Affinage

ARHGEF9

Rho guanine nucleotide exchange factor 9 · UniProt O43307

Length
516 aa
Mass
61.0 kDa
Annotated
2026-06-09
34 papers in source corpus 12 papers cited in narrative 12 extracted findings
Cross-family judge vs UniProt: Affinage preferred faithfulness: 6/6 claims corpus-supported (100%)

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

ARHGEF9 encodes collybistin, a neuronal Cdc42-specific guanine nucleotide exchange factor that organizes inhibitory postsynaptic densities by driving submembrane clustering of gephyrin and GABA-A receptors (PMID:18615734, PMID:35169261). Membrane targeting depends on the PH domain, which binds phosphatidylinositol-3-phosphate (PI3P) rather than PIP3, and PH-domain truncation or PI3P-binding-disrupting mutations abolishes collybistin-mediated translocation of gephyrin and GABA-A receptors to submembrane microaggregates (PMID:18615734, PMID:26834553). Collybistin directly binds the α2 subunit of GABA-A receptors through a motif in its large intracellular loop, an interaction required to maintain its expression at specific inhibitory synapses (PMID:35169261). Loss of collybistin function disorganizes inhibitory postsynaptic densities at the axon initial segment, causes aggregation of postsynaptic proteins, reduces gephyrin phosphorylation, and impairs GABAergic transmission, producing seizures, memory and social deficits, and behavioral abnormalities in mouse models that phenocopy ARHGEF9 patient features (PMID:35169261, PMID:39374387, PMID:41174051). Multiple patient- and ASD-associated missense, synonymous, and splice-site variants act through these mechanisms—disrupting gephyrin clustering, PI3P binding, or producing truncated transcripts—establishing ARHGEF9 dysfunction as a cause of epilepsy, intellectual disability, and autism-spectrum phenotypes (PMID:26834553, PMID:31942680, PMID:41174051). Outside neurons, collybistin functions downstream of IQGAP1 and Cdc42 to control actin-driven cell migration, focal-adhesion tension, filopodia stabilization, and myoblast differentiation (PMID:26633832, PMID:36039362, PMID:39992578).

Mechanistic history

Synthesis pass · year-by-year structured walk · 12 steps
  1. 2009 High

    Established the lipid specificity and membrane-trafficking function of collybistin's PH domain, redefining how it targets gephyrin to synapses.

    Evidence Lipid-binding assay (PI3P vs PIP3) plus expression of PH-domain-truncated collybistin in cultured neurons with gephyrin/GABA-A readout

    PMID:18615734

    Open questions at the time
    • Did not resolve how PI3P generation is regulated at the synapse
    • No structural detail of the PH-lipid interface
  2. 2015 Medium

    Placed collybistin in a non-neuronal IQGAP1-Cdc42 signaling axis controlling cell migration, showing its GEF role extends beyond synapse assembly.

    Evidence siRNA epistasis against multiple GEFs/GTPases with migration assay and Cdc42 activity measurement

    PMID:26633832

    Open questions at the time
    • Direct biochemical link between collybistin and IQGAP1 not shown
    • Whether GEF catalytic activity is required not isolated
  3. 2016 High

    Demonstrated that a disease-associated PH-domain mutation acts by abolishing PI3P binding and gephyrin clustering, providing a structural mechanism for pathogenicity.

    Evidence PI3P-binding assay with recombinant mutant, in vitro gephyrin clustering assay, and molecular modeling of R338W

    PMID:26834553

    Open questions at the time
    • Modeling not validated by experimental structure
    • In vivo consequence of R338W not tested
  4. 2018 Medium

    Characterized the spatial and developmental expression of collybistin in brain, supporting a synaptic localization consistent with its postsynaptic role.

    Evidence Western blot across tissues, IHC across developmental stages, immunofluorescence in cultured hippocampal neurons

    PMID:30083020

    Open questions at the time
    • No functional consequence tied to the observed localization
    • Dendritic spine localization only partial
  5. 2020 Medium

    Extended the variant-to-mechanism link by showing additional patient missense and splice variants impair gephyrin clustering or produce truncated protein.

    Evidence In vitro gephyrin clustering assay with missense variants and splicing analysis of a splice-site variant

    PMID:31942680

    Open questions at the time
    • No in vivo modeling of these specific variants
    • Mechanism of clustering disruption for I294T/R357I not resolved
  6. 2022 High

    Identified a direct collybistin-GABA-A receptor α2 interaction and showed its disruption causes synapse-specific collybistin downregulation and a patient-like phenotype in mice.

