{"gene":"MEI1","run_date":"2026-04-28T18:30:28","timeline":{"discoveries":[{"year":2002,"finding":"MEI1 is required for homologous chromosome synapsis during meiosis I; in mei1/mei1 spermatocytes, chromosomes arrest at zygotene with failure of synapsis, and RAD51 fails to associate with meiotic chromosomes despite evidence of chromosomal breaks, suggesting a defect upstream of recombinational repair.","method":"Phenotype-driven forward genetic screen; immunocytochemistry for RAD51 on meiotic chromosome spreads from mei1/mei1 mice","journal":"Developmental biology","confidence":"High","confidence_rationale":"Tier 2 — clean KO mouse with defined cellular phenotype; replicated and extended in subsequent papers","pmids":["11820814"],"is_preprint":false},{"year":2003,"finding":"MEI1 is required for the formation of genetically programmed meiotic double-strand breaks (DSBs): mutant spermatocytes show reduced γH2AX at leptonema (comparable to Spo11-null animals), and RAD51 loading is restored by cisplatin treatment, demonstrating that the recombinational repair machinery is intact but DSB induction is defective.","method":"γH2AX immunostaining, cisplatin rescue experiment, positional cloning of Mei1","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1–2 — multiple orthogonal methods (γH2AX, cisplatin rescue, Spo11 comparison) in a single rigorous study","pmids":["14668445"],"is_preprint":false},{"year":2005,"finding":"MEI1 acts epistatically upstream of DMC1 in the mammalian meiotic recombination pathway: double-mutant Mei1−/−; Dmc1−/− mice display the same phenotype as Mei1−/− alone (not the more severe Dmc1−/− oogenesis defect), genetically positioning MEI1 upstream of DMC1 (DSB repair).","method":"Genetic epistasis analysis using Mei1−/−; Dmc1−/− double-knockout mice with sex-specific meiotic phenotype comparison","journal":"Chromosoma","confidence":"High","confidence_rationale":"Tier 2 — classic genetic epistasis with double-mutant analysis across two sexes","pmids":["15928951"],"is_preprint":false},{"year":2023,"finding":"MEI1 protein interacts with key meiotic DSB-formation complex proteins ANKRD31, IHO1, REC114, and MEI4; pathogenic missense variants disrupt these interactions, providing a molecular basis for how MEI1 participates in DSB formation machinery.","method":"Co-immunoprecipitation assays with wild-type and mutant MEI1 constructs","journal":"Journal of human genetics","confidence":"Medium","confidence_rationale":"Tier 2 — reciprocal co-IP with multiple partners; single study","pmids":["36759719"],"is_preprint":false},{"year":2021,"finding":"Protein-truncating and missense mutations in MEI1 reduce MEI1 protein levels, while splicing mutations cause abnormal alternative splicing of MEI1 mRNA, as demonstrated by western blotting and minigene analysis in vitro.","method":"Western blotting, minigene splicing assay in vitro","journal":"Human reproduction (Oxford, England)","confidence":"Medium","confidence_rationale":"Tier 2 — two orthogonal methods (western blot + minigene) in a single study","pmids":["34037756"],"is_preprint":false},{"year":2024,"finding":"Novel frameshift variants in MEI1 do not alter subcellular localization of MEI1 but significantly reduce its mRNA and protein expression levels in transfected HEK293T cells; associated embryos show widespread aneuploidy and abnormal global DNA methylation levels.","method":"Immunofluorescence, western blotting, qPCR in transfected HEK293T cells; whole-genome sequencing and whole-genome bisulfite sequencing of patient embryos","journal":"Molecular genetics and genomics : MGG","confidence":"Medium","confidence_rationale":"Tier 2–3 — multiple orthogonal methods; single study","pmids":["38416203"],"is_preprint":false},{"year":2025,"finding":"A whole exon 19 deletion in MEI1 produces a truncated MEI1 protein (confirmed by western blot) with near-absent expression of the deleted exon; associated arrested embryos show high rates of chromosomal aneuploidy.","method":"cDNA amplification and sequencing, western blotting in transfected cells, preimplantation genetic testing of embryos","journal":"Reproductive sciences (Thousand Oaks, Calif.)","confidence":"Medium","confidence_rationale":"Tier 2–3 — western blot and cDNA sequencing confirm truncated protein; single study","pmids":["40164922"],"is_preprint":false},{"year":2015,"finding":"Expression of bovine MEI1 (bMei1) is regulated by DNA methylation: promoter and gene-body hypermethylation correlates with reduced expression in meiosis-arrested cattle-yak testis, and treatment with the methyltransferase inhibitor 5-aza-2'-deoxycytidine reactivates MEI1 expression in bovine