{"gene":"USH2A","run_date":"2026-04-28T21:43:01","timeline":{"discoveries":[{"year":1999,"finding":"USH2A encodes usherin, a protein with laminin epidermal growth factor-like (LE) domains and fibronectin type III repeats characteristic of extracellular matrix/basal lamina proteins; missense mutations within the fifth LE domain (Cys759Phe) cause recessive retinitis pigmentosa without hearing loss, establishing domain-function relationships","method":"Direct DNA sequencing, mutation analysis, protein domain prediction","journal":"American journal of human genetics","confidence":"Medium","confidence_rationale":"Tier 3 — single study, sequence-based domain inference with clinical correlation; no in vitro functional assay","pmids":["10775529"],"is_preprint":false},{"year":2004,"finding":"The long isoform of USH2A encodes a transmembrane protein (usherin isoform b) with an extracellular domain containing a Laminin N-terminal domain, laminin G repeats, 28 fibronectin type III repeats, a transmembrane region, and a C-terminal intracellular PDZ-binding motif; pathogenic mutations in the novel exons 22–73 cause both hearing loss and retinitis pigmentosa","method":"Gene cloning, exon identification, expression profiling, mutation analysis","journal":"American journal of human genetics","confidence":"Medium","confidence_rationale":"Tier 3 — structural inference from sequence; domain architecture validated by mutational data but no direct protein biochemistry","pmids":["15015129"],"is_preprint":false},{"year":2006,"finding":"Whirlin (DFNB31/USH2D) directly associates with USH2A isoform b (usherin) and VLGR1b; this ternary complex co-localizes at photoreceptor synaptic regions, connecting cilia, and outer limiting membrane, and at cochlear outer hair cell synaptic regions, identifying usherin as a component of a PDZ scaffold-organized periciliary/synaptic interactome","method":"Yeast two-hybrid, co-immunoprecipitation, immunohistochemistry, confocal microscopy","journal":"Human molecular genetics","confidence":"High","confidence_rationale":"Tier 2 — reciprocal interaction assays plus co-localization across multiple tissues; replicated in subsequent studies","pmids":["16434480"],"is_preprint":false},{"year":2010,"finding":"The N-terminal PDZ domains of the whirlin long isoform mediate assembly of a multi-protein USH2 complex that includes usherin (USH2A) and VLGR1; this complex localizes to the periciliary membrane complex (PMC) in photoreceptors. Loss of any single USH2 protein disrupts normal localization of all USH2 proteins and causes protein destabilization, establishing that the three USH2 proteins form an obligatory functional complex in vivo","method":"Targeted gene knockout mice, immunofluorescence, Western blot, electroretinography, histology","journal":"PLoS genetics","confidence":"High","confidence_rationale":"Tier 2 — multiple USH2 KO mouse models with orthogonal readouts; replicated across labs","pmids":["20502675"],"is_preprint":false},{"year":2011,"finding":"AAV-mediated whirlin transgene expression in whirlin knockout photoreceptors recruits USH2A and VLGR1 back to the periciliary membrane complex, restoring the USH2 protein complex; this demonstrates that whirlin is upstream of USH2A localization in photoreceptors","method":"AAV subretinal injection, immunofluorescence, immunoelectron microscopy, Western blot, electroretinography","journal":"Investigative ophthalmology & visual science","confidence":"High","confidence_rationale":"Tier 2 — in vivo rescue experiment with multiple orthogonal readouts establishing pathway hierarchy","pmids":["21212183"],"is_preprint":false},{"year":2011,"finding":"A deep-intronic mutation in USH2A (c.7595-2144A>G) creates a pseudoexon (PE40) insertion into the mature transcript, generating a premature stop codon and a predicted truncated nonfunctional usherin protein; confirmed by RNA analysis from nasal cells and minigene assay","method":"RNA analysis from patient nasal epithelial cells, minigene splice assay, sequencing","journal":"Human mutation","confidence":"High","confidence_rationale":"Tier 2 — functional RNA analysis plus minigene assay demonstrating aberrant splicing mechanism","pmids":["22009552"],"is_preprint":false},{"year":2014,"finding":"The common c.2299delG mutation in USH2A exon 13 disrupts an exonic splicing enhancer and creates an exonic splicing silencer, leading to aberrant splicing of exons 12–13 in addition to the predicted frameshift; shown by RT-PCR in patient nasal epithelial cells","method":"RT-PCR from patient nasal epithelial cells, bioinformatics splice prediction","journal":"Experimental eye research","confidence":"Medium","confidence_rationale":"Tier 2 — functional RNA analysis in patient cells; single lab","pmids":["24607488"],"is_preprint":false},{"year":2016,"finding":"Antisense oligonucleotides targeting the PE40 splice acceptor site and exonic splice enhancer regions of USH2A pre-mRNA significantly correct aberrant splicing caused by the deep-intronic c.7595-2144A>G mutation in patient fibroblasts and a minigene assay","method":"AON treatment in patient-derived fibroblasts, minigene splice assay","journal":"Molecular therapy. Nucleic acids","confidence":"High","confidence_rationale":"Tier 2 — functional splice correction in patient cells with multiple AON designs; moderate evidence","pmids":["27802265"],"is_preprint":false},{"year":2017,"finding":"SANS (USH1G) directly interacts with usherin (USH2A) and both assemble into a ternary USH1/USH2 complex together with whirlin (USH2D) via mutual interactions; the complex localizes to the periciliary region, inner segment, and synapses of rodent and human photoreceptors, and pathogenic mutations in USH1G disrupt this complex","method":"Yeast two-hybrid, co-immunoprecipitation, proximity ligation assay, immunohistochemistry, mutagenesis","journal":"Human molecular genetics","confidence":"High","confidence_rationale":"Tier 2 — multiple orthogonal interaction assays plus in situ complex detection; validates cross-type USH protein network","pmids":["28137943"],"is_preprint":false},{"year":2017,"finding":"Myosin VIIa (USH1B) is indispensable for USH2 complex (USH2A/ADGRV1/WHRN/PDZD7) assembly at ankle links in cochlear hair cells, indicating a transport/anchoring role; however, myosin VIIa is not required for USH2 complex assembly in photoreceptors, demonstrating tissue-specific differences in USH2 complex organization","method":"USH1 mutant mice, immunofluorescence, FLAG pull-down assay","journal":"Human molecular genetics","confidence":"High","confidence_rationale":"Tier 2 — genetic epistasis using multiple USH1 KO mouse models with defined cellular phenotypes","pmids":["28031293"],"is_preprint":false},{"year":2015,"finding":"USH2A proteins (USH2A, ADGRV1, WHRN, PDZD7) assemble into the ankle link complex (ALC) at cochlear hair cell stereociliary bundles; individual USH2 proteins make distinct contributions to ALC assembly during development, with ADGRV1 being the most critical, and loss of individual proteins leads to variable stereociliary morphological and functional defects correlating with ALC disruption severity","method":"Multiple USH2 KO mouse models, immunofluorescence, scanning