct functions.","method":"Acute OPHN1 synthesis blockade; Co-immunoprecipitation with endophilin A2/3 and Homer1b/c; hippocampal slice electrophysiology; surface AMPAR quantification; shRNA knockdown","journal":"Neuron","confidence":"High","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal methods (translational blockade, Co-IP, electrophysiology, surface receptor assay) in a single rigorous study establishing two distinct mechanistic roles","pmids":["22017989"],"is_preprint":false},{"year":2014,"finding":"OPHN1 physically interacts with Homer1b/c, and this interaction is crucial for positioning the endocytic zone (EZ) adjacent to the postsynaptic density (PSD) in dendritic spines. Disruption of the OPHN1-Homer1b/c interaction displaces EZs from the PSD, impairs AMPAR recycling and accumulation at synapses, and reduces activity-dependent synaptic potentiation in rat hippocampus.","method":"Co-immunoprecipitation; shRNA knockdown; live-cell fluorescence imaging of EZ positioning; AMPAR surface quantification; electrophysiology in hippocampal slices","journal":"The Journal of neuroscience : the official journal of the Society for Neuroscience","confidence":"High","confidence_rationale":"Tier 2 / Moderate — reciprocal Co-IP, shRNA loss-of-function, live imaging of EZ displacement, AMPAR recycling assay, and electrophysiology in a single focused study","pmids":["24966368"],"is_preprint":false},{"year":2013,"finding":"An in-frame deletion removing 37 amino acids from the conserved N-terminal BAR domain of OPHN1 produces a stable mutant transcript and is associated with hippocampal alterations not seen in canonical loss-of-function mutations, suggesting the BAR domain has a distinct functional role in the hippocampus.","method":"cDNA expression analysis; mRNA splicing analysis; MRI neuroimaging correlation with BAR domain deletion","journal":"European journal of human genetics : EJHG","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single family, molecular characterization of mutant transcript but no direct functional assay of BAR domain activity","pmids":["24105372"],"is_preprint":false},{"year":2014,"finding":"OPHN1 transcript undergoes ADAR2-mediated A-to-I RNA editing and alternative splicing in human brain during development, with editing detectable from gestational week 18 and peaking at weeks 20–33 coinciding with increased OPHN1 expression and the appearance of a novel splicing isoform.","method":"Sequencing of OPHN1 cDNA from human fetal and adult brain; RT-PCR; A-to-I editing quantification","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct sequencing demonstrating RNA editing and alternative splicing at defined developmental stages, single lab but multiple methods","pmids":["24637888"],"is_preprint":false},{"year":2026,"finding":"A K306N variant in the PH domain of OPHN1 (outside the BAR and GAP domains) enhances OPHN1 binding to phosphatidylinositol phosphates PI4P and PI5P, and is associated with cyclic strabismus without intellectual disability, suggesting that PH domain-mediated phosphoinositide binding influences subcellular localization of OPHN1.","method":"Identification of hemizygous variant; in vitro phosphoinositide binding assay; clinical phenotyping","journal":"Scientific reports","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single patient, in vitro lipid binding assay but no direct functional rescue or localization experiment confirming the proposed mechanism","pmids":["42031848"],"is_preprint":false},{"year":2025,"finding":"Postnatal Ophn1 deficiency specifically in hippocampal astrocytes impairs synaptic transmission, short-term plasticity, and spatial working memory in adults. The mechanism involves an adenosine A1 receptor-dependent presynaptic pathway associated with increased astroglial synapse coverage (morphological rearrangement). These deficits are rescued by pharmacological inhibition of the RhoA/ROCK pathway.","method":"Cell-type-specific conditional Ophn1 knockdown (postnatal, astrocyte-restricted); electrophysiology; behavioral testing (spatial working memory); morphological analysis of astroglial coverage; pharmacological RhoA/ROCK inhibition rescue","journal":"bioRxiv","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — conditional