{"gene":"SEPTIN12","run_date":"2026-06-10T07:46:30","timeline":{"discoveries":[{"year":2007,"finding":"SEPT12 was identified as a novel septin via yeast two-hybrid screen using SEPT5 as bait; it purifies with bound nucleotide, binds phosphoinositides, and co-localizes with SEPT4 into robust curved filaments when co-expressed in CHO cells, placing it at the sperm annulus.","method":"Yeast two-hybrid screen, nucleotide binding assay, phosphoinositide binding assay, co-expression/co-localization in CHO cells, RT-PCR, Northern blot, Western blot","journal":"Cell motility and the cytoskeleton","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal biochemical methods (nucleotide binding, lipid binding, co-localization), single lab","pmids":["17685441"],"is_preprint":false},{"year":2007,"finding":"SEPT12 interacts with SEPT6 in vitro and in vivo (co-IP); co-expression of SEPT12 alters the filamentous structure of SEPT6 in HeLa cells. SEPT12 localizes to central spindle and midbody during anaphase and cytokinesis.","method":"Co-immunoprecipitation (in vitro and in vivo), co-expression in HeLa cells, immunocytochemistry","journal":"Journal of biochemistry and molecular biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reciprocal Co-IP plus co-expression functional readout, single lab, two methods","pmids":["18047794"],"is_preprint":false},{"year":2008,"finding":"SEPT12 binds GTP in vitro; a G56N mutation in the GTP-binding motif abolishes binding. GTP binding is required for filament formation (G56N forms aggregates instead of filaments) and for interaction with SEPT11, but not for self-interaction.","method":"In vitro GTP-binding assay, site-directed mutagenesis, immunocytochemistry in HeLa cells","journal":"Molecules and cells","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro biochemical assay combined with mutagenesis and cellular phenotype, single lab but multiple orthogonal methods","pmids":["18443421"],"is_preprint":false},{"year":2012,"finding":"Two missense mutations in the GTPase domain (T89M and D197N) identified in infertile men: T89M significantly reduces GTP hydrolytic activity; D197N interferes with GTP binding. Both mutant proteins restrict wild-type SEPT12 filament formation in a dose-dependent dominant-negative manner, disrupting sperm annulus integrity.","method":"GTP hydrolysis assay, GTP binding assay, filament formation assay, in silico structural modeling","journal":"Human mutation","confidence":"High","confidence_rationale":"Tier 1 / Moderate — enzymatic activity assays with mutagenesis plus dominant-negative filament assay, single lab with multiple orthogonal methods","pmids":["22275165"],"is_preprint":false},{"year":2012,"finding":"A c.474G>A splice-site variant causes exon 5 skipping, producing a truncated SEPT12 lacking the C-terminal half; this truncated protein inhibits wild-type SEPT12 filament formation in a dose-dependent manner (ex vivo), and is associated with bent tail and nuclear DNA damage in sperm.","method":"DNA sequencing, RT-PCR splice assay, filament formation assay (ex vivo), immunocytochemistry","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — molecular characterization of variant plus functional filament assay, single lab, two methods","pmids":["22479503"],"is_preprint":false},{"year":2013,"finding":"SEPT12 interacts with α- and β-tubulins by co-IP; SEPT12 co-localizes with tubulins during spermiogenesis in transgenic mice. shRNA-mediated loss of SEPT12 disrupts α- and β-tubulin organization and impairs sperm head morphogenesis and tail elongation.","method":"Co-immunoprecipitation, SEPTIN12-transgenic mouse model, shRNA knockdown, confocal microscopy","journal":"International journal of molecular sciences","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP plus in vivo transgenic localization and shRNA loss-of-function, single lab","pmids":["24213608"],"is_preprint":false},{"year":2015,"finding":"SEPT12 assembles octameric filaments with SEPT7, SEPT6, SEPT2, and SEPT4 (arrangements 12-7-6-2-2-6-7-12 or 12-7-6-4-4-6-7-12) at the sperm annulus. The GTP-binding domain of SEPT12 is required for interaction with SEPT7, and N- and C-termini are required for SEPT12 self-polymerization into filaments. The D197N knock-in mouse shows disorganized annulus, bent tail, reduced sperm motility, and loss of SEPT ring structure.","method":"Co-immunoprecipitation, deletion/domain mapping, knock-in mouse model (D197N), electron microscopy, immunofluorescence","journal":"Journal of cell science","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — domain mapping with mutagenesis, Co-IP, knock-in mouse with multiple phenotypic readouts, replicated with human patient data","pmids":["25588830"],"is_preprint":false},{"year":2015,"finding":"SEPT12 interacts with SPAG4 (SUN4) in a male germ cell line (co-IP). SEPT12, SPAG4, and