mammary epithelial cells.","method":"Bisulfite sequencing of promoter/gene body methylation, 5-aza-CdR pharmacological demethylation, real-time PCR","journal":"Gene","confidence":"Medium","confidence_rationale":"Tier 2–3 — pharmacological rescue of methylation-silenced expression; single study in a mammalian ortholog model","pmids":["26165450"],"is_preprint":false},{"year":2026,"finding":"Biallelic pathogenic variants in MEI1 disrupt its interaction with the meiotic DSB-formation complex components ANKRD31, IHO1, REC114, and MEI4, mechanistically linking MEI1 to DSB formation machinery and explaining meiotic arrest in NOA patients.","method":"Co-immunoprecipitation assays in a cohort-level study (n=626 NOA patients screened)","journal":"Journal of assisted reproduction and genetics","confidence":"Medium","confidence_rationale":"Tier 2 — co-IP with multiple partners; single lab study but large patient cohort","pmids":["41706353"],"is_preprint":false}],"current_model":"MEI1 is a vertebrate-specific, gonad-expressed protein required for the formation of genetically programmed meiotic double-strand breaks (DSBs) upstream of DMC1-mediated recombinational repair; it physically interacts with the DSB-formation complex (ANKRD31, IHO1, REC114, MEI4), and loss of MEI1 results in failure of chromosome synapsis, absent RAD51/γH2AX foci at leptonema, and meiotic arrest in both sexes, with pathogenic variants reducing protein levels or disrupting complex interactions."},"narrative":{"teleology":[{"year":2002,"claim":"Identification of MEI1 as a gene required for meiotic chromosome synapsis established that a previously unknown factor was needed for proper prophase I progression, as mei1 mutant spermatocytes arrested at zygotene with failed synapsis and absent RAD51 loading despite evidence of chromosome breaks.","evidence":"Forward genetic screen in mice; immunocytochemistry on mei1/mei1 meiotic chromosome spreads","pmids":["11820814"],"confidence":"High","gaps":["Whether MEI1 functions in DSB formation versus DSB processing was unresolved","Molecular mechanism and protein interactions unknown","Female meiotic phenotype not yet characterized"]},{"year":2003,"claim":"Demonstration that MEI1 loss abolishes meiotic DSB formation (not just repair) resolved the key mechanistic ambiguity—reduced γH2AX at leptonema comparable to Spo11-null animals and cisplatin rescue of RAD51 loading proved MEI1 acts at or upstream of DSB induction.","evidence":"γH2AX immunostaining, cisplatin rescue experiment, and comparison to Spo11-null phenotype in mei1 mutant mice","pmids":["14668445"],"confidence":"High","gaps":["Whether MEI1 directly participates in DSB catalysis or acts as an accessory factor was unknown","No binding partners identified","No enzymatic activity established for MEI1"]},{"year":2005,"claim":"Genetic epistasis analysis placed MEI1 definitively upstream of DMC1-mediated repair, ordering the meiotic recombination pathway: Mei1−/−;Dmc1−/− double mutants phenocopied Mei1−/− alone rather than the more severe Dmc1−/− oogenesis defect.","evidence":"Double-knockout mouse analysis with sex-specific meiotic phenotype comparison","pmids":["15928951"],"confidence":"High","gaps":["Biochemical partners and the protein complex through which MEI1 promotes DSBs remained unidentified","Whether MEI1 is required for SPO11 recruitment to chromatin was untested"]},{"year":2015,"claim":"Discovery that MEI1 expression is regulated by DNA methylation expanded understanding of how meiotic entry controls DSB machinery: promoter hypermethylation correlated with meiotic arrest in cattle-yak testis, and pharmacological demethylation reactivated expression.","evidence":"Bisulfite sequencing and 5-aza-CdR treatment in bovine cells and tissues","pmids":["26165450"],"confidence":"Medium","gaps":["Whether epigenetic regulation of MEI1 is conserved in human germ cells was not tested","Downstream consequences of methylation-mediated silencing on DSB formation not directly measured"]},{"year":2021,"claim":"Characterization of human pathogenic MEI1 variants established the molecular consequences of disease-associated mutations: protein-truncating and missense variants reduce protein levels, while splicing mutations cause aberrant mRNA processing.","evidence":"Western blotting and minigene splicing assays in vitro","pmids":["34037756"],"confidence":"Medium","gaps":["Effect of these variants on DSB-complex interactions was not assessed","In vivo validation in germ cells was lacking"]},{"year":2023,"claim":"Identification of MEI1's physical interaction with ANKRD31, IHO1, REC114, and MEI4 provided the first molecular explanation