cell-type-specific KO with electrophysiology, behavior, morphology, and pharmacological rescue; preprint, single lab","pmids":["bio_10.1101_2025.01.09.632152"],"is_preprint":true}],"current_model":"OPHN1 is a RhoGAP protein (with BAR, PH, RhoGAP, and proline-rich domains) that suppresses Rho GTPase signaling to regulate the actin cytoskeleton; at presynaptic terminals it complexes with endophilin A1 to support synaptic vesicle endocytosis, while postsynaptically it interacts with Homer1b/c to position the endocytic zone adjacent to the PSD for AMPAR recycling and synaptic potentiation, and its rapid mGluR1-triggered dendritic synthesis mediates mGluR-LTD via endophilin A2/3; additionally, astroglial OPHN1 controls hippocampal synaptic transmission and short-term plasticity through a RhoA/ROCK- and adenosine A1 receptor-dependent mechanism."},"narrative":{"mechanistic_narrative":"OPHN1 is a Rho GTPase-activating protein that couples suppression of Rho signaling to control of the actin cytoskeleton and to membrane dynamics at neuronal synapses [PMID:12932438, PMID:19481455]. Its RhoGAP domain inhibits Rho pathways and is held in check by an intramolecular autoinhibitory mechanism mediated by its amino-terminal region, while a distinct carboxy-terminal domain binds F-actin and localizes the protein to the tips of growing neurites [PMID:12932438]. At presynaptic terminals OPHN1 complexes with the membrane curvature-generating protein endophilin A1, and both this interaction and its Rho-GAP activity are required to set the kinetic efficiency of synaptic vesicle endocytosis [PMID:19481455]. Postsynaptically, OPHN1 binds Homer1b/c to position the endocytic zone adjacent to the postsynaptic density, a configuration needed for AMPA receptor recycling, surface accumulation, and activity-dependent synaptic potentiation [PMID:24966368]. A mechanistically separate function operates during plasticity: mGluR1 activation triggers rapid dendritic synthesis of OPHN1, and this newly made protein mediates mGluR-LTD and persistent loss of surface AMPARs through interactions with endophilin A2/3, distinct from its Homer1b/c-dependent role in basal synaptic strength [PMID:22017989]. Beyond neurons, OPHN1 in hippocampal astrocytes controls synaptic transmission and short-term plasticity via an adenosine A1 receptor-dependent presynaptic pathway whose deficits are reversed by RhoA/ROCK inhibition [PMID:bio_10.1101_2025.01.09.632152].","teleology":[{"year":2003,"claim":"Established OPHN1 as an actin-regulatory RhoGAP and defined its domain logic, answering what biochemical activity the protein carries and how that activity is controlled.","evidence":"Overexpression, co-localization, and domain deletion analysis in fibroblasts with in vivo actin cytoskeleton assays","pmids":["12932438"],"confidence":"Medium","gaps":["Activity demonstrated largely by overexpression in non-neuronal cells, not endogenous neuronal context","Identity of the Rho-family substrate(s) preferentially regulated not resolved","Physiological trigger that relieves N-terminal autoinhibition unknown"]},{"year":2009,"claim":"Showed OPHN1 acts presynaptically through a defined partner, answering how its GAP activity is deployed at synapses by linking it to endophilin A1 and synaptic vesicle endocytosis.","evidence":"Reciprocal Co-IP, shRNA knockdown in hippocampal neurons, FM-dye live imaging of SV cycling, and domain-specific epistasis","pmids":["19481455"],"confidence":"High","gaps":["How Rho-GAP activity and endophilin binding are coordinated mechanistically not resolved","Whether OPHN1 acts during a specific endocytic step versus globally unclear"]},{"year":2011,"claim":"Separated two OPHN1 functions, answering whether basal and plasticity roles are the same mechanism by showing mGluR1-triggered dendritic synthesis drives mGluR-LTD via endophilin A2/3 while basal strength requires GAP activity plus Homer1b/c.","evidence":"Acute translational blockade, Co-IP with endophilin A2/3 and Homer1b/c, hippocampal slice electrophysiology, surface AMPAR quantification, and shRNA","pmids":["22017989"],"confidence":"High","gaps":["Signaling that couples mGluR1 activation to OPHN1 mRNA translation not defined","How locally