Affinage

FRMD7

FERM domain-containing protein 7 · UniProt Q6ZUT3

Length
714 aa
Mass
81.6 kDa
Annotated
2026-04-28
64 papers in source corpus 13 papers cited in narrative 14 extracted findings

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

FRMD7 is a FERM domain-containing protein that orchestrates the development and wiring of direction-selective retinal circuits underlying the horizontal optokinetic reflex. Expressed specifically in starburst amacrine cells, FRMD7 promotes neurite outgrowth by modulating actin and microtubule cytoskeletal dynamics through Rac1 GTPase signaling and interacts with the scaffolding protein CASK at the plasma membrane to support neurite extension (PMID:19892780, PMID:23406872, PMID:23946638). FRMD7 also directly binds the GABA-A receptor subunit GABRA2, regulating inhibitory receptor localization and thereby establishing the asymmetric inhibitory input onto direction-selective ganglion cells required for horizontal direction selectivity (PMID:32446246, PMID:26711119). Loss-of-function mutations in FRMD7 cause X-linked idiopathic infantile nystagmus by selectively abolishing horizontal direction selectivity in retinal ganglion cells (PMID:17013395, PMID:26711119).

Mechanistic history

Synthesis pass · year-by-year structured walk · 9 steps
  1. 2006 High

    Identification of FRMD7 as the causative gene for X-linked idiopathic infantile nystagmus established that a previously uncharacterized FERM-domain protein is required for gaze stability and eye-movement control.

    Evidence Mutation screening across multiple families (22 mutations), in situ hybridization showing expression in embryonic brain and developing retina

    PMID:17013395

    Open questions at the time
    • Cellular function of FRMD7 unknown
    • Retinal cell-type specificity of expression unresolved
    • Mechanism linking FRMD7 loss to nystagmus not established
  2. 2009 High

    Demonstrating that FRMD7 knockdown impairs neurite development during neuronal differentiation established a functional role in neuronal morphogenesis rather than merely a genetic association with disease.

    Evidence shRNA knockdown in retinoic acid-differentiated Neuro-2A cells with neurite morphometry

    PMID:19892780

    Open questions at the time
    • Molecular mechanism of neurite regulation unknown
    • Whether effect is cell-autonomous in retinal neurons not tested
  3. 2011 Medium

    Characterization of FRMD7 subcellular localization and splice variants revealed that the C-terminus is essential for cytoplasmic retention and F-actin co-localization, and that two isoforms (FL and S) physically interact, linking FRMD7 to cytoskeletal regulation.

    Evidence EGFP-tagged constructs with confocal microscopy and phalloidin staining; co-IP of isoforms in NT2 cells

    PMID:21386928 PMID:22128244

    Open questions at the time
    • Direct actin-binding activity not demonstrated biochemically
    • Functional significance of isoform interaction unclear
    • Studies performed in non-retinal cell lines
  4. 2012 Medium

    FRMD7 overexpression upregulated cytoskeletal genes (MAP2, NF-L, NF-M, MAPT) and enhanced neurite outgrowth, broadening its role from actin to microtubule/neurofilament dynamics.

    Evidence Transfection in Neuro-2A cells with qRT-PCR and confocal microscopy

    PMID:22690121

    Open questions at the time
    • Whether cytoskeletal gene regulation is direct or indirect unknown
    • No in vivo validation
  5. 2013 High

    Discovery of the FRMD7–CASK interaction and its requirement for plasma membrane localization and neurite extension provided the first defined molecular partnership, while identification of Rac1 GTPase modulation revealed a signaling mechanism for cytoskeletal regulation.