    Evidence Gabra2-1 knock-in mouse, IHC, electrophysiology, EEG, and behavioral assays

    PMID:35169261

    Open questions at the time
    • Binding motif mapped genetically, not by structure
    • Why CCK basket cell synapses are selectively affected unclear
  7. 2022 Medium

    Defined a cell-biological role for collybistin in actin-based mechanics, linking it to focal-adhesion tension, contractility, and filopodia stabilization in melanoma cells.

    Evidence Genetic morphological screen, siRNA depletion, traction force microscopy, 3D invasion assay, actin imaging

    PMID:36039362

    Open questions at the time
    • Whether Cdc42 GEF activity mediates these effects not directly tested
    • Direct cytoskeletal partners not identified
  8. 2022 Low

    Showed that even a synonymous ARHGEF9 variant can cause loss of function through aberrant splicing, broadening the pathogenic variant spectrum.

    Evidence RT-PCR splicing analysis of a single patient-derived sample

    PMID:36184101

    Open questions at the time
    • Single patient with no functional reconstitution
    • Protein-level consequence not directly assessed
  9. 2023 Medium

    Linked inflammatory neuropathology to region-specific Arhgef9 alternative splicing under Sam68 control, implicating splicing regulation in collybistin function.

    Evidence Laser microdissection, RT-PCR for exon 11a inclusion, IHC for Sam68 in EAE vs control mice

    PMID:36710925

    Open questions at the time
    • Sam68-Arhgef9 regulatory link is correlational
    • Functional impact of exon 11a inclusion on protein activity unknown
  10. 2024 High

    Localized collybistin's critical role to the axon initial segment, showing loss of function disorganizes axo-axonic inhibitory synapses and disrupts action potential generation.

    Evidence Patient-derived variant knock-in mouse, AIS immunofluorescence, electrophysiology, in vivo seizure monitoring

    PMID:39374387

    Open questions at the time
    • Molecular trigger for protein aggregation at AIS not resolved
    • Whether AIS defect alone accounts for seizures unclear
  11. 2025 High

    Integrated ASD-associated variants with mPFC-specific collybistin function, tying loss of function to reduced gephyrin phosphorylation, impaired GABAergic transmission, and altered vocalization.

    Evidence COS-7 clustering and PI3P-binding assays, hippocampal neuron synapse density, patch-clamp, mPFC conditional knockout, phosphoproteomics, ultrasonic vocalization assay

    PMID:41174051

    Open questions at the time
    • Kinase responsible for gephyrin phosphorylation not identified
    • How distinct variants converge on the same phenotype not mechanistically separated
  12. 2025 Medium

    Demonstrated a role for collybistin in skeletal muscle regeneration via actin-dependent myoblast migration and differentiation, extending its cytoskeletal function to a new tissue.

    Evidence Mouse muscle injury model, C2C12 differentiation and migration assays, knockdown, phalloidin staining, marker Western blots

    PMID:39992578

    Open questions at the time
    • Cdc42/GEF dependence in muscle not demonstrated
    • Direct interaction partners in myoblasts not identified

Open questions

Synthesis pass · forward-looking unresolved questions
  • How collybistin's catalytic GEF activity, PI3P-dependent membrane targeting, and receptor/gephyrin scaffolding are coordinated and regulated to assemble synapse-specific inhibitory densities remains unresolved.
  • No high-resolution structure of full-length collybistin or its receptor complexes
  • Kinases/phosphatases controlling gephyrin phosphorylation downstream of collybistin not defined
  • Mechanism selecting specific inhibitory synapse subtypes unclear

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0008289 lipid binding 3 GO:0008092 cytoskeletal protein binding 2 GO:0060090 molecular adaptor activity 2 GO:0060089 molecular transducer activity 1 GO:0140096 catalytic activity, acting on a protein 1
Localization
GO:0005856 cytoskeleton 2 GO:0005886 plasma membrane 2
Pathway
R-HSA-112316 Neuronal System 3 R-HSA-1266738 Developmental Biology 1 R-HSA-162582 Signal Transduction 1
Partners
CDC42GABRA2GPHNIQGAP1
Complex memberships
inhibitory postsynaptic density