synthesized OPHN1 selects endophilin A2/3 over A1 unknown"]},{"year":2014,"claim":"Explained how OPHN1 organizes the postsynaptic membrane, answering why Homer1b/c binding matters by showing it positions the endocytic zone next to the PSD for AMPAR recycling and potentiation.","evidence":"Reciprocal Co-IP, shRNA knockdown, live imaging of endocytic zone positioning, AMPAR surface assays, and hippocampal slice electrophysiology","pmids":["24966368"],"confidence":"High","gaps":["Structural basis of the OPHN1-Homer1b/c interaction not determined","Whether GAP activity contributes to EZ positioning separate from the scaffolding role unclear"]},{"year":2014,"claim":"Documented developmental regulation of the transcript, answering whether OPHN1 is post-transcriptionally tuned by showing ADAR2-mediated A-to-I editing and alternative splicing peaking during human fetal brain development.","evidence":"Sequencing of OPHN1 cDNA from fetal and adult human brain with RT-PCR and editing quantification","pmids":["24637888"],"confidence":"Medium","gaps":["Functional consequence of edited/spliced isoforms on protein activity not tested","Whether editing alters domain function or localization unknown"]},{"year":2013,"claim":"Probed the BAR domain's specific contribution, addressing whether N-terminal regions have hippocampus-specific roles via an in-frame BAR-domain deletion associated with hippocampal alterations distinct from null mutations.","evidence":"cDNA and splicing analysis of a single family with MRI correlation","pmids":["24105372"],"confidence":"Low","gaps":["Single family with no direct functional assay of BAR domain activity","Mechanism linking BAR deletion to hippocampal phenotype not established"]},{"year":2026,"claim":"Implicated the PH domain in phosphoinositide-directed localization, addressing how OPHN1 is targeted within cells via a K306N variant that enhances PI4P/PI5P binding and is linked to cyclic strabismus without intellectual disability.","evidence":"Single-patient variant identification, in vitro phosphoinositide binding assay, and clinical phenotyping","pmids":["42031848"],"confidence":"Low","gaps":["Single patient with in vitro binding only, no functional rescue or localization experiment","Causal link between altered lipid binding and the strabismus phenotype unproven"]},{"year":2025,"claim":"Extended OPHN1 function beyond neurons, addressing the cell-autonomy of its synaptic roles by showing astrocyte-specific deficiency impairs transmission and memory via an adenosine A1 receptor pathway rescuable by RhoA/ROCK inhibition.","evidence":"Postnatal astrocyte-restricted conditional Ophn1 knockdown with electrophysiology, behavior, morphology, and pharmacological rescue (preprint)","pmids":["bio_10.1101_2025.01.09.632152"],"confidence":"Medium","gaps":["Preprint, single lab, not peer-reviewed","How astroglial RhoA/ROCK signaling engages presynaptic A1 receptors mechanistically unclear","Relative contribution of astroglial versus neuronal OPHN1 to circuit phenotypes not partitioned"]},{"year":null,"claim":"How OPHN1's autoinhibition, phosphoinositide binding, and partner selection are integrated to direct context-specific functions across pre-, post-synaptic, and astroglial compartments remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No structural model integrating BAR, PH, GAP, and proline-rich domains in a functional state","Upstream signals relieving autoinhibition in each compartment not identified","Preferred Rho-family substrate(s) in vivo not defined"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[0]},{"term_id":"GO:0008092","term_label":"cytoskeletal protein binding","supporting_discovery_ids":[0]},{"term_id":"GO:0008289","term_label":"lipid binding","supporting_discovery_ids":[6]},{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[3]}],"localization":[{"term_id":"GO:0005856","term_label":"cytoskeleton","supporting_discovery_ids":[0]},{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[1,3]}],"pathway":[{"term_id":"R-HSA-112316","term_label":"Neuronal System","supporting_discovery_ids":[2,3]},{"term_id":"R-HSA-5653656","term_label":"Vesicle-mediated