    Evidence IP-MS, reciprocal co-IP, domain mapping of disease mutations disrupting CASK binding; GST-PAK2 affinity precipitation for Rac1 activity

    PMID:23406872 PMID:23946638

    Open questions at the time
    • Whether FRMD7 directly activates a Rac1 GEF or acts as a scaffold unknown
    • Structural basis of FRMD7–CASK interface unresolved
  6. 2015 High

    Frmd7 knockout mice revealed that FRMD7 is expressed exclusively in starburst amacrine cells and is required for asymmetric inhibitory wiring onto direction-selective ganglion cells, explaining how its loss selectively abolishes horizontal direction selectivity and the optokinetic reflex.

    Evidence Knockout mouse with patch-clamp electrophysiology, immunohistochemistry, and behavioral optokinetic testing

    PMID:26711119

    Open questions at the time
    • Molecular mechanism by which FRMD7 specifies asymmetric wiring not identified
    • Whether FRMD7 acts pre- or post-synaptically in starburst amacrine cells unclear
  7. 2019 Medium

    Patient-derived reprogrammed neurons confirmed that FRMD7 mutations cell-autonomously reduce neurite complexity and dysregulate Rho GTPase expression, validating findings in a human neuronal context.

    Evidence Direct neuronal reprogramming from patient fibroblasts, morphometry, and qRT-PCR

    PMID:31743612

    Open questions at the time
    • Rho GTPase upregulation may be compensatory rather than causal
    • Retinal-specific neuron subtypes not recapitulated in this model
  8. 2020 High

    Identification of a direct FRMD7–GABRA2 interaction linked FRMD7 to inhibitory synapse receptor trafficking, providing a molecular explanation for the loss of asymmetric GABAergic input seen in knockout mice.

    Evidence GST pull-down and co-IP for biochemical interaction; FRAP and locomotion rescue in C. elegans frm-3 mutants

    PMID:32446246

    Open questions at the time
    • Whether FRMD7 regulates GABRA2 localization specifically in starburst amacrine cell dendrites not shown in mammalian retina
    • Relationship between CASK and GABRA2 binding (simultaneous or competitive) unknown
  9. 2024 Medium

    Demonstration that frameshift FRMD7 truncations escape NMD but undergo ubiquitin–proteasomal degradation clarified that loss-of-function through protein instability, rather than mRNA decay, is a common pathogenic mechanism.

    Evidence Western blot with proteasome inhibitor treatment and qPCR for mRNA levels

    PMID:38279119

    Open questions at the time
    • Whether all IIN-causing truncations share this degradation fate not tested
    • Protein half-life in native retinal neurons unknown

Open questions

Synthesis pass · forward-looking unresolved questions
  • The structural basis of FRMD7's interactions with CASK and GABRA2, whether these interactions are simultaneous or mutually exclusive, and how FRMD7 molecularly instructs the asymmetric wiring of starburst amacrine cell dendrites remain unresolved.
  • No crystal or cryo-EM structure of FRMD7 or its complexes
  • Whether FRMD7 functions as a GEF scaffold or direct Rac1 activator not determined
  • Mechanism linking FRMD7–GABRA2 interaction to directional asymmetry in mammalian retina not established

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0008092 cytoskeletal protein binding 2 GO:0060090 molecular adaptor activity 2
Localization
GO:0005829 cytosol 2 GO:0005886 plasma membrane 2
Pathway
R-HSA-112316 Neuronal System 2 R-HSA-1266738 Developmental Biology 2 R-HSA-162582 Signal Transduction 2
Partners
CASKGABRA2RAC1