for how MEI1 participates in the DSB-formation complex, and pathogenic missense variants disrupted these interactions.","evidence":"Co-immunoprecipitation with wild-type and mutant MEI1 constructs","pmids":["36759719"],"confidence":"Medium","gaps":["Stoichiometry and architecture of the MEI1-containing complex remain undefined","No structural data available","Whether MEI1 directly contacts SPO11 or acts exclusively through ANKRD31/IHO1/REC114/MEI4 is unknown"]},{"year":2024,"claim":"Frameshift MEI1 variants were shown to reduce mRNA and protein expression without altering subcellular localization, and associated embryos exhibited widespread aneuploidy and aberrant DNA methylation, connecting MEI1 deficiency to post-zygotic genomic instability.","evidence":"Immunofluorescence, western blot, qPCR in HEK293T cells; whole-genome and bisulfite sequencing of patient embryos","pmids":["38416203"],"confidence":"Medium","gaps":["Causal relationship between MEI1 loss and abnormal DNA methylation in embryos not mechanistically established","Overexpression in somatic cells may not recapitulate germ-cell biology"]},{"year":2025,"claim":"Replication of MEI1-complex interaction disruption across a large NOA cohort and additional truncating variants confirmed that biallelic MEI1 loss-of-function is a recurring cause of human meiotic arrest and male infertility.","evidence":"Co-immunoprecipitation assays, cDNA sequencing, western blotting, and preimplantation genetic testing across multiple patient cohorts","pmids":["41706353","40164922"],"confidence":"Medium","gaps":["No animal model rescue experiment has been performed with human variants","Genotype-phenotype correlations across different variant classes are incomplete"]},{"year":null,"claim":"The structural basis of MEI1's role within the DSB-formation complex, whether MEI1 directly contacts SPO11 or chromatin, and the mechanism by which MEI1 deficiency leads to aberrant embryonic DNA methylation remain unresolved.","evidence":"","pmids":[],"confidence":"Low","gaps":["No structural or cryo-EM model of the MEI1-containing complex exists","Whether MEI1 has intrinsic enzymatic or chromatin-binding activity is unknown","Mechanism linking MEI1 loss to global DNA methylation changes in embryos is unexplored"]}],"mechanism_profile":{"molecular_activity":[],"localization":[{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[0,1]}],"pathway":[{"term_id":"R-HSA-1474165","term_label":"Reproduction","supporting_discovery_ids":[0,1,2,3]}],"complexes":["Meiotic DSB-formation complex (ANKRD31–IHO1–REC114–MEI4–MEI1)"],"partners":["ANKRD31","IHO1","REC114","MEI4"],"other_free_text":[]},"mechanistic_narrative":"MEI1 is a vertebrate-specific meiotic protein essential for the formation of genetically programmed double-strand breaks (DSBs) during meiotic prophase I, functioning upstream of recombinational repair in both sexes. MEI1-deficient spermatocytes arrest at zygotene with absent γH2AX foci at leptonema and failure of RAD51 loading—phenocopying Spo11 loss—yet retain intact repair machinery as demonstrated by cisplatin-induced rescue of RAD51 foci; genetic epistasis places MEI1 upstream of DMC1 [PMID:11820814, PMID:14668445, PMID:15928951]. MEI1 physically interacts with the meiotic DSB-formation complex components ANKRD31, IHO1, REC114, and MEI4, and pathogenic variants that reduce MEI1 protein levels or disrupt these interactions cause meiotic arrest and embryonic aneuploidy [PMID:36759719, PMID:34037756, PMID:38416203]. Biallelic loss-of-function variants in MEI1 are a recognized cause of non-obstructive azoospermia and early embryonic arrest in humans [PMID:41706353, PMID:40164922]."},"prefetch_data":{"uniprot":{"accession":"Q5TIA1","full_name":"Meiosis inhibitor protein 1","aliases":["Meiosis defective protein 1"],"length_aa":1274,"mass_kda":141.2,"function":"Required for normal meiotic chromosome synapsis. May be involved in the formation of meiotic double-strand breaks (DSBs) in spermatocytes (By similarity)","subcellular_location":"","url":"https://www.uniprot.org/uniprotkb/Q5TIA1/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/MEI1","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/MEI1","total_profiled":1310},"omim":[{"mim_id":"618431","title":"HYDATIDIFORM MOLE, RECURRENT, 3; HYDM3","url":"https://www.omim.org/entry/618431"},{"mim_id":"608797","title":"MEIOTIC DOUBLE-STRANDED BREAK FORMATION PROTEIN 1; MEI1","url":"https://www.omim.org/entry/608797"},{"mim_id":"605114","title":"SPO11 INITIATOR OF MEIOTIC DOUBLE-STRANDED BREAKS; SPO11","url":"https://www.omim.org/entry/605114"},{"mim_id":"603171","title":"NEURAL PRECURSOR CELL