transport","supporting_discovery_ids":[1,3]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[0,7]}],"complexes":[],"partners":["SH3GL2","SH3GL1","HOMER1"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"O60890","full_name":"Oligophrenin-1","aliases":[],"length_aa":802,"mass_kda":91.6,"function":"Stimulates GTP hydrolysis of members of the Rho family. Its action on RHOA activity and signaling is implicated in growth and stabilization of dendritic spines, and therefore in synaptic function. Critical for the stabilization of AMPA receptors at postsynaptic sites. Critical for the regulation of synaptic vesicle endocytosis at presynaptic terminals. Required for the localization of NR1D1 to dendrites, can suppress its repressor activity and protect it from proteasomal degradation (By similarity)","subcellular_location":"Postsynapse; Presynapse; Cell projection, axon; Cell projection, dendritic spine; Cell projection, dendrite; Cytoplasm","url":"https://www.uniprot.org/uniprotkb/O60890/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/OPHN1","classification":"Not Classified","n_dependent_lines":3,"n_total_lines":1208,"dependency_fraction":0.0024834437086092716},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/OPHN1","total_profiled":1310},"omim":[{"mim_id":"614294","title":"CHROMOSOME 15q25 DELETION SYNDROME","url":"https://www.omim.org/entry/614294"},{"mim_id":"304110","title":"CRANIOFRONTONASAL SYNDROME; CFNS","url":"https://www.omim.org/entry/304110"},{"mim_id":"300979","title":"CHROMOSOME Xq25 DUPLICATION SYNDROME","url":"https://www.omim.org/entry/300979"},{"mim_id":"300486","title":"INTELLECTUAL DEVELOPMENTAL DISORDER, X-LINKED, SYNDROMIC, BILLUART TYPE; MRXSBL","url":"https://www.omim.org/entry/300486"},{"mim_id":"300454","title":"INTELLECTUAL DEVELOPMENTAL DISORDER, X-LINKED 77; XLID77","url":"https://www.omim.org/entry/300454"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Nucleoplasm","reliability":"Approved"},{"location":"Plasma membrane","reliability":"Approved"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/OPHN1"},"hgnc":{"alias_symbol":["OPN1","ARHGAP41"],"prev_symbol":["MRX60"]},"alphafold":{"accession":"O60890","domains":[{"cath_id":"1.20.1270.60","chopping":"10-254","consensus_level":"high","plddt":93.6786,"start":10,"end":254},{"cath_id":"2.30.29.30","chopping":"268-352","consensus_level":"high","plddt":85.7002,"start":268,"end":352},{"cath_id":"1.10.555.10","chopping":"385-565","consensus_level":"medium","plddt":92.2272,"start":385,"end":565}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/O60890","model_url":"https://alphafold.ebi.ac.uk/files/AF-O60890-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-O60890-F1-predicted_aligned_error_v6.png","plddt_mean":73.81},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=OPHN1","jax_strain_url":"https://www.jax.org/strain/search?query=OPHN1"},"sequence":{"accession":"O60890","fasta_url":"https://rest.uniprot.org/uniprotkb/O60890.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/O60890/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/O60890"}},"corpus_meta":[{"pmid":"12805098","id":"PMC_12805098","title":"Oligophrenin 1 (OPHN1) gene mutation causes syndromic X-linked mental retardation with epilepsy, rostral ventricular enlargement and cerebellar hypoplasia.","date":"2003","source":"Brain : a journal of neurology","url":"https://pubmed.ncbi.nlm.nih.gov/12805098","citation_count":96,"is_preprint":false},{"pmid":"12932438","id":"PMC_12932438","title":"The RhoGAP activity of OPHN1, a new F-actin-binding protein, is negatively controlled by its amino-terminal domain.","date":"2003","source":"Molecular and cellular neurosciences","url":"https://pubmed.ncbi.nlm.nih.gov/12932438","citation_count":83,"is_preprint":false},{"pmid":"19481455","id":"PMC_19481455","title":"The Rho-linked mental retardation protein OPHN1 controls synaptic vesicle endocytosis via endophilin A1.","date":"2009","source":"Current biology : CB","url":"https://pubmed.ncbi.nlm.nih.gov/19481455","citation_count":63,"is_preprint":false},{"pmid":"22017989","id":"PMC_22017989","title":"Rapid synthesis of the X-linked mental retardation protein OPHN1 mediates mGluR-dependent LTD through interaction with the endocytic