{"gene":"TULP1","run_date":"2026-06-10T10:51:56","timeline":{"discoveries":[{"year":1999,"finding":"Tulp1 protein is found exclusively in photoreceptors, localizing predominantly in the inner segments as a soluble ~70 kDa protein. In tulp1-/- mice, rod and cone opsins exhibit prominent ectopic localization and massive extracellular vesicles accumulate around the distal inner segments, consistent with a role in polarized transport of nascent opsin to the outer segments.","method":"Immunoblotting, immunocytochemistry, light and electron microscopy, electroretinography in tulp1-/- knockout mice","journal":"Investigative ophthalmology & visual science","confidence":"High","confidence_rationale":"Tier 2 / Strong — clean KO model with defined cellular phenotype (opsin mislocalization, vesicle accumulation) using multiple orthogonal methods; foundational paper replicated by subsequent studies","pmids":["10549638"],"is_preprint":false},{"year":2005,"finding":"TULP1 interacts with F-actin in photoreceptor cells. TULP1 associates with the membranous fraction of cells, likely through binding phosphorylated phospholipids, and co-sediments with actin. In photoreceptor cells, TULP1 and actin co-localize at the inner segment, connecting cilium, and outer limiting membrane.","method":"Immunoprecipitation from retinal lysates, liquid chromatography tandem mass spectrometry, co-sedimentation assays, subcellular fractionation, phospholipid binding assays, immunocytochemistry","journal":"Investigative ophthalmology & visual science","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reciprocal co-IP and co-sedimentation in retinal lysate plus localization, single lab, multiple orthogonal methods","pmids":["16303976"],"is_preprint":false},{"year":2009,"finding":"Tulp1 localizes to the photoreceptor synapse, and in tulp1-/- mice the spatial relationship between ribbon-associated proteins Bassoon and Piccolo is disrupted, few intact ribbons are present, and bipolar cell dendrites are stunted — demonstrating that Tulp1 is essential for photoreceptor synaptic ribbon integrity and normal bipolar cell dendrite development.","method":"Immunohistochemistry in tulp1-/- and rd10 mice prior to degeneration; electroretinography; comparison with rd10 controls","journal":"Investigative ophthalmology & visual science","confidence":"High","confidence_rationale":"Tier 2 / Strong — clean KO with defined synaptic phenotype using multiple markers and appropriate degeneration controls; replicated in a companion paper (PMID 20238006)","pmids":["19218615","20238006"],"is_preprint":false},{"year":2011,"finding":"In tulp1-/- photoreceptors, guanylate cyclase 1 and guanylate cyclase activating proteins 1 and 2 are mislocalized, and arrestin fails to translocate to the outer segment in response to light. Rab8 and Rab11 (rhodopsin transport machinery proteins) show abnormal distribution, implicating Tulp1 in vesicular docking and fusion near the connecting cilium for the opsin and guanylate cyclase carrier pathways.","method":"Immunohistochemistry for multiple outer segment proteins in tulp1-/- mice prior to degeneration; light-stimulated arrestin translocation assay","journal":"Experimental eye research","confidence":"High","confidence_rationale":"Tier 2 / Strong — defined molecular phenotypes for multiple transport substrates in KO retina with appropriate temporal controls; multiple orthogonal immunolocalization experiments in single rigorous study","pmids":["21867699"],"is_preprint":false},{"year":2016,"finding":"Tulp1 is highly enriched in the periactive zone of photoreceptor presynaptic terminals where it co-localizes with major endocytic proteins. In Tulp1 knockout mice, endocytic proteins are no longer enriched at the periactive zone and endocytic activity near the synaptic ribbon is reduced. Additionally, Tulp1 interacts with the synaptic ribbon protein RIBEYE, and this interaction is important to maintain synaptic ribbon integrity.","method":"Immunolocalization, analysis of endocytic activity in Tulp1 KO mice, protein interaction studies identifying Tulp1-RIBEYE interaction","journal":"The Journal of neuroscience","confidence":"High","confidence_rationale":"Tier 2 / Strong — KO mouse model with defined endocytic phenotype plus novel protein interaction (RIBEYE), multiple orthogonal methods in a single rigorous study","pmids":["26911694"],"is_preprint":false},{"year":2016,"finding":"Common missense mutations in TULP1 produce misfolded protein products that accumulate within the endoplasmic reticulum (ER), causing prolonged ER stress and activation of the unfolded protein response (UPR). The PERK and IRE1 apoptotic arms of the UPR are activated, along with significant upregulation of CHOP, leading to photoreceptor cell death.","method":"Transfection of mutant TULP1-GFP constructs in hTERT-RPE-1 cells; ER tracker staining; confocal microscopy; western blotting for UPR markers (BiP/GRP-78, phospho-PERK, CHOP); qPCR","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — cell-based assay with multiple UPR markers for multiple mutants, single lab, orthogonal methods (microscopy + western blot + qPCR)","pmids":["26987071"],"is_preprint":false},{"year":2014,"finding":"Tulp1 interacts with both MAP1B (by immunoprecipitation and proximity ligation assay localized to the outer nuclear layer and inner segment) and is functionally linked to MAP1A. In tulp1-/- retinas, MAP1A and MAP1B are no longer localized to the outer segment of photoreceptors, suggesting their transport to the outer segment is Tulp1-dependent.","method":"Western blots, immunoprecipitation, immunohistochemistry, proximity ligation assay (PLA) in wild-type and tulp1-/- mouse retinas","journal":"Advances in experimental medicine and biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reciprocal Co-IP with PLA localization confirmation, single lab, two orthogonal methods","pmids":["24664738"],"is_preprint":false},{"year":2020,"finding":"TULP1 (and its homolog TUB) interact with photoreceptor disc component PRCD via the highly conserved C-terminal tubby domain. This interaction is required for PRCD's exclusive localization to photoreceptor outer segment discs, as PRCD localization is altered in TULP1- and TUB-deficient mouse retinas.","method":"Yeast two-hybrid (Ras recruitment system) on bovine retina cDNA library; co-immunoprecipitation in transfected mammalian cells; immunohistochemistry in TULP1- and TUB-deficient mouse retinas","journal":"International journal of molecular sciences","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — yeast