EXPRESSED, DEVELOPMENTALLY DOWNREGULATED 8; NEDD8","url":"https://www.omim.org/entry/603171"},{"mim_id":"231090","title":"HYDATIDIFORM MOLE, RECURRENT, 1; HYDM1","url":"https://www.omim.org/entry/231090"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"","locations":[],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in many","driving_tissues":[{"tissue":"lymphoid tissue","ntpm":20.7},{"tissue":"testis","ntpm":36.6}],"url":"https://www.proteinatlas.org/search/MEI1"},"hgnc":{"alias_symbol":["MGC40042","SPATA38"],"prev_symbol":[]},"alphafold":{"accession":"Q5TIA1","domains":[{"cath_id":"-","chopping":"1169-1246","consensus_level":"medium","plddt":77.4112,"start":1169,"end":1246},{"cath_id":"1.25.40","chopping":"414-475_493-526_537-588","consensus_level":"medium","plddt":90.6471,"start":414,"end":588},{"cath_id":"1.25.10","chopping":"810-817_826-1031_1066-1076","consensus_level":"medium","plddt":80.44,"start":810,"end":1076}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q5TIA1","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q5TIA1-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q5TIA1-F1-predicted_aligned_error_v6.png","plddt_mean":83.69},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=MEI1","jax_strain_url":"https://www.jax.org/strain/search?query=MEI1"},"sequence":{"accession":"Q5TIA1","fasta_url":"https://rest.uniprot.org/uniprotkb/Q5TIA1.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q5TIA1/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q5TIA1"}},"corpus_meta":[{"pmid":"11820814","id":"PMC_11820814","title":"The mouse meiotic mutation mei1 disrupts chromosome synapsis with sexually dimorphic consequences for meiotic progression.","date":"2002","source":"Developmental biology","url":"https://pubmed.ncbi.nlm.nih.gov/11820814","citation_count":119,"is_preprint":false},{"pmid":"14668445","id":"PMC_14668445","title":"Positional cloning and characterization of Mei1, a vertebrate-specific gene required for normal meiotic chromosome synapsis in mice.","date":"2003","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/14668445","citation_count":108,"is_preprint":false},{"pmid":"8150281","id":"PMC_8150281","title":"mei-1, a gene required for meiotic spindle formation in Caenorhabditis elegans, is a member of a family of ATPases.","date":"1994","source":"Genetics","url":"https://pubmed.ncbi.nlm.nih.gov/8150281","citation_count":88,"is_preprint":false},{"pmid":"8027178","id":"PMC_8027178","title":"Localization of the mei-1 gene product of Caenorhaditis elegans, a meiotic-specific spindle component.","date":"1994","source":"The Journal of cell biology","url":"https://pubmed.ncbi.nlm.nih.gov/8027178","citation_count":80,"is_preprint":false},{"pmid":"15928951","id":"PMC_15928951","title":"Mei1 is epistatic to Dmc1 during mouse meiosis.","date":"2005","source":"Chromosoma","url":"https://pubmed.ncbi.nlm.nih.gov/15928951","citation_count":57,"is_preprint":false},{"pmid":"29659827","id":"PMC_29659827","title":"A MEI1 homozygous missense mutation associated with meiotic arrest in a consanguineous family.","date":"2018","source":"Human reproduction (Oxford, England)","url":"https://pubmed.ncbi.nlm.nih.gov/29659827","citation_count":51,"is_preprint":false},{"pmid":"9725834","id":"PMC_9725834","title":"Genetic and molecular characterization of the caenorhabditis elegans gene, mel-26, a postmeiotic negative regulator of mei-1, a meiotic-specific spindle component.","date":"1998","source":"Genetics","url":"https://pubmed.ncbi.nlm.nih.gov/9725834","citation_count":51,"is_preprint":false},{"pmid":"16683055","id":"PMC_16683055","title":"Polymorphic alleles of the human MEI1 gene are associated with human azoospermia by meiotic arrest.","date":"2006","source":"Journal of human genetics","url":"https://pubmed.ncbi.nlm.nih.gov/16683055","citation_count":49,"is_preprint":false},{"pmid":"12904209","id":"PMC_12904209","title":"The Arabidopsis MEI1 gene encodes a protein with five BRCT domains that is involved in meiosis-specific DNA repair events independent of SPO11-induced DSBs.","date":"2003","source":"The Plant journal : for cell and molecular biology","url":"https://pubmed.ncbi.nlm.nih.gov/12904209","citation_count":44,"is_preprint":false},{"pmid":"8514128","id":"PMC_8514128","title":"Genetic studies of mei-1 gene activity during the transition from meiosis to mitosis in Caenorhabditis elegans.","date":"1993","source":"Genetics","url":"https://pubmed.ncbi.nlm.nih.gov/8514128","citation_count":39,"is_preprint":false},{"pmid":"17069791","id":"PMC_17069791","title":"The C. elegans anaphase promoting complex and MBK-2/DYRK kinase act redundantly with CUL-3/MEL-26 