machinery.","date":"2011","source":"Neuron","url":"https://pubmed.ncbi.nlm.nih.gov/22017989","citation_count":58,"is_preprint":false},{"pmid":"17941886","id":"PMC_17941886","title":"Contiguous gene deletions involving EFNB1, OPHN1, PJA1 and EDA in patients with craniofrontonasal syndrome.","date":"2007","source":"Clinical genetics","url":"https://pubmed.ncbi.nlm.nih.gov/17941886","citation_count":36,"is_preprint":false},{"pmid":"2222462","id":"PMC_2222462","title":"Expression of constitutive and inducible HSP70 and HSP47 is enhanced in cells persistently spread on OPN1 or collagen.","date":"1990","source":"Biochemical and biophysical research communications","url":"https://pubmed.ncbi.nlm.nih.gov/2222462","citation_count":26,"is_preprint":false},{"pmid":"20528889","id":"PMC_20528889","title":"Novel intragenic deletion in OPHN1 in a family causing XLMR with cerebellar hypoplasia and distinctive facial appearance.","date":"2011","source":"Clinical genetics","url":"https://pubmed.ncbi.nlm.nih.gov/20528889","citation_count":26,"is_preprint":false},{"pmid":"16158428","id":"PMC_16158428","title":"Delineation of the clinical phenotype associated with OPHN1 mutations based on the clinical and neuropsychological evaluation of three families.","date":"2005","source":"American journal of medical genetics. 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OPHN1 colocalizes with actin at the tip of growing neurites, and the F-actin interaction is mediated by a novel carboxyl-terminal domain.\",\n      \"method\": \"Overexpression in fibroblasts; co-localization studies; domain deletion/overexpression analysis; in vivo actin cytoskeleton assays\",\n      \"journal\": \"Molecular and cellular neurosciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple cellular assays (overexpression, co-localization, domain analysis) in a single lab establishing RhoGAP activity and autoinhibitory mechanism\",\n      \"pmids\": [\"12932438\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"OPHN1 forms a complex with endophilin A1 (a membrane curvature-generating protein) at presynaptic sites, and both this interaction and OPHN1's Rho-GAP activity are required for OPHN1's role in controlling the kinetic efficiency of synaptic vesicle endocytosis at hippocampal synapses. OPHN1 knockdown impairs the SV cycling/endocytosis rate.\",\n      \"method\": \"Co-immunoprecipitation; shRNA knockdown in hippocampal neurons; live fluorescence imaging of SV cycling (FM dye assays); epistasis with endophilin A1\",\n      \"journal\": \"Current biology : CB\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal Co-IP identifying complex, shRNA loss-of-function with defined endocytosis phenotype, and domain-specific rescue in neurons\",\n      \"pmids\": [\"19481455\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"mGluR1 activation induces rapid dendritic synthesis of OPHN1 (independent of FMRP), and this newly synthesized OPHN1 mediates mGluR-LTD and persistent decreases in surface AMPARs via interactions with endophilin A2/3. Separately, OPHN1's role in basal synaptic strength requires its Rho-GAP activity and interaction with Homer1b/c, distinguishing two mechanistically distinct functions.\",\n      \"method\": \"Acute OPHN1 synthesis blockade; Co-immunoprecipitation with endophilin A2/3 and Homer1b/c; hippocampal slice electrophysiology; surface AMPAR quantification; shRNA knockdown\",\n      \"journal\": \"Neuron\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal methods (translational blockade, Co-IP, electrophysiology, surface receptor assay) in a single rigorous study establishing two distinct mechanistic roles\",\n      \"pmids\": [\"22017989\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"OPHN1 physically interacts with Homer1b/c, and this interaction is crucial for positioning the endocytic zone (EZ) adjacent to the postsynaptic density (PSD) in dendritic spines. Disruption of the OPHN1-Homer1b/c interaction displaces EZs from the PSD, impairs AMPAR recycling and accumulation at synapses, and reduces activity-dependent synaptic potentiation in rat hippocampus.