{"gene":"CATSPER4","run_date":"2026-06-09T22:57:17","timeline":{"discoveries":[{"year":2007,"finding":"Targeted disruption of murine CatSper4 abrogated ICatSper (the alkalinization-activated voltage-sensitive Ca2+-selective current), sperm hyperactivated motility, and male fertility without affecting spermatogenesis or initial motility. Direct protein interactions among all four CatSpers were demonstrated, establishing CatSper4 as an essential component of the flagellar CatSper channel complex.","method":"Knockout mouse model (targeted gene disruption), electrophysiology (ICatSper recording), sperm motility analysis, co-immunoprecipitation (direct protein interactions among CatSpers)","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — genetic KO with defined electrophysiological phenotype (ICatSper loss) and direct protein interaction data; independently replicated by a second lab (PMID:17344468)","pmids":["17227845"],"is_preprint":false},{"year":2007,"finding":"CatSper4 knockout male mice are completely infertile due to rapid loss of sperm motility and absence of hyperactivated motility under capacitating conditions, confirming CATSPER4 is required for hyperactivated motility during capacitation.","method":"Knockout mouse model (targeted gene disruption), computer-assisted sperm analysis (CASA), capacitation assay","journal":"Biology of reproduction","confidence":"High","confidence_rationale":"Tier 2 / Strong — independent replication of KO phenotype with defined motility readout, corroborating PMID:17227845","pmids":["17344468"],"is_preprint":false},{"year":2003,"finding":"In silico analysis identified coiled-coil protein-protein interaction domains in the C-terminal tails of all four CatSper proteins (including CatSper4), suggesting they form a heterotetrameric channel. CatSper4 carries a single channel-forming domain with a predicted pore-loop containing the consensus sequence TxDxW and is expressed in the testis.","method":"In silico gene identification, sequence analysis, expression evidence (testis expression)","journal":"Reproductive biology and endocrinology : RB&E","confidence":"Low","confidence_rationale":"Tier 4 / Weak — computational prediction of coiled-coil domains and pore-loop; no in vitro or in vivo functional validation of the interaction in this paper","pmids":["12932298"],"is_preprint":false},{"year":2023,"finding":"CATSPERθ (encoded by Tmem249) facilitates CatSper channel assembly by serving as a scaffold for the pore-forming subunit CATSPER4. CATSPERθ localizes at the interface of a CatSper dimer and can self-interact. Genetic ablation of any other CatSper transmembrane subunit (including CATSPER4) results in loss of CATSPERθ protein in spermatid cells during spermatogenesis, indicating mutual interdependence for protein stability and flagellar trafficking.","method":"Knockout mouse models (CATSPERθ and individual CatSper subunit KOs), co-immunoprecipitation/scaffold assay, immunofluorescence localization, Western blotting","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple KO models with defined molecular phenotypes, protein interaction data, and localization; published in peer-reviewed journal with preprint version also available","pmids":["37725640","36993167"],"is_preprint":false},{"year":2026,"finding":"The murine Catsper4 promoter contains a cAMP-responsive element (CRE) at +91 bp relative to the transcription start site. CREMτ binds to this CRE both in vitro and in vivo. A core promoter region spans -99 to +63 bp. Deletion of a 65 bp region at the 3'-end of the predicted promoter significantly enhanced transcription, and removal of a 239 bp 5'-flanking region also increased transcriptional activity.","method":"Promoter deletion/reporter assays, electrophoretic mobility shift assay (EMSA), chromatin immunoprecipitation (ChIP), ChIP-seq data analysis (H3K4me3, H3K4me1, H3K27ac histone marks), site-directed mutagenesis of CRE, CREMτ overexpression","journal":"Reproductive sciences (Thousand Oaks, Calif.)","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal methods (EMSA, ChIP, reporter assays, mutagenesis) in a single study establishing CREMτ as a transcriptional regulator of Catsper4; single lab, not yet replicated","pmids":["41680579"],"is_preprint":false}],"current_model":"CATSPER4 is a pore-forming transmembrane subunit of the sperm-specific CatSper heterotetrameric calcium channel in the sperm flagellum; it is essential for the ICatSper current, sperm hyperactivated motility, and male fertility, interacts directly with the other CatSper subunits (interdependency for protein stability), serves as a scaffold target for the assembly factor CATSPERθ during flagellar trafficking, and its expression in the testis is transcriptionally regulated by CREMτ binding to a CRE in its promoter."