two-hybrid discovery confirmed by co-IP in mammalian cells plus functional localization evidence in KO mice, single lab, multiple orthogonal methods","pmids":["33213002"],"is_preprint":false},{"year":2021,"finding":"Tulp1 has two distinct photoreceptor compartment-specific interactomes: (1) an inner segment (IS)-specific interaction with the motor protein Kinesin family member 3a (Kif3a), (2) a synaptic-specific interaction with the scaffold protein Ribeye, and (3) an interaction with microtubule-associated protein 1B (MAP1B) in both compartments. Tulp1 and its binding partners co-localize to their respective compartments, supporting an adapter function linking vesicles to molecular motors.","method":"Serial tangential sectioning to isolate photoreceptor compartments; immunoprecipitation followed by liquid chromatography tandem mass spectrometry; immunolocalization studies","journal":"International journal of molecular sciences","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — compartment-specific Co-IP/MS with immunolocalization confirmation, single lab, two orthogonal methods","pmids":["34360830"],"is_preprint":false},{"year":2014,"finding":"Tulp1 and Tubby (TUB) interact, forming heterodimers or heterooligomers, and this interaction was functionally revealed by their synergistic stimulation of retinal pigment epithelium (RPE) phagocytosis through MerTK-dependent signaling with non-muscle myosin II redistribution.","method":"ORF phage display; yeast two-hybrid; protein pull-down assays; RPE phagocytosis assays; non-muscle myosin II redistribution assay","journal":"Advances in experimental medicine and biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — interaction confirmed by three orthogonal methods (phage display, Y2H, pull-down) with functional phagocytosis assay, single lab","pmids":["24664737"],"is_preprint":false},{"year":2012,"finding":"A protective allele of Mtap1a (encoding MAP1A) significantly reduces photoreceptor degeneration in Tulp1 mutant (Tulp1tm1Pjn/tm1Pjn) mice, demonstrating a functional genetic interaction between Tulp1 and MAP1A in photoreceptor maintenance.","method":"Quantitative trait locus (QTL) analysis in F2 intercross; histological phenotyping; transgenic rescue experiment crossing Mtap1a129P2/OlaHsd allele into Tulp1-deficient mice","journal":"Investigative ophthalmology & visual science","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic epistasis confirmed by QTL mapping plus transgenic rescue, single lab, two orthogonal genetic methods","pmids":["22323461"],"is_preprint":false},{"year":2022,"finding":"In zebrafish tulp1 double knockout (tulp1-dKO), photoreceptor cilium length is significantly reduced, and expression of tektin2 (tekt2), a ciliary/flagellar microtubule structural component, is downregulated. Dual-luciferase reporter assays show that Tulp1a and Tulp1b transcriptionally activate the tekt2 promoter, providing a mechanism by which loss of Tulp1 causes ciliary defects and opsin mislocalization. Additionally, ferroptosis pathway genes are upregulated in tulp1-dKO retinas with mitochondrial shrinkage and iron/lipid droplet deposition.","method":"Zebrafish single and double knockouts; immunofluorescence for opsins; RNA-seq; dual-luciferase reporter assay for tekt2 promoter; electron microscopy; iron and lipid droplet staining","journal":"Cell death & disease","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — KO model with defined ciliary and trafficking phenotype plus luciferase assay for transcriptional mechanism, single lab, multiple orthogonal methods","pmids":["36396940"],"is_preprint":false},{"year":2021,"finding":"The TULP1 p.P388S missense mutation does not alter subcellular distribution or induce ER stress compared to wild-type TULP1, but significantly lowers protein stability as demonstrated by steady-state and cycloheximide-chase experiments in cultured cells.","method":"Exome sequencing; transfection of mutant TULP1 in cultured cells; western blotting (steady-state and cycloheximide-chase); confocal microscopy; qPCR for ER stress markers","journal":"Molecular vision","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — cell-based assay with cycloheximide-chase kinetics plus negative ER stress result, single lab, multiple orthogonal methods","pmids":["33907372"],"is_preprint":false},{"year":2026,"finding":"Knock-in mice expressing the Tulp1F492L mutation (C-terminal tubby domain) show rapid photoreceptor degeneration, rod and cone opsin mistrafficking, abnormal ribbon synapses, and activation of the IRE1 branch of the ER-UPR. Knock-in mice expressing Tulp1D89Y (outside the tubby domain) show preserved retinal morphology and function up to 12 months, indicating mutation location within the protein determines disease severity and mechanism.","method":"Novel knock-in mouse models; immunohistochemistry; ERG; western blot for UPR markers (IRE1 branch); comparison with Tulp1-/- mice","journal":"Human molecular genetics","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — two independent knock-in models plus KO comparison with multiple orthogonal readouts (morphology, function, trafficking, UPR); rigorous mutagenesis-informed mechanistic dissection","pmids":["41493298"],"is_preprint":false},{"year":2025,"finding":"The m6A reader YTHDF1 binds m6A-modified TULP1 mRNA at the coding sequence and enhances its translational efficiency without altering mRNA levels. Loss of Ythdf1 in mice results in reduced TULP1 protein, impaired scotopic ERG responses, and progressive retinal degeneration.","method":"Ythdf1 knockout mice; MeRIP sequencing; RIP sequencing; single-cell RNA-seq; ERG; integrative bioinformatic analysis","journal":"Zoological research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — KO model with defined retinal phenotype, MeRIP-seq and RIP-seq confirming direct m6A-YTHDF1-Tulp1 interaction, single lab, multiple orthogonal methods","pmids":["40116022"],"is_preprint":false},{"year":1999,"finding":"Tulp1 mRNA and protein expression in the retina is restricted to photoreceptor cells, with TULP1 immunoreactivity in the outer plexiform layer and inner segments. Each tubby family member has distinct cell-specific expression in the retina, explaining their inability to compensate for each other.","method":"In situ hybridization with riboprobes; immunohistochemistry in tubby and wild-type mice","journal":"Investigative ophthalmology & visual science","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — two orthogonal methods (ISH and IHC) in multiple mouse models, single lab","pmids":["10509669"],"is_preprint":false}],"current_model":"TULP1 is a photoreceptor-specific cytoplasmic protein (localized to the inner segment, connecting cilium, and synaptic terminal) that functions as an adapter/scaffold for vesicular protein trafficking from the inner segment to the outer segment — mediating transport of rhodopsin, cone opsins, guanylate cyclase 1, GCAP1/2, and PRCD via interactions with F-actin, MAP1B, and the motor protein Kif3a — and is also essential for periactive zone endocytosis at the ribbon synapse through interaction with RIBEYE and recruitment of endocytic machinery; missense mutations in the conserved C-terminal tubby domain cause protein misfolding, ER accumulation, and activation of the IRE1 branch of the unfolded protein response leading to photoreceptor apoptosis, while TULP1 mRNA translation is post-transcriptionally regulated by the m6A reader YTHDF1."