Evidence

Reading pass · 12 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
2009 The pleckstrin homology (PH) domain of collybistin (ARHGEF9) binds phosphatidylinositol-3-phosphate (PI3P/PtdIns-3-P), not phosphatidylinositol 3,4,5-trisphosphate (PIP3) as previously suggested. Expression of truncated collybistin proteins lacking the PH domain in cultured neurons interferes with synaptic localization of endogenous gephyrin and GABA-A receptors, establishing a role for the PH domain in membrane trafficking of gephyrin and selected GABA-A receptor subtypes. Lipid-binding assay (PI3P vs PIP3 binding), expression of truncated collybistin in cultured neurons with immunocytochemical readout of gephyrin and GABA-A receptor localization Human mutation High 18615734
2016 The missense mutation R338W in the PH domain of collybistin (ARHGEF9) disrupts PI3P binding and abolishes the ability of collybistin to translocate EGFP-gephyrin to submembrane microaggregates in an in vitro clustering assay. Molecular modeling indicates the R338W substitution causes steric clashes with adjacent residues (K363 and N335) and disrupts local PH domain folding. PI3P-binding assay with recombinant CB2SH3-(R338W), in vitro gephyrin clustering assay in transfected cells, molecular modeling Frontiers in molecular neuroscience High 26834553
2015 ARHGEF9 (as the Cdc42-specific GEF collybistin) functions downstream of IQGAP1 and Cdc42 in a signaling pathway that regulates eukaryotic cell migration. LAI-1-dependent inhibition of cell migration required ARHGEF9 but not other modulators of Cdc42, RhoA, Rac1, or Ran GTPase; depletion of ARHGEF9 phenocopied Cdc42 inactivation in this context. siRNA knockdown of ARHGEF9 and other GEFs/GTPases in migration assay, Cdc42 activity measurement, IQGAP1 localization by immunofluorescence PLoS pathogens Medium 26633832
2020 Two ARHGEF9 missense variants (p.I294T and p.R357I) disrupt collybistin-mediated accumulation of gephyrin in submembrane microclusters in vitro. A splicing variant (c.381+3A>G) produces aberrant transcripts leading to a truncated protein product. In vitro gephyrin clustering assay with transfected cells expressing missense variants; transcriptional/splicing analysis of the splice-site variant Journal of molecular neuroscience Medium 31942680
2022 Collybistin (ARHGEF9) directly interacts with the α2 subunit of GABA-A receptors via a binding motif in its large intracellular loop; disruption of this interaction (Gabra2-1 knock-in mutation replacing the Cb-binding motif with the gephyrin-binding motif from α1) causes strong downregulation of Cb expression particularly at CCK basket cell inhibitory synapses. The Gabra2-1 mice phenocopy ARHGEF9 patient features including deficits in working/recognition memory, hyperactivity, anxiety, reduced social preference, spontaneous seizures, and EEG abnormalities including sleep disturbance. Knock-in mouse model (Gabra2-1), immunohistochemistry, electrophysiology, EEG, behavioral assays Molecular psychiatry High 35169261
2024 In a mouse model carrying a patient-derived ARHGEF9 variant associated with severe disease, collybistin (ARHGEF9) is required for proper organization of the postsynaptic density of inhibitory synapses at the axon initial segment (AIS). Loss of function causes aggregation of postsynaptic proteins, loss of functional inhibitory synapses at the AIS, altered axo-axonic synaptic inhibition, and disrupted action potential generation. Patient-derived variant knock-in mouse model, immunofluorescence of AIS postsynaptic protein aggregation, electrophysiology (axo-axonic inhibition, action potential recording), in vivo seizure monitoring Proceedings of the National Academy of Sciences of the United States of America High 39374387