},"narrative":{"mechanistic_narrative":"CATSPER4 is an essential pore-forming subunit of the sperm-specific CatSper Ca2+ channel required for the alkalinization-activated, voltage-sensitive Ca2+-selective current (ICatSper) that drives hyperactivated flagellar motility during capacitation [PMID:17227845, PMID:17344468]. Targeted disruption in mice abolishes ICatSper, eliminates hyperactivated motility, and causes complete male infertility without disrupting spermatogenesis or initial motility, while the four CatSper subunits interact directly and form an interdependent heterotetrameric channel complex [PMID:17227845, PMID:17344468]. Channel assembly depends on CATSPERθ (Tmem249), which acts as a scaffold for CATSPER4 during flagellar trafficking; loss of any CatSper transmembrane subunit, including CATSPER4, destabilizes CATSPERθ in spermatids, reflecting mutual interdependence for protein stability [PMID:37725640, PMID:36993167]. Testis expression of Catsper4 is transcriptionally controlled by CREMτ binding to a cAMP-responsive element in its core promoter [PMID:41680579].","teleology":[{"year":2007,"claim":"Establishing whether CATSPER4 is functionally required for the sperm Ca2+ current resolved its role as a genuine channel component rather than a predicted accessory protein.","evidence":"Targeted knockout mouse with ICatSper electrophysiology, sperm motility analysis, and co-immunoprecipitation of CatSper subunits","pmids":["17227845"],"confidence":"High","gaps":["Did not define which CATSPER4 residues contribute to the conduction pore","Direct interactions shown by Co-IP do not establish subunit stoichiometry or architecture"]},{"year":2007,"claim":"Independent replication confirmed that CATSPER4 loss specifically eliminates hyperactivated motility under capacitating conditions, tying the channel to a defined motility transition.","evidence":"Independent knockout mouse with computer-assisted sperm analysis and capacitation assays","pmids":["17344468"],"confidence":"High","gaps":["Does not separate CATSPER4's contribution from that of other CatSper subunits within the shared current","Mechanism linking Ca2+ entry to flagellar waveform change not addressed"]},{"year":2023,"claim":"Identifying CATSPERθ as a scaffold for CATSPER4 explained how the channel is assembled and trafficked to the flagellum and revealed reciprocal stability dependence among subunits.","evidence":"Multiple knockout mouse models, scaffold/Co-IP assays, immunofluorescence localization, and Western blotting","pmids":["37725640","36993167"],"confidence":"High","gaps":["Sequence of assembly events and the trafficking route to the flagellum not fully resolved","Whether CATSPERθ contacts CATSPER4 directly or via an intermediate not defined"]},{"year":2026,"claim":"Mapping a functional CRE in the Catsper4 promoter and demonstrating CREMτ binding identified a transcriptional mechanism for testis-restricted expression.","evidence":"Promoter reporter/deletion assays, EMSA, ChIP, CRE mutagenesis, and CREMτ overexpression","pmids":["41680579"],"confidence":"Medium","gaps":["Single lab, not yet independently replicated","Functional consequence of CREMτ loss on endogenous Catsper4 expression in vivo not established","Identity of the repressive elements in the deleted flanking regions unknown"]},{"year":null,"claim":"The molecular architecture of the human CATSPER4 pore and its quantitative contribution to ion selectivity within the assembled channel remain undefined.","evidence":"","pmids":[],"confidence":"Low","gaps":["No structural model of CATSPER4 within the human channel in the corpus","Human fertility phenotype of CATSPER4 variants not characterized in the available timeline"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0005215","term_label":"transporter activity","supporting_discovery_ids":[0]},{"term_id":"GO:0005198","term_label":"structural molecule activity","supporting_discovery_ids":[0,3]}],"localization":[{"term_id":"GO:0005929","term_label":"cilium","supporting_discovery_ids":[0,3]},{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[0]}],"pathway":[{"term_id":"R-HSA-1474165","term_label":"Reproduction","supporting_discovery_ids":[0,1]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[0]}],"complexes":["CatSper channel"],"partners":["CATSPER1","CATSPER2","CATSPER3","CATSPERΘ/TMEM249","CREMΤ"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q7RTX7","full_name":"Cation