electron microscopy, auditory function testing","journal":"Human molecular genetics","confidence":"High","confidence_rationale":"Tier 2 — systematic in vivo characterization with multiple mutant lines and orthogonal readouts","pmids":["26401052"],"is_preprint":false},{"year":2018,"finding":"Knockout of ush2a in zebrafish causes disruption of fibronectin assembly at the retinal basement membrane, weakening cell adhesion, along with progressive rod-then-cone photoreceptor degeneration; upregulation of Ush1b and Ush1c expression was observed when Ush2a was absent","method":"TALEN-generated ush2a-/- zebrafish, ERG, histology, immunohistochemistry, Western blot","journal":"Human genetics","confidence":"Medium","confidence_rationale":"Tier 2 — KO zebrafish model with defined molecular and functional phenotypes; single lab","pmids":["30242501"],"is_preprint":false},{"year":2019,"finding":"USH2A (usherin) protein is expressed in terminal Schwann cells within Meissner's corpuscles in fingertip skin (not in sensory neurons); loss of USH2A reduces mechanoreceptor vibration sensitivity of rapidly adapting mechanoreceptors, and patients with biallelic USH2A mutations have specific impairment in vibrotactile touch perception","method":"Immunohistochemistry, Ush2a-/- mouse electrophysiology, human psychophysical testing","journal":"Nature neuroscience","confidence":"High","confidence_rationale":"Tier 2 — localization by IHC combined with in vivo functional recordings in KO mice and human patient testing; moderate-to-strong evidence from orthogonal approaches","pmids":["33288907"],"is_preprint":false},{"year":2021,"finding":"Morpholino-induced skipping of ush2a exon 13 in zebrafish ush2armc1 mutants restores production of a shortened usherin protein (usherinΔexon13) and completely rescues retinal function, demonstrating that an usherin protein lacking the exon 13-encoded region is functional","method":"Zebrafish morpholino exon skipping, ERG, Western blot, immunohistochemistry","journal":"Molecular therapy : the journal of the American Society of Gene Therapy","confidence":"High","confidence_rationale":"Tier 2 — in vivo functional rescue experiment in zebrafish disease model with ERG readout","pmids":["33895329"],"is_preprint":false},{"year":2019,"finding":"CRISPR/Cas9-based deletion of mouse Ush2a exon 12 (ortholog of human exon 13) produces a shortened Ush2a-ΔEx12 protein that localizes correctly in the cochlea and, when expressed on an Ush2a null background, restores impaired hair cell structure and auditory function","method":"CRISPR/Cas9 exon deletion in mice, immunohistochemistry, auditory brainstem response testing","journal":"Advances in experimental medicine and biology","confidence":"High","confidence_rationale":"Tier 2 — in vivo functional rescue in KO mouse background with defined structural and functional readouts","pmids":["31884594"],"is_preprint":false},{"year":2023,"finding":"ADGRV1 inhibits WHRN phosphorylation through regional cAMP-PKA signaling; phosphorylated WHRN recruits the E3 ligase WDSUB1 (identified by yeast two-hybrid), which ubiquitinates USH2A in a WHRN phosphorylation-dependent manner, regulating USH2A stability; the deafness-associated ADGRV1 Y6236fsX1 mutation fails to inhibit WHRN phosphorylation, leading to increased USH2A ubiquitination and destabilization","method":"Adgrv1 Y6236fsX1 knock-in mice, yeast two-hybrid, FlAsH-BRET assay, NMR spectrometry, mutagenesis, ubiquitination assays, stereocilia imaging, MET recordings","journal":"Advanced science (Weinheim, Baden-Wurttemberg, Germany)","confidence":"High","confidence_rationale":"Tier 1 — multiple orthogonal methods including NMR, BRET, mutagenesis, and in vivo model; single lab but exceptionally rigorous","pmids":["37066759"],"is_preprint":false},{"year":2023,"finding":"S/MAR non-viral episomal vectors carrying full-length USH2A cDNA (15.6 kb) drive persistent usherin expression in patient-derived fibroblasts and, after injection into ush2au507 zebrafish, rescue Usher 2 complex localization in photoreceptors for up to 12 months, demonstrating that full-length usherin can restore the USH2 complex in vivo","method":"S/MAR plasmid transfection, Western blot, immunofluorescence, zebrafish microinjection","journal":"Molecular therapy : the journal of the American Society of Gene Therapy","confidence":"Medium","confidence_rationale":"Tier 2 — in vitro and in vivo rescue with functional complex localization readout; single lab","pmids":["37337429"],"is_preprint":false},{"year":2011,"finding":"Splice-site variants in USH2A (c.1841-2A>G, c.2167+5G>A, c.5298+1G>C) abolish consensus splice sites and produce exon skipping; c.2167+5G>A additionally activates a cryptic donor splice site; demonstrated by hybrid minigene assays","method":"Hybrid minigene splice assay, bioinformatics","journal":"Clinical genetics","confidence":"Medium","confidence_rationale":"Tier 2 — functional minigene assay directly demonstrating splicing mechanism","pmids":["20497194"],"is_preprint":false},{"year":2002,"finding":"USH2A mRNA is expressed specifically in the outer nuclear layer of the retina (photoreceptors) in rat, mouse, and human, and in cochlea; during rat retinal development, expression appears in the neuroepithelium at embryonic day 17, establishing the cellular source of usherin in the primary disease-affected tissues","method":"In situ hybridization, gene cloning, radiation hybrid mapping","journal":"Genomics","confidence":"Medium","confidence_rationale":"Tier 2 — direct localization by in situ hybridization across three species; no functional consequence experiment","pmids":["12160733"],"is_preprint":false},{"year":2023,"finding":"Excision of USH2A exon pairs 30-31 or 39-40 using CRISPR-Cas9 in zebrafish restores usherin expression in the retina and rescues photopigment mislocalization; ASO-induced dual exon skipping achieves the same in vitro, demonstrating that protein domain-oriented multi-exon skipping maintains a functional usherin","method":"CRISPR-Cas9 zebrafish exon deletion, immunohistochemistry, in vitro ASO assay","journal":"Molecular therapy. Nucleic acids","confidence":"Medium","confidence_rationale":"Tier 2 — in vivo and in vitro functional rescue; single lab","pmids":["37313440"],"is_preprint":false}],"current_model":"Usherin (USH2A) is a large transmembrane extracellular matrix protein expressed in photoreceptors, cochlear hair cells, and Meissner's corpuscle Schwann cells that functions as an obligatory scaffold within a multiprotein ankle-link/periciliary complex (with ADGRV1, whirlin/WHRN, PDZD7, and SANS) required for stereociliary bundle integrity in cochlear hair cells and for protein trafficking through the connecting cilium/periciliary membrane in photoreceptors; its stability is regulated by ADGRV1-mediated suppression of WHRN phosphorylation, which controls WDSUB1 E3-ligase-dependent ubiquitination of usherin, and loss of any single USH2 complex member destabilizes the entire complex, causing progressive photoreceptor degeneration and sensorineural hearing loss."