{"gene":"ARHGAP39","run_date":"2026-04-28T17:12:37","timeline":{"discoveries":[{"year":2004,"finding":"Drosophila Vilse (ortholog of human ARHGAP39) directly binds to the intracellular domain of the Robo receptor and promotes hydrolysis of RacGTP and, less efficiently, Cdc42GTP, acting downstream of Robo to mediate midline repulsion via localized inactivation of Rac.","method":"Direct binding assay (pull-down), in vitro GTPase activity assay, genetic epistasis (dosage-sensitive interactions with robo, slit, rac mutants; overexpression rescue of robo mutant phenotype)","journal":"Genes & development","confidence":"High","confidence_rationale":"Tier 1 — in vitro GAP activity assay + direct binding + genetic epistasis, foundational study with 100 citations","pmids":["15342493"],"is_preprint":false},{"year":2005,"finding":"Drosophila CrossGAP/Vilse (ortholog of ARHGAP39) physically associates with the Robo receptor and transduces repulsive axon guidance signals downstream of Robo by regulating Rac-dependent cytoskeletal changes; dosage-sensitive genetic interactions among CrGAP, Robo, and Rac support this pathway position.","method":"Co-immunoprecipitation (physical association with Robo), genetic epistasis (dosage-sensitive interactions), gain- and loss-of-function phenotypic analysis","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 — reciprocal co-IP + epistasis, independently replicates Vilse-Robo interaction found in PMID:15342493","pmids":["15755809"],"is_preprint":false},{"year":2014,"finding":"CNK2 scaffold constitutively binds ARHGAP39/Vilse via the WW domains of Vilse and a proline motif in CNK2; CNK2 acts as a spatial modulator of Rac cycling during spine morphogenesis, and disruption of the CNK2–Vilse interaction impairs the RacGDP/GTP balance required for dendritic spine formation in hippocampal neurons.","method":"Mass spectrometry identification of endogenous CNK2 interactors, co-immunoprecipitation, domain-mapping mutagenesis (WW domain/proline motif), protein depletion and rescue experiments with spine morphology readout","journal":"Current biology : CB","confidence":"High","confidence_rationale":"Tier 2 — reciprocal co-IP + domain mutagenesis + functional rescue, multiple orthogonal methods in single study","pmids":["24656827"],"is_preprint":false},{"year":2017,"finding":"Forebrain-specific knockout of Vilse/ARHGAP39 in mice (Camk2a-Cre) causes changes in dendritic complexity, reduced spine density, impaired synaptic transmission and plasticity in hippocampal CA1, and deficits in spatial memory, establishing a required role for ARHGAP39 in dendritic architecture and synaptic function.","method":"Conditional knockout (Camk2a-Cre), dendritic morphology analysis, electrophysiology (LTP measurement), behavioral tests (water maze, Y-maze)","journal":"Scientific reports","confidence":"High","confidence_rationale":"Tier 2 — clean conditional KO with multiple orthogonal phenotypic readouts (morphology, electrophysiology, behavior)","pmids":["28368047"],"is_preprint":false},{"year":2025,"finding":"Purified recombinant ARHGAP39 protein facilitates GTP hydrolysis for both RhoA and Rac1 in vitro; loss of ARHGAP39 in hepatocellular cancer cells increases migration and invasion, and is associated with upregulation of MMP13 and LAMB1.","method":"In vitro GTPase activity assay with purified recombinant protein, CRISPR-Cas9 knockout, migration/invasion assays, RNA-seq","journal":"Oncology research","confidence":"Medium","confidence_rationale":"Tier 1 for enzymatic activity (in vitro reconstitution), but single lab, single study","pmids":["39866228"],"is_preprint":false}],"current_model":"ARHGAP39/Vilse is a RhoGAP that directly binds Robo receptors and inactivates Rac (and to a lesser extent Cdc42 and RhoA) by stimulating GTP hydrolysis, thereby mediating cytoskeletal changes downstream of Slit-Robo repulsion; in mammalian neurons it is constitutively scaffolded by CNK2 to spatially regulate Rac cycling, and is required for dendritic spine morphogenesis, synaptic plasticity, and spatial memory."