channel sperm-associated protein 4","aliases":[],"length_aa":472,"mass_kda":54.1,"function":"Pore-forming subunit of the CatSper complex, a sperm-specific voltage-gated calcium channel that plays a central role in calcium-dependent physiological responses essential for successful fertilization, such as sperm hyperactivation, acrosome reaction and chemotaxis towards the oocyte","subcellular_location":"Cell projection, cilium, flagellum membrane","url":"https://www.uniprot.org/uniprotkb/Q7RTX7/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/CATSPER4","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/CATSPER4","total_profiled":1310},"omim":[{"mim_id":"613452","title":"CATION CHANNEL, SPERM-ASSOCIATED, AUXILIARY SUBUNIT GAMMA; CATSPERG","url":"https://www.omim.org/entry/613452"},{"mim_id":"611169","title":"CATION CHANNEL, SPERM-ASSOCIATED, AUXILIARY SUBUNIT BETA; CATSPERB","url":"https://www.omim.org/entry/611169"},{"mim_id":"609121","title":"CATION CHANNEL, SPERM-ASSOCIATED, 4; CATSPER4","url":"https://www.omim.org/entry/609121"},{"mim_id":"609120","title":"CATION CHANNEL, SPERM-ASSOCIATED, 3; CATSPER3","url":"https://www.omim.org/entry/609120"},{"mim_id":"607249","title":"CATION CHANNEL, SPERM-ASSOCIATED, 2; CATSPER2","url":"https://www.omim.org/entry/607249"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"","locations":[],"tissue_specificity":"Tissue enriched","tissue_distribution":"Detected in single","driving_tissues":[{"tissue":"testis","ntpm":11.0}],"url":"https://www.proteinatlas.org/search/CATSPER4"},"hgnc":{"alias_symbol":[],"prev_symbol":[]},"alphafold":{"accession":"Q7RTX7","domains":[{"cath_id":"1.20.120.350","chopping":"72-197","consensus_level":"high","plddt":77.7197,"start":72,"end":197},{"cath_id":"1.10.287.70","chopping":"208-319","consensus_level":"high","plddt":88.6695,"start":208,"end":319}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q7RTX7","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q7RTX7-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q7RTX7-F1-predicted_aligned_error_v6.png","plddt_mean":68.0},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=CATSPER4","jax_strain_url":"https://www.jax.org/strain/search?query=CATSPER4"},"sequence":{"accession":"Q7RTX7","fasta_url":"https://rest.uniprot.org/uniprotkb/Q7RTX7.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q7RTX7/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q7RTX7"}},"corpus_meta":[{"pmid":"17227845","id":"PMC_17227845","title":"All four CatSper ion channel proteins are required for male fertility and sperm cell hyperactivated motility.","date":"2007","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/17227845","citation_count":412,"is_preprint":false},{"pmid":"17344468","id":"PMC_17344468","title":"Catsper3 and Catsper4 are essential for sperm hyperactivated motility and male fertility in the mouse.","date":"2007","source":"Biology of reproduction","url":"https://pubmed.ncbi.nlm.nih.gov/17344468","citation_count":145,"is_preprint":false},{"pmid":"18340633","id":"PMC_18340633","title":"The mouse sperm proteome characterized via IPG strip prefractionation and LC-MS/MS identification.","date":"2008","source":"Proteomics","url":"https://pubmed.ncbi.nlm.nih.gov/18340633","citation_count":127,"is_preprint":false},{"pmid":"12932298","id":"PMC_12932298","title":"Identification of human and mouse CatSper3 and CatSper4 genes: characterisation of a common interaction domain and evidence for expression in testis.","date":"2003","source":"Reproductive biology and endocrinology : RB&E","url":"https://pubmed.ncbi.nlm.nih.gov/12932298","citation_count":119,"is_preprint":false},{"pmid":"21255775","id":"PMC_21255775","title":"A comprehensive gene mutation screen in men with asthenozoospermia.","date":"2011","source":"Fertility and sterility","url":"https://pubmed.ncbi.nlm.nih.gov/21255775","citation_count":31,"is_preprint":false},{"pmid":"37725640","id":"PMC_37725640","title":"A CUG-initiated CATSPERθ functions in the CatSper channel assembly and serves as a checkpoint for flagellar trafficking.","date":"2023","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/37725640","citation_count":20,"is_preprint":false},{"pmid":"34585662","id":"PMC_34585662","title":"Effect of freeze-thawing process on lipid peroxidation, miRNAs, ion channels, apoptosis and global DNA methylation in ram spermatozoa.","date":"2021","source":"Reproduction, fertility, and development","url":"https://pubmed.ncbi.nlm.nih.gov/34585662","citation_count":18,"is_preprint":false},{"pmid":"33536540","id":"PMC_33536540","title":"Detection of