ubiquitin ligase to degrade MEI-1 microtubule-severing activity after meiosis.","date":"2006","source":"Developmental biology","url":"https://pubmed.ncbi.nlm.nih.gov/17069791","citation_count":33,"is_preprint":false},{"pmid":"34037756","id":"PMC_34037756","title":"Novel biallelic mutations in MEI1: expanding the phenotypic spectrum to human embryonic arrest and recurrent implantation failure.","date":"2021","source":"Human reproduction (Oxford, England)","url":"https://pubmed.ncbi.nlm.nih.gov/34037756","citation_count":32,"is_preprint":false},{"pmid":"22621901","id":"PMC_22621901","title":"UNC-89 (obscurin) binds to MEL-26, a BTB-domain protein, and affects the function of MEI-1 (katanin) in striated muscle of Caenorhabditis elegans.","date":"2012","source":"Molecular biology of the cell","url":"https://pubmed.ncbi.nlm.nih.gov/22621901","citation_count":32,"is_preprint":false},{"pmid":"26165450","id":"PMC_26165450","title":"Molecular characterization and epigenetic regulation of Mei1 in cattle and cattle-yak.","date":"2015","source":"Gene","url":"https://pubmed.ncbi.nlm.nih.gov/26165450","citation_count":20,"is_preprint":false},{"pmid":"23918937","id":"PMC_23918937","title":"Microtubule severing by the katanin complex is activated by PPFR-1-dependent MEI-1 dephosphorylation.","date":"2013","source":"The Journal of cell biology","url":"https://pubmed.ncbi.nlm.nih.gov/23918937","citation_count":19,"is_preprint":false},{"pmid":"36759719","id":"PMC_36759719","title":"Bi-allelic MEI1 variants cause meiosis arrest and non-obstructive azoospermia.","date":"2023","source":"Journal of human genetics","url":"https://pubmed.ncbi.nlm.nih.gov/36759719","citation_count":17,"is_preprint":false},{"pmid":"35596132","id":"PMC_35596132","title":"Recombination rates in pigs differ between breeds, sexes and individuals, and are associated with the RNF212, SYCP2, PRDM7, MEI1 and MSH4 loci.","date":"2022","source":"Genetics, selection, evolution : GSE","url":"https://pubmed.ncbi.nlm.nih.gov/35596132","citation_count":14,"is_preprint":false},{"pmid":"38416203","id":"PMC_38416203","title":"Novel MEI1 mutations cause chromosomal and DNA methylation abnormalities leading to embryonic arrest and implantation failure.","date":"2024","source":"Molecular genetics and genomics : MGG","url":"https://pubmed.ncbi.nlm.nih.gov/38416203","citation_count":7,"is_preprint":false},{"pmid":"40164922","id":"PMC_40164922","title":"Identification of the novel homozygous whole exon deletion in MEI1 underlying azoospermia and embryonic arrest in one consanguineous family.","date":"2025","source":"Reproductive sciences (Thousand Oaks, Calif.)","url":"https://pubmed.ncbi.nlm.nih.gov/40164922","citation_count":1,"is_preprint":false},{"pmid":"41375492","id":"PMC_41375492","title":"The Impact of MEI1 Alternative Splicing Events on Spermatogenesis in Mongolian Horses.","date":"2025","source":"Animals : an open access journal from MDPI","url":"https://pubmed.ncbi.nlm.nih.gov/41375492","citation_count":0,"is_preprint":false},{"pmid":"41315153","id":"PMC_41315153","title":"Novel variants in MEI1 cause female infertility characterized by early embryonic arrest and implantation failure.","date":"2025","source":"Journal of assisted reproduction and genetics","url":"https://pubmed.ncbi.nlm.nih.gov/41315153","citation_count":0,"is_preprint":false},{"pmid":"41444636","id":"PMC_41444636","title":"Novel biallelic MEI1 variants cause female infertility characterized by multiple pronuclei formation and aberrant embryonic development.","date":"2025","source":"Journal of ovarian research","url":"https://pubmed.ncbi.nlm.nih.gov/41444636","citation_count":0,"is_preprint":false},{"pmid":"41706353","id":"PMC_41706353","title":"A common cause of non-obstructive azoospermia: biallelic MEI1 variants and implications for infertility diagnostics.","date":"2026","source":"Journal of assisted reproduction and genetics","url":"https://pubmed.ncbi.nlm.nih.gov/41706353","citation_count":0,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":13215,"output_tokens":2026,"usd":0.035018},"stage2":{"model":"claude-opus-4-6","input_tokens":5377,"output_tokens":2253,"usd":0.124815},"total_usd":0.159833,"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\": 2002,\n      \"finding\": \"MEI1 is required for homologous chromosome synapsis during meiosis I; in mei1/mei1 spermatocytes, chromosomes arrest at zygotene with failure of synapsis, and RAD51 fails to associate with meiotic chromosomes despite evidence of chromosomal breaks, suggesting a defect upstream of recombinational repair.