Evidence

Reading pass · 14 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
2006 FRMD7 was identified as a novel FERM domain-containing protein expressed in human embryonic brain and developing neural retina, with mutations causing X-linked idiopathic congenital nystagmus, suggesting a specific role in control of eye movement and gaze stability. Mutation screening, in situ hybridization, expression analysis Nature genetics High 17013395
2009 FRMD7 knockdown during retinoic acid-induced neuronal differentiation of Neuro-2A cells results in altered neurite development, demonstrating a functional role for FRMD7 in neuronal outgrowth and development. shRNA knockdown, in situ hybridization, immunohistochemistry, neurite morphometry Human molecular genetics High 19892780
2013 FRMD7 directly interacts with the plasma membrane scaffolding protein CASK; CASK promotes FRMD7 co-localization at the plasma membrane where together they enhance neurite length. IIN-associated FRMD7 mutations impair CASK interaction and plasma membrane co-localization. C-terminal CASK mutations that cause nystagmus specifically disrupt CASK–FRMD7 interaction. Immunoprecipitation–mass spectrometry (IP-MS), co-immunoprecipitation, co-localization imaging, neurite outgrowth assay, domain-mapping of CASK mutations Human molecular genetics High 23406872
2015 FRMD7 is specifically expressed in starburst amacrine cells of the retina. Loss of FRMD7 leads to selective loss of horizontal direction selectivity in retinal ganglion cells and a transition from asymmetric to symmetric inhibitory input to direction-selective ganglion cells, establishing FRMD7 as a key regulator of neuronal circuit asymmetry required for the horizontal optokinetic reflex. Frmd7 knockout mouse, immunohistochemistry, electrophysiology (patch-clamp), optokinetic reflex behavioral testing Neuron High 26711119
2011 The C-terminus of FRMD7 is essential for its cytoplasmic subcellular localization; a truncating mutation (c.1003C>T) causes nuclear mislocalization and loss of co-localization with F-actin, whereas missense mutations do not alter F-actin co-localization. EGFP-tagged constructs in Neuro-2A and HEK293T cells, confocal microscopy, rhodamine-phalloidin staining Molecular vision Medium 21386928
2013 An IIN-associated FRMD7 missense mutant (C271Y) accumulates in the nucleus rather than the cytoplasm, possibly due to disruption of a nuclear export sequence downstream of the FERM-adjacent domain; this mutant acts in a dominant-negative manner to inhibit neurite formation. Transfection of tagged mutant constructs, immunofluorescence localization, neurite outgrowth assay Human molecular genetics Medium 23406872
2012 Overexpression of FRMD7 in Neuro-2A cells promotes neurite outgrowth after retinoic acid-induced differentiation and upregulates mRNA expression of neuronal cytoskeletal genes including MAP2, NF-L, NF-M, and MAPT, suggesting involvement in cytoskeletal dynamics of both F-actin and microtubules/neurofilaments. Transfection of full-length FRMD7 in Neuro-2A cells, quantitative RT-PCR, rhodamine-phalloidin staining, confocal microscopy Molecular vision Medium 22690121
2013 A novel FRMD7 missense mutation (c.635T>C, p.L212P) reduces Rac1 GTPase signaling activation compared to wild-type FRMD7, as measured by GST-PAK2 affinity precipitation, implicating FRMD7 in Rac1-mediated neurite development. GST-PAK2 affinity precipitation, co-transfection of FRMD7 and Rac1 in HEK293T cells Molecular vision Medium 23946638
2011 Two FRMD7 isoforms (FRMD7-FL and the shorter splice variant FRMD7-S) co-localize and co-immunoprecipitate with each other in NT2 cells, and FRMD7-FL overexpression upregulates FRMD7-S expression and alters neurite development. Co-immunoprecipitation, immunofluorescence, RT-PCR, neurite morphometry in NT2 cells Molecular vision Medium 22128244
2019 FRMD7 mutations in human fibroblast-reprogrammed neurons (iNs) reduce complexity of neuronal processes (total neurite length, number of terminals, maturation rate), and are accompanied by significantly increased expression of the three main Rho GTPases. Direct neuronal reprogramming from fibroblasts, immunofluorescence morphometry, RT-PCR for Rho GTPases Brain and behavior Medium 31743612
2020 FRMD7 directly interacts with the loop between transmembrane domains 3 and 4 of GABRA2 (a GABA-A receptor subunit critical for receptor transport and localization). IIN-associated FRMD7 mutants (p.Ala194Thr, p.Arg325Gly) show decreased binding to GABRA2. In frm-3 (nematode FRMD7 homolog) null C. elegans, FRMD7 mutants fail to rescue locomotion defects and impair GABAAR fluorescence recovery after photobleaching. GST pull-down, co-immunoprecipitation, FRAP in C. elegans, locomotion rescue assay Investigative ophthalmology & visual science High 32446246
2019 A novel FRMD7 missense mutation (p.K269Q) inhibits neurite formation and extension, and disrupts FRMD7 interaction with CASK, supporting a model in which FRMD7–CASK interaction is required for normal neurite outgrowth. Transfection, neurite outgrowth assay, co-immunoprecipitation Acta biochimica et biophysica Sinica Medium 30576400
2020 Frmd7 knockout mice generated by EUCOMM/COMP repository confirm FRMD7 expression in the retina restricted to starburst amacrine cells and show a specific horizontal optokinetic reflex defect with unchanged gross retinal morphology and electrophysiology. Antibody and X-gal staining for expression, high-speed eye tracking, electroretinography, histology Genes High 33007925
2024 Two frameshift FRMD7 mutations produce truncated proteins that escape nonsense-mediated mRNA decay (NMD) but are degraded via the ubiquitin–proteasomal pathway, suggesting that loss-of-function through proteasomal degradation of truncated proteins is a pathogenic mechanism. Western blot, qPCR, plasmid expression of mutant constructs, proteasome inhibitor assays BMC medical genomics Medium 38279119

