{"gene":"LRIT3","run_date":"2026-04-28T18:30:27","timeline":{"discoveries":[{"year":2012,"finding":"LRIT3 is expressed in the outer plexiform layer of the human retina in a punctate pattern resembling the dendritic tips of bipolar cells, consistent with a role in ON-bipolar cell signaling, identified via mutations causing complete congenital stationary night blindness (cCSNB) with loss of b-wave amplitude reflecting abnormal ON-bipolar cell function.","method":"Whole-exome sequencing, Sanger sequencing, human retinal immunohistochemistry with anti-LRIT3 antibody","journal":"American journal of human genetics","confidence":"Medium","confidence_rationale":"Tier 2 — direct antibody localization in human retina, but no functional mechanistic dissection beyond disease association","pmids":["23246293"],"is_preprint":false},{"year":2014,"finding":"Lrit3 knockout mice (nob6) exhibit a no b-wave (nob) ERG phenotype with lacking or severely reduced b-wave amplitudes in scotopic and photopic conditions, thinned inner nuclear layer by SD-OCT, and strongly decreased optomotor responses, establishing LRIT3 loss-of-function causes ON-bipolar cell signaling defect without retinal degeneration.","method":"Lrit3 knockout mouse generation, ERG, optomotor testing, SD-OCT, fundus imaging, histology","journal":"PloS one","confidence":"High","confidence_rationale":"Tier 2 — clean KO with multiple orthogonal functional readouts, replicated across labs","pmids":["24598786"],"is_preprint":false},{"year":2015,"finding":"LRIT3 localizes at the dendritic tips of depolarizing bipolar cells (DBCs) in the outer plexiform layer (OPL) co-localizing with mGluR6, and is required for correct localization of TRPM1 to the dendritic tips of all depolarizing bipolar cells; additionally, mGluR6, GPR179, RGS7, RGS11, and Gβ5 are lost from cone ON-bipolar cell dendritic tips (but not rod bipolar cell tips) in Lrit3 knockout mice, and peanut agglutinin (PNA) labeling is severely reduced in the OPL, suggesting LRIT3 also plays a role in cone synapse formation.","method":"Immunofluorescence confocal microscopy of wild-type and Lrit3nob6/nob6 retinal sections using antibodies against LRIT3, TRPM1, mGluR6, GPR179, RGS7, RGS11, Gβ5; PNA labeling","journal":"The European journal of neuroscience","confidence":"High","confidence_rationale":"Tier 2 — multiple signalplex components tested in KO vs. WT with rigorous immunofluorescence, replicated across labs","pmids":["25997951"],"is_preprint":false},{"year":2017,"finding":"In Lrit3-knockout (nob6) mice, synaptic contacts made by ON-bipolar cells but not OFF-bipolar cells with cone pedicles are structurally disorganized, while molecules essential for OFF-bipolar cell signaling (GluR1, GluR5) are normally targeted to the synapse; multielectrode array recordings confirm complete loss of ON-pathway function but robust (though altered) OFF-pathway signaling, demonstrating LRIT3 selectively coordinates transsynaptic communication between cones and ON-bipolar cells during synapse formation.","method":"Electron microscopy, immunostaining and confocal microscopy (GluR1, GluR5), multielectrode array electrophysiology (retinal ganglion cells), ERG in patient with LRIT3 mutations","journal":"Investigative ophthalmology & visual science","confidence":"High","confidence_rationale":"Tier 2 — multiple orthogonal methods (EM ultrastructure, immunostaining, electrophysiology) in KO model","pmids":["28334377"],"is_preprint":false},{"year":2019,"finding":"LRIT3 is expressed presynaptically in rod photoreceptors (not postsynaptically on depolarizing bipolar cells), and selective restoration of LRIT3 expression in Lrit3-/- rods via AAV rescues postsynaptic glutamate signalplex assembly on DBC dendrites and restores rod-driven vision, demonstrating LRIT3 acts as a transsynaptic organizer of the postsynaptic signaling complex.","method":"Cell-type-specific AAV-mediated LRIT3 re-expression in rods of Lrit3-/- mice, immunofluorescence for signalplex components, ERG functional rescue","journal":"Cell reports","confidence":"High","confidence_rationale":"Tier 2 — AAV rescue with cell-type specificity + immunofluorescence validation + functional ERG readout, published in high-impact journal","pmids":["31189098"],"is_preprint":false},{"year":2019,"finding":"In the canine LRIT3-CSNB model, the truncated mutant LRIT3 protein retains correct subcellular localization to the region of ON-bipolar cell dendritic tips (with reduced immunolabeling), establishing that loss of function rather than mislocalization underlies the signaling defect in this in vivo model.","method":"Genome-wide association study, whole-genome sequencing, immunohistochemistry in canine retina","journal":"Scientific reports","confidence":"Medium","confidence_rationale":"Tier 3 — immunolocalization in disease model, single method for mechanistic insight","pmids":["31578364"],"is_preprint":false},{"year":2020,"finding":"LRIT3 interacts with and is required for expression of nyctalopin at all DBC dendritic tips (thus controlling TRPM1 localization), but DBC signalplex components (including nyctalopin) are not required for LRIT3 expression, placing LRIT3 upstream of nyctalopin in signalplex assembly; loss of LRIT3 also reduces excitatory input to OFF-bipolar cells (type 1 BCs) and disrupts OFF