},"narrative":{"teleology":[{"year":1999,"claim":"Identification of USH2A as a laminin/fibronectin-domain extracellular matrix protein linked domain structure to disease: the Cys759Phe mutation in the fifth LE domain caused recessive RP without hearing loss, establishing that specific domain lesions determine clinical outcome.","evidence":"Mutation analysis and domain prediction in RP families","pmids":["10775529"],"confidence":"Medium","gaps":["No biochemical validation of domain function","Short isoform only; full gene structure unknown"]},{"year":2004,"claim":"Discovery of the long transmembrane isoform (isoform b) resolved how a secreted ECM-like protein could function as a cell-surface receptor/scaffold: the extended protein contains a transmembrane domain and a C-terminal PDZ-binding motif, and mutations in the novel exons cause combined hearing loss and RP.","evidence":"Gene cloning and mutation screening across exons 22–73","pmids":["15015129"],"confidence":"Medium","gaps":["No direct protein biochemistry confirming membrane insertion","PDZ-binding partner identity not yet determined"]},{"year":2006,"claim":"The first identification of usherin's direct binding partners — whirlin (WHRN) and VLGR1 — established usherin as part of a PDZ scaffold-organized multiprotein complex at photoreceptor connecting cilia, synapses, and cochlear hair cells.","evidence":"Yeast two-hybrid and co-immunoprecipitation with co-localization by immunohistochemistry","pmids":["16434480"],"confidence":"High","gaps":["Stoichiometry and assembly order unknown","No structural data on the ternary complex"]},{"year":2010,"claim":"Knockout mouse studies demonstrated that USH2A, ADGRV1, and WHRN form an obligatory complex: loss of any one member destabilized and mislocalized all others at the periciliary membrane, directly linking complex integrity to photoreceptor survival.","evidence":"Multiple USH2 KO mouse models with immunofluorescence, Western blot, and ERG","pmids":["20502675"],"confidence":"High","gaps":["Mechanism of mutual stabilization unknown","Whether complex disruption causes degeneration through trafficking defects versus structural failure unresolved"]},{"year":2011,"claim":"AAV-mediated whirlin re-expression in whirlin-KO photoreceptors recruited USH2A and ADGRV1 back to the periciliary membrane, placing whirlin upstream of usherin localization and establishing a hierarchy within USH2 complex assembly.","evidence":"AAV subretinal injection in Whrn-KO mice with immunofluorescence and immunoelectron microscopy","pmids":["21212183"],"confidence":"High","gaps":["Whether whirlin directly chaperones usherin transport or merely anchors it at the destination unknown","Rescue of photoreceptor degeneration not fully demonstrated"]},{"year":2011,"claim":"Characterization of splicing mutations (deep-intronic and splice-site variants) revealed that many USH2A pathogenic alleles act through aberrant mRNA processing rather than simple protein truncation, opening therapeutic avenues for splice correction.","evidence":"Patient nasal epithelial cell RNA analysis and minigene splice assays for c.7595-2144A>G and other variants","pmids":["22009552","20497194"],"confidence":"High","gaps":["In vivo splicing consequences in retinal tissue not directly assessed","Quantitative contribution of aberrant transcripts versus normal transcripts unknown"]},{"year":2015,"claim":"Systematic comparison of USH2 protein contributions to the cochlear ankle-link complex showed that ADGRV1 is the most critical organizer and that individual USH2 proteins make distinct, non-redundant contributions to stereociliary bundle morphogenesis and auditory function.","evidence":"Multiple USH2 KO mouse models with scanning electron microscopy and auditory testing","pmids":["26401052"],"confidence":"High","gaps":["Molecular basis for differential contributions of USH2A versus ADGRV1 at ankle links unresolved","Direct extracellular interactions between USH2A and ADGRV1 ectodomains not characterized"]},{"year":2017,"claim":"SANS (USH1G) was identified as a direct interactor of usherin, bridging the USH1 and USH2 protein networks into a ternary USH1/USH2 complex; pathogenic USH1G mutations disrupt this complex, explaining the phenotypic overlap between Usher syndrome types.","evidence":"Yeast two-hybrid, co-IP, proximity ligation assay, and immunohistochemistry in rodent and human retina","pmids":["28137943"],"confidence":"High","gaps":["Structural basis of USH1–USH2 bridging interaction unknown","Functional consequence of USH1/USH2 complex disruption in photoreceptors not directly shown in this study"]},{"year":2017,"claim":"Myosin VIIa was shown to be indispensable for USH2 complex assembly at cochlear ankle links but dispensable in photoreceptors, establishing tissue-specific mechanisms of USH2 complex organization.","evidence":"USH1 mutant mice with immunofluorescence and FLAG pull-down","pmids":["28031293"],"confidence":"High","gaps":["Identity of the motor/transport system for USH2 complex in photoreceptors unknown","Whether myosin VIIa directly transports usherin or facilitates its retention unresolved"]},{"year":2019,"claim":"Usherin was localized to terminal Schwann cells of Meissner's corpuscles and shown to be required for vibrotactile mechanoreceptor sensitivity, extending usherin function beyond the retina and cochlea to somatosensory mechanotransduction.","evidence":"Immunohistochemistry in human/mouse skin, Ush2a-KO mouse electrophysiology, and psychophysical testing in USH2A patients","pmids":["33288907"],"confidence":"High","gaps":["Molecular mechanism by which usherin contributes to mechanoreceptor function unknown","Whether the USH2 complex is present in Schwann cells not determined"]},{"year":2019,"claim":"Exon skipping strategies demonstrated that usherin protein lacking the exon 13-encoded region retains function: CRISPR deletion of mouse exon 12 restored cochlear structure and hearing, and morpholino-induced skipping in zebrafish rescued retinal function, validating a therapeutic concept.","evidence":"CRISPR exon deletion in mice with ABR; morpholino exon skipping in zebrafish with ERG","pmids":["31884594","33895329"],"confidence":"High","gaps":["Long-term durability of exon-skipping rescue not established","Whether exon 13-deleted usherin fully recapitulates all wild-type functions unknown"]},{"year":2023,"claim":"The molecular mechanism controlling usherin stability was elucidated: ADGRV1 suppresses WHRN phosphorylation via local cAMP-PKA signaling; phosphorylated WHRN recruits the E3 ligase WDSUB1, which ubiquitinates and destabilizes USH2A, explaining how ADGRV1 loss-of-function leads to usherin degradation.","evidence":"Adgrv1 knock-in mice, yeast two-hybrid, FlAsH-BRET, NMR, ubiquitination assays, and MET recordings","pmids":["37066759"],"confidence":"High","gaps":["Specific ubiquitination sites on USH2A not mapped","Whether deubiquitinating enzymes counteract WDSUB1 activity unknown","Pathway validated primarily in cochlear context; retinal applicability not directly shown"]},{"year":2023,"claim":"Multi-exon skipping strategies (exon pairs 30–31 and 39–40) and non-viral episomal full-length USH2A cDNA delivery both restored usherin expression and USH2 complex localization in zebrafish, broadening the therapeutic toolkit for the oversized USH2A gene.","evidence":"CRISPR