\",\n      \"method\": \"Co-immunoprecipitation; shRNA knockdown; live-cell fluorescence imaging of EZ positioning; AMPAR surface quantification; electrophysiology in hippocampal slices\",\n      \"journal\": \"The Journal of neuroscience : the official journal of the Society for Neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal Co-IP, shRNA loss-of-function, live imaging of EZ displacement, AMPAR recycling assay, and electrophysiology in a single focused study\",\n      \"pmids\": [\"24966368\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"An in-frame deletion removing 37 amino acids from the conserved N-terminal BAR domain of OPHN1 produces a stable mutant transcript and is associated with hippocampal alterations not seen in canonical loss-of-function mutations, suggesting the BAR domain has a distinct functional role in the hippocampus.\",\n      \"method\": \"cDNA expression analysis; mRNA splicing analysis; MRI neuroimaging correlation with BAR domain deletion\",\n      \"journal\": \"European journal of human genetics : EJHG\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single family, molecular characterization of mutant transcript but no direct functional assay of BAR domain activity\",\n      \"pmids\": [\"24105372\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"OPHN1 transcript undergoes ADAR2-mediated A-to-I RNA editing and alternative splicing in human brain during development, with editing detectable from gestational week 18 and peaking at weeks 20–33 coinciding with increased OPHN1 expression and the appearance of a novel splicing isoform.\",\n      \"method\": \"Sequencing of OPHN1 cDNA from human fetal and adult brain; RT-PCR; A-to-I editing quantification\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct sequencing demonstrating RNA editing and alternative splicing at defined developmental stages, single lab but multiple methods\",\n      \"pmids\": [\"24637888\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"A K306N variant in the PH domain of OPHN1 (outside the BAR and GAP domains) enhances OPHN1 binding to phosphatidylinositol phosphates PI4P and PI5P, and is associated with cyclic strabismus without intellectual disability, suggesting that PH domain-mediated phosphoinositide binding influences subcellular localization of OPHN1.\",\n      \"method\": \"Identification of hemizygous variant; in vitro phosphoinositide binding assay; clinical phenotyping\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single patient, in vitro lipid binding assay but no direct functional rescue or localization experiment confirming the proposed mechanism\",\n      \"pmids\": [\"42031848\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Postnatal Ophn1 deficiency specifically in hippocampal astrocytes impairs synaptic transmission, short-term plasticity, and spatial working memory in adults. The mechanism involves an adenosine A1 receptor-dependent presynaptic pathway associated with increased astroglial synapse coverage (morphological rearrangement). These deficits are rescued by pharmacological inhibition of the RhoA/ROCK pathway.\",\n      \"method\": \"Cell-type-specific conditional Ophn1 knockdown (postnatal, astrocyte-restricted); electrophysiology; behavioral testing (spatial working memory); morphological analysis of astroglial coverage; pharmacological RhoA/ROCK inhibition rescue\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — conditional cell-type-specific KO with electrophysiology, behavior, morphology, and pharmacological rescue; preprint, single lab\",\n      \"pmids\": [\"bio_10.1101_2025.01.09.632152\"],\n      \"is_preprint\": true\n    }\n  ],\n  \"current_model\": \"OPHN1 is a RhoGAP protein (with BAR, PH, RhoGAP, and proline-rich domains) that suppresses Rho GTPase signaling to regulate the actin cytoskeleton; at presynaptic terminals it complexes with endophilin A1 to support synaptic vesicle endocytosis, while postsynaptically it interacts with Homer1b/c to position the endocytic zone adjacent to the PSD for AMPAR recycling and synaptic potentiation, and its rapid mGluR1-triggered dendritic synthesis mediates mGluR-LTD via endophilin A2/3; additionally, astroglial OPHN1 controls hippocampal synaptic transmission and short-term plasticity through a RhoA/ROCK- and adenosine A1 receptor-dependent mechanism.