retinal ganglion cell responses.","method":"Co-immunoprecipitation, immunofluorescence, whole-cell electrophysiology, multielectrode array (MEA) electrophysiology, glutamate imaging in Lrit3-/- mice","journal":"eNeuro","confidence":"High","confidence_rationale":"Tier 2 — reciprocal epistasis established by KO analysis, Co-IP for interaction, multiple electrophysiological readouts","pmids":["31959619"],"is_preprint":false},{"year":2012,"finding":"LRIT3 functions as a modulator of FGFR1, with its LRR and immunoglobulin-like domains interacting with FGFR1 to regulate FGFR-mediated signaling pathways (MAPK, PI3K/AKT, PLC-γ).","method":"Co-immunoprecipitation, cell-based signaling assays","journal":"FEBS letters","confidence":"Low","confidence_rationale":"Tier 3 — single lab, single Co-IP, no mutagenesis validation; context inconsistent with main retinal function described across corpus","pmids":["22673519"],"is_preprint":false},{"year":2023,"finding":"rAAV-mediated expression of LRIT3 specifically in cone photoreceptors of Lrit3-/- mice rescues assembly of cone DBC signalplex components and partially restores downstream visual function (light-adapted ERG b-wave, electrophysiological recordings of BCs and RGCs), confirming LRIT3 acts trans-synaptically from cones to organize the postsynaptic signalplex on cone DBCs.","method":"rAAV-mediated cone-specific LRIT3 expression in Lrit3-/- mice, ERG, whole-cell electrophysiology of BCs and RGCs, immunofluorescence for signalplex components","journal":"iScience","confidence":"High","confidence_rationale":"Tier 2 — cell-type-specific rescue with multiple functional and molecular readouts, consistent with prior rod-specific rescue study","pmids":["37091241"],"is_preprint":false},{"year":2024,"finding":"Loss of LRIT3 in Lrit3-/- mice drastically reduces retinal dopamine and DOPAC levels and impairs recovery from lens-induced myopia, establishing that LRIT3-dependent ON-pathway signaling is required for normal dopaminergic regulation of refractive development.","method":"UPLC quantification of dopamine/DOPAC in isolated Lrit3-/- retinas, infrared photorefractometry, lens-induced myopia protocol","journal":"Investigative ophthalmology & visual science","confidence":"Medium","confidence_rationale":"Tier 2 — KO with defined biochemical and functional readout, single study","pmids":["39250117"],"is_preprint":false},{"year":2025,"finding":"Domain-deletion analysis via rAAV expression in Lrit3-/- retinas shows: (1) the LRR domain is required for trafficking LRIT3 to the synapse in cones (but not rods) and for rod bipolar cell signalplex reassembly and function; (2) the IG domain is required for TRPM1 localization to the signalplex and for function, but not for synaptic localization of LRIT3; (3) the FN3 domain is dispensable for signalplex assembly or function. This supports a model in which the LRR domain trans-synaptically binds nyctalopin and the IG domain interacts with TRPM1.","method":"rAAV-mediated expression of LRIT3 deletion constructs in Lrit3-/- mouse retinas, immunofluorescence (LRIT3 trafficking, signalplex component localization), ERG functional analysis","journal":"bioRxiv","confidence":"Medium","confidence_rationale":"Tier 2 — systematic domain mutagenesis with functional readout, preprint not yet peer-reviewed","pmids":["41000924"],"is_preprint":true}],"current_model":"LRIT3 is a single-pass transmembrane LRR-IG-FN3 domain protein expressed presynaptically in rod and cone photoreceptors, where it acts as a transsynaptic organizer: its LRR domain mediates synaptic trafficking (in cones) and trans-synaptic interaction with nyctalopin, while its IG domain is required for TRPM1 localization to the postsynaptic depolarizing bipolar cell signalplex, thereby controlling the assembly of the mGluR6 glutamate signaling complex on DBC dendrites and enabling both ON- and OFF-pathway visual function."},"narrative":{"teleology":[{"year":2012,"claim":"Identification of LRIT3 as a disease gene for cCSNB established that it is required for ON-bipolar cell function and localized it to the outer plexiform layer of the retina, opening the question of its precise molecular role at the photoreceptor–bipolar cell synapse.","evidence":"Whole-exome sequencing of cCSNB families plus immunohistochemistry in human retina","pmids":["23246293"],"confidence":"Medium","gaps":["Localization appeared postsynaptic at this stage; presynaptic vs. postsynaptic identity unresolved","No functional mechanistic dissection beyond disease association","Molecular partners unknown"]},{"year":2014,"claim":"Generation of an Lrit3-knockout mouse confirmed that LRIT3 loss abolishes ON-bipolar cell signaling (nob ERG phenotype) without causing retinal degeneration, establishing a clean functional model for mechanistic studies.","evidence":"Lrit3-KO mouse with ERG, optomotor testing, SD-OCT, and histology","pmids":["24598786"],"confidence":"High","gaps":["Molecular mechanism by which LRIT3 supports DBC signaling unknown","Whether LRIT3 is pre- or postsynaptic unresolved"]},{"year":2015,"claim":"Immunolocalization in the KO revealed that LRIT3 is required for TRPM1 targeting to all DBC dendritic tips and for the entire cone DBC signalplex (mGluR6, GPR179, RGS7/11, Gβ5), establishing it as an upstream organizer of the postsynaptic