},"narrative":{"teleology":[{"year":2004,"claim":"The identification of Vilse as a direct Robo-binding RhoGAP that preferentially inactivates Rac resolved how Slit-Robo repulsive signaling is transduced into cytoskeletal changes at the midline.","evidence":"Direct pull-down, in vitro GAP assays, and genetic epistasis with robo/slit/rac in Drosophila","pmids":["15342493"],"confidence":"High","gaps":["Structural basis of the Vilse–Robo interaction unknown","Relative contributions of Rac versus Cdc42 inactivation to midline repulsion unresolved","Mammalian relevance of the Robo–Vilse axis not yet tested"]},{"year":2005,"claim":"Independent replication confirmed the Vilse–Robo physical association and placed CrossGAP/Vilse genetically between Robo and Rac in repulsive guidance, solidifying the pathway model.","evidence":"Reciprocal co-immunoprecipitation and dosage-sensitive genetic interactions in Drosophila","pmids":["15755809"],"confidence":"High","gaps":["Whether Vilse is the sole GAP downstream of Robo or acts redundantly with other GAPs unclear","Regulation of Vilse recruitment to Robo (e.g., phosphorylation-dependent) unknown"]},{"year":2014,"claim":"Discovery that CNK2 constitutively scaffolds ARHGAP39 via WW-domain/proline-motif contacts and that this complex controls Rac cycling during spine morphogenesis revealed a mammalian spatial regulation mechanism for ARHGAP39's GAP activity.","evidence":"Mass spectrometry, co-immunoprecipitation, domain-mapping mutagenesis, and spine morphology rescue in rat hippocampal neurons","pmids":["24656827"],"confidence":"High","gaps":["Whether Robo-dependent and CNK2-dependent pools of ARHGAP39 overlap or are functionally distinct is unknown","Upstream signals that modulate the CNK2–ARHGAP39 complex not identified","Stoichiometry and structural details of the CNK2–ARHGAP39 complex unresolved"]},{"year":2017,"claim":"Conditional knockout of ARHGAP39 in the mouse forebrain established that its GAP activity is required in vivo for dendritic complexity, spine density, hippocampal LTP, and spatial memory, moving the gene from a guidance effector to a regulator of synaptic plasticity.","evidence":"Camk2a-Cre conditional KO, Golgi staining, electrophysiology, Morris water maze and Y-maze","pmids":["28368047"],"confidence":"High","gaps":["Whether the synaptic phenotype reflects Rac, RhoA, or Cdc42 dysregulation specifically is unresolved","Cell-type-specific requirements beyond excitatory CA1 neurons not examined","No human genetic disease link yet established"]},{"year":2025,"claim":"Reconstitution of purified ARHGAP39 confirmed dual GAP activity toward both RhoA and Rac1 in vitro and implicated loss of ARHGAP39 in hepatocellular carcinoma cell migration, broadening its known substrate range and linking it to cancer-relevant phenotypes.","evidence":"In vitro GTPase assay with recombinant protein, CRISPR-Cas9 knockout in HCC cell lines, migration/invasion assays, RNA-seq","pmids":["39866228"],"confidence":"Medium","gaps":["Single-lab finding; RhoA GAP activity in a cellular context not independently confirmed","Causal role of MMP13/LAMB1 upregulation downstream of ARHGAP39 loss not tested","In vivo tumor model validation absent"]},{"year":null,"claim":"Key unresolved questions include the structural basis of ARHGAP39 substrate selectivity across Rac1, Cdc42, and RhoA, the signals that regulate its localization or activity in neurons versus non-neuronal contexts, and whether ARHGAP39 mutations cause human neurological or developmental disease.","evidence":"","pmids":[],"confidence":"High","gaps":["No crystal or cryo-EM structure of the GAP domain with any substrate","Post-translational regulation (phosphorylation, ubiquitination) of ARHGAP39 unexplored","No human genetic studies linking ARHGAP39 variants to Mendelian or neurodevelopmental disorders"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[0,1,2,4]},{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[0,4]}],"localization":[{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[2]}],"pathway":[{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[0,1,2]},{"term_id":"R-HSA-1266738","term_label":"Developmental