selection signatures for response to Aleutian mink disease virus infection in American mink.","date":"2021","source":"Scientific reports","url":"https://pubmed.ncbi.nlm.nih.gov/33536540","citation_count":18,"is_preprint":false},{"pmid":"28948304","id":"PMC_28948304","title":"Histological analysis and identification of spermatogenesis-related genes in 2-, 6-, and 12-month-old sheep testes.","date":"2017","source":"Die Naturwissenschaften","url":"https://pubmed.ncbi.nlm.nih.gov/28948304","citation_count":18,"is_preprint":false},{"pmid":"21970684","id":"PMC_21970684","title":"Molecular cloning, spatial and temporal expression analysis of CatSper genes in the Chinese Meishan pigs.","date":"2011","source":"Reproductive biology and endocrinology : RB&E","url":"https://pubmed.ncbi.nlm.nih.gov/21970684","citation_count":10,"is_preprint":false},{"pmid":"37815627","id":"PMC_37815627","title":"Transcriptome Analysis Reveals Spermatogenesis-Related CircRNAs and LncRNAs in Goat Spermatozoa.","date":"2023","source":"Biochemical genetics","url":"https://pubmed.ncbi.nlm.nih.gov/37815627","citation_count":8,"is_preprint":false},{"pmid":"38038214","id":"PMC_38038214","title":"Reduction of cryopreservation-induced structural, functional and molecular damages in ram sperm by hydrated C60 fullerene.","date":"2023","source":"Reproduction in domestic animals = Zuchthygiene","url":"https://pubmed.ncbi.nlm.nih.gov/38038214","citation_count":4,"is_preprint":false},{"pmid":"36993167","id":"PMC_36993167","title":"A CUG-initiated CATSPERθ functions in the CatSper channel assembly and serves as a checkpoint for flagellar trafficking.","date":"2023","source":"bioRxiv : the preprint server for biology","url":"https://pubmed.ncbi.nlm.nih.gov/36993167","citation_count":3,"is_preprint":false},{"pmid":"39506588","id":"PMC_39506588","title":"Identification of Potential Biomarkers Associated with Spermatogenesis in Azoospermia.","date":"2024","source":"Clinical laboratory","url":"https://pubmed.ncbi.nlm.nih.gov/39506588","citation_count":2,"is_preprint":false},{"pmid":"36472830","id":"PMC_36472830","title":"In Silico Analysis of CatSper Family Genes and APOB Gene Regulation in Male Infertility.","date":"2022","source":"Advances in experimental medicine and biology","url":"https://pubmed.ncbi.nlm.nih.gov/36472830","citation_count":1,"is_preprint":false},{"pmid":"41680579","id":"PMC_41680579","title":"Molecular Characterization of the Murine Catsper4 Promoter and its Regulation by CREMτ.","date":"2026","source":"Reproductive sciences (Thousand Oaks, Calif.)","url":"https://pubmed.ncbi.nlm.nih.gov/41680579","citation_count":0,"is_preprint":false},{"pmid":"41043282","id":"PMC_41043282","title":"Integrated application of transcriptomics and metabolomics provides insights into sexual dimorphism in Apostichopus japonicus.","date":"2025","source":"Comparative biochemistry and physiology. Part D, Genomics & proteomics","url":"https://pubmed.ncbi.nlm.nih.gov/41043282","citation_count":0,"is_preprint":false},{"pmid":"41543154","id":"PMC_41543154","title":"<p>Echinacoside alleviates asthenozoospermia by upregulating Sox5‑mediated transcriptional activation of the CatSper gene</p>.","date":"2026","source":"Molecular medicine reports","url":"https://pubmed.ncbi.nlm.nih.gov/41543154","citation_count":0,"is_preprint":false},{"pmid":"41762345","id":"PMC_41762345","title":"Intraepididymal platelet-rich plasma improves semen cryoresistance via antioxidant, lipid and molecular modulation during the non-breeding season in rams.","date":"2026","source":"Veterinary research communications","url":"https://pubmed.ncbi.nlm.nih.gov/41762345","citation_count":0,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":12789,"output_tokens":1516,"usd":0.030554,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":8238,"output_tokens":1866,"usd":0.04392,"stage2_stop_reason":"end_turn"},"total_usd":0.074474,"stage1_batch_id":"msgbatch_01ACAxJQabDsht39JXeWG22d","stage2_batch_id":"msgbatch_01QEU22A9U5sbPTgsMzTmvSf","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2007,\n      \"finding\": \"Targeted disruption of murine CatSper4 abrogated ICatSper (the alkalinization-activated voltage-sensitive Ca2+-selective current), sperm hyperactivated motility, and male fertility without affecting spermatogenesis or initial motility. Direct protein interactions among all four CatSpers were demonstrated, establishing CatSper4 as an essential component of the flagellar CatSper channel complex.