exon deletion in zebrafish, ASO-mediated exon skipping in vitro, S/MAR episomal vector injection in zebrafish","pmids":["37313440","37337429"],"confidence":"Medium","gaps":["Long-term efficacy and safety of episomal vectors in mammalian retina not tested","Functional rescue (ERG) not shown for multi-exon or episomal approaches","Delivery efficiency in human photoreceptors unknown"]},{"year":null,"claim":"The structural basis of usherin's extracellular interactions, the precise cargo trafficking role of the USH2 complex at the connecting cilium, and whether pharmacological stabilization of usherin (e.g., by inhibiting WDSUB1) can prevent retinal degeneration remain unresolved.","evidence":"","pmids":[],"confidence":"Low","gaps":["No high-resolution structure of usherin or the USH2 complex","Cargo molecules trafficked by the USH2 periciliary complex not identified","No pharmacological intervention targeting the WDSUB1-usherin degradation axis tested in vivo"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0005198","term_label":"structural molecule activity","supporting_discovery_ids":[0,1,3,10]},{"term_id":"GO:0098631","term_label":"cell adhesion mediator activity","supporting_discovery_ids":[11]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[1,2,3,4]},{"term_id":"GO:0005929","term_label":"cilium","supporting_discovery_ids":[2,3,4]},{"term_id":"GO:0031012","term_label":"extracellular matrix","supporting_discovery_ids":[0,11]}],"pathway":[{"term_id":"R-HSA-9709957","term_label":"Sensory Perception","supporting_discovery_ids":[3,10,12,14]},{"term_id":"R-HSA-392499","term_label":"Metabolism of proteins","supporting_discovery_ids":[15]}],"complexes":["USH2 complex (ankle-link complex)","USH1/USH2 ternary complex"],"partners":["WHRN","ADGRV1","PDZD7","SANS","MYO7A","WDSUB1"],"other_free_text":[]},"mechanistic_narrative":"USH2A encodes usherin, a large transmembrane protein with extensive extracellular laminin and fibronectin type III repeat domains that functions as an obligatory scaffold within the USH2 multiprotein complex (with ADGRV1, whirlin/WHRN, PDZD7, and SANS) at the periciliary membrane of photoreceptors and the ankle-link complex of cochlear hair cell stereocilia [PMID:20502675, PMID:26401052, PMID:28137943]. Loss of any single USH2 complex member destabilizes the entire complex and disrupts protein trafficking through the connecting cilium in photoreceptors and stereociliary bundle integrity in hair cells, causing progressive retinal degeneration and sensorineural hearing loss (Usher syndrome type 2A) [PMID:20502675, PMID:15015129]. USH2A protein stability is regulated by ADGRV1-mediated suppression of WHRN phosphorylation, which controls WDSUB1 E3-ligase-dependent ubiquitination of usherin; pathogenic ADGRV1 mutations release this brake, leading to usherin degradation [PMID:37066759]. Usherin is also expressed in terminal Schwann cells of Meissner's corpuscles, where it is required for normal vibrotactile mechanoreceptor sensitivity [PMID:33288907]."},"prefetch_data":{"uniprot":{"accession":"O75445","full_name":"Usherin","aliases":["Usher syndrome type IIa protein","Usher syndrome type-2A protein"],"length_aa":5202,"mass_kda":575.6,"function":"Involved in hearing and vision as member of the USH2 complex. In the inner ear, required for the maintenance of the hair bundle ankle formation, which connects growing stereocilia in developing cochlear hair cells. In retina photoreceptors, the USH2 complex is required for the maintenance of periciliary membrane complex that seems to play a role in regulating intracellular protein transport","subcellular_location":"Secreted","url":"https://www.uniprot.org/uniprotkb/O75445/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/USH2A","classification":"Not Classified","n_dependent_lines":0,"n_total_lines":1208,"dependency_fraction":0.0},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/USH2A","total_profiled":1310},"omim":[{"mim_id":"620905","title":"DOUBLE ZINC RIBBON AND ANKYRIN REPEAT DOMAINS 1; DZANK1","url":"https://www.omim.org/entry/620905"},{"mim_id":"620802","title":"WD REPEAT-, STERILE ALPHA MOTIF-, AND U-BOX DOMAIN-CONTAINING PROTEIN 1; WDSUB1","url":"https://www.omim.org/entry/620802"},{"mim_id":"618358","title":"CONE-ROD DYSTROPHY AND HEARING LOSS 2; CRDHL2","url":"https://www.omim.org/entry/618358"},{"mim_id":"613809","title":"RETINITIS PIGMENTOSA 39; RP39","url":"https://www.omim.org/entry/613809"},{"mim_id":"612971","title":"PDZ DOMAIN-CONTAINING 7; PDZD7","url":"https://www.omim.org/entry/612971"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Acrosome","reliability":"Approved"},{"location":"Equatorial segment","reliability":"Approved"},{"location":"Mid piece","reliability":"Approved"},{"location":"Principal piece","reliability":"Approved"},{"location":"End piece","reliability":"Additional"}],"tissue_specificity":"Group enriched","tissue_distribution":"Detected in some","driving_tissues":[{"tissue":"liver","ntpm":6.5},{"tissue":"retina","ntpm":17.8}],"url":"https://www.proteinatlas.org/search/USH2A"},"hgnc":{"alias_symbol":["RP39"],"prev_symbol":["USH2"]},"alphafold":{"accession":"O75445","domains":[],"viewer_url":"https://alphafold.ebi.ac.uk/entry/O75445","model_url":"https://alphafold.ebi.ac.uk/files/AF-O75445-2-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-O75445-2-F1-predicted_aligned_error_v6.png","plddt_mean":81.19},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=USH2A","jax_strain_url":"https://www.jax.org/strain/search?query=USH2A"},"sequence":{"accession":"O75445","fasta_url":"https://rest.uniprot.org/uniprotkb/O75445.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/O75445/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/O75445"}},"corpus_meta":[{"pmid":"10775529","id":"PMC_10775529","title":"Missense mutation in the USH2A gene: association with recessive retinitis pigmentosa without hearing loss.","date":"2000","source":"American journal of human genetics","url":"https://pubmed.ncbi.nlm.nih.gov/10775529","citation_count":219,"is_preprint":false},{"pmid":"15015129","id":"PMC_15015129","title":"Identification of 51 novel exons of the Usher syndrome type 2A (USH2A) gene that encode multiple conserved functional domains and that are mutated in patients with Usher syndrome type II.","date":"2004","source":"American journal of human genetics","url":"https://pubmed.ncbi.nlm.nih.gov/15015129","citation_count":167,"is_preprint":false},{"pmid":"16434480","id":"PMC_16434480","title":"The DFNB31 gene product whirlin connects to the Usher protein network in the cochlea and retina by direct association with USH2A and VLGR1.","date":"2006","source":"Human molecular genetics","url":"https://pubmed.ncbi.nlm.nih.gov/16434480","citation_count":156,"is_preprint":false},{"pmid":"20507924","id":"PMC_20507924","title":"Novel mutations in the long isoform of the USH2A gene in patients with Usher syndrome type II or non-syndromic retinitis pigmentosa.","date":"2010","source":"Journal of medical genetics","url":"https://pubmed.ncbi.nlm.nih.gov/20507924","citation_count":142,"is_preprint":false},{"pmid":"33895329","id":"PMC_33895329","title":"Antisense oligonucleotide-based treatment of retinitis pigmentosa caused by USH2A exon 13 mutations.","date":"2021","source":"Molecular therapy : the journal of the American Society of Gene Therapy","url":"https://pubmed.ncbi.nlm.nih.gov/33895329","citation_count":123,"is_preprint":false},{"pmid":"27802265","id":"PMC_27802265","title":"Antisense Oligonucleotide-based Splice Correction for USH2A-associated Retinal Degeneration Caused by a Frequent Deep-intronic Mutation.","date":"2016","source":"Molecular therapy. 