2025 ASD-associated ARHGEF9 variant p.R290C promotes abnormal gephyrin clustering in COS-7 cells and reduces inhibitory synapse density in cultured hippocampal neurons. Variants p.V374F and p.G485S (with p.R290C) induce defective inhibitory synaptic transmission; p.G485S specifically decreases PI3P-binding activity. Conditional knockout of collybistin in medial prefrontal cortex (mPFC) reduces gephyrin phosphorylation levels and impairs ultrasonic vocalization; ASD-associated ARHGEF9 variants fail to rescue impaired GABAergic transmission and reduced gephyrin phosphorylation in mPFC-specific Cb-cKO mice. Transfection of variants in COS-7 cells (gephyrin clustering assay), primary hippocampal neuron culture (synapse density), whole-cell patch-clamp electrophysiology, PI3P-binding assay, mPFC-specific conditional knockout mouse, proteomics (phosphorylation), ultrasonic vocalization behavioral assay Molecular psychiatry High 41174051
2022 ARHGEF9/Collybistin is required for melanoma cell shape determination on both soft and stiff substrates and in 3D matrices. Depletion of ARHGEF9 results in loss of tension at focal adhesions, decreased cell-wide contractility, inability to stabilize protrusions, and loss of actin-rich filopodia that normally establish and stabilize adhesions. Genetic screens with single-cell quantitative morphological analysis, siRNA depletion, traction force microscopy (focal adhesion tension), 3D invasion assay, fluorescence imaging of actin/filopodia iScience Medium 36039362
2023 In the EAE mouse model of multiple sclerosis, inflammation induces region-specific alternative splicing of Arhgef9 (increased inclusion of alternative exon 11a selectively in CA3 and dentate gyrus), coinciding with downregulation of the splicing factor Sam68 that normally represses this splicing event. Laser microdissection of hippocampal subfields, RT-PCR for exon 11a inclusion, immunohistochemistry for Sam68 and parvalbumin in EAE vs. control mice Frontiers in molecular neuroscience Medium 36710925
2018 ARHGEF9 protein exhibits tissue-dependent and developmental stage-dependent expression in mouse brain (cerebral cortex, hippocampus, cerebellum), and shows partial localization at dendritic spines in cultured hippocampal neurons. Western blotting across mouse tissues, immunohistochemistry at multiple developmental stages, immunofluorescence in cultured hippocampal neurons with validated polyclonal antibody Acta histochemica et cytochemica Medium 30083020
2025 ARHGEF9 expression increases significantly during skeletal muscle regeneration after injury in mice and co-localizes with actin filaments during C2C12 myoblast differentiation. Inhibition of ARHGEF9 reduces myoblast migration rate, actin filament polymerization, expression of migration-related proteins, and differentiation capacity of C2C12 myoblasts. Mouse muscle injury model (ARHGEF9 protein expression by Western blot), C2C12 myoblast differentiation assay, siRNA/inhibitor-based knockdown, migration assay, phalloidin staining for actin filaments, Western blot for migration/differentiation markers Journal of muscle research and cell motility Medium 39992578
2022 A synonymous ARHGEF9 variant (c.741C>T, p.Cys247Cys) causes abnormal splicing of exon 5 resulting in a 55-bp deletion, demonstrating that synonymous variants in ARHGEF9 can produce loss-of-function via splicing disruption. RNA splicing analysis (RT-PCR) on patient-derived sample confirming aberrant transcript and 55-bp exon 5 deletion Chinese journal of medical genetics Low 36184101