\",\n      \"method\": \"Knockout mouse model (targeted gene disruption), electrophysiology (ICatSper recording), sperm motility analysis, co-immunoprecipitation (direct protein interactions among CatSpers)\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — genetic KO with defined electrophysiological phenotype (ICatSper loss) and direct protein interaction data; independently replicated by a second lab (PMID:17344468)\",\n      \"pmids\": [\"17227845\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"CatSper4 knockout male mice are completely infertile due to rapid loss of sperm motility and absence of hyperactivated motility under capacitating conditions, confirming CATSPER4 is required for hyperactivated motility during capacitation.\",\n      \"method\": \"Knockout mouse model (targeted gene disruption), computer-assisted sperm analysis (CASA), capacitation assay\",\n      \"journal\": \"Biology of reproduction\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — independent replication of KO phenotype with defined motility readout, corroborating PMID:17227845\",\n      \"pmids\": [\"17344468\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"In silico analysis identified coiled-coil protein-protein interaction domains in the C-terminal tails of all four CatSper proteins (including CatSper4), suggesting they form a heterotetrameric channel. CatSper4 carries a single channel-forming domain with a predicted pore-loop containing the consensus sequence TxDxW and is expressed in the testis.\",\n      \"method\": \"In silico gene identification, sequence analysis, expression evidence (testis expression)\",\n      \"journal\": \"Reproductive biology and endocrinology : RB&E\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 4 / Weak — computational prediction of coiled-coil domains and pore-loop; no in vitro or in vivo functional validation of the interaction in this paper\",\n      \"pmids\": [\"12932298\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"CATSPERθ (encoded by Tmem249) facilitates CatSper channel assembly by serving as a scaffold for the pore-forming subunit CATSPER4. CATSPERθ localizes at the interface of a CatSper dimer and can self-interact. Genetic ablation of any other CatSper transmembrane subunit (including CATSPER4) results in loss of CATSPERθ protein in spermatid cells during spermatogenesis, indicating mutual interdependence for protein stability and flagellar trafficking.\",\n      \"method\": \"Knockout mouse models (CATSPERθ and individual CatSper subunit KOs), co-immunoprecipitation/scaffold assay, immunofluorescence localization, Western blotting\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple KO models with defined molecular phenotypes, protein interaction data, and localization; published in peer-reviewed journal with preprint version also available\",\n      \"pmids\": [\"37725640\", \"36993167\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"The murine Catsper4 promoter contains a cAMP-responsive element (CRE) at +91 bp relative to the transcription start site. CREMτ binds to this CRE both in vitro and in vivo. A core promoter region spans -99 to +63 bp. Deletion of a 65 bp region at the 3'-end of the predicted promoter significantly enhanced transcription, and removal of a 239 bp 5'-flanking region also increased transcriptional activity.\",\n      \"method\": \"Promoter deletion/reporter assays, electrophoretic mobility shift assay (EMSA), chromatin immunoprecipitation (ChIP), ChIP-seq data analysis (H3K4me3, H3K4me1, H3K27ac histone marks), site-directed mutagenesis of CRE, CREMτ overexpression\",\n      \"journal\": \"Reproductive sciences (Thousand Oaks, Calif.)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal methods (EMSA, ChIP, reporter assays, mutagenesis) in a single study establishing CREMτ as a transcriptional regulator of Catsper4; single lab, not yet replicated\",\n      \"pmids\": [\"41680579\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"CATSPER4 is a pore-forming transmembrane subunit of the sperm-specific CatSper heterotetrameric calcium channel in the sperm flagellum; it is essential for the ICatSper current, sperm hyperactivated motility, and male fertility, interacts directly with the other CatSper subunits (interdependency for protein stability), serves as a scaffold target for the assembly factor CATSPERθ during flagellar trafficking, and its expression in the testis is transcriptionally regulated by CREMτ binding to a CRE in its promoter.