\",\n      \"method\": \"Phenotype-driven forward genetic screen; immunocytochemistry for RAD51 on meiotic chromosome spreads from mei1/mei1 mice\",\n      \"journal\": \"Developmental biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — clean KO mouse with defined cellular phenotype; replicated and extended in subsequent papers\",\n      \"pmids\": [\"11820814\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"MEI1 is required for the formation of genetically programmed meiotic double-strand breaks (DSBs): mutant spermatocytes show reduced γH2AX at leptonema (comparable to Spo11-null animals), and RAD51 loading is restored by cisplatin treatment, demonstrating that the recombinational repair machinery is intact but DSB induction is defective.\",\n      \"method\": \"γH2AX immunostaining, cisplatin rescue experiment, positional cloning of Mei1\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — multiple orthogonal methods (γH2AX, cisplatin rescue, Spo11 comparison) in a single rigorous study\",\n      \"pmids\": [\"14668445\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"MEI1 acts epistatically upstream of DMC1 in the mammalian meiotic recombination pathway: double-mutant Mei1−/−; Dmc1−/− mice display the same phenotype as Mei1−/− alone (not the more severe Dmc1−/− oogenesis defect), genetically positioning MEI1 upstream of DMC1 (DSB repair).\",\n      \"method\": \"Genetic epistasis analysis using Mei1−/−; Dmc1−/− double-knockout mice with sex-specific meiotic phenotype comparison\",\n      \"journal\": \"Chromosoma\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — classic genetic epistasis with double-mutant analysis across two sexes\",\n      \"pmids\": [\"15928951\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"MEI1 protein interacts with key meiotic DSB-formation complex proteins ANKRD31, IHO1, REC114, and MEI4; pathogenic missense variants disrupt these interactions, providing a molecular basis for how MEI1 participates in DSB formation machinery.\",\n      \"method\": \"Co-immunoprecipitation assays with wild-type and mutant MEI1 constructs\",\n      \"journal\": \"Journal of human genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal co-IP with multiple partners; single study\",\n      \"pmids\": [\"36759719\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Protein-truncating and missense mutations in MEI1 reduce MEI1 protein levels, while splicing mutations cause abnormal alternative splicing of MEI1 mRNA, as demonstrated by western blotting and minigene analysis in vitro.\",\n      \"method\": \"Western blotting, minigene splicing assay in vitro\",\n      \"journal\": \"Human reproduction (Oxford, England)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — two orthogonal methods (western blot + minigene) in a single study\",\n      \"pmids\": [\"34037756\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"Novel frameshift variants in MEI1 do not alter subcellular localization of MEI1 but significantly reduce its mRNA and protein expression levels in transfected HEK293T cells; associated embryos show widespread aneuploidy and abnormal global DNA methylation levels.\",\n      \"method\": \"Immunofluorescence, western blotting, qPCR in transfected HEK293T cells; whole-genome sequencing and whole-genome bisulfite sequencing of patient embryos\",\n      \"journal\": \"Molecular genetics and genomics : MGG\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 — multiple orthogonal methods; single study\",\n      \"pmids\": [\"38416203\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"A whole exon 19 deletion in MEI1 produces a truncated MEI1 protein (confirmed by western blot) with near-absent expression of the deleted exon; associated arrested embryos show high rates of chromosomal aneuploidy.\",\n      \"method\": \"cDNA amplification and sequencing, western blotting in transfected cells, preimplantation genetic testing of embryos\",\n      \"journal\": \"Reproductive sciences (Thousand Oaks, Calif.)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 — western blot and cDNA sequencing confirm truncated protein; single study\",\n      \"pmids\": [\"40164922\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Expression of bovine MEI1 (bMei1) is regulated by DNA methylation: promoter and gene-body hypermethylation correlates with reduced expression in meiosis-arrested cattle-yak testis, and treatment with the methyltransferase inhibitor 5-aza-2'-deoxycytidine reactivates MEI1 expression in bovine mammary epithelial cells.