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vision","url":"https://pubmed.ncbi.nlm.nih.gov/20309401","citation_count":12,"is_preprint":false},{"pmid":"10916187","id":"PMC_10916187","title":"Prevalence of 2314delG mutation in Spanish patients with Usher syndrome type II (USH2).","date":"2000","source":"Ophthalmic genetics","url":"https://pubmed.ncbi.nlm.nih.gov/10916187","citation_count":12,"is_preprint":false},{"pmid":"34781295","id":"PMC_34781295","title":"Spectral-Domain Optical Coherence Tomography Analysis in Syndromic and Nonsyndromic Forms of Retinitis Pigmentosa due to USH2A Genetic Variants.","date":"2021","source":"Ophthalmic research","url":"https://pubmed.ncbi.nlm.nih.gov/34781295","citation_count":12,"is_preprint":false},{"pmid":"31766479","id":"PMC_31766479","title":"Double Hyperautofluorescent Rings in Patients with USH2A-Retinopathy.","date":"2019","source":"Genes","url":"https://pubmed.ncbi.nlm.nih.gov/31766479","citation_count":12,"is_preprint":false},{"pmid":"31566003","id":"PMC_31566003","title":"Novel USH1G homozygous variant underlying USH2-like phenotype of Usher syndrome.","date":"2019","source":"European journal of ophthalmology","url":"https://pubmed.ncbi.nlm.nih.gov/31566003","citation_count":10,"is_preprint":false},{"pmid":"33535592","id":"PMC_33535592","title":"USH2A-Related Retinitis Pigmentosa: Staging of Disease Severity and Morpho-Functional Studies.","date":"2021","source":"Diagnostics (Basel, Switzerland)","url":"https://pubmed.ncbi.nlm.nih.gov/33535592","citation_count":10,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":51801,"output_tokens":4628,"usd":0.112411},"stage2":{"model":"claude-opus-4-6","input_tokens":8122,"output_tokens":3294,"usd":0.18444},"total_usd":0.296851,"stage1_batch_id":"msgbatch_01RPbVc9PDH9zQmYK5Hs6srm","stage2_batch_id":"msgbatch_01JVbVLzeKN2yVrsGp3zC8aM","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 1999,\n      \"finding\": \"USH2A encodes usherin, a protein with laminin epidermal growth factor-like (LE) domains and fibronectin type III repeats characteristic of extracellular matrix/basal lamina proteins; missense mutations within the fifth LE domain (Cys759Phe) cause recessive retinitis pigmentosa without hearing loss, establishing domain-function relationships\",\n      \"method\": \"Direct DNA sequencing, mutation analysis, protein domain prediction\",\n      \"journal\": \"American journal of human genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — single study, sequence-based domain inference with clinical correlation; no in vitro functional assay\",\n      \"pmids\": [\"10775529\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"The long isoform of USH2A encodes a transmembrane protein (usherin isoform b) with an extracellular domain containing a Laminin N-terminal domain, laminin G repeats, 28 fibronectin type III repeats, a transmembrane region, and a C-terminal intracellular PDZ-binding motif; pathogenic mutations in the novel exons 22–73 cause both hearing loss and retinitis pigmentosa\",\n      \"method\": \"Gene cloning, exon identification, expression profiling, mutation analysis\",\n      \"journal\": \"American journal of human genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — structural inference from sequence; domain architecture validated by mutational data but no direct protein biochemistry\",\n      \"pmids\": [\"15015129\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"Whirlin (DFNB31/USH2D) directly associates with USH2A isoform b (usherin) and VLGR1b; this ternary complex co-localizes at photoreceptor synaptic regions, connecting cilia, and outer limiting membrane, and at cochlear outer hair cell synaptic regions, identifying usherin as a component of a PDZ scaffold-organized periciliary/synaptic interactome\",\n      \"method\": \"Yeast two-hybrid, co-immunoprecipitation, immunohistochemistry, confocal microscopy\",\n      \"journal\": \"Human molecular genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal interaction assays plus co-localization across multiple tissues; replicated in subsequent studies\",\n      \"pmids\": [\"16434480\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"The N-terminal PDZ domains of the whirlin long isoform mediate assembly of a multi-protein USH2 complex that includes usherin (USH2A) and VLGR1; this complex localizes to the periciliary membrane complex (PMC) in photoreceptors. Loss of any single USH2 protein disrupts normal localization of all USH2 proteins and causes protein destabilization, establishing that the three USH2 proteins form an obligatory functional complex in vivo\",\n      \"method\": \"Targeted gene knockout mice, immunofluorescence, Western blot, electroretinography, histology\",\n      \"journal\": \"PLoS genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple USH2 KO mouse models with orthogonal readouts; replicated across labs\",\n      \"pmids\": [\"20502675\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"AAV-mediated whirlin transgene expression in whirlin knockout photoreceptors recruits USH2A and VLGR1 back to the periciliary membrane complex, restoring the USH2 protein complex; this demonstrates that whirlin is upstream of USH2A localization in photoreceptors\",\n      \"method\": \"AAV subretinal injection, immunofluorescence, immunoelectron microscopy, Western blot, electroretinography\",\n      \"journal\": \"Investigative ophthalmology & visual science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — in vivo rescue experiment with multiple orthogonal readouts establishing pathway hierarchy\",\n      \"pmids\": [\"21212183\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"A deep-intronic mutation in USH2A (c.7595-2144A>G) creates a pseudoexon (PE40) insertion into the mature transcript, generating a premature stop codon and a predicted truncated nonfunctional usherin protein; confirmed by RNA analysis from nasal cells and minigene assay\",\n      \"method\": \"RNA analysis from patient nasal epithelial cells, minigene splice assay, sequencing\",\n      \"journal\": \"Human mutation\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — functional RNA analysis plus minigene assay demonstrating aberrant splicing mechanism\",\n      \"pmids\": [\"22009552\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"The common c.2299delG mutation in USH2A exon 13 disrupts an exonic splicing enhancer and creates an exonic splicing silencer, leading to aberrant splicing of exons 12–13 in addition to the predicted frameshift; shown by RT-PCR in patient nasal epithelial cells\",\n      \"method\": \"RT-PCR from patient nasal epithelial cells, bioinformatics splice prediction\",\n      \"journal\": \"Experimental eye