LAMINB1 form complexes at the nuclear periphery of round spermatids. A SEPT12 disease mutation disrupts these nuclear envelope complexes (co-IP). SEPT12 links SEPT proteins to the SUN/LAMIN nuclear envelope complex during postmeiotic germ cell development.","method":"Yeast two-hybrid, co-immunoprecipitation, co-localization by confocal microscopy in germ cell line and human spermatogenic cells","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Y2H plus reciprocal Co-IP plus localization, single lab","pmids":["25775403"],"is_preprint":false},{"year":2016,"finding":"SEPT12 interacts with NDC1 (nuclear pore complex protein) in male germ cell line (co-IP). NDC1 overexpression restricts SEPT12 localization to the nucleus and represses SEPT12 filament formation. In D197N mutant sperm, NDC1 disperses from the sperm neck to manchette region and annulus.","method":"Yeast two-hybrid, co-immunoprecipitation, overexpression/localization in germ cell line, knock-in mouse model","journal":"International journal of molecular sciences","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Y2H identification validated by Co-IP, functional overexpression, and in vivo mouse model, single lab","pmids":["27854341"],"is_preprint":false},{"year":2018,"finding":"SEPT12 phosphorylation on Ser198 by Protein Kinase A (PKA) regulates sperm annulus architecture. A phosphomimetic SEPT12 S198 knock-in mouse shows poor male fertility, weak sperm motility, and loss of the sperm annulus. Phosphorylation at Ser198 interferes with SEPT12 polymerization into complexes and filaments.","method":"Knock-in mouse model (phosphomimetic), fertility assays, sperm motility analysis, filament polymerization assay, PKA kinase identification","journal":"Cytoskeleton (Hoboken, N.J.)","confidence":"High","confidence_rationale":"Tier 1-2 / Moderate — phosphorylation site identified with writer (PKA), phosphomimetic knock-in mouse with functional consequences, multiple readouts","pmids":["30160375"],"is_preprint":false},{"year":2018,"finding":"CDC42 negatively regulates SEPT12 polymerization. Wild-type CDC42 and constitutively active CDC42Q61L substantially repress SEPT12 polymerization, whereas dominant-negative CDC42T17N does not. CDC42 and SEPT12 co-localize in perinuclear manchette and midpiece regions of spermatids/spermatozoa.","method":"Ectopic expression analysis with CDC42 mutants, filament formation assay, scanning electron microscopy, co-localization by immunofluorescence","journal":"International journal of molecular sciences","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — gain/loss-of-function CDC42 mutants with functional filament readout and co-localization, single lab","pmids":["30189608"],"is_preprint":false},{"year":2018,"finding":"The SEPT12 gene promoter is a 245 bp region upstream of the transcription start site. Androgen receptor (AR) and estrogen receptor α (ERα) directly bind this region (confirmed by chromatin immunoprecipitation). Truncation of AR or ERα binding sites decreases promoter activity; treatment with 17β-estradiol or 5α-dihydrotestosterone enhances promoter activity.","method":"Promoter deletion analysis, chromatin immunoprecipitation (ChIP), luciferase reporter assay","journal":"Biochimie","confidence":"Medium","confidence_rationale":"Tier 1-2 / Moderate — ChIP plus reporter assay with deletion constructs and hormone treatment, single lab","pmids":["30513371"],"is_preprint":false},{"year":2019,"finding":"SEPT12 expression alters nuclear membrane localization of SPAG4 (SUN4) and also alters localization of LAMINA/C; this effect is specific to SEPT12 and not observed with SEPT1, SEPT6, SEPT7, or SEPT11.","method":"Confocal microscopy after SEPT12 overexpression in testicular cancer cell line, comparison with other septins","journal":"International journal of molecular sciences","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — cell-based localization with specificity controls across multiple septins, single lab","pmids":["30866452"],"is_preprint":false},{"year":2020,"finding":"SEPT12 forms a complex with SEPT1, SEPT2, SEPT10, and SEPT11 at the sperm neck. The D197N mutation disrupts this complex and causes defective connecting pieces (head-tail junction). SEPT12 interacts and co-localizes with γ-tubulin in elongating spermatids, suggesting SEPT12 and pericentriolar materials jointly form connecting pieces.","method":"Co-immunoprecipitation, electron microscopy, immunofluorescence, D197N knock-in mouse model","journal":"Molecular human reproduction","confidence":"High","confidence_rationale":"Tier 1-2 / Moderate — Co-IP plus knock-in mouse model plus EM structural analysis plus multiple partner identifications, single lab with multiple orthogonal methods","pmids":["32392324"],"is_preprint":false},{"year":2022,"finding":"Homozygous Septin12 knockout (but not