\",\n      \"method\": \"Bisulfite sequencing of promoter/gene body methylation, 5-aza-CdR pharmacological demethylation, real-time PCR\",\n      \"journal\": \"Gene\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 — pharmacological rescue of methylation-silenced expression; single study in a mammalian ortholog model\",\n      \"pmids\": [\"26165450\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"Biallelic pathogenic variants in MEI1 disrupt its interaction with the meiotic DSB-formation complex components ANKRD31, IHO1, REC114, and MEI4, mechanistically linking MEI1 to DSB formation machinery and explaining meiotic arrest in NOA patients.\",\n      \"method\": \"Co-immunoprecipitation assays in a cohort-level study (n=626 NOA patients screened)\",\n      \"journal\": \"Journal of assisted reproduction and genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — co-IP with multiple partners; single lab study but large patient cohort\",\n      \"pmids\": [\"41706353\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"MEI1 is a vertebrate-specific, gonad-expressed protein required for the formation of genetically programmed meiotic double-strand breaks (DSBs) upstream of DMC1-mediated recombinational repair; it physically interacts with the DSB-formation complex (ANKRD31, IHO1, REC114, MEI4), and loss of MEI1 results in failure of chromosome synapsis, absent RAD51/γH2AX foci at leptonema, and meiotic arrest in both sexes, with pathogenic variants reducing protein levels or disrupting complex interactions.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"MEI1 is a vertebrate-specific meiotic protein essential for the formation of genetically programmed double-strand breaks (DSBs) during meiotic prophase I, functioning upstream of recombinational repair in both sexes. MEI1-deficient spermatocytes arrest at zygotene with absent γH2AX foci at leptonema and failure of RAD51 loading—phenocopying Spo11 loss—yet retain intact repair machinery as demonstrated by cisplatin-induced rescue of RAD51 foci; genetic epistasis places MEI1 upstream of DMC1 [PMID:11820814, PMID:14668445, PMID:15928951]. MEI1 physically interacts with the meiotic DSB-formation complex components ANKRD31, IHO1, REC114, and MEI4, and pathogenic variants that reduce MEI1 protein levels or disrupt these interactions cause meiotic arrest and embryonic aneuploidy [PMID:36759719, PMID:34037756, PMID:38416203]. Biallelic loss-of-function variants in MEI1 are a recognized cause of non-obstructive azoospermia and early embryonic arrest in humans [PMID:41706353, PMID:40164922].\",\n  \"teleology\": [\n    {\n      \"year\": 2002,\n      \"claim\": \"Identification of MEI1 as a gene required for meiotic chromosome synapsis established that a previously unknown factor was needed for proper prophase I progression, as mei1 mutant spermatocytes arrested at zygotene with failed synapsis and absent RAD51 loading despite evidence of chromosome breaks.\",\n      \"evidence\": \"Forward genetic screen in mice; immunocytochemistry on mei1/mei1 meiotic chromosome spreads\",\n      \"pmids\": [\"11820814\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Whether MEI1 functions in DSB formation versus DSB processing was unresolved\",\n        \"Molecular mechanism and protein interactions unknown\",\n        \"Female meiotic phenotype not yet characterized\"\n      ]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"Demonstration that MEI1 loss abolishes meiotic DSB formation (not just repair) resolved the key mechanistic ambiguity—reduced γH2AX at leptonema comparable to Spo11-null animals and cisplatin rescue of RAD51 loading proved MEI1 acts at or upstream of DSB induction.\",\n      \"evidence\": \"γH2AX immunostaining, cisplatin rescue experiment, and comparison to Spo11-null phenotype in mei1 mutant mice\",\n      \"pmids\": [\"14668445\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Whether MEI1 directly participates in DSB catalysis or acts as an accessory factor was unknown\",\n        \"No binding partners identified\",\n        \"No enzymatic activity established for MEI1\"\n      ]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Genetic epistasis analysis placed MEI1 definitively upstream of DMC1-mediated repair, ordering the meiotic recombination pathway: Mei1−/−;Dmc1−/− double mutants phenocopied Mei1−/− alone rather than the more severe Dmc1−/− oogenesis defect.\",\n      \"evidence\": \"Double-knockout mouse analysis with sex-specific meiotic phenotype comparison\",\n      \"pmids\": [\"15928951\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Biochemical partners and the protein complex through which MEI1 promotes DSBs remained unidentified\",\n        \"Whether MEI1 is required for SPO11 recruitment to chromatin was untested\"\n      ]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Discovery that MEI1 expression is regulated by DNA methylation expanded understanding of how meiotic entry controls DSB machinery: promoter hypermethylation correlated with meiotic arrest in cattle-yak testis, and pharmacological demethylation reactivated expression.