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"OPHN1 is a Rho GTPase-activating protein that couples suppression of Rho signaling to control of the actin cytoskeleton and to membrane dynamics at neuronal synapses [#0, #1]. Its RhoGAP domain inhibits Rho pathways and is held in check by an intramolecular autoinhibitory mechanism mediated by its amino-terminal region, while a distinct carboxy-terminal domain binds F-actin and localizes the protein to the tips of growing neurites [#0]. At presynaptic terminals OPHN1 complexes with the membrane curvature-generating protein endophilin A1, and both this interaction and its Rho-GAP activity are required to set the kinetic efficiency of synaptic vesicle endocytosis [#1]. Postsynaptically, OPHN1 binds Homer1b/c to position the endocytic zone adjacent to the postsynaptic density, a configuration needed for AMPA receptor recycling, surface accumulation, and activity-dependent synaptic potentiation [#3]. A mechanistically separate function operates during plasticity: mGluR1 activation triggers rapid dendritic synthesis of OPHN1, and this newly made protein mediates mGluR-LTD and persistent loss of surface AMPARs through interactions with endophilin A2/3, distinct from its Homer1b/c-dependent role in basal synaptic strength [#2]. Beyond neurons, OPHN1 in hippocampal astrocytes controls synaptic transmission and short-term plasticity via an adenosine A1 receptor-dependent presynaptic pathway whose deficits are reversed by RhoA/ROCK inhibition [#7].\",\n  \"teleology\": [\n    {\n      \"year\": 2003,\n      \"claim\": \"Established OPHN1 as an actin-regulatory RhoGAP and defined its domain logic, answering what biochemical activity the protein carries and how that activity is controlled.\",\n      \"evidence\": \"Overexpression, co-localization, and domain deletion analysis in fibroblasts with in vivo actin cytoskeleton assays\",\n      \"pmids\": [\"12932438\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Activity demonstrated largely by overexpression in non-neuronal cells, not endogenous neuronal context\",\n        \"Identity of the Rho-family substrate(s) preferentially regulated not resolved\",\n        \"Physiological trigger that relieves N-terminal autoinhibition unknown\"\n      ]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Showed OPHN1 acts presynaptically through a defined partner, answering how its GAP activity is deployed at synapses by linking it to endophilin A1 and synaptic vesicle endocytosis.\",\n      \"evidence\": \"Reciprocal Co-IP, shRNA knockdown in hippocampal neurons, FM-dye live imaging of SV cycling, and domain-specific epistasis\",\n      \"pmids\": [\"19481455\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"How Rho-GAP activity and endophilin binding are coordinated mechanistically not resolved\",\n        \"Whether OPHN1 acts during a specific endocytic step versus globally unclear\"\n      ]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Separated two OPHN1 functions, answering whether basal and plasticity roles are the same mechanism by showing mGluR1-triggered dendritic synthesis drives mGluR-LTD via endophilin A2/3 while basal strength requires GAP activity plus Homer1b/c.\",\n      \"evidence\": \"Acute translational blockade, Co-IP with endophilin A2/3 and Homer1b/c, hippocampal slice electrophysiology, surface AMPAR quantification, and shRNA\",\n      \"pmids\": [\"22017989\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Signaling that couples mGluR1 activation to OPHN1 mRNA translation not defined\",\n        \"How locally synthesized OPHN1 selects endophilin A2/3 over A1 unknown\"\n      ]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Explained how OPHN1 organizes the postsynaptic membrane, answering why Homer1b/c binding matters by showing it positions the endocytic zone next to the PSD for AMPAR recycling and potentiation.\",\n      \"evidence\": \"Reciprocal Co-IP, shRNA knockdown, live imaging of endocytic zone positioning, AMPAR surface assays, and hippocampal slice electrophysiology\",\n      \"pmids\": [\"24966368\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Structural basis of the OPHN1-Homer1b/c interaction not determined\",\n        \"Whether GAP activity contributes to EZ positioning separate from the scaffolding role unclear\"\n      ]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Documented developmental regulation of the transcript, answering whether OPHN1 is post-transcriptionally tuned by showing ADAR2-mediated A-to-I editing and alternative splicing peaking during human fetal brain development.