heterozygous) male mice are infertile with reduced sperm counts and abnormal morphology. Loss of PLCζ around the acrosome in Septin12-null sperm is identified as the likely mechanism for fertilization failure, which can be rescued by artificial oocyte activation (AOA).","method":"Septin12 knockout mouse model, ICSI with AOA, immunofluorescence for PLCζ localization","journal":"Frontiers in cell and developmental biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — knockout mouse plus functional ICSI/AOA rescue plus immunofluorescence mechanistic marker, single lab","pmids":["35547809"],"is_preprint":false},{"year":2024,"finding":"SUN5 interacts with SEPT12 (and LAMINB1) in mouse testis, identified by immunoprecipitation-mass spectrometry and validated by further studies. The SUN5-SEPT12 interaction promotes their co-aggregation at the sperm neck; Sun5 deficiency disrupts the LaminB1/SUN5/SEPT12 complex, causing separation of the SEPT12-proximal centriole from the nucleus and breakage of the head-to-tail junction.","method":"Immunoprecipitation-mass spectrometry, co-immunoprecipitation, immunofluorescence, Sun5 knockout mouse model","journal":"Molecular human reproduction","confidence":"High","confidence_rationale":"Tier 1-2 / Moderate — IP-MS identification, validated by Co-IP, functional knockout mouse showing complex disruption and structural consequence, multiple orthogonal methods","pmids":["38870534"],"is_preprint":false},{"year":2025,"finding":"A novel SEPT12 T96I mutation causes male infertility; overexpression of SEPT12 T96I in NT2/D1 cells impairs SEPT7 filament formation, demonstrating that SEPT12 filament integrity is required for proper SEPT7 filament organization. Sperm from T96I carriers show obliquely positioned annulus with SEPT12/SEPT7 co-localization defects, large nuclear vacuoles, and acrosomal decondensation.","method":"Immunofluorescence, transmission electron microscopy, overexpression in NT2/D1 cells","journal":"Frontiers in cell and developmental biology","confidence":"Medium","confidence_rationale":"Tier 2-3 / Moderate — cell-based overexpression with functional filament readout, TEM structural analysis, and patient sperm phenotype, single lab","pmids":["39850804"],"is_preprint":false}],"current_model":"SEPTIN12 (SEPT12) is a testis-specific GTP-binding cytoskeletal protein that forms octameric heterofilaments with SEPT2, SEPT4, SEPT6, and SEPT7 at the sperm annulus, and with SEPT1, SEPT2, SEPT10, and SEPT11 at the sperm neck; its GTP-binding domain drives interaction with partner septins (especially SEPT7), while its N- and C-termini mediate self-polymerization into filaments that provide mechanical support for sperm motility and head-tail junction integrity. SEPT12 also links the cytoskeleton to the nuclear envelope by interacting with the SUN-domain proteins SPAG4/SUN4 and SUN5, and with LAMINB1, maintaining nuclear envelope integrity in postmeiotic germ cells; it additionally interacts with α/β-tubulins to coordinate sperm head morphogenesis and tail elongation, and its polymerization is negatively regulated by CDC42 and by PKA-mediated phosphorylation on Ser198. Disease mutations (T89M, D197N, T96I) impair GTP hydrolysis or binding, disrupt filament formation in a dominant-negative manner, and cause teratozoospermia/oligozoospermia in men, while homozygous knockout in mice causes infertility partly through loss of PLCζ and fertilization failure."},"narrative":{"mechanistic_narrative":"SEPTIN12 (SEPT12) is a testis-enriched GTP-binding septin that polymerizes into cytoskeletal heterofilaments essential for sperm morphogenesis and male fertility [PMID:17685441, PMID:25588830]. It binds GTP and hydrolyzes it, and this nucleotide state governs its behavior: GTP binding is required for filament formation and for interaction with partner septins such as SEPT11, while self-interaction is GTP-independent [PMID:18443421]. SEPT12 assembles into octameric filaments with SEPT7, SEPT6, SEPT2, and SEPT4 at the sperm annulus, with its GTP-binding domain mediating the SEPT7 interaction and its N- and C-termini driving self-polymerization [PMID:25588830]; at the sperm neck it forms a distinct complex with SEPT1, SEPT2, SEPT10, and SEPT11 that, together with γ-tubulin, builds the head-to-tail connecting piece [PMID:32392324]. Beyond septin networks, SEPT12 interacts with α/β-tubulins to organize the microtubule cytoskeleton during sperm head morphogenesis and tail elongation [PMID:24213608], and it tethers the cytoskeleton to the nuclear envelope through the SUN-domain proteins SPAG4/SUN4 and SUN5 together with LAMINB1, an arrangement required to keep the proximal centriole anchored to the nucleus [PMID:25775403, PMID:38870534, PMID:30866452]. SEPT12 polymerization is negatively regulated by CDC42 in its active state and by PKA-mediated phosphorylation on