Source papers

Stage 0 corpus · 64 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
2006 Mutations in FRMD7, a newly identified member of the FERM family, cause X-linked idiopathic congenital nystagmus. Nature genetics 147 17013395
2015 Congenital Nystagmus Gene FRMD7 Is Necessary for Establishing a Neuronal Circuit Asymmetry for Direction Selectivity. Neuron 116 26711119
2007 Nitration in neurodegeneration: deciphering the "Hows" "nYs". Biochemistry 84 17542619
2008 Phenotypical characteristics of idiopathic infantile nystagmus with and without mutations in FRMD7. Brain : a journal of neurology 72 18372314
1999 A gene for X-linked idiopathic congenital nystagmus (NYS1) maps to chromosome Xp11.4-p11.3. American journal of human genetics 68 10090899
2009 The nystagmus-associated FRMD7 gene regulates neuronal outgrowth and development. Human molecular genetics 61 19892780
2014 Abnormal retinal development associated with FRMD7 mutations. Human molecular genetics 54 24688117
2013 A novel interaction between FRMD7 and CASK: evidence for a causal role in idiopathic infantile nystagmus. Human molecular genetics 51 23406872
2011 The Role of FRMD7 in Idiopathic Infantile Nystagmus. Journal of ophthalmology 42 21904664
1988 A site-specific single strand endonuclease activity induced by NYs-1 virus infection of a Chlorella-like green alga. Nucleic acids research 41 3186439
2007 Novel mutations of the FRMD7 gene in X-linked congenital motor nystagmus. Molecular vision 39 17893669
2007 Novel mutations in FRMD7 in X-linked congenital nystagmus. Mutation in brief #963. Online. Human mutation 38 17397053
2007 Allelic variation of the FRMD7 gene in congenital idiopathic nystagmus. Archives of ophthalmology (Chicago, Ill. : 1960) 37 17846367
2012 Incrimination of Anopheles (Anopheles) intermedius Peryassú, An. (Nyssorhynchus) nuneztovari Gabaldón, An. (Nys.) oswaldoi Peryassú as natural vectors of Plasmodium falciparum in French Guiana. Memorias do Instituto Oswaldo Cruz 34 22510842
2004 Cloning of CviPII nicking and modification system from chlorella virus NYs-1 and application of Nt.CviPII in random DNA amplification. Nucleic acids research 32 15570069
2007 FRMD7 mutations in Chinese families with X-linked congenital motor nystagmus. Molecular vision 31 17768376
2008 Five novel mutations of the FRMD7 gene in Chinese families with X-linked infantile nystagmus. Molecular vision 30 18431453
2015 Novel FRMD7 Mutations and Genomic Rearrangement Expand the Molecular Pathogenesis of X-Linked Idiopathic Infantile Nystagmus. Investigative ophthalmology & visual science 27 25678693
2008 A novel mutation in FRMD7 causing X-linked idiopathic congenital nystagmus in a large family. Molecular vision 25 18246032
2008 A novel frameshift mutation in FRMD7 causing X-linked idiopathic congenital nystagmus. Genetic testing 22 19072571
2007 Skewed X inactivation in an X linked nystagmus family resulted from a novel, p.R229G, missense mutation in the FRMD7 gene. The British journal of ophthalmology 20 17962394
2001 Clinical and genetic analysis of a family with X-linked congenital nystagmus (NYS1). Ophthalmic genetics 20 11803490