},"narrative":{"mechanistic_narrative":"TULP1 is a photoreceptor-specific cytoplasmic protein required for the polarized transport of nascent phototransduction proteins from the inner segment to the outer segment and for synaptic integrity at the photoreceptor ribbon terminal [PMID:10549638, PMID:19218615, PMID:20238006]. In Tulp1-deficient retinas, rod and cone opsins are ectopically localized and extracellular vesicles accumulate around the distal inner segments, while guanylate cyclase 1, GCAP1/2, and light-driven arrestin translocation are also disrupted, alongside abnormal distribution of the Rab8/Rab11 rhodopsin transport machinery — defining TULP1 as an adapter for vesicular docking and trafficking near the connecting cilium [PMID:10549638, PMID:21867699]. TULP1 acts as a trafficking adapter through compartment-specific interactions: it binds F-actin, MAP1B, and the kinesin motor Kif3a in the inner segment, and the photoreceptor disc protein PRCD via its conserved C-terminal tubby domain, directing PRCD to outer segment discs [PMID:16303976, PMID:24664738, PMID:33213002, PMID:34360830]. At the presynaptic terminal, TULP1 is enriched in the periactive zone where it organizes endocytic machinery and interacts with the ribbon protein RIBEYE to maintain ribbon synapse integrity and normal bipolar cell dendrite development [PMID:19218615, PMID:20238006, PMID:26911694]. Missense mutations in the C-terminal tubby domain cause protein misfolding and ER accumulation that activates the IRE1 branch of the unfolded protein response and drives photoreceptor apoptosis, whereas mutations outside this domain preserve retinal function — establishing that mutation location dictates disease mechanism and severity [PMID:26987071, PMID:41493298]. TULP1 expression is further controlled post-transcriptionally by the m6A reader YTHDF1, which enhances TULP1 mRNA translation; its loss reduces TULP1 protein and causes progressive retinal degeneration [PMID:40116022].","teleology":[{"year":1999,"claim":"Established that TULP1 is a photoreceptor-restricted protein whose loss causes opsin mislocalization, framing it as a candidate mediator of polarized outer segment transport.","evidence":"Immunoblotting, microscopy, and electroretinography in tulp1-/- mice; in situ hybridization and IHC across tubby family members","pmids":["10549638","10509669"],"confidence":"High","gaps":["The molecular partners mediating transport were not yet identified","Mechanism of opsin mistrafficking versus a general secretion defect was undefined"]},{"year":2005,"claim":"Identified F-actin and membrane phospholipid binding as the biochemical basis for TULP1 association with the trafficking compartments, beginning to define its adapter mechanism.","evidence":"Co-IP/LC-MS/MS, co-sedimentation, phospholipid binding, and immunocytochemistry in retinal lysates","pmids":["16303976"],"confidence":"Medium","gaps":["Did not link actin binding to specific cargo transport","Single lab, not reciprocally confirmed across systems"]},{"year":2009,"claim":"Extended TULP1 function beyond trafficking to the synapse, showing it is required for ribbon synapse integrity and bipolar dendrite development.","evidence":"Immunohistochemistry in tulp1-/- and rd10 mice with degeneration controls and ERG","pmids":["19218615","20238006"],"confidence":"High","gaps":["The synaptic binding partner was not yet identified","Whether the synaptic role is independent of trafficking was unclear"]},{"year":2011,"claim":"Broadened the substrate repertoire to guanylate cyclase 1, GCAP1/2, and arrestin translocation, and implicated Rab8/Rab11, positioning TULP1 at vesicular docking/fusion near the connecting cilium.","evidence":"Immunohistochemistry for multiple outer segment proteins and arrestin translocation assay in tulp1-/- mice before degeneration","pmids":["21867699"],"confidence":"High","gaps":["Direct physical interaction with Rab proteins not demonstrated","Did not resolve whether TULP1 acts in cargo selection or vesicle delivery"]},{"year":2012,"claim":"Demonstrated a functional genetic interaction with MAP1A, showing modifier alleles alter photoreceptor degeneration in Tulp1 mutants.","evidence":"QTL analysis and transgenic rescue crossing a protective Mtap1a allele into Tulp1-deficient mice","pmids":["22323461"],"confidence":"Medium","gaps":["Genetic interaction does not establish direct physical mechanism","How MAP1A modifies degeneration was not defined"]},{"year":2014,"claim":"Identified MAP1B as a direct partner and connected TULP1 to TUB heterodimerization with a role in RPE phagocytosis, expanding its interactome.","evidence":"Co-IP, PLA, phage display, Y2H, pull-down, and RPE phagocytosis assays in mouse retina and cultured cells","pmids":["24664738","24664737"],"confidence":"Medium","gaps":["MerTK-dependent phagocytosis role not validated in vivo for TULP1","Cytoskeletal partner interactions confirmed in single lab only"]},{"year":2016,"claim":"Resolved the synaptic mechanism by showing TULP1 organizes periactive zone endocytosis and binds RIBEYE, and separately linked tubby-domain missense mutations to ER stress and UPR-driven death.","evidence":"Endocytic activity analysis and RIBEYE interaction in Tulp1 KO mice; mutant TULP1-GFP transfection with ER tracker, UPR western blots, and qPCR in RPE-1 cells","pmids":["26911694","26987071"],"confidence":"High","gaps":["UPR activation shown in cell lines, not yet in vivo","Which endocytic proteins TULP1 directly contacts was not resolved"]},{"year":2020,"claim":"Mapped PRCD trafficking to the conserved C-terminal tubby domain, linking domain function to outer segment disc cargo delivery.","evidence":"Yeast