research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — functional RNA analysis in patient cells; single lab\",\n      \"pmids\": [\"24607488\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Antisense oligonucleotides targeting the PE40 splice acceptor site and exonic splice enhancer regions of USH2A pre-mRNA significantly correct aberrant splicing caused by the deep-intronic c.7595-2144A>G mutation in patient fibroblasts and a minigene assay\",\n      \"method\": \"AON treatment in patient-derived fibroblasts, minigene splice assay\",\n      \"journal\": \"Molecular therapy. Nucleic acids\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — functional splice correction in patient cells with multiple AON designs; moderate evidence\",\n      \"pmids\": [\"27802265\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"SANS (USH1G) directly interacts with usherin (USH2A) and both assemble into a ternary USH1/USH2 complex together with whirlin (USH2D) via mutual interactions; the complex localizes to the periciliary region, inner segment, and synapses of rodent and human photoreceptors, and pathogenic mutations in USH1G disrupt this complex\",\n      \"method\": \"Yeast two-hybrid, co-immunoprecipitation, proximity ligation assay, immunohistochemistry, mutagenesis\",\n      \"journal\": \"Human molecular genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal interaction assays plus in situ complex detection; validates cross-type USH protein network\",\n      \"pmids\": [\"28137943\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Myosin VIIa (USH1B) is indispensable for USH2 complex (USH2A/ADGRV1/WHRN/PDZD7) assembly at ankle links in cochlear hair cells, indicating a transport/anchoring role; however, myosin VIIa is not required for USH2 complex assembly in photoreceptors, demonstrating tissue-specific differences in USH2 complex organization\",\n      \"method\": \"USH1 mutant mice, immunofluorescence, FLAG pull-down assay\",\n      \"journal\": \"Human molecular genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic epistasis using multiple USH1 KO mouse models with defined cellular phenotypes\",\n      \"pmids\": [\"28031293\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"USH2A proteins (USH2A, ADGRV1, WHRN, PDZD7) assemble into the ankle link complex (ALC) at cochlear hair cell stereociliary bundles; individual USH2 proteins make distinct contributions to ALC assembly during development, with ADGRV1 being the most critical, and loss of individual proteins leads to variable stereociliary morphological and functional defects correlating with ALC disruption severity\",\n      \"method\": \"Multiple USH2 KO mouse models, immunofluorescence, scanning electron microscopy, auditory function testing\",\n      \"journal\": \"Human molecular genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — systematic in vivo characterization with multiple mutant lines and orthogonal readouts\",\n      \"pmids\": [\"26401052\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Knockout of ush2a in zebrafish causes disruption of fibronectin assembly at the retinal basement membrane, weakening cell adhesion, along with progressive rod-then-cone photoreceptor degeneration; upregulation of Ush1b and Ush1c expression was observed when Ush2a was absent\",\n      \"method\": \"TALEN-generated ush2a-/- zebrafish, ERG, histology, immunohistochemistry, Western blot\",\n      \"journal\": \"Human genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — KO zebrafish model with defined molecular and functional phenotypes; single lab\",\n      \"pmids\": [\"30242501\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"USH2A (usherin) protein is expressed in terminal Schwann cells within Meissner's corpuscles in fingertip skin (not in sensory neurons); loss of USH2A reduces mechanoreceptor vibration sensitivity of rapidly adapting mechanoreceptors, and patients with biallelic USH2A mutations have specific impairment in vibrotactile touch perception\",\n      \"method\": \"Immunohistochemistry, Ush2a-/- mouse electrophysiology, human psychophysical testing\",\n      \"journal\": \"Nature neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — localization by IHC combined with in vivo functional recordings in KO mice and human patient testing; moderate-to-strong evidence from orthogonal approaches\",\n      \"pmids\": [\"33288907\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Morpholino-induced skipping of ush2a exon 13 in zebrafish ush2armc1 mutants restores production of a shortened usherin protein (usherinΔexon13) and completely rescues retinal function, demonstrating that an usherin protein lacking the exon 13-encoded region is functional\",\n      \"method\": \"Zebrafish morpholino exon skipping, ERG, Western blot, immunohistochemistry\",\n      \"journal\": \"Molecular therapy : the journal of the American Society of Gene Therapy\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — in vivo functional rescue experiment in zebrafish disease model with ERG readout\",\n      \"pmids\": [\"33895329\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"CRISPR/Cas9-based deletion of mouse Ush2a exon 12 (ortholog of human exon 13) produces a shortened Ush2a-ΔEx12 protein that localizes correctly in the cochlea and, when expressed on an Ush2a null background, restores impaired hair cell structure and auditory function\",\n      \"method\": \"CRISPR/Cas9 exon deletion in mice, immunohistochemistry, auditory brainstem response testing\",\n      \"journal\": \"Advances in experimental medicine and biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — in vivo functional rescue in KO mouse background with defined structural and functional readouts\",\n      \"pmids\": [\"31884594\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"ADGRV1 inhibits WHRN phosphorylation through regional cAMP-PKA signaling; phosphorylated WHRN recruits the E3 ligase WDSUB1 (identified by yeast two-hybrid), which ubiquitinates USH2A in a WHRN phosphorylation-dependent manner, regulating USH2A stability; the deafness-associated ADGRV1 Y6236fsX1 mutation fails to inhibit WHRN phosphorylation, leading to increased USH2A ubiquitination and destabilization\",\n      \"method\": \"Adgrv1 Y6236fsX1 knock-in mice, yeast two-hybrid, FlAsH-BRET assay, NMR spectrometry, mutagenesis, ubiquitination assays, stereocilia imaging, MET recordings\",\n      \"journal\": \"Advanced science (Weinheim, Baden-Wurttemberg, Germany)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — multiple orthogonal methods including NMR, BRET, mutagenesis, and in vivo model; single lab but exceptionally rigorous\",\n      \"pmids\": [\"37066759\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"S/MAR non-viral episomal vectors carrying full-length USH2A cDNA (15.6 kb) drive persistent usherin expression in patient-derived fibroblasts and, after injection into ush2au507 zebrafish, rescue Usher 2 complex localization in photoreceptors for up to 12 months, demonstrating that full-length usherin can restore the USH2 complex in vivo\",\n      \"method\": \"S/MAR plasmid transfection, Western blot, immunofluorescence, zebrafish microinjection\",\n      \"journal\": \"Molecular therapy : the journal of the American Society of Gene Therapy\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — in vitro and in vivo rescue with functional complex localization readout; single lab\",\n      \"pmids\": [\"37337429\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Splice-site variants in USH2A (c.1841-2A>G, c.2167+5G>A, c.5298+1G>C) abolish consensus splice sites and produce exon skipping; c.2167+5G>A additionally activates a cryptic donor splice site; demonstrated by hybrid minigene assays\",\n      \"method\": \"Hybrid minigene splice assay, bioinformatics\",\n      \"journal\": \"Clinical genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — functional minigene assay directly demonstrating splicing mechanism\",\n      \"pmids\": [\"20497194\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"USH2A mRNA is expressed specifically in the outer nuclear layer of the retina (photoreceptors) in rat, mouse, and human, and in cochlea; during rat retinal development, expression appears in the neuroepithelium at embryonic day 17, establishing the cellular source of usherin in the primary disease-affected tissues\",\n      \"method\": \"In situ hybridization, gene cloning, radiation hybrid mapping\",\n      \"journal\": \"Genomics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct localization by in situ hybridization across three species; no functional consequence experiment\",\n      \"pmids\": [\"12160733\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"Excision of USH2A exon pairs 30-31 or 39-40 using CRISPR-Cas9 in zebrafish restores usherin expression in the retina and rescues photopigment mislocalization; ASO-induced dual exon skipping achieves the same in vitro, demonstrating that protein domain-oriented multi-exon skipping maintains a functional usherin\",\n      \"method\": \"CRISPR-Cas9 zebrafish exon deletion, immunohistochemistry, in vitro ASO assay\",\n      \"journal\": \"Molecular therapy. Nucleic acids\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — in vivo and in vitro functional rescue; single lab\",\n      \"pmids\": [\"37313440\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"Usherin (USH2A) is a large transmembrane extracellular matrix protein expressed in photoreceptors, cochlear hair cells, and Meissner's corpuscle Schwann cells that functions as an obligatory scaffold within a multiprotein ankle-link/periciliary complex (with ADGRV1, whirlin/WHRN, PDZD7, and SANS) required for stereociliary bundle integrity in cochlear hair cells and for protein trafficking through the connecting cilium/periciliary membrane in photoreceptors; its stability is regulated by ADGRV1-mediated suppression of WHRN phosphorylation, which controls WDSUB1 E3-ligase-dependent ubiquitination of usherin, and loss of any single USH2 complex member destabilizes the entire complex, causing progressive photoreceptor degeneration and sensorineural hearing loss.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"USH2A encodes usherin, a large transmembrane protein with extensive extracellular laminin and fibronectin type III repeat domains that functions as an obligatory scaffold within the USH2 multiprotein complex (with ADGRV1, whirlin/WHRN, PDZD7, and SANS) at the periciliary membrane of photoreceptors and the ankle-link complex of cochlear hair cell stereocilia [PMID:20502675, PMID:26401052, PMID:28137943]. Loss of any single USH2 complex member destabilizes the entire complex and disrupts protein trafficking through the connecting cilium in photoreceptors and stereociliary bundle integrity in hair cells, causing progressive retinal degeneration and sensorineural hearing loss (Usher syndrome type 2A) [PMID:20502675, PMID:15015129]. USH2A protein stability is regulated by ADGRV1-mediated suppression of WHRN phosphorylation, which controls WDSUB1 E3-ligase-dependent ubiquitination of usherin; pathogenic ADGRV1 mutations release this brake, leading to usherin degradation [PMID:37066759]. Usherin is also expressed in terminal Schwann cells of Meissner's corpuscles, where it is required for normal vibrotactile mechanoreceptor sensitivity [PMID:33288907].\",\n  \"teleology\": [\n    {\n      \"year\": 1999,\n      \"claim\": \"Identification of USH2A as a laminin/fibronectin-domain extracellular matrix protein linked domain structure to disease: the Cys759Phe mutation in the fifth LE domain caused recessive RP without hearing loss, establishing that specific domain lesions determine clinical outcome.\",\n      \"evidence\": \"Mutation analysis and domain prediction in RP families\",\n      \"pmids\": [\"10775529\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No biochemical validation of domain function\", \"Short isoform only; full gene structure unknown\"]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"Discovery of the long transmembrane isoform (isoform b) resolved how a secreted ECM-like protein could function as a cell-surface receptor/scaffold: the extended protein contains a transmembrane domain and a C-terminal PDZ-binding motif, and mutations in the novel exons cause combined hearing loss and RP.\",\n      \"evidence\": \"Gene cloning and mutation screening across exons 22–73\",\n      \"pmids\": [\"15015129\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No direct protein biochemistry confirming membrane insertion\", \"PDZ-binding partner identity not yet determined\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"The first identification of usherin's direct binding partners — whirlin (WHRN) and VLGR1 — established usherin as part of a PDZ scaffold-organized multiprotein complex at photoreceptor connecting cilia, synapses, and cochlear hair cells.\",\n      \"evidence\": \"Yeast two-hybrid and co-immunoprecipitation with co-localization by immunohistochemistry\",\n      \"pmids\": [\"16434480\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Stoichiometry and assembly order unknown\", \"No structural data on the ternary complex\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Knockout mouse studies demonstrated that USH2A, ADGRV1, and WHRN form an obligatory complex: loss of any one member destabilized and mislocalized all others at the periciliary membrane, directly linking complex integrity to photoreceptor survival.\",\n      \"evidence\": \"Multiple USH2 KO mouse models with immunofluorescence, Western blot, and ERG\",\n      \"pmids\": [\"20502675\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism of mutual stabilization unknown\", \"Whether complex disruption causes degeneration through trafficking defects versus structural failure unresolved\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"AAV-mediated whirlin re-expression in whirlin-KO photoreceptors recruited USH2A and ADGRV1 back to the periciliary membrane, placing whirlin upstream of usherin localization and establishing a hierarchy within USH2 complex assembly.