2018 Genotype and Phenotype Spectrum of FRMD7-Associated Infantile Nystagmus Syndrome. Investigative ophthalmology & visual science 18 30025138
2011 Expression and localization of FRMD7 in human fetal brain, and a role for F-actin. Molecular vision 17 21386928
2010 Novel intragenic FRMD7 deletion in a pedigree with congenital X-linked nystagmus. Ophthalmic genetics 17 20450309
2015 A start codon mutation of the FRMD7 gene in two Korean families with idiopathic infantile nystagmus. Scientific reports 16 26268155
2012 Novel homozygous, heterozygous and hemizygous FRMD7 gene mutations segregated in the same consanguineous family with congenital X-linked nystagmus. European journal of human genetics : EJHG 15 22490987
2007 X-linked idiopathic infantile nystagmus associated with a missense mutation in FRMD7. Molecular vision 15 18087240
2013 A novel missense mutation in the FERM domain containing 7 (FRMD7) gene causing X-linked idiopathic congenital nystagmus in a Chinese family. Molecular vision 14 23946638
2011 A novel frame-shift mutation in FRMD7 causes X-linked idiopathic congenital nystagmus in a Chinese family. Molecular vision 14 22065930
2014 Identification of three novel mutations in the FRMD7 gene for X-linked idiopathic congenital nystagmus. Scientific reports 13 24434814
2009 Frmd7 expression in developing mouse brain. Eye (London, England) 13 19265863
2017 Novel mutations of FRMD7 in Chinese patients with congenital motor nystagmus. Molecular medicine reports 12 28656292
2012 FERM domain containing protein 7 (FRMD7) upregulates the expression of neuronal cytoskeletal proteins and promotes neurite outgrowth in Neuro-2a cells. Molecular vision 12 22690121
2013 Identifcation of a novel mutation p.I240T in the FRMD7 gene in a family with congenital nystagmus. Scientific reports 11 24169426
2017 Clinical feature and waveform in infantile nystagmus syndrome in children with FRMD7 gene mutations. Science China. Life sciences 10 28623544
2020 FRMD7 Mutations Disrupt the Interaction with GABRA2 and May Result in Infantile Nystagmus Syndrome. Investigative ophthalmology & visual science 9 32446246
2015 A novel mutation in FRMD7 causes X-linked idiopathic congenital nystagmus in a North Indian family. Neuroscience letters 9 25916882
2012 A novel splicing mutation of the FRMD7 gene in a Chinese family with X-linked congenital nystagmus. Molecular vision 9 22262942
2011 Identification of a novel FRMD7 splice variant and functional analysis of two FRMD7 transcripts during human NT2 cell differentiation. Molecular vision 9 22128244
2022 Correlations of FRMD7 gene mutations with ocular oscillations. Scientific reports 8 35705619
2019 A Disease-Causing FRMD7 Variant in a Chinese Family with Infantile Nystagmus. Journal of molecular neuroscience : MN 7 30618027
2019 Nystagmus-related FRMD7 gene influences the maturation and complexities of neuronal processes in human neurons. Brain and behavior 7 31743612
2020 Characterization of the Frmd7 Knock-Out Mice Generated by the EUCOMM/COMP Repository as a Model for Idiopathic Infantile Nystagmus (IIN). Genes 6 33007925