signaling complex.","evidence":"Confocal immunofluorescence for multiple signalplex components in WT vs. Lrit3-KO retinal sections; PNA labeling","pmids":["25997951"],"confidence":"High","gaps":["Whether LRIT3 acts from the pre- or postsynaptic side still unresolved","Direct protein–protein interactions not yet demonstrated","Role at cone vs. rod synapses only partially distinguished"]},{"year":2017,"claim":"Ultrastructural and electrophysiological analysis showed that LRIT3 loss selectively disorganizes ON-bipolar but not OFF-bipolar synaptic contacts at cone pedicles, demonstrating pathway-specific transsynaptic coordination.","evidence":"Electron microscopy, immunostaining for GluR1/GluR5, MEA recordings of retinal ganglion cells in Lrit3-KO mice","pmids":["28334377"],"confidence":"High","gaps":["Mechanism of selective ON-pathway disruption unknown","Pre- vs. postsynaptic site of LRIT3 action still unresolved"]},{"year":2019,"claim":"AAV-mediated restoration of LRIT3 selectively in rods of Lrit3-KO mice rescued postsynaptic signalplex assembly and rod-driven ERG b-waves, proving that LRIT3 is presynaptic and acts transsynaptically to organize the DBC signaling complex.","evidence":"Cell-type-specific AAV expression in rods, immunofluorescence for signalplex, ERG rescue","pmids":["31189098"],"confidence":"High","gaps":["Cone-specific rescue not yet performed","Direct transsynaptic binding partner not identified","Domain requirements unknown"]},{"year":2020,"claim":"Co-immunoprecipitation and epistasis analysis placed LRIT3 upstream of nyctalopin in signalplex assembly—LRIT3 interacts with and is required for nyctalopin expression at DBC tips, while DBC components are dispensable for LRIT3 expression—and additionally revealed that LRIT3 loss disrupts OFF-pathway signaling indirectly.","evidence":"Co-IP, immunofluorescence, whole-cell and MEA electrophysiology, glutamate imaging in Lrit3-KO mice","pmids":["31959619"],"confidence":"High","gaps":["Whether LRIT3–nyctalopin interaction is direct or mediated by other synaptic proteins","Structural basis of the interaction unknown","Mechanism of OFF-pathway disruption not fully delineated"]},{"year":2023,"claim":"Cone-specific AAV rescue in Lrit3-KO mice restored cone DBC signalplex and partially recovered photopic ERG and downstream RGC responses, confirming that the transsynaptic organizing principle operates at both rod and cone synapses.","evidence":"rAAV cone-specific LRIT3 expression, ERG, whole-cell electrophysiology, immunofluorescence in Lrit3-KO mice","pmids":["37091241"],"confidence":"High","gaps":["Incomplete functional rescue in cones suggests additional factors","Domain requirements for cone vs. rod function unknown"]},{"year":2024,"claim":"LRIT3-dependent ON-pathway signaling was linked to retinal dopamine regulation and refractive development, revealing a broader physiological consequence of ON-pathway dysfunction beyond night blindness.","evidence":"UPLC dopamine/DOPAC quantification and lens-induced myopia experiments in Lrit3-KO mice","pmids":["39250117"],"confidence":"Medium","gaps":["Single study; whether dopamine reduction is a direct or indirect consequence of ON-pathway loss is unclear","Whether LRIT3 mutations contribute to human myopia not tested"]},{"year":2025,"claim":"Systematic domain-deletion analysis revealed that the LRR domain mediates synaptic trafficking in cones and transsynaptic signalplex assembly (likely via nyctalopin binding), the IG domain is required specifically for TRPM1 localization and function, and the FN3 domain is dispensable, providing a modular mechanistic model for LRIT3 transsynaptic signaling.","evidence":"rAAV-mediated expression of LRIT3 domain-deletion constructs in Lrit3-KO retinas, immunofluorescence, ERG (preprint)","pmids":["41000924"],"confidence":"Medium","gaps":["Preprint not yet peer-reviewed","Direct binding between LRR domain and nyctalopin or IG domain and TRPM1 not biochemically demonstrated","Structural basis for domain-specific interactions unknown"]},{"year":null,"claim":"Whether LRIT3 directly binds nyctalopin via its LRR domain and TRPM1 via its IG domain in trans remains to be biochemically demonstrated, and no high-resolution structural model of these transsynaptic complexes exists.","evidence":"","pmids":[],"confidence":"High","gaps":["No reconstituted binding assay for LRIT3–nyctalopin or LRIT3–TRPM1","No crystal or cryo-EM structure of LRIT3 or its complexes","Mechanism underlying differential trafficking requirements in rods vs. cones unexplained"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0098631","term_label":"cell adhesion mediator activity","supporting_discovery_ids":[4,6,8,10]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[0,2,4,10]}],"pathway":[{"term_id":"R-HSA-112316","term_label":"Neuronal System","supporting_discovery_ids":[1,3,4,8]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[2,6]}],"complexes":[],"partners":["NYX","TRPM1","GRM6"],"other_free_text":[]},"mechanistic_narrative":"LRIT3 is a presynaptic transmembrane protein expressed in rod and cone photoreceptors that functions as a transsynaptic organizer of the postsynaptic glutamate signaling complex on depolarizing bipolar cell (DBC) dendrites, thereby enabling ON-pathway visual signaling. Cell-type-specific AAV rescue in Lrit3-knockout mice demonstrates that LRIT3 expressed in rods or cones is sufficient to restore assembly of the DBC signalplex—including nyctalopin and TRPM1—on postsynaptic dendrites [PMID:31189098, PMID:37091241]. LRIT3 interacts with and is required for nyctalopin expression at DBC dendritic tips, and its immunoglobulin domain is specifically required for TRPM1 localization, while its leucine-rich repeat domain mediates transsynaptic interaction with nyctalopin and is necessary for synaptic trafficking in cones [PMID:31959619, PMID:41000924]. Loss-of-function mutations in LRIT3 cause complete congenital stationary night blindness (cCSNB) in humans, characterized by abolished ON-bipolar cell responses [PMID:23246293, PMID:24598786]."