Ser198, both of which suppress filament assembly [PMID:30189608, PMID:30160375]. Transcription of the gene is hormonally controlled by direct androgen receptor and estrogen receptor α binding to its promoter [PMID:30513371]. Dominant-negative GTPase-domain mutations (T89M, D197N, T96I) and a splice variant impair GTP hydrolysis or binding, block filament formation, and cause teratozoospermia/oligozoospermia in men [PMID:22275165, PMID:22479503, PMID:39850804], while homozygous Septin12 knockout in mice causes infertility associated with loss of PLCζ and fertilization failure [PMID:35547809].","teleology":[{"year":2007,"claim":"Establishing SEPT12 as a bona fide septin required showing it had the biochemical hallmarks of the family and a defined cellular home, which placed it at the sperm annulus as a nucleotide- and lipid-binding filament protein.","evidence":"Yeast two-hybrid (SEPT5 bait), nucleotide and phosphoinositide binding assays, co-expression with SEPT4 in CHO cells","pmids":["17685441","18047794"],"confidence":"Medium","gaps":["Did not resolve the in vivo filament composition","Reported midbody/cytokinesis localization in cell lines was not reconciled with the testis-specific role"]},{"year":2008,"claim":"Determining how nucleotide state controls SEPT12 assembly distinguished GTP-dependent functions (filament formation, partner-septin binding) from GTP-independent self-interaction.","evidence":"In vitro GTP-binding assay with G56N GTP-motif mutant and immunocytochemistry in HeLa cells","pmids":["18443421"],"confidence":"High","gaps":["GTP hydrolysis kinetics not measured","Did not address whether hydrolysis versus binding drives filament dynamics"]},{"year":2012,"claim":"Linking SEPT12 to human disease showed that GTPase-domain mutations act dominant-negatively to poison wild-type filament assembly, explaining infertility phenotypes.","evidence":"GTP hydrolysis/binding assays and dose-dependent filament assays for T89M and D197N; splice variant causing exon 5 skipping with ex vivo filament assay","pmids":["22275165","22479503"],"confidence":"High","gaps":["Dominant-negative mechanism shown in cell lines, not yet in vivo at this stage","Effect on annulus shown indirectly"]},{"year":2013,"claim":"Connecting SEPT12 to the microtubule cytoskeleton revealed a role beyond septin filaments in organizing tubulin during sperm head and tail shaping.","evidence":"Co-IP with α/β-tubulin, transgenic mouse co-localization, shRNA knockdown with confocal microscopy","pmids":["24213608"],"confidence":"Medium","gaps":["Direct versus indirect tubulin binding not resolved","Mechanism of tubulin organization unknown"]},{"year":2015,"claim":"Defining the native filament architecture and a parallel nuclear-envelope role established both the octameric annulus filament stoichiometry and a SEPT12-SUN/LAMIN linkage in postmeiotic germ cells.","evidence":"Domain mapping, Co-IP, D197N knock-in mouse with EM for annulus filaments; Y2H and Co-IP for SPAG4/SUN4-LAMINB1 complexes","pmids":["25588830","25775403"],"confidence":"High","gaps":["How the GTP-binding domain selects SEPT7 structurally not solved","Functional consequence of nuclear-envelope linkage not yet tested in vivo"]},{"year":2016,"claim":"Identifying NDC1 as a partner provided a mechanism that can sequester SEPT12 to the nucleus and repress its filament assembly, adding spatial regulation.","evidence":"Y2H, Co-IP, NDC1 overexpression/localization, D197N knock-in mouse","pmids":["27854341"],"confidence":"Medium","gaps":["Physiological trigger for NDC1-mediated sequestration unknown","Reciprocal regulation not quantified"]},{"year":2018,"claim":"Two regulatory inputs onto SEPT12 polymerization were defined—PKA phosphorylation at Ser198 and active CDC42—both suppressing filament assembly, and the SEPT12 gene was placed under direct hormonal transcriptional control.","evidence":"Phosphomimetic S198 knock-in mouse with fertility/motility assays; CDC42 mutant expression with filament assays; ChIP and luciferase reporter for AR/ERα promoter binding","pmids":["30160375","30189608","30513371"],"confidence":"High","gaps":["How PKA and CDC42 inputs are integrated in time/space unknown","Endogenous Ser198 phosphorylation dynamics during spermiogenesis not mapped"]},{"year":2019,"claim":"A specificity test showed that SEPT12, uniquely among tested septins, remodels nuclear-membrane localization of SUN4 and LAMIN A/C, reinforcing its dedicated nuclear-envelope-tethering role.","evidence":"SEPT12 overexpression in a testicular cancer cell line with comparison against SEPT1/6/7/11","pmids":["30866452"],"confidence":"Medium","gaps":["Overexpression artifact versus physiological effect not excluded","Direct versus indirect remodeling not resolved"]},{"year":2020,"claim":"Resolving a second, neck-localized SEPT12 complex and its tie to pericentriolar