2019 Next-generation sequencing identifies a novel frameshift variant in FRMD7 in a Chinese family with idiopathic infantile nystagmus. Journal of clinical laboratory analysis 6 31495972
2013 Novel mutation c.980_983delATTA compound with c.986C>A mutation of the FRMD7 gene in a Chinese family with X-linked idiopathic congenital nystagmus. Journal of Zhejiang University. Science. B 6 23733424
2011 Prolonged pursuit by optokinetic drum testing in asymptomatic female carriers of novel FRMD7 splice mutation c.1050 +5 G>A. Archives of ophthalmology (Chicago, Ill. : 1960) 6 21746984
2019 A novel frameshift mutation in FRMD7 causes X-linked infantile nystagmus in a Chinese family. BMC medical genetics 5 30616528
2023 FRMD7 Gene Alterations in a Pakistani Family Associated with Congenital Idiopathic Nystagmus. Genes 4 36833273
2018 Identification of a novel idiopathic congenital nystagmus‑causing missense mutation, p.G296C, in the FRMD7 gene. Molecular medicine reports 4 30015830
2015 A FRMD7 variant in a Japanese family causes congenital nystagmus. Human genome variation 4 27081518
2014 Expression of a novel splice variant of FRMD7 in developing human fetal brains that is upregulated upon the differentiation of NT2 cells. Experimental and therapeutic medicine 4 25187810
2019 Identification and functional characterization of a novel missense mutation in FRMD7 responsible for idiopathic congenital nystagmus. Acta biochimica et biophysica Sinica 3 30576400
2008 [The G990T mutation of the FRMD7 gene in a Chinese family with congenital idiopathic nystagmus]. Zhonghua yi xue yi chuan xue za zhi = Zhonghua yixue yichuanxue zazhi = Chinese journal of medical genetics 3 18247295
2024 Truncated FRMD7 proteins in congenital Nystagmus: novel frameshift mutations and proteasomal pathway implications. BMC medical genomics 2 38279119
2023 Case report: A novel pathogenic FRMD7 variant in a Turner syndrome patient with familial idiopathic infantile nystagmus. Frontiers in neurology 2 37545716
2019 Clinical and molecular findings of FRMD7 related congenital nystagmus as adifferential diagnosis of ocular albinism. Ophthalmic genetics 2 30942644
2024 Differences of ocular oscillations and neuro-retinal structures in patients with nystagmus caused by GPR143 and FRMD7 gene variants. Indian journal of ophthalmology 1 38648460
2023 Best-corrected visual acuity results facilitate molecular diagnosis of infantile nystagmus patients harboring FRMD7 mutations. Experimental eye research 1 37423457
2023 X-linked FRMD7 gene mutation in idiopathic congenital nystagmus and its role in eye movement: A case report and literature review. Frontiers in ophthalmology 1 38983508
2026 Genetic Landscape and Clinical Characterization of FRMD7-Related Infantile Nystagmus Based on Large In-House Datasets and Literature Review. Investigative ophthalmology & visual science 0 41532703
2025 Functional analysis of a novel segment deletion in the FRMD7 gene causing X-linked idiopathic congenital nystagmus. Genomics 0 41130545
2024 Surgical outcomes of a congenital nystagmus family with a missense mutation in the FRMD7 gene. Heliyon 0 39108919
1989 [Genetic mapping of the NYS1 gene in Saccharomyces cerevisiae]. Genetika 0 2689284