},"prefetch_data":{"uniprot":{"accession":"Q3SXY7","full_name":"Leucine-rich repeat, immunoglobulin-like domain and transmembrane domain-containing protein 3","aliases":[],"length_aa":679,"mass_kda":74.8,"function":"Plays a role in the synapse formation and synaptic transmission between cone photoreceptor cells and retinal bipolar cells (By similarity). Required for normal transmission of a light-evoked stimulus from the cone photoreceptor cells to the ON-bipolar cells and ON-ganglion cells in the inner retina (PubMed:28334377). Required in retinal ON-bipolar cells for normal localization of the cation channel TRPM1 at dendrite tips (By similarity). Seems to play a specific role in synaptic contacts made by ON-bipolar cells with cone photoreceptor pedicles (By similarity). May also have a role in cone synapse formation (By similarity). Might facilitate FGFR1 exit from the endoplasmic reticulum to the Golgi (PubMed:22673519). Could be a regulator of the FGFRs (PubMed:22673519)","subcellular_location":"Cell projection, dendrite; Perikaryon; Endoplasmic reticulum membrane","url":"https://www.uniprot.org/uniprotkb/Q3SXY7/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/LRIT3","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/LRIT3","total_profiled":1310},"omim":[{"mim_id":"615058","title":"NIGHT BLINDNESS, CONGENITAL STATIONARY, TYPE 1F; CSNB1F","url":"https://www.omim.org/entry/615058"},{"mim_id":"615004","title":"LEUCINE-RICH REPEAT, IMMUNOGLOBULIN-LIKE, AND TRANSMEMBRANE DOMAINS-CONTAINING PROTEIN 3; LRIT3","url":"https://www.omim.org/entry/615004"},{"mim_id":"310500","title":"NIGHT BLINDNESS, CONGENITAL STATIONARY, TYPE 1A; CSNB1A","url":"https://www.omim.org/entry/310500"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Nucleoplasm","reliability":"Approved"},{"location":"Mitochondria","reliability":"Approved"},{"location":"Cytosol","reliability":"Approved"}],"tissue_specificity":"Tissue enriched","tissue_distribution":"Detected in single","driving_tissues":[{"tissue":"retina","ntpm":16.3}],"url":"https://www.proteinatlas.org/search/LRIT3"},"hgnc":{"alias_symbol":["FLJ44691","FIGLER4","CSNB1F"],"prev_symbol":[]},"alphafold":{"accession":"Q3SXY7","domains":[{"cath_id":"3.80.10.10","chopping":"20-181_192-246","consensus_level":"medium","plddt":89.8711,"start":20,"end":246},{"cath_id":"2.60.40.10","chopping":"253-347","consensus_level":"high","plddt":92.0587,"start":253,"end":347},{"cath_id":"2.60.40.10","chopping":"487-572","consensus_level":"high","plddt":77.5114,"start":487,"end":572}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q3SXY7","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q3SXY7-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q3SXY7-F1-predicted_aligned_error_v6.png","plddt_mean":69.62},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=LRIT3","jax_strain_url":"https://www.jax.org/strain/search?query=LRIT3"},"sequence":{"accession":"Q3SXY7","fasta_url":"https://rest.uniprot.org/uniprotkb/Q3SXY7.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q3SXY7/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q3SXY7"}},"corpus_meta":[{"pmid":"23246293","id":"PMC_23246293","title":"Whole-exome sequencing identifies LRIT3 mutations as a cause of autosomal-recessive complete congenital stationary night blindness.","date":"2012","source":"American journal of human genetics","url":"https://pubmed.ncbi.nlm.nih.gov/23246293","citation_count":108,"is_preprint":false},{"pmid":"24598786","id":"PMC_24598786","title":"Lrit3 deficient mouse (nob6): a novel model of complete congenital stationary night blindness (cCSNB).","date":"2014","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/24598786","citation_count":49,"is_preprint":false},{"pmid":"25997951","id":"PMC_25997951","title":"LRIT3 is essential to localize TRPM1 to the dendritic tips of depolarizing bipolar cells and may play a role in cone synapse formation.","date":"2015","source":"The European journal of neuroscience","url":"https://pubmed.ncbi.nlm.nih.gov/25997951","citation_count":48,"is_preprint":false},{"pmid":"31189098","id":"PMC_31189098","title":"Presynaptic Expression of LRIT3 Transsynaptically Organizes the Postsynaptic Glutamate Signaling Complex Containing TRPM1.","date":"2019","source":"Cell reports","url":"https://pubmed.ncbi.nlm.nih.gov/31189098","citation_count":42,"is_preprint":false},{"pmid":"35316139","id":"PMC_35316139","title":"Targeting ON-bipolar cells by AAV gene therapy stably reverses LRIT3-congenital stationary night