two-hybrid, co-IP in mammalian cells, and IHC in TULP1- and TUB-deficient mouse retinas","pmids":["33213002"],"confidence":"Medium","gaps":["Structural basis of tubby-domain cargo recognition unresolved","Whether PRCD competes with other cargos for the domain unknown"]},{"year":2021,"claim":"Defined compartment-specific interactomes, showing TULP1 links cargo to the kinesin motor Kif3a in the inner segment and to RIBEYE at the synapse, with MAP1B shared, supporting an adapter model; one tubby-domain variant lowered stability without ER stress.","evidence":"Compartment-isolating tangential sectioning with Co-IP/MS and immunolocalization; cycloheximide-chase stability assays for p.P388S in cultured cells","pmids":["34360830","33907372"],"confidence":"Medium","gaps":["Motor-coupling of cargo not reconstituted biochemically","Genotype-mechanism relationship of variants only partly explained"]},{"year":2022,"claim":"Revealed a transcriptional role in cilium biogenesis, with Tulp1 activating the tekt2 promoter, and tied loss to ferroptosis-associated degeneration in zebrafish.","evidence":"Zebrafish single/double knockouts, RNA-seq, dual-luciferase tekt2 promoter assay, EM, and iron/lipid droplet staining","pmids":["36396940"],"confidence":"Medium","gaps":["Whether mammalian TULP1 acts transcriptionally is untested","Direct DNA binding by TULP1 not demonstrated"]},{"year":2025,"claim":"Identified post-transcriptional control of TULP1 by the m6A reader YTHDF1, which enhances TULP1 translation and is required to sustain protein levels and retinal function.","evidence":"Ythdf1 KO mice, MeRIP-seq, RIP-seq, single-cell RNA-seq, and ERG","pmids":["40116022"],"confidence":"Medium","gaps":["Functional contribution of m6A regulation to disease not established","Other regulators of TULP1 translation unknown"]},{"year":2026,"claim":"Demonstrated in knock-in mice that tubby-domain mutations drive rapid degeneration with mistrafficking and IRE1-branch UPR activation, while a mutation outside the domain spares the retina, proving mutation location dictates mechanism and severity.","evidence":"Tulp1F492L and Tulp1D89Y knock-in mice with IHC, ERG, and UPR western blots compared to Tulp1-/- mice","pmids":["41493298"],"confidence":"High","gaps":["Structural explanation for tubby-domain misfolding not resolved","Therapeutic modulation of the IRE1 arm not tested"]},{"year":null,"claim":"How TULP1 mechanistically couples phospholipid/actin binding to motor-driven cargo selection, and whether its zebrafish transcriptional/ciliary role applies in mammals, remain open.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No reconstituted cargo-motor transport complex","Direct DNA-binding/transcriptional activity unconfirmed in mammals","No high-resolution structure of cargo-bound tubby domain"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[1,6,7,8]},{"term_id":"GO:0008092","term_label":"cytoskeletal protein binding","supporting_discovery_ids":[1,6,8]},{"term_id":"GO:0008289","term_label":"lipid binding","supporting_discovery_ids":[1]}],"localization":[{"term_id":"GO:0005929","term_label":"cilium","supporting_discovery_ids":[1,3]},{"term_id":"GO:0005856","term_label":"cytoskeleton","supporting_discovery_ids":[1,6]},{"term_id":"GO:0005783","term_label":"endoplasmic reticulum","supporting_discovery_ids":[5,13]}],"pathway":[],"complexes":[],"partners":["ACTB","MAP1B","MAP1A","KIF3A","RIBEYE","PRCD","TUB","YTHDF1"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"O00294","full_name":"Tubby-related protein 1","aliases":["Tubby-like protein 1"],"length_aa":542,"mass_kda":60.6,"function":"Required for normal development of photoreceptor synapses. Required for normal photoreceptor function and for long-term survival of photoreceptor cells. Interacts with cytoskeleton proteins and may play a role in protein transport in photoreceptor cells (By similarity). Binds lipids, especially phosphatidylinositol 3-phosphate, phosphatidylinositol 4-phosphate, phosphatidylinositol 5-phosphate, phosphatidylinositol 3,4-bisphosphate, phosphatidylinositol 4,5-bisphosphate, phosphatidylinositol 3,4,5-bisphosphate, phosphatidylserine and phosphatidic acid (in vitro). Contribute to stimulation of phagocytosis of apoptotic retinal pigment epithelium (RPE) cells and macrophages","subcellular_location":"Cytoplasm; Cell membrane; Secreted; Synapse","url":"https://www.uniprot.org/uniprotkb/O00294/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/TULP1","classification":"Not Classified","n_dependent_lines":56,"n_total_lines":1208,"dependency_fraction":0.046357615894039736},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/TULP1","total_profiled":1310},"omim":[{"mim_id":"617631","title":"IQ DOMAIN-CONTAINING PROTEIN E; IQCE","url":"https://www.omim.org/entry/617631"},{"mim_id":"613843","title":"LEBER CONGENITAL AMAUROSIS 15; LCA15","url":"https://www.omim.org/entry/613843"},{"mim_id":"611131","title":"RETINITIS PIGMENTOSA 37; RP37","url":"https://www.omim.org/entry/611131"},{"mim_id":"611040","title":"MICROPHTHALMIA, ISOLATED 5; MCOP5","url":"https://www.omim.org/entry/611040"},{"mim_id":"606227","title":"MEMBRANE-TYPE FRIZZLED-RELATED PROTEIN; MFRP","url":"https://www.omim.org/entry/606227"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"","locations":[],"tissue_specificity":"Tissue enriched","tissue_distribution":"Detected in some","driving_tissues":[{"tissue":"retina","ntpm":194.3}],"url":"https://www.proteinatlas.org/search/TULP1"},"hgnc":{"alias_symbol":["TUBL1","LCA15"],"prev_symbol":["RP14"]},"alphafold":{"accession":"O00294","domains":[{"cath_id":"3.20.90.10","chopping":"287-536","consensus_level":"medium","plddt":89.6329,"start":287,"end":536}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/O00294","model_url":"https://alphafold.ebi.ac.uk/files/AF-O00294-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-O00294-F1-predicted_aligned_error_v6.png","plddt_mean":65.38},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=TULP1","jax_strain_url":"https://www.jax.org/strain/search?query=TULP1"},"sequence":{"accession":"O00294","fasta_url":"https://rest.uniprot.org/uniprotkb/O00294.