\",\n      \"evidence\": \"Bisulfite sequencing and 5-aza-CdR treatment in bovine cells and tissues\",\n      \"pmids\": [\"26165450\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Whether epigenetic regulation of MEI1 is conserved in human germ cells was not tested\",\n        \"Downstream consequences of methylation-mediated silencing on DSB formation not directly measured\"\n      ]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Characterization of human pathogenic MEI1 variants established the molecular consequences of disease-associated mutations: protein-truncating and missense variants reduce protein levels, while splicing mutations cause aberrant mRNA processing.\",\n      \"evidence\": \"Western blotting and minigene splicing assays in vitro\",\n      \"pmids\": [\"34037756\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Effect of these variants on DSB-complex interactions was not assessed\",\n        \"In vivo validation in germ cells was lacking\"\n      ]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Identification of MEI1's physical interaction with ANKRD31, IHO1, REC114, and MEI4 provided the first molecular explanation for how MEI1 participates in the DSB-formation complex, and pathogenic missense variants disrupted these interactions.\",\n      \"evidence\": \"Co-immunoprecipitation with wild-type and mutant MEI1 constructs\",\n      \"pmids\": [\"36759719\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Stoichiometry and architecture of the MEI1-containing complex remain undefined\",\n        \"No structural data available\",\n        \"Whether MEI1 directly contacts SPO11 or acts exclusively through ANKRD31/IHO1/REC114/MEI4 is unknown\"\n      ]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Frameshift MEI1 variants were shown to reduce mRNA and protein expression without altering subcellular localization, and associated embryos exhibited widespread aneuploidy and aberrant DNA methylation, connecting MEI1 deficiency to post-zygotic genomic instability.\",\n      \"evidence\": \"Immunofluorescence, western blot, qPCR in HEK293T cells; whole-genome and bisulfite sequencing of patient embryos\",\n      \"pmids\": [\"38416203\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Causal relationship between MEI1 loss and abnormal DNA methylation in embryos not mechanistically established\",\n        \"Overexpression in somatic cells may not recapitulate germ-cell biology\"\n      ]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Replication of MEI1-complex interaction disruption across a large NOA cohort and additional truncating variants confirmed that biallelic MEI1 loss-of-function is a recurring cause of human meiotic arrest and male infertility.\",\n      \"evidence\": \"Co-immunoprecipitation assays, cDNA sequencing, western blotting, and preimplantation genetic testing across multiple patient cohorts\",\n      \"pmids\": [\"41706353\", \"40164922\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"No animal model rescue experiment has been performed with human variants\",\n        \"Genotype-phenotype correlations across different variant classes are incomplete\"\n      ]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"The structural basis of MEI1's role within the DSB-formation complex, whether MEI1 directly contacts SPO11 or chromatin, and the mechanism by which MEI1 deficiency leads to aberrant embryonic DNA methylation remain unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\n        \"No structural or cryo-EM model of the MEI1-containing complex exists\",\n        \"Whether MEI1 has intrinsic enzymatic or chromatin-binding activity is unknown\",\n        \"Mechanism linking MEI1 loss to global DNA methylation changes in embryos is unexplored\"\n      ]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [],\n    \"localization\": [\n      {\n        \"term_id\": \"GO:0005634\",\n        \"supporting_discovery_ids\": [0, 1]\n      }\n    ],\n    \"pathway\": [\n      {\n        \"term_id\": \"R-HSA-1474165\",\n        \"supporting_discovery_ids\": [0, 1, 2, 3]\n      }\n    ],\n    \"complexes\": [\n      \"Meiotic DSB-formation complex (ANKRD31–IHO1–REC114–MEI4–MEI1)\"\n    ],\n    \"partners\": [\n      \"ANKRD31\",\n      \"IHO1\",\n      \"REC114\",\n      \"MEI4\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}