Biology","supporting_discovery_ids":[0,1]},{"term_id":"R-HSA-112316","term_label":"Neuronal System","supporting_discovery_ids":[2,3]}],"complexes":["CNK2–ARHGAP39 complex"],"partners":["CNK2","ROBO1"],"other_free_text":[]},"mechanistic_narrative":"ARHGAP39 (Vilse/CrossGAP) is a RhoGAP that inactivates Rac and, less efficiently, Cdc42 and RhoA by stimulating GTP hydrolysis, functioning as a key effector of cytoskeletal remodeling downstream of Slit-Robo repulsive signaling and during neuronal morphogenesis. ARHGAP39 directly binds the intracellular domain of the Robo receptor and transduces repulsive axon guidance signals by locally inactivating Rac [PMID:15342493, PMID:15755809]. In mammalian hippocampal neurons, ARHGAP39 is constitutively scaffolded by CNK2 via its WW domains, and this interaction is required for proper Rac GDP/GTP cycling during dendritic spine formation [PMID:24656827]. Forebrain-specific loss of ARHGAP39 in mice reduces spine density, impairs hippocampal synaptic plasticity (LTP), and causes spatial memory deficits, establishing its requirement for dendritic architecture and higher cognitive function [PMID:28368047]."},"prefetch_data":{"uniprot":{"accession":"Q9C0H5","full_name":"Rho GTPase-activating protein 39","aliases":[],"length_aa":1083,"mass_kda":121.3,"function":"","subcellular_location":"Nucleus","url":"https://www.uniprot.org/uniprotkb/Q9C0H5/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/ARHGAP39","classification":"Not Classified","n_dependent_lines":1,"n_total_lines":1208,"dependency_fraction":0.0008278145695364238},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/ARHGAP39","total_profiled":1310},"omim":[{"mim_id":"615880","title":"RHO GTPase-ACTIVATING PROTEIN 39; ARHGAP39","url":"https://www.omim.org/entry/615880"},{"mim_id":"302802","title":"CHARCOT-MARIE-TOOTH DISEASE, X-LINKED RECESSIVE, 3; CMTX3","url":"https://www.omim.org/entry/302802"},{"mim_id":"300724","title":"CONNECTOR ENHANCER OF KINASE SUPPRESSOR OF RAS 2; CNKSR2","url":"https://www.omim.org/entry/300724"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Nucleoplasm","reliability":"Approved"}],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in many","driving_tissues":[{"tissue":"brain","ntpm":16.1},{"tissue":"testis","ntpm":20.3}],"url":"https://www.proteinatlas.org/search/ARHGAP39"},"hgnc":{"alias_symbol":["KIAA1688","Vilse","CrGAP"],"prev_symbol":[]},"alphafold":{"accession":"Q9C0H5","domains":[{"cath_id":"-","chopping":"31-111","consensus_level":"high","plddt":82.0662,"start":31,"end":111},{"cath_id":"1.25.40.530","chopping":"691-882","consensus_level":"high","plddt":88.6088,"start":691,"end":882},{"cath_id":"1.10.555.10","chopping":"893-1080","consensus_level":"high","plddt":93.0506,"start":893,"end":1080}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9C0H5","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q9C0H5-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q9C0H5-F1-predicted_aligned_error_v6.png","plddt_mean":58.56},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=ARHGAP39","jax_strain_url":"https://www.jax.org/strain/search?query=ARHGAP39"},"sequence":{"accession":"Q9C0H5","fasta_url":"https://rest.uniprot.org/uniprotkb/Q9C0H5.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q9C0H5/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9C0H5"}},"corpus_meta":[{"pmid":"15342493","id":"PMC_15342493","title":"Vilse, a conserved Rac/Cdc42 GAP mediating Robo repulsion in tracheal cells and axons.","date":"2004","source":"Genes & development","url":"https://pubmed.ncbi.nlm.nih.gov/15342493","citation_count":100,"is_preprint":false},{"pmid":"15755809","id":"PMC_15755809","title":"Cross GTPase-activating protein (CrossGAP)/Vilse links the Roundabout receptor to Rac to regulate midline repulsion.","date":"2005","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/15755809","citation_count":69,"is_preprint":false},{"pmid":"24656827","id":"PMC_24656827","title":"The