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/O00294/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/O00294"}},"corpus_meta":[{"pmid":"9462750","id":"PMC_9462750","title":"Recessive mutations in the gene encoding the tubby-like protein TULP1 in patients with retinitis pigmentosa.","date":"1998","source":"Nature genetics","url":"https://pubmed.ncbi.nlm.nih.gov/9462750","citation_count":180,"is_preprint":false},{"pmid":"9462751","id":"PMC_9462751","title":"TULP1 mutation in two extended Dominican kindreds with autosomal recessive retinitis pigmentosa.","date":"1998","source":"Nature genetics","url":"https://pubmed.ncbi.nlm.nih.gov/9462751","citation_count":138,"is_preprint":false},{"pmid":"10549638","id":"PMC_10549638","title":"Retinal degeneration in tulp1-/- mice: vesicular accumulation in the interphotoreceptor matrix.","date":"1999","source":"Investigative ophthalmology & visual science","url":"https://pubmed.ncbi.nlm.nih.gov/10549638","citation_count":120,"is_preprint":false},{"pmid":"9096357","id":"PMC_9096357","title":"Molecular characterization of TUB, TULP1, and TULP2, members of the novel tubby gene family and their possible relation to ocular diseases.","date":"1997","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/9096357","citation_count":120,"is_preprint":false},{"pmid":"10509669","id":"PMC_10509669","title":"Cell-specific expression of tubby gene family members (tub, Tulp1,2, and 3) in the retina.","date":"1999","source":"Investigative ophthalmology & visual science","url":"https://pubmed.ncbi.nlm.nih.gov/10509669","citation_count":62,"is_preprint":false},{"pmid":"16303976","id":"PMC_16303976","title":"Tubby-like protein 1 (TULP1) interacts with F-actin in photoreceptor cells.","date":"2005","source":"Investigative ophthalmology & visual science","url":"https://pubmed.ncbi.nlm.nih.gov/16303976","citation_count":52,"is_preprint":false},{"pmid":"17962469","id":"PMC_17962469","title":"Novel TULP1 mutation causing leber congenital amaurosis or early onset retinal degeneration.","date":"2007","source":"Investigative ophthalmology & visual 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In tulp1-/- mice, rod and cone opsins exhibit prominent ectopic localization and massive extracellular vesicles accumulate around the distal inner segments, consistent with a role in polarized transport of nascent opsin to the outer segments.\",\n      \"method\": \"Immunoblotting, immunocytochemistry, light and electron microscopy, electroretinography in tulp1-/- knockout mice\",\n      \"journal\": \"Investigative ophthalmology & visual science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — clean KO model with defined cellular phenotype (opsin mislocalization, vesicle accumulation) using multiple orthogonal methods; foundational paper replicated by subsequent studies\",\n      \"pmids\": [\"10549638\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"TULP1 interacts with F-actin in photoreceptor cells. TULP1 associates with the membranous fraction of cells, likely through binding phosphorylated phospholipids, and co-sediments with actin. In photoreceptor cells, TULP1 and actin co-localize at the inner segment, connecting cilium, and outer limiting membrane.\",\n      \"method\": \"Immunoprecipitation from retinal lysates, liquid chromatography tandem mass spectrometry, co-sedimentation assays, subcellular fractionation, phospholipid binding assays, immunocytochemistry\",\n      \"journal\": \"Investigative ophthalmology & visual science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal co-IP and co-sedimentation in retinal lysate plus localization, single lab, multiple orthogonal methods\",\n      \"pmids\": [\"16303976\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Tulp1 localizes to the photoreceptor synapse, and in tulp1-/- mice the spatial relationship between ribbon-associated proteins Bassoon and Piccolo is disrupted, few intact ribbons are present, and bipolar cell dendrites are stunted — demonstrating that Tulp1 is essential for photoreceptor synaptic ribbon integrity and normal bipolar cell dendrite development.\",\n      \"method\": \"Immunohistochemistry in tulp1-/- and rd10 mice prior to degeneration; electroretinography; comparison with rd10 controls\",\n      \"journal\": \"Investigative ophthalmology & visual science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — clean KO with defined synaptic phenotype using multiple markers and appropriate degeneration controls; replicated in a companion paper (PMID 20238006)\",\n      \"pmids\": [\"19218615\", \"20238006\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"In tulp1-/- photoreceptors, guanylate cyclase 1 and guanylate cyclase activating proteins 1 and 2 are mislocalized, and arrestin fails to translocate to the outer segment in response to light. Rab8 and Rab11 (rhodopsin transport machinery proteins) show abnormal distribution, implicating Tulp1 in vesicular docking and fusion near the connecting cilium for the opsin and guanylate cyclase carrier pathways.\",\n      \"method\": \"Immunohistochemistry for multiple outer segment proteins in tulp1-/- mice prior to degeneration; light-stimulated arrestin translocation assay\",\n      \"journal\": \"Experimental eye research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — defined molecular phenotypes for multiple transport substrates in KO retina with appropriate temporal controls; multiple orthogonal immunolocalization experiments in single rigorous study\",\n      \"pmids\": [\"21867699\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Tulp1 is highly enriched in the periactive zone of photoreceptor presynaptic terminals where it co-localizes with major endocytic proteins. In Tulp1 knockout mice, endocytic proteins are no longer enriched at the periactive zone and endocytic activity near the synaptic ribbon is reduced. Additionally, Tulp1 interacts with the synaptic ribbon protein RIBEYE, and this interaction is important to maintain synaptic ribbon integrity.\",\n      \"method\": \"Immunolocalization, analysis of endocytic activity in Tulp1 KO mice, protein interaction studies identifying Tulp1-RIBEYE interaction\",\n      \"journal\": \"The Journal of neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — KO mouse model with defined endocytic phenotype plus novel protein interaction (RIBEYE), multiple orthogonal methods in a single rigorous study\",\n      \"pmids\": [\"26911694\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Common missense mutations in TULP1 produce misfolded protein products that accumulate within the endoplasmic reticulum (ER), causing prolonged ER stress and activation of the unfolded protein response (UPR). The PERK and IRE1 apoptotic arms of the UPR are activated, along with significant upregulation of CHOP, leading to photoreceptor cell death.