blindness.","date":"2022","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/35316139","citation_count":28,"is_preprint":false},{"pmid":"31959619","id":"PMC_31959619","title":"LRIT3 is Required for Nyctalopin Expression and Normal ON and OFF Pathway Signaling in the Retina.","date":"2020","source":"eNeuro","url":"https://pubmed.ncbi.nlm.nih.gov/31959619","citation_count":27,"is_preprint":false},{"pmid":"28334377","id":"PMC_28334377","title":"LRIT3 Differentially Affects Connectivity and Synaptic Transmission of Cones to ON- and OFF-Bipolar Cells.","date":"2017","source":"Investigative ophthalmology & visual science","url":"https://pubmed.ncbi.nlm.nih.gov/28334377","citation_count":23,"is_preprint":false},{"pmid":"31578364","id":"PMC_31578364","title":"Genome-wide association study and whole-genome sequencing identify a deletion in LRIT3 associated with canine congenital stationary night blindness.","date":"2019","source":"Scientific reports","url":"https://pubmed.ncbi.nlm.nih.gov/31578364","citation_count":17,"is_preprint":false},{"pmid":"22673519","id":"PMC_22673519","title":"Leucine-rich repeat, immunoglobulin-like and transmembrane domain 3 (LRIT3) is a modulator of FGFR1.","date":"2012","source":"FEBS letters","url":"https://pubmed.ncbi.nlm.nih.gov/22673519","citation_count":14,"is_preprint":false},{"pmid":"39250117","id":"PMC_39250117","title":"Loss of ON-Pathway Function in Mice Lacking Lrit3 Decreases Recovery From Lens-Induced Myopia.","date":"2024","source":"Investigative ophthalmology & visual science","url":"https://pubmed.ncbi.nlm.nih.gov/39250117","citation_count":7,"is_preprint":false},{"pmid":"37220680","id":"PMC_37220680","title":"Extended functional rescue following AAV gene therapy in a canine model of LRIT3-congenital stationary night blindness.","date":"2023","source":"Vision research","url":"https://pubmed.ncbi.nlm.nih.gov/37220680","citation_count":6,"is_preprint":false},{"pmid":"27428514","id":"PMC_27428514","title":"Mutation screening of the LRIT3, CABP4, and GPR179 genes in Chinese patients with Schubert-Bornschein congenital stationary night blindness.","date":"2016","source":"Ophthalmic genetics","url":"https://pubmed.ncbi.nlm.nih.gov/27428514","citation_count":4,"is_preprint":false},{"pmid":"37091241","id":"PMC_37091241","title":"LRIT3 expression in cone photoreceptors restores post-synaptic bipolar cell signalplex assembly and partial function in Lrit3  mice.","date":"2023","source":"iScience","url":"https://pubmed.ncbi.nlm.nih.gov/37091241","citation_count":4,"is_preprint":false},{"pmid":"41000924","id":"PMC_41000924","title":"Domain-specific functions of LRIT3 in synaptic assembly and retinal signal transmission.","date":"2025","source":"bioRxiv : the preprint server for biology","url":"https://pubmed.ncbi.nlm.nih.gov/41000924","citation_count":0,"is_preprint":false},{"pmid":null,"id":"bio_10.1101_2025.07.25.666812","title":"Gene augmentation therapy treats mature mice with complete congenital stationary night blindness (cCSNB), improving retinal function and visual acuity","date":"2025-07-31","source":"bioRxiv","url":"https://doi.org/10.1101/2025.07.25.666812","citation_count":0,"is_preprint":true}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":8910,"output_tokens":2986,"usd":0.03576},"stage2":{"model":"claude-opus-4-6","input_tokens":6316,"output_tokens":2409,"usd":0.137708},"total_usd":0.173468,"stage1_batch_id":"msgbatch_01Mgbec4vM6c9vXht7JVJzss","stage2_batch_id":"msgbatch_01JkuuH5RB2BdJNsgnhjbC6s","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2012,\n      \"finding\": \"LRIT3 is expressed in the outer plexiform layer of the human retina in a punctate pattern resembling the dendritic tips of bipolar cells, consistent with a role in ON-bipolar cell signaling, identified via mutations causing complete congenital stationary night blindness (cCSNB) with loss of b-wave amplitude reflecting abnormal ON-bipolar cell function.\",\n      \"method\": \"Whole-exome sequencing, Sanger sequencing, human retinal immunohistochemistry with anti-LRIT3 antibody\",\n      \"journal\": \"American journal of human genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct antibody localization in human retina, but no functional mechanistic dissection beyond disease association\",\n      \"pmids\": [\"23246293\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Lrit3 knockout mice (nob6) exhibit a no b-wave (nob) ERG phenotype with lacking or severely reduced b-wave amplitudes in scotopic and photopic conditions, thinned inner nuclear layer by SD-OCT, and strongly decreased optomotor responses, establishing LRIT3 loss-of-function causes ON-bipolar cell signaling defect without retinal degeneration.\",\n      \"method\": \"Lrit3 knockout mouse generation, ERG, optomotor testing, SD-OCT, fundus imaging, histology\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — clean KO with multiple orthogonal functional readouts, replicated across labs\",\n      \"pmids\": [\"24598786\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"LRIT3 localizes at the dendritic tips of depolarizing bipolar cells (DBCs) in the outer plexiform layer (OPL) co-localizing with mGluR6, and is required for correct localization of TRPM1 to the dendritic tips of all depolarizing bipolar cells; additionally, mGluR6, GPR179, RGS7, RGS11, and Gβ5 are lost from cone ON-bipolar cell dendritic tips (but not rod bipolar cell tips) in Lrit3 knockout mice, and peanut agglutinin (PNA) labeling is severely reduced in the OPL, suggesting LRIT3 also plays a role in cone synapse formation.