CNK2 scaffold interacts with vilse and modulates Rac cycling during spine morphogenesis in hippocampal neurons.","date":"2014","source":"Current biology : CB","url":"https://pubmed.ncbi.nlm.nih.gov/24656827","citation_count":54,"is_preprint":false},{"pmid":"30406180","id":"PMC_30406180","title":"Porf-2 = Arhgap39 = Vilse: A Pivotal Role in Neurodevelopment, Learning and Memory.","date":"2018","source":"eNeuro","url":"https://pubmed.ncbi.nlm.nih.gov/30406180","citation_count":15,"is_preprint":false},{"pmid":"28368047","id":"PMC_28368047","title":"Important roles of Vilse in dendritic architecture and synaptic plasticity.","date":"2017","source":"Scientific reports","url":"https://pubmed.ncbi.nlm.nih.gov/28368047","citation_count":14,"is_preprint":false},{"pmid":"29177429","id":"PMC_29177429","title":"Identification of a basidiomycete-specific Vilse-like GTPase activating proteins (GAPs) and its roles in the production of virulence factors in Cryptococcus neoformans.","date":"2017","source":"FEMS yeast research","url":"https://pubmed.ncbi.nlm.nih.gov/29177429","citation_count":10,"is_preprint":false},{"pmid":"39866228","id":"PMC_39866228","title":"Loss of Arhgap39 facilitates cell migration and invasion in murine hepatocellular cancer cells.","date":"2025","source":"Oncology research","url":"https://pubmed.ncbi.nlm.nih.gov/39866228","citation_count":1,"is_preprint":false},{"pmid":"39455833","id":"PMC_39455833","title":"A homozygous variant in ARHGAP39 is associated with lethal cerebellar vermis hypoplasia in a consanguineous Saudi family.","date":"2024","source":"Scientific reports","url":"https://pubmed.ncbi.nlm.nih.gov/39455833","citation_count":1,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":5144,"output_tokens":1346,"usd":0.017811},"stage2":{"model":"claude-opus-4-6","input_tokens":4563,"output_tokens":1856,"usd":0.103822},"total_usd":0.121633,"stage1_batch_id":"msgbatch_01TqNM6p6FsoMBT2jzQTwKBr","stage2_batch_id":"msgbatch_01Ya473eco8sTHbvRymQaU8o","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2004,\n      \"finding\": \"Drosophila Vilse (ortholog of human ARHGAP39) directly binds to the intracellular domain of the Robo receptor and promotes hydrolysis of RacGTP and, less efficiently, Cdc42GTP, acting downstream of Robo to mediate midline repulsion via localized inactivation of Rac.\",\n      \"method\": \"Direct binding assay (pull-down), in vitro GTPase activity assay, genetic epistasis (dosage-sensitive interactions with robo, slit, rac mutants; overexpression rescue of robo mutant phenotype)\",\n      \"journal\": \"Genes & development\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — in vitro GAP activity assay + direct binding + genetic epistasis, foundational study with 100 citations\",\n      \"pmids\": [\"15342493\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"Drosophila CrossGAP/Vilse (ortholog of ARHGAP39) physically associates with the Robo receptor and transduces repulsive axon guidance signals downstream of Robo by regulating Rac-dependent cytoskeletal changes; dosage-sensitive genetic interactions among CrGAP, Robo, and Rac support this pathway position.\",\n      \"method\": \"Co-immunoprecipitation (physical association with Robo), genetic epistasis (dosage-sensitive interactions), gain- and loss-of-function phenotypic analysis\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal co-IP + epistasis, independently replicates Vilse-Robo interaction found in PMID:15342493\",\n      \"pmids\": [\"15755809\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"CNK2 scaffold constitutively binds ARHGAP39/Vilse via the WW domains of Vilse and a proline motif in CNK2; CNK2 acts as a spatial modulator of Rac cycling during spine morphogenesis, and disruption of the CNK2–Vilse interaction impairs the RacGDP/GTP balance required for dendritic spine formation in hippocampal neurons.