\",\n      \"method\": \"Transfection of mutant TULP1-GFP constructs in hTERT-RPE-1 cells; ER tracker staining; confocal microscopy; western blotting for UPR markers (BiP/GRP-78, phospho-PERK, CHOP); qPCR\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — cell-based assay with multiple UPR markers for multiple mutants, single lab, orthogonal methods (microscopy + western blot + qPCR)\",\n      \"pmids\": [\"26987071\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Tulp1 interacts with both MAP1B (by immunoprecipitation and proximity ligation assay localized to the outer nuclear layer and inner segment) and is functionally linked to MAP1A. In tulp1-/- retinas, MAP1A and MAP1B are no longer localized to the outer segment of photoreceptors, suggesting their transport to the outer segment is Tulp1-dependent.\",\n      \"method\": \"Western blots, immunoprecipitation, immunohistochemistry, proximity ligation assay (PLA) in wild-type and tulp1-/- mouse retinas\",\n      \"journal\": \"Advances in experimental medicine and biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal Co-IP with PLA localization confirmation, single lab, two orthogonal methods\",\n      \"pmids\": [\"24664738\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"TULP1 (and its homolog TUB) interact with photoreceptor disc component PRCD via the highly conserved C-terminal tubby domain. This interaction is required for PRCD's exclusive localization to photoreceptor outer segment discs, as PRCD localization is altered in TULP1- and TUB-deficient mouse retinas.\",\n      \"method\": \"Yeast two-hybrid (Ras recruitment system) on bovine retina cDNA library; co-immunoprecipitation in transfected mammalian cells; immunohistochemistry in TULP1- and TUB-deficient mouse retinas\",\n      \"journal\": \"International journal of molecular sciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — yeast two-hybrid discovery confirmed by co-IP in mammalian cells plus functional localization evidence in KO mice, single lab, multiple orthogonal methods\",\n      \"pmids\": [\"33213002\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Tulp1 has two distinct photoreceptor compartment-specific interactomes: (1) an inner segment (IS)-specific interaction with the motor protein Kinesin family member 3a (Kif3a), (2) a synaptic-specific interaction with the scaffold protein Ribeye, and (3) an interaction with microtubule-associated protein 1B (MAP1B) in both compartments. Tulp1 and its binding partners co-localize to their respective compartments, supporting an adapter function linking vesicles to molecular motors.\",\n      \"method\": \"Serial tangential sectioning to isolate photoreceptor compartments; immunoprecipitation followed by liquid chromatography tandem mass spectrometry; immunolocalization studies\",\n      \"journal\": \"International journal of molecular sciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — compartment-specific Co-IP/MS with immunolocalization confirmation, single lab, two orthogonal methods\",\n      \"pmids\": [\"34360830\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Tulp1 and Tubby (TUB) interact, forming heterodimers or heterooligomers, and this interaction was functionally revealed by their synergistic stimulation of retinal pigment epithelium (RPE) phagocytosis through MerTK-dependent signaling with non-muscle myosin II redistribution.\",\n      \"method\": \"ORF phage display; yeast two-hybrid; protein pull-down assays; RPE phagocytosis assays; non-muscle myosin II redistribution assay\",\n      \"journal\": \"Advances in experimental medicine and biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — interaction confirmed by three orthogonal methods (phage display, Y2H, pull-down) with functional phagocytosis assay, single lab\",\n      \"pmids\": [\"24664737\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"A protective allele of Mtap1a (encoding MAP1A) significantly reduces photoreceptor degeneration in Tulp1 mutant (Tulp1tm1Pjn/tm1Pjn) mice, demonstrating a functional genetic interaction between Tulp1 and MAP1A in photoreceptor maintenance.\",\n      \"method\": \"Quantitative trait locus (QTL) analysis in F2 intercross; histological phenotyping; transgenic rescue experiment crossing Mtap1a129P2/OlaHsd allele into Tulp1-deficient mice\",\n      \"journal\": \"Investigative ophthalmology & visual science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic epistasis confirmed by QTL mapping plus transgenic rescue, single lab, two orthogonal genetic methods\",\n      \"pmids\": [\"22323461\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"In zebrafish tulp1 double knockout (tulp1-dKO), photoreceptor cilium length is significantly reduced, and expression of tektin2 (tekt2), a ciliary/flagellar microtubule structural component, is downregulated. Dual-luciferase reporter assays show that Tulp1a and Tulp1b transcriptionally activate the tekt2 promoter, providing a mechanism by which loss of Tulp1 causes ciliary defects and opsin mislocalization. Additionally, ferroptosis pathway genes are upregulated in tulp1-dKO retinas with mitochondrial shrinkage and iron/lipid droplet deposition.\",\n      \"method\": \"Zebrafish single and double knockouts; immunofluorescence for opsins; RNA-seq; dual-luciferase reporter assay for tekt2 promoter; electron microscopy; iron and lipid droplet staining\",\n      \"journal\": \"Cell death & disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — KO model with defined ciliary and trafficking phenotype plus luciferase assay for transcriptional mechanism, single lab, multiple orthogonal methods\",\n      \"pmids\": [\"36396940\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"The TULP1 p.P388S missense mutation does not alter subcellular distribution or induce ER stress compared to wild-type TULP1, but significantly lowers protein stability as demonstrated by steady-state and cycloheximide-chase experiments in cultured cells.\",\n      \"method\": \"Exome sequencing; transfection of mutant TULP1 in cultured cells; western blotting (steady-state and cycloheximide-chase); confocal microscopy; qPCR for ER stress markers\",\n      \"journal\": \"Molecular vision\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — cell-based assay with cycloheximide-chase kinetics plus negative ER stress result, single lab, multiple orthogonal methods\",\n      \"pmids\": [\"33907372\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"Knock-in mice expressing the Tulp1F492L mutation (C-terminal tubby domain) show rapid photoreceptor degeneration, rod and cone opsin mistrafficking, abnormal ribbon synapses, and activation of the IRE1 branch of the ER-UPR. Knock-in mice expressing Tulp1D89Y (outside the tubby domain) show preserved retinal morphology and function up to 12 months, indicating mutation location within the protein determines disease severity and mechanism.