γ-tubulin explained how SEPT12 contributes to the head-tail connecting piece, with the D197N mutation breaking this junction.","evidence":"Co-IP (SEPT1/2/10/11 and γ-tubulin), EM, immunofluorescence, D197N knock-in mouse","pmids":["32392324"],"confidence":"High","gaps":["Assembly order of the neck complex unknown","Relationship between annulus and neck filament pools not defined"]},{"year":2022,"claim":"A definitive loss-of-function model showed homozygous Septin12 knockout causes infertility and linked the fertilization defect to loss of acrosomal PLCζ, rescuable by artificial oocyte activation.","evidence":"Septin12 knockout mouse, ICSI with AOA, PLCζ immunofluorescence","pmids":["35547809"],"confidence":"Medium","gaps":["Mechanistic link between SEPT12 and PLCζ retention not established","Whether PLCζ loss is direct or secondary to morphological defects unclear"]},{"year":2024,"claim":"Identifying SUN5 as a SEPT12/LAMINB1 partner defined the molecular tether anchoring the proximal centriole to the nucleus, whose loss breaks the head-to-tail junction.","evidence":"IP-mass spectrometry, Co-IP, immunofluorescence, Sun5 knockout mouse","pmids":["38870534"],"confidence":"High","gaps":["Direct binding interface between SUN5 and SEPT12 not mapped","Stoichiometry of the LaminB1/SUN5/SEPT12 complex unknown"]},{"year":2025,"claim":"A new patient mutation (T96I) demonstrated that SEPT12 filament integrity is required for proper SEPT7 filament organization, tying a specific GTPase-domain lesion to annulus and acrosome defects.","evidence":"Overexpression in NT2/D1 cells, immunofluorescence, TEM, patient sperm phenotyping","pmids":["39850804"],"confidence":"Medium","gaps":["Effect on SEPT7 shown by overexpression rather than endogenous assay","Quantitative impact on GTP binding/hydrolysis for T96I not measured"]},{"year":null,"claim":"The mechanism by which SEPT12 filaments retain or position acrosomal PLCζ, and the structural basis of partner-septin selection, remain unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No high-resolution structure of SEPT12-containing filaments","Direct biochemical link from SEPT12 to PLCζ not established","Integration of CDC42, PKA, and NDC1 regulation during spermiogenesis unmapped"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0003924","term_label":"GTPase activity","supporting_discovery_ids":[2,3]},{"term_id":"GO:0005198","term_label":"structural molecule activity","supporting_discovery_ids":[0,6]},{"term_id":"GO:0008092","term_label":"cytoskeletal protein binding","supporting_discovery_ids":[5,13]},{"term_id":"GO:0008289","term_label":"lipid binding","supporting_discovery_ids":[0]}],"localization":[{"term_id":"GO:0005856","term_label":"cytoskeleton","supporting_discovery_ids":[0,6]},{"term_id":"GO:0005635","term_label":"nuclear envelope","supporting_discovery_ids":[7,12,15]}],"pathway":[{"term_id":"R-HSA-1474165","term_label":"Reproduction","supporting_discovery_ids":[6,14]},{"term_id":"R-HSA-1266738","term_label":"Developmental Biology","supporting_discovery_ids":[5,13]}],"complexes":["sperm annulus septin octamer (SEPT12-SEPT7-SEPT6-SEPT2/SEPT4)","sperm neck septin complex (SEPT12-SEPT1-SEPT2-SEPT10-SEPT11)","LaminB1/SUN5/SEPT12 nuclear-envelope complex"],"partners":["SEPT7","SEPT6","SEPT11","SPAG4","SUN5","LAMINB1","NDC1","CDC42"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q8IYM1","full_name":"Septin-12","aliases":[],"length_aa":358,"mass_kda":40.7,"function":"Filament-forming cytoskeletal GTPase (By similarity). Involved in spermatogenesis. Involved in the morphogenesis of sperm heads and the elongation of sperm tails probably implicating the association with alpha- and beta-tubulins (PubMed:24213608). Forms a filamentous structure with SEPTIN7, SEPTIN6, SEPTIN2 and probably SEPTIN4 at the sperm annulus which is required for the structural integrity and motility of the sperm tail during postmeiotic differentiation (PubMed:25588830). May play a role in cytokinesis (Potential)","subcellular_location":"Cytoplasm; Cytoplasm, cytoskeleton; Cytoplasm, cytoskeleton, spindle; Nucleus; Cell projection, cilium, flagellum","url":"https://www.uniprot.org/uniprotkb/Q8IYM1/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/SEPTIN12","classification":"Not Classified","n_dependent_lines":1,"n_total_lines":1090,"dependency_fraction":0.0009174311926605505},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/SEPTIN12","total_profiled":1310},"omim":[{"mim_id":"614822","title":"SPERMATOGENIC FAILURE 10; SPGF10","url":"https://www.omim.org/entry/614822"},{"mim_id":"611562","title":"SEPTIN 12; SEPTIN12","url":"https://www.omim.org/entry/611562"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Microtubules","reliability":"Supported"},{"location":"Annulus","reliability":"Additional"}],"tissue_specificity":"Tissue enriched","tissue_distribution":"Detected