\",\n      \"method\": \"Mass spectrometry identification of endogenous CNK2 interactors, co-immunoprecipitation, domain-mapping mutagenesis (WW domain/proline motif), protein depletion and rescue experiments with spine morphology readout\",\n      \"journal\": \"Current biology : CB\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal co-IP + domain mutagenesis + functional rescue, multiple orthogonal methods in single study\",\n      \"pmids\": [\"24656827\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Forebrain-specific knockout of Vilse/ARHGAP39 in mice (Camk2a-Cre) causes changes in dendritic complexity, reduced spine density, impaired synaptic transmission and plasticity in hippocampal CA1, and deficits in spatial memory, establishing a required role for ARHGAP39 in dendritic architecture and synaptic function.\",\n      \"method\": \"Conditional knockout (Camk2a-Cre), dendritic morphology analysis, electrophysiology (LTP measurement), behavioral tests (water maze, Y-maze)\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — clean conditional KO with multiple orthogonal phenotypic readouts (morphology, electrophysiology, behavior)\",\n      \"pmids\": [\"28368047\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Purified recombinant ARHGAP39 protein facilitates GTP hydrolysis for both RhoA and Rac1 in vitro; loss of ARHGAP39 in hepatocellular cancer cells increases migration and invasion, and is associated with upregulation of MMP13 and LAMB1.\",\n      \"method\": \"In vitro GTPase activity assay with purified recombinant protein, CRISPR-Cas9 knockout, migration/invasion assays, RNA-seq\",\n      \"journal\": \"Oncology research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 for enzymatic activity (in vitro reconstitution), but single lab, single study\",\n      \"pmids\": [\"39866228\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"ARHGAP39/Vilse is a RhoGAP that directly binds Robo receptors and inactivates Rac (and to a lesser extent Cdc42 and RhoA) by stimulating GTP hydrolysis, thereby mediating cytoskeletal changes downstream of Slit-Robo repulsion; in mammalian neurons it is constitutively scaffolded by CNK2 to spatially regulate Rac cycling, and is required for dendritic spine morphogenesis, synaptic plasticity, and spatial memory.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"ARHGAP39 (Vilse/CrossGAP) is a RhoGAP that inactivates Rac and, less efficiently, Cdc42 and RhoA by stimulating GTP hydrolysis, functioning as a key effector of cytoskeletal remodeling downstream of Slit-Robo repulsive signaling and during neuronal morphogenesis. ARHGAP39 directly binds the intracellular domain of the Robo receptor and transduces repulsive axon guidance signals by locally inactivating Rac [PMID:15342493, PMID:15755809]. In mammalian hippocampal neurons, ARHGAP39 is constitutively scaffolded by CNK2 via its WW domains, and this interaction is required for proper Rac GDP/GTP cycling during dendritic spine formation [PMID:24656827]. Forebrain-specific loss of ARHGAP39 in mice reduces spine density, impairs hippocampal synaptic plasticity (LTP), and causes spatial memory deficits, establishing its requirement for dendritic architecture and higher cognitive function [PMID:28368047].\",\n  \"teleology\": [\n    {\n      \"year\": 2004,\n      \"claim\": \"The identification of Vilse as a direct Robo-binding RhoGAP that preferentially inactivates Rac resolved how Slit-Robo repulsive signaling is transduced into cytoskeletal changes at the midline.\",\n      \"evidence\": \"Direct pull-down, in vitro GAP assays, and genetic epistasis with robo/slit/rac in Drosophila\",\n      \"pmids\": [\"15342493\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Structural basis of the Vilse–Robo interaction unknown\",\n        \"Relative contributions of Rac versus Cdc42 inactivation to midline repulsion unresolved\",\n        \"Mammalian relevance of the Robo–Vilse axis not yet tested\"\n      ]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Independent replication confirmed the Vilse–Robo physical association and placed CrossGAP/Vilse genetically between Robo and Rac in repulsive guidance, solidifying the pathway model.