Source papers

Stage 0 corpus · 34 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
2009 A balanced chromosomal translocation disrupting ARHGEF9 is associated with epilepsy, anxiety, aggression, and mental retardation. Human mutation 115 18615734
1997 Posterior end mark 2 (pem-2), pem-4, pem-5, and pem-6: maternal genes with localized mRNA in the ascidian embryo. Developmental biology 72 9441682
2007 ARHGEF9 disruption in a female patient is associated with X linked mental retardation and sensory hyperarousal. Journal of medical genetics 57 17893116
2017 ARHGEF9 mutations in epileptic encephalopathy/intellectual disability: toward understanding the mechanism underlying phenotypic variation. Neurogenetics 47 29130122
2015 Inter-kingdom Signaling by the Legionella Quorum Sensing Molecule LAI-1 Modulates Cell Migration through an IQGAP1-Cdc42-ARHGEF9-Dependent Pathway. PLoS pathogens 42 26633832
2017 ARHGEF9 disease: Phenotype clarification and genotype-phenotype correlation. Neurology. Genetics 41 28589176
2011 De novo Xq11.11 microdeletion including ARHGEF9 in a boy with mental retardation, epilepsy, macrosomia, and dysmorphic features. American journal of medical genetics. Part A 41 21626670
2016 Missense Mutation R338W in ARHGEF9 in a Family with X-linked Intellectual Disability with Variable Macrocephaly and Macro-Orchidism. Frontiers in molecular neuroscience 23 26834553
2019 Identification of TAF1, SAT1, and ARHGEF9 as DNA methylation biomarkers for hepatocellular carcinoma. Journal of cellular physiology 21 31283007
2017 The phenotypic spectrum of ARHGEF9 includes intellectual disability, focal epilepsy and febrile seizures. Journal of neurology 20 28620718
2016 Xq11.1-11.2 deletion involving ARHGEF9 in a girl with autism spectrum disorder. European journal of medical genetics 19 27238888
2022 Human ARHGEF9 intellectual disability syndrome is phenocopied by a mutation that disrupts collybistin binding to the GABAA receptor α2 subunit. Molecular psychiatry 15 35169261
2020 Clinical and Molecular Characterization of Three Novel ARHGEF9 Mutations in Patients with Developmental Delay and Epilepsy. Journal of molecular neuroscience : MN 14 31942680
2022 ARHGEF9 gene variant leads to developmental and epileptic encephalopathy: Genotypic phenotype analysis and treatment exploration. Molecular genetics & genomic medicine 13 35638461
2018 Autism spectrum disorder in females with ARHGEF9 alterations and a random pattern of X chromosome inactivation. European journal of medical genetics 12 30048823
2022 LncRNA-p21 suppresses cell proliferation and induces apoptosis in gastric cancer by sponging miR-514b-3p and up-regulating ARHGEF9 expression. Biological chemistry 8 35947460
2020 De novo ARHGEF9 missense variants associated with neurodevelopmental disorder in females: expanding the genotypic and phenotypic spectrum of ARHGEF9 disease in females. Neurogenetics 8 32939676
2018 Biochemical and Morphological Characterization of a Guanine Nucleotide Exchange Factor ARHGEF9 in Mouse Tissues. Acta histochemica et cytochemica 7 30083020
2012 Gain of FAM123B and ARHGEF9 in an Obese Man with Intellectual Disability, Congenital Heart Defects and Multiple Supernumerary Ring Chromosomes. Molecular syndromology 7 23599698
2023 Regionally restricted modulation of Sam68 expression and Arhgef9 alternative splicing in the hippocampus of a murine model of multiple sclerosis. Frontiers in molecular neuroscience 6 36710925
2022 ARHGEF9 regulates melanoma morphogenesis in environments with diverse geometry and elasticity by promoting filopodial-driven adhesion. iScience 6 36039362
2024 Association analysis of polymorphisms in SLK, ARHGEF9, WWC2, GAB3, and FSHR genes with reproductive traits in different sheep breeds. Frontiers in genetics 5 38680425
2023 Increased delivery and cytotoxicity of doxorubicin in HeLa cells using the synthetic cationic peptide pEM-2 functionalized liposomes. Colloids and surfaces. B, Biointerfaces 5 37379702
2024 Impaired axon initial segment structure and function in a model of ARHGEF9 developmental and epileptic encephalopathy. Proceedings of the National Academy of Sciences of the United States of America 4 39374387
2009 ARHGEF9 disruption in a female patient is associated with X linked mental retardation and sensory hyperarousal. BMJ case reports 4 21731583
2021 A novel de novo hemizygous ARHGEF9 mutation associated with severe intellectual disability and epilepsy: a case report. The Journal of international medical research 3 34851771
2025 Autism-associated ARHGEF9 variants impair GABAergic synapses and ultrasonic communication by reducing gephyrin phosphorylation. Molecular psychiatry 2 41174051
2021 Loss-of-function variants in ARHGEF9 are associated with an X-linked intellectual disability dominant disorder. Human mutation 2 33600053
2023 Peptide ARHGEF9 Inhibits Glioma Progression via PI3K/AKT/mTOR Pathway. Disease markers 1 36852158
2026 Developmental and Epileptic Encephalopathy Due to a Novel ARHGEF9 Deletion Variant: Case Series of Two Siblings. Revista de neurologia 0 42216460
2025 The influences of ARHGEF9 on myoblasts migration and differentiation. Journal of muscle research and cell motility 0 39992578
2023 Retracted: Peptide ARHGEF9 Inhibits Glioma Progression via PI3K/AKT/mTOR Pathway. Disease markers 0 37593569
2022 [Clinical analysis of early-onset infantile epileptic encephalopathy associated with synonymous variant of the ARHGEF9 gene]. Zhonghua yi xue yi chuan xue za zhi = Zhonghua yixue yichuanxue zazhi = Chinese journal of medical genetics 0 36184101
2019 [Patients with ARHGEF9-mutation: a case report and implications of genetic disorders in child psychiatry]. Tijdschrift voor psychiatrie 0 31907904

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