\",\n      \"evidence\": \"Sequencing of OPHN1 cDNA from fetal and adult human brain with RT-PCR and editing quantification\",\n      \"pmids\": [\"24637888\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Functional consequence of edited/spliced isoforms on protein activity not tested\",\n        \"Whether editing alters domain function or localization unknown\"\n      ]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Probed the BAR domain's specific contribution, addressing whether N-terminal regions have hippocampus-specific roles via an in-frame BAR-domain deletion associated with hippocampal alterations distinct from null mutations.\",\n      \"evidence\": \"cDNA and splicing analysis of a single family with MRI correlation\",\n      \"pmids\": [\"24105372\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\n        \"Single family with no direct functional assay of BAR domain activity\",\n        \"Mechanism linking BAR deletion to hippocampal phenotype not established\"\n      ]\n    },\n    {\n      \"year\": 2026,\n      \"claim\": \"Implicated the PH domain in phosphoinositide-directed localization, addressing how OPHN1 is targeted within cells via a K306N variant that enhances PI4P/PI5P binding and is linked to cyclic strabismus without intellectual disability.\",\n      \"evidence\": \"Single-patient variant identification, in vitro phosphoinositide binding assay, and clinical phenotyping\",\n      \"pmids\": [\"42031848\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\n        \"Single patient with in vitro binding only, no functional rescue or localization experiment\",\n        \"Causal link between altered lipid binding and the strabismus phenotype unproven\"\n      ]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Extended OPHN1 function beyond neurons, addressing the cell-autonomy of its synaptic roles by showing astrocyte-specific deficiency impairs transmission and memory via an adenosine A1 receptor pathway rescuable by RhoA/ROCK inhibition.\",\n      \"evidence\": \"Postnatal astrocyte-restricted conditional Ophn1 knockdown with electrophysiology, behavior, morphology, and pharmacological rescue (preprint)\",\n      \"pmids\": [\"bio_10.1101_2025.01.09.632152\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Preprint, single lab, not peer-reviewed\",\n        \"How astroglial RhoA/ROCK signaling engages presynaptic A1 receptors mechanistically unclear\",\n        \"Relative contribution of astroglial versus neuronal OPHN1 to circuit phenotypes not partitioned\"\n      ]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How OPHN1's autoinhibition, phosphoinositide binding, and partner selection are integrated to direct context-specific functions across pre-, post-synaptic, and astroglial compartments remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"No structural model integrating BAR, PH, GAP, and proline-rich domains in a functional state\",\n        \"Upstream signals relieving autoinhibition in each compartment not identified\",\n        \"Preferred Rho-family substrate(s) in vivo not defined\"\n      ]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [0]},\n      {\"term_id\": \"GO:0008092\", \"supporting_discovery_ids\": [0]},\n      {\"term_id\": \"GO:0008289\", \"supporting_discovery_ids\": [6]},\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [3]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005856\", \"supporting_discovery_ids\": [0]},\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [1, 3]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-112316\", \"supporting_discovery_ids\": [2, 3]},\n      {\"term_id\": \"R-HSA-5653656\", \"supporting_discovery_ids\": [1, 3]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [0, 7]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\n      \"SH3GL2\",\n      \"SH3GL1\",\n      \"HOMER1\"\n    ],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":5,"faith_total":5,"faith_pct":100.0}}