in some","driving_tissues":[{"tissue":"testis","ntpm":103.7}],"url":"https://www.proteinatlas.org/search/SEPTIN12"},"hgnc":{"alias_symbol":["FLJ25410"],"prev_symbol":["SEPT12"]},"alphafold":{"accession":"Q8IYM1","domains":[{"cath_id":"3.40.50.300","chopping":"37-55_63-113_125-319","consensus_level":"high","plddt":90.4296,"start":37,"end":319}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q8IYM1","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q8IYM1-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q8IYM1-F1-predicted_aligned_error_v6.png","plddt_mean":81.44},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=SEPTIN12","jax_strain_url":"https://www.jax.org/strain/search?query=SEPTIN12"},"sequence":{"accession":"Q8IYM1","fasta_url":"https://rest.uniprot.org/uniprotkb/Q8IYM1.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q8IYM1/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q8IYM1"}},"corpus_meta":[{"pmid":"22275165","id":"PMC_22275165","title":"SEPT12 mutations cause male infertility with defective sperm annulus.","date":"2012","source":"Human mutation","url":"https://pubmed.ncbi.nlm.nih.gov/22275165","citation_count":102,"is_preprint":false},{"pmid":"25588830","id":"PMC_25588830","title":"SEPT12 orchestrates the formation of mammalian sperm annulus by organizing core octameric complexes with other SEPT proteins.","date":"2015","source":"Journal of cell science","url":"https://pubmed.ncbi.nlm.nih.gov/25588830","citation_count":68,"is_preprint":false},{"pmid":"17685441","id":"PMC_17685441","title":"Sept12 is a component of the mammalian sperm tail annulus.","date":"2007","source":"Cell motility and the cytoskeleton","url":"https://pubmed.ncbi.nlm.nih.gov/17685441","citation_count":59,"is_preprint":false},{"pmid":"25775403","id":"PMC_25775403","title":"SEPT12/SPAG4/LAMINB1 complexes are required for maintaining the integrity of the nuclear envelope in postmeiotic male germ cells.","date":"2015","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/25775403","citation_count":48,"is_preprint":false},{"pmid":"22479503","id":"PMC_22479503","title":"SEPTIN12 genetic variants confer susceptibility to teratozoospermia.","date":"2012","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/22479503","citation_count":41,"is_preprint":false},{"pmid":"20801438","id":"PMC_20801438","title":"SEPT12 deficiency causes sperm nucleus damage and developmental arrest of preimplantation embryos.","date":"2011","source":"Fertility and sterility","url":"https://pubmed.ncbi.nlm.nih.gov/20801438","citation_count":34,"is_preprint":false},{"pmid":"24213608","id":"PMC_24213608","title":"SEPT12-microtubule complexes are required for sperm head and tail formation.","date":"2013","source":"International journal of molecular sciences","url":"https://pubmed.ncbi.nlm.nih.gov/24213608","citation_count":23,"is_preprint":false},{"pmid":"27854341","id":"PMC_27854341","title":"SEPT12-NDC1 Complexes Are Required for Mammalian Spermiogenesis.","date":"2016","source":"International journal of molecular sciences","url":"https://pubmed.ncbi.nlm.nih.gov/27854341","citation_count":21,"is_preprint":false},{"pmid":"21636737","id":"PMC_21636737","title":"Single-nucleotide polymorphisms in the SEPTIN12 gene may be a genetic risk factor for Japanese patients with Sertoli cell-only syndrome.","date":"2011","source":"Journal of andrology","url":"https://pubmed.ncbi.nlm.nih.gov/21636737","citation_count":20,"is_preprint":false},{"pmid":"32392324","id":"PMC_32392324","title":"The SEPT12 complex is required for the establishment of a functional sperm head-tail junction.","date":"2020","source":"Molecular human reproduction","url":"https://pubmed.ncbi.nlm.nih.gov/32392324","citation_count":18,"is_preprint":false},{"pmid":"30189608","id":"PMC_30189608","title":"CDC42 Negatively Regulates Testis-Specific SEPT12 Polymerization.","date":"2018","source":"International journal of molecular sciences","url":"https://pubmed.ncbi.nlm.nih.gov/30189608","citation_count":17,"is_preprint":false},{"pmid":"30866452","id":"PMC_30866452","title":"Testis-Specific SEPT12 Expression Affects SUN Protein Localization and is Involved in Mammalian Spermiogenesis.","date":"2019","source":"International journal of molecular sciences","url":"https://pubmed.ncbi.nlm.nih.gov/30866452","citation_count":15,"is_preprint":false},{"pmid":"30160375","id":"PMC_30160375","title":"Regulation of septin phosphorylation: SEPT12 phosphorylation in sperm septin assembly.","date":"2018","source":"Cytoskeleton (Hoboken, N.J.)","url":"https://pubmed.ncbi.nlm.nih.gov/30160375","citation_count":14,"is_preprint":false},{"pmid":"18047794","id":"PMC_18047794","title":"SEPT12 interacts with SEPT6 and this interaction alters the filament structure of SEPT6 in Hela cells.","date":"2007","source":"Journal of biochemistry and molecular