\",\n      \"method\": \"Novel knock-in mouse models; immunohistochemistry; ERG; western blot for UPR markers (IRE1 branch); comparison with Tulp1-/- mice\",\n      \"journal\": \"Human molecular genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — two independent knock-in models plus KO comparison with multiple orthogonal readouts (morphology, function, trafficking, UPR); rigorous mutagenesis-informed mechanistic dissection\",\n      \"pmids\": [\"41493298\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"The m6A reader YTHDF1 binds m6A-modified TULP1 mRNA at the coding sequence and enhances its translational efficiency without altering mRNA levels. Loss of Ythdf1 in mice results in reduced TULP1 protein, impaired scotopic ERG responses, and progressive retinal degeneration.\",\n      \"method\": \"Ythdf1 knockout mice; MeRIP sequencing; RIP sequencing; single-cell RNA-seq; ERG; integrative bioinformatic analysis\",\n      \"journal\": \"Zoological research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — KO model with defined retinal phenotype, MeRIP-seq and RIP-seq confirming direct m6A-YTHDF1-Tulp1 interaction, single lab, multiple orthogonal methods\",\n      \"pmids\": [\"40116022\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"Tulp1 mRNA and protein expression in the retina is restricted to photoreceptor cells, with TULP1 immunoreactivity in the outer plexiform layer and inner segments. Each tubby family member has distinct cell-specific expression in the retina, explaining their inability to compensate for each other.\",\n      \"method\": \"In situ hybridization with riboprobes; immunohistochemistry in tubby and wild-type mice\",\n      \"journal\": \"Investigative ophthalmology & visual science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — two orthogonal methods (ISH and IHC) in multiple mouse models, single lab\",\n      \"pmids\": [\"10509669\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"TULP1 is a photoreceptor-specific cytoplasmic protein (localized to the inner segment, connecting cilium, and synaptic terminal) that functions as an adapter/scaffold for vesicular protein trafficking from the inner segment to the outer segment — mediating transport of rhodopsin, cone opsins, guanylate cyclase 1, GCAP1/2, and PRCD via interactions with F-actin, MAP1B, and the motor protein Kif3a — and is also essential for periactive zone endocytosis at the ribbon synapse through interaction with RIBEYE and recruitment of endocytic machinery; missense mutations in the conserved C-terminal tubby domain cause protein misfolding, ER accumulation, and activation of the IRE1 branch of the unfolded protein response leading to photoreceptor apoptosis, while TULP1 mRNA translation is post-transcriptionally regulated by the m6A reader YTHDF1.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"TULP1 is a photoreceptor-specific cytoplasmic protein required for the polarized transport of nascent phototransduction proteins from the inner segment to the outer segment and for synaptic integrity at the photoreceptor ribbon terminal [#0, #2]. In Tulp1-deficient retinas, rod and cone opsins are ectopically localized and extracellular vesicles accumulate around the distal inner segments, while guanylate cyclase 1, GCAP1/2, and light-driven arrestin translocation are also disrupted, alongside abnormal distribution of the Rab8/Rab11 rhodopsin transport machinery — defining TULP1 as an adapter for vesicular docking and trafficking near the connecting cilium [#0, #3]. TULP1 acts as a trafficking adapter through compartment-specific interactions: it binds F-actin, MAP1B, and the kinesin motor Kif3a in the inner segment, and the photoreceptor disc protein PRCD via its conserved C-terminal tubby domain, directing PRCD to outer segment discs [#1, #6, #7, #8]. At the presynaptic terminal, TULP1 is enriched in the periactive zone where it organizes endocytic machinery and interacts with the ribbon protein RIBEYE to maintain ribbon synapse integrity and normal bipolar cell dendrite development [#2, #4]. Missense mutations in the C-terminal tubby domain cause protein misfolding and ER accumulation that activates the IRE1 branch of the unfolded protein response and drives photoreceptor apoptosis, whereas mutations outside this domain preserve retinal function — establishing that mutation location dictates disease mechanism and severity [#5, #13]. TULP1 expression is further controlled post-transcriptionally by the m6A reader YTHDF1, which enhances TULP1 mRNA translation; its loss reduces TULP1 protein and causes progressive retinal degeneration [#14].\",\n  \"teleology\": [\n    {\n      \"year\": 1999,\n      \"claim\": \"Established that TULP1 is a photoreceptor-restricted protein whose loss causes opsin mislocalization, framing it as a candidate mediator of polarized outer segment transport.\",\n      \"evidence\": \"Immunoblotting, microscopy, and electroretinography in tulp1-/- mice; in situ hybridization and IHC across tubby family members\",\n      \"pmids\": [\"10549638\", \"10509669\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"The molecular partners mediating transport were not yet identified\", \"Mechanism of opsin mistrafficking versus a general secretion defect was undefined\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Identified F-actin and membrane phospholipid binding as the biochemical basis for TULP1 association with the trafficking compartments, beginning to define its adapter mechanism.\",\n      \"evidence\": \"Co-IP/LC-MS/MS, co-sedimentation, phospholipid binding, and immunocytochemistry in retinal lysates\",\n      \"pmids\": [\"16303976\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Did not link actin binding to specific cargo transport\", \"Single lab, not reciprocally confirmed across systems\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Extended TULP1 function beyond trafficking to the synapse, showing it is required for ribbon synapse integrity and bipolar dendrite development.\",\n      \"evidence\": \"Immunohistochemistry in tulp1-/- and rd10 mice with degeneration controls and ERG\",\n      \"pmids\": [\"19218615\", \"20238006\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"The synaptic binding partner was not yet identified\", \"Whether the synaptic role is independent of trafficking was unclear\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Broadened the substrate repertoire to guanylate cyclase 1, GCAP1/2, and arrestin translocation, and implicated Rab8/Rab11, positioning TULP1 at vesicular docking/fusion near the connecting cilium.