\",\n      \"method\": \"Immunofluorescence confocal microscopy of wild-type and Lrit3nob6/nob6 retinal sections using antibodies against LRIT3, TRPM1, mGluR6, GPR179, RGS7, RGS11, Gβ5; PNA labeling\",\n      \"journal\": \"The European journal of neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple signalplex components tested in KO vs. WT with rigorous immunofluorescence, replicated across labs\",\n      \"pmids\": [\"25997951\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"In Lrit3-knockout (nob6) mice, synaptic contacts made by ON-bipolar cells but not OFF-bipolar cells with cone pedicles are structurally disorganized, while molecules essential for OFF-bipolar cell signaling (GluR1, GluR5) are normally targeted to the synapse; multielectrode array recordings confirm complete loss of ON-pathway function but robust (though altered) OFF-pathway signaling, demonstrating LRIT3 selectively coordinates transsynaptic communication between cones and ON-bipolar cells during synapse formation.\",\n      \"method\": \"Electron microscopy, immunostaining and confocal microscopy (GluR1, GluR5), multielectrode array electrophysiology (retinal ganglion cells), ERG in patient with LRIT3 mutations\",\n      \"journal\": \"Investigative ophthalmology & visual science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal methods (EM ultrastructure, immunostaining, electrophysiology) in KO model\",\n      \"pmids\": [\"28334377\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"LRIT3 is expressed presynaptically in rod photoreceptors (not postsynaptically on depolarizing bipolar cells), and selective restoration of LRIT3 expression in Lrit3-/- rods via AAV rescues postsynaptic glutamate signalplex assembly on DBC dendrites and restores rod-driven vision, demonstrating LRIT3 acts as a transsynaptic organizer of the postsynaptic signaling complex.\",\n      \"method\": \"Cell-type-specific AAV-mediated LRIT3 re-expression in rods of Lrit3-/- mice, immunofluorescence for signalplex components, ERG functional rescue\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — AAV rescue with cell-type specificity + immunofluorescence validation + functional ERG readout, published in high-impact journal\",\n      \"pmids\": [\"31189098\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"In the canine LRIT3-CSNB model, the truncated mutant LRIT3 protein retains correct subcellular localization to the region of ON-bipolar cell dendritic tips (with reduced immunolabeling), establishing that loss of function rather than mislocalization underlies the signaling defect in this in vivo model.\",\n      \"method\": \"Genome-wide association study, whole-genome sequencing, immunohistochemistry in canine retina\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — immunolocalization in disease model, single method for mechanistic insight\",\n      \"pmids\": [\"31578364\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"LRIT3 interacts with and is required for expression of nyctalopin at all DBC dendritic tips (thus controlling TRPM1 localization), but DBC signalplex components (including nyctalopin) are not required for LRIT3 expression, placing LRIT3 upstream of nyctalopin in signalplex assembly; loss of LRIT3 also reduces excitatory input to OFF-bipolar cells (type 1 BCs) and disrupts OFF retinal ganglion cell responses.\",\n      \"method\": \"Co-immunoprecipitation, immunofluorescence, whole-cell electrophysiology, multielectrode array (MEA) electrophysiology, glutamate imaging in Lrit3-/- mice\",\n      \"journal\": \"eNeuro\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal epistasis established by KO analysis, Co-IP for interaction, multiple electrophysiological readouts\",\n      \"pmids\": [\"31959619\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"LRIT3 functions as a modulator of FGFR1, with its LRR and immunoglobulin-like domains interacting with FGFR1 to regulate FGFR-mediated signaling pathways (MAPK, PI3K/AKT, PLC-γ).\",\n      \"method\": \"Co-immunoprecipitation, cell-based signaling assays\",\n      \"journal\": \"FEBS letters\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 — single lab, single Co-IP, no mutagenesis validation; context inconsistent with main retinal function described across corpus\",\n      \"pmids\": [\"22673519\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"rAAV-mediated expression of LRIT3 specifically in cone photoreceptors of Lrit3-/- mice rescues assembly of cone DBC signalplex components and partially restores downstream visual function (light-adapted ERG b-wave, electrophysiological recordings of BCs and RGCs), confirming LRIT3 acts trans-synaptically from cones to organize the postsynaptic signalplex on cone DBCs.