\",\n      \"evidence\": \"AAV subretinal injection in Whrn-KO mice with immunofluorescence and immunoelectron microscopy\",\n      \"pmids\": [\"21212183\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether whirlin directly chaperones usherin transport or merely anchors it at the destination unknown\", \"Rescue of photoreceptor degeneration not fully demonstrated\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Characterization of splicing mutations (deep-intronic and splice-site variants) revealed that many USH2A pathogenic alleles act through aberrant mRNA processing rather than simple protein truncation, opening therapeutic avenues for splice correction.\",\n      \"evidence\": \"Patient nasal epithelial cell RNA analysis and minigene splice assays for c.7595-2144A>G and other variants\",\n      \"pmids\": [\"22009552\", \"20497194\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"In vivo splicing consequences in retinal tissue not directly assessed\", \"Quantitative contribution of aberrant transcripts versus normal transcripts unknown\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Systematic comparison of USH2 protein contributions to the cochlear ankle-link complex showed that ADGRV1 is the most critical organizer and that individual USH2 proteins make distinct, non-redundant contributions to stereociliary bundle morphogenesis and auditory function.\",\n      \"evidence\": \"Multiple USH2 KO mouse models with scanning electron microscopy and auditory testing\",\n      \"pmids\": [\"26401052\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular basis for differential contributions of USH2A versus ADGRV1 at ankle links unresolved\", \"Direct extracellular interactions between USH2A and ADGRV1 ectodomains not characterized\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"SANS (USH1G) was identified as a direct interactor of usherin, bridging the USH1 and USH2 protein networks into a ternary USH1/USH2 complex; pathogenic USH1G mutations disrupt this complex, explaining the phenotypic overlap between Usher syndrome types.\",\n      \"evidence\": \"Yeast two-hybrid, co-IP, proximity ligation assay, and immunohistochemistry in rodent and human retina\",\n      \"pmids\": [\"28137943\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of USH1–USH2 bridging interaction unknown\", \"Functional consequence of USH1/USH2 complex disruption in photoreceptors not directly shown in this study\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Myosin VIIa was shown to be indispensable for USH2 complex assembly at cochlear ankle links but dispensable in photoreceptors, establishing tissue-specific mechanisms of USH2 complex organization.\",\n      \"evidence\": \"USH1 mutant mice with immunofluorescence and FLAG pull-down\",\n      \"pmids\": [\"28031293\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Identity of the motor/transport system for USH2 complex in photoreceptors unknown\", \"Whether myosin VIIa directly transports usherin or facilitates its retention unresolved\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Usherin was localized to terminal Schwann cells of Meissner's corpuscles and shown to be required for vibrotactile mechanoreceptor sensitivity, extending usherin function beyond the retina and cochlea to somatosensory mechanotransduction.\",\n      \"evidence\": \"Immunohistochemistry in human/mouse skin, Ush2a-KO mouse electrophysiology, and psychophysical testing in USH2A patients\",\n      \"pmids\": [\"33288907\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular mechanism by which usherin contributes to mechanoreceptor function unknown\", \"Whether the USH2 complex is present in Schwann cells not determined\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Exon skipping strategies demonstrated that usherin protein lacking the exon 13-encoded region retains function: CRISPR deletion of mouse exon 12 restored cochlear structure and hearing, and morpholino-induced skipping in zebrafish rescued retinal function, validating a therapeutic concept.\",\n      \"evidence\": \"CRISPR exon deletion in mice with ABR; morpholino exon skipping in zebrafish with ERG\",\n      \"pmids\": [\"31884594\", \"33895329\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Long-term durability of exon-skipping rescue not established\", \"Whether exon 13-deleted usherin fully recapitulates all wild-type functions unknown\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"The molecular mechanism controlling usherin stability was elucidated: ADGRV1 suppresses WHRN phosphorylation via local cAMP-PKA signaling; phosphorylated WHRN recruits the E3 ligase WDSUB1, which ubiquitinates and destabilizes USH2A, explaining how ADGRV1 loss-of-function leads to usherin degradation.\",\n      \"evidence\": \"Adgrv1 knock-in mice, yeast two-hybrid, FlAsH-BRET, NMR, ubiquitination assays, and MET recordings\",\n      \"pmids\": [\"37066759\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Specific ubiquitination sites on USH2A not mapped\", \"Whether deubiquitinating enzymes counteract WDSUB1 activity unknown\", \"Pathway validated primarily in cochlear context; retinal applicability not directly shown\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Multi-exon skipping strategies (exon pairs 30–31 and 39–40) and non-viral episomal full-length USH2A cDNA delivery both restored usherin expression and USH2 complex localization in zebrafish, broadening the therapeutic toolkit for the oversized USH2A gene.\",\n      \"evidence\": \"CRISPR exon deletion in zebrafish, ASO-mediated exon skipping in vitro, S/MAR episomal vector injection in zebrafish\",\n      \"pmids\": [\"37313440\", \"37337429\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Long-term efficacy and safety of episomal vectors in mammalian retina not tested\", \"Functional rescue (ERG) not shown for multi-exon or episomal approaches\", \"Delivery efficiency in human photoreceptors unknown\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"The structural basis of usherin's extracellular interactions, the precise cargo trafficking role of the USH2 complex at the connecting cilium, and whether pharmacological stabilization of usherin (e.g., by inhibiting WDSUB1) can prevent retinal degeneration remain unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No high-resolution structure of usherin or the USH2 complex\", \"Cargo molecules trafficked by the USH2 periciliary complex not identified\", \"No pharmacological intervention targeting the WDSUB1-usherin degradation axis tested in vivo\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0005198\", \"supporting_discovery_ids\": [0, 1, 3, 10]},\n      {\"term_id\": \"GO:0098631\", \"supporting_discovery_ids\": [11]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [1, 2, 3, 4]},\n      {\"term_id\": \"GO:0005929\", \"supporting_discovery_ids\": [2, 3, 4]},\n      {\"term_id\": \"GO:0031012\", \"supporting_discovery_ids\": [0, 11]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-9709957\", \"supporting_discovery_ids\": [3, 10, 12, 14]},\n      {\"term_id\": \"R-HSA-392499\", \"supporting_discovery_ids\": [15]}\n    ],\n    \"complexes\": [\n      \"USH2 complex (ankle-link complex)\",\n      \"USH1/USH2 ternary complex\"\n    ],\n    \"partners\": [\n      \"WHRN\",\n      \"ADGRV1\",\n      \"PDZD7\",\n      \"SANS\",\n      \"MYO7A\",\n      \"WDSUB1\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}