\",\n      \"evidence\": \"Immunohistochemistry for multiple outer segment proteins and arrestin translocation assay in tulp1-/- mice before degeneration\",\n      \"pmids\": [\"21867699\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct physical interaction with Rab proteins not demonstrated\", \"Did not resolve whether TULP1 acts in cargo selection or vesicle delivery\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Demonstrated a functional genetic interaction with MAP1A, showing modifier alleles alter photoreceptor degeneration in Tulp1 mutants.\",\n      \"evidence\": \"QTL analysis and transgenic rescue crossing a protective Mtap1a allele into Tulp1-deficient mice\",\n      \"pmids\": [\"22323461\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Genetic interaction does not establish direct physical mechanism\", \"How MAP1A modifies degeneration was not defined\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Identified MAP1B as a direct partner and connected TULP1 to TUB heterodimerization with a role in RPE phagocytosis, expanding its interactome.\",\n      \"evidence\": \"Co-IP, PLA, phage display, Y2H, pull-down, and RPE phagocytosis assays in mouse retina and cultured cells\",\n      \"pmids\": [\"24664738\", \"24664737\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"MerTK-dependent phagocytosis role not validated in vivo for TULP1\", \"Cytoskeletal partner interactions confirmed in single lab only\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Resolved the synaptic mechanism by showing TULP1 organizes periactive zone endocytosis and binds RIBEYE, and separately linked tubby-domain missense mutations to ER stress and UPR-driven death.\",\n      \"evidence\": \"Endocytic activity analysis and RIBEYE interaction in Tulp1 KO mice; mutant TULP1-GFP transfection with ER tracker, UPR western blots, and qPCR in RPE-1 cells\",\n      \"pmids\": [\"26911694\", \"26987071\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"UPR activation shown in cell lines, not yet in vivo\", \"Which endocytic proteins TULP1 directly contacts was not resolved\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Mapped PRCD trafficking to the conserved C-terminal tubby domain, linking domain function to outer segment disc cargo delivery.\",\n      \"evidence\": \"Yeast two-hybrid, co-IP in mammalian cells, and IHC in TULP1- and TUB-deficient mouse retinas\",\n      \"pmids\": [\"33213002\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Structural basis of tubby-domain cargo recognition unresolved\", \"Whether PRCD competes with other cargos for the domain unknown\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Defined compartment-specific interactomes, showing TULP1 links cargo to the kinesin motor Kif3a in the inner segment and to RIBEYE at the synapse, with MAP1B shared, supporting an adapter model; one tubby-domain variant lowered stability without ER stress.\",\n      \"evidence\": \"Compartment-isolating tangential sectioning with Co-IP/MS and immunolocalization; cycloheximide-chase stability assays for p.P388S in cultured cells\",\n      \"pmids\": [\"34360830\", \"33907372\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Motor-coupling of cargo not reconstituted biochemically\", \"Genotype-mechanism relationship of variants only partly explained\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Revealed a transcriptional role in cilium biogenesis, with Tulp1 activating the tekt2 promoter, and tied loss to ferroptosis-associated degeneration in zebrafish.\",\n      \"evidence\": \"Zebrafish single/double knockouts, RNA-seq, dual-luciferase tekt2 promoter assay, EM, and iron/lipid droplet staining\",\n      \"pmids\": [\"36396940\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether mammalian TULP1 acts transcriptionally is untested\", \"Direct DNA binding by TULP1 not demonstrated\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Identified post-transcriptional control of TULP1 by the m6A reader YTHDF1, which enhances TULP1 translation and is required to sustain protein levels and retinal function.\",\n      \"evidence\": \"Ythdf1 KO mice, MeRIP-seq, RIP-seq, single-cell RNA-seq, and ERG\",\n      \"pmids\": [\"40116022\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Functional contribution of m6A regulation to disease not established\", \"Other regulators of TULP1 translation unknown\"]\n    },\n    {\n      \"year\": 2026,\n      \"claim\": \"Demonstrated in knock-in mice that tubby-domain mutations drive rapid degeneration with mistrafficking and IRE1-branch UPR activation, while a mutation outside the domain spares the retina, proving mutation location dictates mechanism and severity.\",\n      \"evidence\": \"Tulp1F492L and Tulp1D89Y knock-in mice with IHC, ERG, and UPR western blots compared to Tulp1-/- mice\",\n      \"pmids\": [\"41493298\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural explanation for tubby-domain misfolding not resolved\", \"Therapeutic modulation of the IRE1 arm not tested\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How TULP1 mechanistically couples phospholipid/actin binding to motor-driven cargo selection, and whether its zebrafish transcriptional/ciliary role applies in mammals, remain open.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No reconstituted cargo-motor transport complex\", \"Direct DNA-binding/transcriptional activity unconfirmed in mammals\", \"No high-resolution structure of cargo-bound tubby domain\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [1, 6, 7, 8]},\n      {\"term_id\": \"GO:0008092\", \"supporting_discovery_ids\": [1, 6, 8]},\n      {\"term_id\": \"GO:0008289\", \"supporting_discovery_ids\": [1]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005929\", \"supporting_discovery_ids\": [1, 3]},\n      {\"term_id\": \"GO:0005856\", \"supporting_discovery_ids\": [1, 6]},\n      {\"term_id\": \"GO:0005783\", \"supporting_discovery_ids\": [5, 13]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"GO:0009536\", \"supporting_discovery_ids\": []}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"ACTB\", \"MAP1B\", \"MAP1A\", \"KIF3A\", \"RIBEYE\", \"PRCD\", \"TUB\", \"YTHDF1\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":6,"faith_total":6,"faith_pct":100.0}}