\",\n      \"method\": \"rAAV-mediated cone-specific LRIT3 expression in Lrit3-/- mice, ERG, whole-cell electrophysiology of BCs and RGCs, immunofluorescence for signalplex components\",\n      \"journal\": \"iScience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — cell-type-specific rescue with multiple functional and molecular readouts, consistent with prior rod-specific rescue study\",\n      \"pmids\": [\"37091241\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"Loss of LRIT3 in Lrit3-/- mice drastically reduces retinal dopamine and DOPAC levels and impairs recovery from lens-induced myopia, establishing that LRIT3-dependent ON-pathway signaling is required for normal dopaminergic regulation of refractive development.\",\n      \"method\": \"UPLC quantification of dopamine/DOPAC in isolated Lrit3-/- retinas, infrared photorefractometry, lens-induced myopia protocol\",\n      \"journal\": \"Investigative ophthalmology & visual science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — KO with defined biochemical and functional readout, single study\",\n      \"pmids\": [\"39250117\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Domain-deletion analysis via rAAV expression in Lrit3-/- retinas shows: (1) the LRR domain is required for trafficking LRIT3 to the synapse in cones (but not rods) and for rod bipolar cell signalplex reassembly and function; (2) the IG domain is required for TRPM1 localization to the signalplex and for function, but not for synaptic localization of LRIT3; (3) the FN3 domain is dispensable for signalplex assembly or function. This supports a model in which the LRR domain trans-synaptically binds nyctalopin and the IG domain interacts with TRPM1.\",\n      \"method\": \"rAAV-mediated expression of LRIT3 deletion constructs in Lrit3-/- mouse retinas, immunofluorescence (LRIT3 trafficking, signalplex component localization), ERG functional analysis\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — systematic domain mutagenesis with functional readout, preprint not yet peer-reviewed\",\n      \"pmids\": [\"41000924\"],\n      \"is_preprint\": true\n    }\n  ],\n  \"current_model\": \"LRIT3 is a single-pass transmembrane LRR-IG-FN3 domain protein expressed presynaptically in rod and cone photoreceptors, where it acts as a transsynaptic organizer: its LRR domain mediates synaptic trafficking (in cones) and trans-synaptic interaction with nyctalopin, while its IG domain is required for TRPM1 localization to the postsynaptic depolarizing bipolar cell signalplex, thereby controlling the assembly of the mGluR6 glutamate signaling complex on DBC dendrites and enabling both ON- and OFF-pathway visual function.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"LRIT3 is a presynaptic transmembrane protein expressed in rod and cone photoreceptors that functions as a transsynaptic organizer of the postsynaptic glutamate signaling complex on depolarizing bipolar cell (DBC) dendrites, thereby enabling ON-pathway visual signaling. Cell-type-specific AAV rescue in Lrit3-knockout mice demonstrates that LRIT3 expressed in rods or cones is sufficient to restore assembly of the DBC signalplex—including nyctalopin and TRPM1—on postsynaptic dendrites [PMID:31189098, PMID:37091241]. LRIT3 interacts with and is required for nyctalopin expression at DBC dendritic tips, and its immunoglobulin domain is specifically required for TRPM1 localization, while its leucine-rich repeat domain mediates transsynaptic interaction with nyctalopin and is necessary for synaptic trafficking in cones [PMID:31959619, PMID:41000924]. Loss-of-function mutations in LRIT3 cause complete congenital stationary night blindness (cCSNB) in humans, characterized by abolished ON-bipolar cell responses [PMID:23246293, PMID:24598786].\",\n  \"teleology\": [\n    {\n      \"year\": 2012,\n      \"claim\": \"Identification of LRIT3 as a disease gene for cCSNB established that it is required for ON-bipolar cell function and localized it to the outer plexiform layer of the retina, opening the question of its precise molecular role at the photoreceptor–bipolar cell synapse.\",\n      \"evidence\": \"Whole-exome sequencing of cCSNB families plus immunohistochemistry in human retina\",\n      \"pmids\": [\"23246293\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Localization appeared postsynaptic at this stage; presynaptic vs. postsynaptic identity unresolved\", \"No functional mechanistic dissection beyond disease association\", \"Molecular partners unknown\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Generation of an Lrit3-knockout mouse confirmed that LRIT3 loss abolishes ON-bipolar cell signaling (nob ERG phenotype) without causing retinal degeneration, establishing a clean functional model for mechanistic studies.\",\n      \"evidence\": \"Lrit3-KO mouse with ERG, optomotor testing, SD-OCT, and histology\",\n      \"pmids\": [\"24598786\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular mechanism by which LRIT3 supports DBC signaling unknown\", \"Whether LRIT3 is pre- or postsynaptic unresolved\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Immunolocalization in the KO revealed that LRIT3 is required for TRPM1 targeting to all DBC dendritic tips and for the entire cone DBC signalplex (mGluR6, GPR179, RGS7/11, Gβ5), establishing it as an upstream organizer of the postsynaptic signaling complex.