biology","url":"https://pubmed.ncbi.nlm.nih.gov/18047794","citation_count":14,"is_preprint":false},{"pmid":"18443421","id":"PMC_18443421","title":"GTP binding is required for SEPT12 to form filaments and to interact with SEPT11.","date":"2008","source":"Molecules and cells","url":"https://pubmed.ncbi.nlm.nih.gov/18443421","citation_count":12,"is_preprint":false},{"pmid":"31880374","id":"PMC_31880374","title":"Single-nucleotide polymorphism c.474G>A in the SEPT12 gene is a predisposing factor in male infertility.","date":"2019","source":"Molecular reproduction and development","url":"https://pubmed.ncbi.nlm.nih.gov/31880374","citation_count":11,"is_preprint":false},{"pmid":"35547809","id":"PMC_35547809","title":"Homozygous Loss of Septin12, but not its Haploinsufficiency, Leads to Male Infertility and Fertilization Failure.","date":"2022","source":"Frontiers in cell and developmental biology","url":"https://pubmed.ncbi.nlm.nih.gov/35547809","citation_count":9,"is_preprint":false},{"pmid":"38870534","id":"PMC_38870534","title":"SUN5 interacts with nuclear membrane LaminB1 and cytoskeletal GTPase Septin12 mediating the sperm head-and-tail junction.","date":"2024","source":"Molecular human reproduction","url":"https://pubmed.ncbi.nlm.nih.gov/38870534","citation_count":8,"is_preprint":false},{"pmid":"22116646","id":"PMC_22116646","title":"Single nucleotide polymorphisms in the SEPTIN12 gene may be associated with azoospermia by meiotic arrest in Japanese men.","date":"2011","source":"Journal of assisted reproduction and genetics","url":"https://pubmed.ncbi.nlm.nih.gov/22116646","citation_count":7,"is_preprint":false},{"pmid":"30488758","id":"PMC_30488758","title":"Association of single nucleotide polymorphism c.673C>A/p.Gln225Lys in SEPT12 gene with spermatogenesis failure in male idiopathic infertility in Northeast China.","date":"2018","source":"The Journal of international medical research","url":"https://pubmed.ncbi.nlm.nih.gov/30488758","citation_count":5,"is_preprint":false},{"pmid":"26568753","id":"PMC_26568753","title":"New single nucleotide polymorphism G5508A in the SEPT12 gene may be associated with idiopathic male infertility in Iranian men.","date":"2015","source":"Iranian journal of reproductive medicine","url":"https://pubmed.ncbi.nlm.nih.gov/26568753","citation_count":3,"is_preprint":false},{"pmid":"39850804","id":"PMC_39850804","title":"A novel SEPT12 mutation, T96I, is associated with sperm head and annulus defects.","date":"2025","source":"Frontiers in cell and developmental biology","url":"https://pubmed.ncbi.nlm.nih.gov/39850804","citation_count":2,"is_preprint":false},{"pmid":"30513371","id":"PMC_30513371","title":"Identification of SEPTIN12 as a novel target of the androgen and estrogen receptors in human testicular cells.","date":"2018","source":"Biochimie","url":"https://pubmed.ncbi.nlm.nih.gov/30513371","citation_count":1,"is_preprint":false},{"pmid":"39672481","id":"PMC_39672481","title":"Sept10 and sept12 are expressed in specific proliferating cells in zebrafish brain.","date":"2024","source":"Gene expression patterns : GEP","url":"https://pubmed.ncbi.nlm.nih.gov/39672481","citation_count":1,"is_preprint":false},{"pmid":"40783874","id":"PMC_40783874","title":"[SEPT12 in male infertility: Advances in studies].","date":"2024","source":"Zhonghua nan ke xue = National journal of andrology","url":"https://pubmed.ncbi.nlm.nih.gov/40783874","citation_count":0,"is_preprint":false},{"pmid":"34057684","id":"PMC_34057684","title":"SEPTIN12 c.474 G > A polymorphism as a risk factor in teratozoospermic patients.","date":"2021","source":"Molecular biology reports","url":"https://pubmed.ncbi.nlm.nih.gov/34057684","citation_count":0,"is_preprint":false},{"pmid":"41927050","id":"PMC_41927050","title":"Functional characterization of porcine septin12 and its role in male reproduction.","date":"2026","source":"Animal bioscience","url":"https://pubmed.ncbi.nlm.nih.gov/41927050","citation_count":0,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":13904,"output_tokens":4312,"usd":0.053196,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":12341,"output_tokens":4335,"usd":0.08504,"stage2_stop_reason":"end_turn"},"total_usd":0.138236,"stage1_batch_id":"msgbatch_013LWZZT6MWaqB9qyTSeQBmU","stage2_batch_id":"msgbatch_0194ZzQaTGNpruoNJBbEMbt3","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2007,\n      \"finding\": \"SEPT12 was identified as a novel septin via yeast two-hybrid screen using SEPT5 as bait; it purifies with bound nucleotide, binds phosphoinositides, and co-localizes with SEPT4 into robust curved filaments when co-expressed in CHO cells, placing it at the sperm annulus.