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"CATSPER4 is an essential pore-forming subunit of the sperm-specific CatSper Ca2+ channel required for the alkalinization-activated, voltage-sensitive Ca2+-selective current (ICatSper) that drives hyperactivated flagellar motility during capacitation [#0, #1]. Targeted disruption in mice abolishes ICatSper, eliminates hyperactivated motility, and causes complete male infertility without disrupting spermatogenesis or initial motility, while the four CatSper subunits interact directly and form an interdependent heterotetrameric channel complex [#0, #1]. Channel assembly depends on CATSPERθ (Tmem249), which acts as a scaffold for CATSPER4 during flagellar trafficking; loss of any CatSper transmembrane subunit, including CATSPER4, destabilizes CATSPERθ in spermatids, reflecting mutual interdependence for protein stability [#3]. Testis expression of Catsper4 is transcriptionally controlled by CREMτ binding to a cAMP-responsive element in its core promoter [#4].\",\n  \"teleology\": [\n    {\n      \"year\": 2007,\n      \"claim\": \"Establishing whether CATSPER4 is functionally required for the sperm Ca2+ current resolved its role as a genuine channel component rather than a predicted accessory protein.\",\n      \"evidence\": \"Targeted knockout mouse with ICatSper electrophysiology, sperm motility analysis, and co-immunoprecipitation of CatSper subunits\",\n      \"pmids\": [\"17227845\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Did not define which CATSPER4 residues contribute to the conduction pore\",\n        \"Direct interactions shown by Co-IP do not establish subunit stoichiometry or architecture\"\n      ]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Independent replication confirmed that CATSPER4 loss specifically eliminates hyperactivated motility under capacitating conditions, tying the channel to a defined motility transition.\",\n      \"evidence\": \"Independent knockout mouse with computer-assisted sperm analysis and capacitation assays\",\n      \"pmids\": [\"17344468\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Does not separate CATSPER4's contribution from that of other CatSper subunits within the shared current\",\n        \"Mechanism linking Ca2+ entry to flagellar waveform change not addressed\"\n      ]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Identifying CATSPERθ as a scaffold for CATSPER4 explained how the channel is assembled and trafficked to the flagellum and revealed reciprocal stability dependence among subunits.\",\n      \"evidence\": \"Multiple knockout mouse models, scaffold/Co-IP assays, immunofluorescence localization, and Western blotting\",\n      \"pmids\": [\"37725640\", \"36993167\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Sequence of assembly events and the trafficking route to the flagellum not fully resolved\",\n        \"Whether CATSPERθ contacts CATSPER4 directly or via an intermediate not defined\"\n      ]\n    },\n    {\n      \"year\": 2026,\n      \"claim\": \"Mapping a functional CRE in the Catsper4 promoter and demonstrating CREMτ binding identified a transcriptional mechanism for testis-restricted expression.\",\n      \"evidence\": \"Promoter reporter/deletion assays, EMSA, ChIP, CRE mutagenesis, and CREMτ overexpression\",\n      \"pmids\": [\"41680579\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Single lab, not yet independently replicated\",\n        \"Functional consequence of CREMτ loss on endogenous Catsper4 expression in vivo not established\",\n        \"Identity of the repressive elements in the deleted flanking regions unknown\"\n      ]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"The molecular architecture of the human CATSPER4 pore and its quantitative contribution to ion selectivity within the assembled channel remain undefined.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\n        \"No structural model of CATSPER4 within the human channel in the corpus\",\n        \"Human fertility phenotype of CATSPER4 variants not characterized in the available timeline\"\n      ]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0005215\", \"supporting_discovery_ids\": [0]},\n      {\"term_id\": \"GO:0005198\", \"supporting_discovery_ids\": [0, 3]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005929\", \"supporting_discovery_ids\": [0, 3]},\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [0]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-1474165\", \"supporting_discovery_ids\": [0, 1]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [0]}\n    ],\n    \"complexes\": [\"CatSper channel\"],\n    \"partners\": [\"CATSPER1\", \"CATSPER2\", \"CATSPER3\", \"CATSPERθ/TMEM249\", \"CREMτ\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":4,"faith_total":4,"faith_pct":100.0}}