\",\n      \"evidence\": \"Confocal immunofluorescence for multiple signalplex components in WT vs. Lrit3-KO retinal sections; PNA labeling\",\n      \"pmids\": [\"25997951\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether LRIT3 acts from the pre- or postsynaptic side still unresolved\", \"Direct protein–protein interactions not yet demonstrated\", \"Role at cone vs. rod synapses only partially distinguished\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Ultrastructural and electrophysiological analysis showed that LRIT3 loss selectively disorganizes ON-bipolar but not OFF-bipolar synaptic contacts at cone pedicles, demonstrating pathway-specific transsynaptic coordination.\",\n      \"evidence\": \"Electron microscopy, immunostaining for GluR1/GluR5, MEA recordings of retinal ganglion cells in Lrit3-KO mice\",\n      \"pmids\": [\"28334377\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism of selective ON-pathway disruption unknown\", \"Pre- vs. postsynaptic site of LRIT3 action still unresolved\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"AAV-mediated restoration of LRIT3 selectively in rods of Lrit3-KO mice rescued postsynaptic signalplex assembly and rod-driven ERG b-waves, proving that LRIT3 is presynaptic and acts transsynaptically to organize the DBC signaling complex.\",\n      \"evidence\": \"Cell-type-specific AAV expression in rods, immunofluorescence for signalplex, ERG rescue\",\n      \"pmids\": [\"31189098\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Cone-specific rescue not yet performed\", \"Direct transsynaptic binding partner not identified\", \"Domain requirements unknown\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Co-immunoprecipitation and epistasis analysis placed LRIT3 upstream of nyctalopin in signalplex assembly—LRIT3 interacts with and is required for nyctalopin expression at DBC tips, while DBC components are dispensable for LRIT3 expression—and additionally revealed that LRIT3 loss disrupts OFF-pathway signaling indirectly.\",\n      \"evidence\": \"Co-IP, immunofluorescence, whole-cell and MEA electrophysiology, glutamate imaging in Lrit3-KO mice\",\n      \"pmids\": [\"31959619\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether LRIT3–nyctalopin interaction is direct or mediated by other synaptic proteins\", \"Structural basis of the interaction unknown\", \"Mechanism of OFF-pathway disruption not fully delineated\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Cone-specific AAV rescue in Lrit3-KO mice restored cone DBC signalplex and partially recovered photopic ERG and downstream RGC responses, confirming that the transsynaptic organizing principle operates at both rod and cone synapses.\",\n      \"evidence\": \"rAAV cone-specific LRIT3 expression, ERG, whole-cell electrophysiology, immunofluorescence in Lrit3-KO mice\",\n      \"pmids\": [\"37091241\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Incomplete functional rescue in cones suggests additional factors\", \"Domain requirements for cone vs. rod function unknown\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"LRIT3-dependent ON-pathway signaling was linked to retinal dopamine regulation and refractive development, revealing a broader physiological consequence of ON-pathway dysfunction beyond night blindness.\",\n      \"evidence\": \"UPLC dopamine/DOPAC quantification and lens-induced myopia experiments in Lrit3-KO mice\",\n      \"pmids\": [\"39250117\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single study; whether dopamine reduction is a direct or indirect consequence of ON-pathway loss is unclear\", \"Whether LRIT3 mutations contribute to human myopia not tested\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Systematic domain-deletion analysis revealed that the LRR domain mediates synaptic trafficking in cones and transsynaptic signalplex assembly (likely via nyctalopin binding), the IG domain is required specifically for TRPM1 localization and function, and the FN3 domain is dispensable, providing a modular mechanistic model for LRIT3 transsynaptic signaling.\",\n      \"evidence\": \"rAAV-mediated expression of LRIT3 domain-deletion constructs in Lrit3-KO retinas, immunofluorescence, ERG (preprint)\",\n      \"pmids\": [\"41000924\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Preprint not yet peer-reviewed\", \"Direct binding between LRR domain and nyctalopin or IG domain and TRPM1 not biochemically demonstrated\", \"Structural basis for domain-specific interactions unknown\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Whether LRIT3 directly binds nyctalopin via its LRR domain and TRPM1 via its IG domain in trans remains to be biochemically demonstrated, and no high-resolution structural model of these transsynaptic complexes exists.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No reconstituted binding assay for LRIT3–nyctalopin or LRIT3–TRPM1\", \"No crystal or cryo-EM structure of LRIT3 or its complexes\", \"Mechanism underlying differential trafficking requirements in rods vs. cones unexplained\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0098631\", \"supporting_discovery_ids\": [4, 6, 8, 10]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [0, 2, 4, 10]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-112316\", \"supporting_discovery_ids\": [1, 3, 4, 8]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [2, 6]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"NYX\", \"TRPM1\", \"GRM6\"],\n    \"other_free_text\": []\n  }\n}\n```"}