\",\n      \"evidence\": \"Reciprocal co-immunoprecipitation and dosage-sensitive genetic interactions in Drosophila\",\n      \"pmids\": [\"15755809\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Whether Vilse is the sole GAP downstream of Robo or acts redundantly with other GAPs unclear\",\n        \"Regulation of Vilse recruitment to Robo (e.g., phosphorylation-dependent) unknown\"\n      ]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Discovery that CNK2 constitutively scaffolds ARHGAP39 via WW-domain/proline-motif contacts and that this complex controls Rac cycling during spine morphogenesis revealed a mammalian spatial regulation mechanism for ARHGAP39's GAP activity.\",\n      \"evidence\": \"Mass spectrometry, co-immunoprecipitation, domain-mapping mutagenesis, and spine morphology rescue in rat hippocampal neurons\",\n      \"pmids\": [\"24656827\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Whether Robo-dependent and CNK2-dependent pools of ARHGAP39 overlap or are functionally distinct is unknown\",\n        \"Upstream signals that modulate the CNK2–ARHGAP39 complex not identified\",\n        \"Stoichiometry and structural details of the CNK2–ARHGAP39 complex unresolved\"\n      ]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Conditional knockout of ARHGAP39 in the mouse forebrain established that its GAP activity is required in vivo for dendritic complexity, spine density, hippocampal LTP, and spatial memory, moving the gene from a guidance effector to a regulator of synaptic plasticity.\",\n      \"evidence\": \"Camk2a-Cre conditional KO, Golgi staining, electrophysiology, Morris water maze and Y-maze\",\n      \"pmids\": [\"28368047\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Whether the synaptic phenotype reflects Rac, RhoA, or Cdc42 dysregulation specifically is unresolved\",\n        \"Cell-type-specific requirements beyond excitatory CA1 neurons not examined\",\n        \"No human genetic disease link yet established\"\n      ]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Reconstitution of purified ARHGAP39 confirmed dual GAP activity toward both RhoA and Rac1 in vitro and implicated loss of ARHGAP39 in hepatocellular carcinoma cell migration, broadening its known substrate range and linking it to cancer-relevant phenotypes.\",\n      \"evidence\": \"In vitro GTPase assay with recombinant protein, CRISPR-Cas9 knockout in HCC cell lines, migration/invasion assays, RNA-seq\",\n      \"pmids\": [\"39866228\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Single-lab finding; RhoA GAP activity in a cellular context not independently confirmed\",\n        \"Causal role of MMP13/LAMB1 upregulation downstream of ARHGAP39 loss not tested\",\n        \"In vivo tumor model validation absent\"\n      ]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Key unresolved questions include the structural basis of ARHGAP39 substrate selectivity across Rac1, Cdc42, and RhoA, the signals that regulate its localization or activity in neurons versus non-neuronal contexts, and whether ARHGAP39 mutations cause human neurological or developmental disease.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"No crystal or cryo-EM structure of the GAP domain with any substrate\",\n        \"Post-translational regulation (phosphorylation, ubiquitination) of ARHGAP39 unexplored\",\n        \"No human genetic studies linking ARHGAP39 variants to Mendelian or neurodevelopmental disorders\"\n      ]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [0, 1, 2, 4]},\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [0, 4]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [2]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [0, 1, 2]},\n      {\"term_id\": \"R-HSA-1266738\", \"supporting_discovery_ids\": [0, 1]},\n      {\"term_id\": \"R-HSA-112316\", \"supporting_discovery_ids\": [2, 3]}\n    ],\n    \"complexes\": [\n      \"CNK2–ARHGAP39 complex\"\n    ],\n    \"partners\": [\n      \"CNK2\",\n      \"ROBO1\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}