\",\n      \"method\": \"Yeast two-hybrid screen, nucleotide binding assay, phosphoinositide binding assay, co-expression/co-localization in CHO cells, RT-PCR, Northern blot, Western blot\",\n      \"journal\": \"Cell motility and the cytoskeleton\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal biochemical methods (nucleotide binding, lipid binding, co-localization), single lab\",\n      \"pmids\": [\"17685441\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"SEPT12 interacts with SEPT6 in vitro and in vivo (co-IP); co-expression of SEPT12 alters the filamentous structure of SEPT6 in HeLa cells. SEPT12 localizes to central spindle and midbody during anaphase and cytokinesis.\",\n      \"method\": \"Co-immunoprecipitation (in vitro and in vivo), co-expression in HeLa cells, immunocytochemistry\",\n      \"journal\": \"Journal of biochemistry and molecular biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal Co-IP plus co-expression functional readout, single lab, two methods\",\n      \"pmids\": [\"18047794\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"SEPT12 binds GTP in vitro; a G56N mutation in the GTP-binding motif abolishes binding. GTP binding is required for filament formation (G56N forms aggregates instead of filaments) and for interaction with SEPT11, but not for self-interaction.\",\n      \"method\": \"In vitro GTP-binding assay, site-directed mutagenesis, immunocytochemistry in HeLa cells\",\n      \"journal\": \"Molecules and cells\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro biochemical assay combined with mutagenesis and cellular phenotype, single lab but multiple orthogonal methods\",\n      \"pmids\": [\"18443421\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"Two missense mutations in the GTPase domain (T89M and D197N) identified in infertile men: T89M significantly reduces GTP hydrolytic activity; D197N interferes with GTP binding. Both mutant proteins restrict wild-type SEPT12 filament formation in a dose-dependent dominant-negative manner, disrupting sperm annulus integrity.\",\n      \"method\": \"GTP hydrolysis assay, GTP binding assay, filament formation assay, in silico structural modeling\",\n      \"journal\": \"Human mutation\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — enzymatic activity assays with mutagenesis plus dominant-negative filament assay, single lab with multiple orthogonal methods\",\n      \"pmids\": [\"22275165\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"A c.474G>A splice-site variant causes exon 5 skipping, producing a truncated SEPT12 lacking the C-terminal half; this truncated protein inhibits wild-type SEPT12 filament formation in a dose-dependent manner (ex vivo), and is associated with bent tail and nuclear DNA damage in sperm.\",\n      \"method\": \"DNA sequencing, RT-PCR splice assay, filament formation assay (ex vivo), immunocytochemistry\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — molecular characterization of variant plus functional filament assay, single lab, two methods\",\n      \"pmids\": [\"22479503\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"SEPT12 interacts with α- and β-tubulins by co-IP; SEPT12 co-localizes with tubulins during spermiogenesis in transgenic mice. shRNA-mediated loss of SEPT12 disrupts α- and β-tubulin organization and impairs sperm head morphogenesis and tail elongation.\",\n      \"method\": \"Co-immunoprecipitation, SEPTIN12-transgenic mouse model, shRNA knockdown, confocal microscopy\",\n      \"journal\": \"International journal of molecular sciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP plus in vivo transgenic localization and shRNA loss-of-function, single lab\",\n      \"pmids\": [\"24213608\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"SEPT12 assembles octameric filaments with SEPT7, SEPT6, SEPT2, and SEPT4 (arrangements 12-7-6-2-2-6-7-12 or 12-7-6-4-4-6-7-12) at the sperm annulus. The GTP-binding domain of SEPT12 is required for interaction with SEPT7, and N- and C-termini are required for SEPT12 self-polymerization into filaments. The D197N knock-in mouse shows disorganized annulus, bent tail, reduced sperm motility, and loss of SEPT ring structure.\",\n      \"method\": \"Co-immunoprecipitation, deletion/domain mapping, knock-in mouse model (D197N), electron microscopy, immunofluorescence\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — domain mapping with mutagenesis, Co-IP, knock-in mouse with multiple phenotypic readouts, replicated with human patient data\",\n      \"pmids\": [\"25588830\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"SEPT12 interacts with SPAG4 (SUN4) in a male germ cell line (co-IP). SEPT12, SPAG4, and LAMINB1 form complexes at the nuclear periphery of round spermatids. A SEPT12 disease mutation disrupts these nuclear envelope complexes (co-IP). SEPT12 links SEPT proteins to the SUN/LAMIN nuclear envelope complex during postmeiotic germ cell development.\",\n      \"method\": \"Yeast two-hybrid, co-immunoprecipitation, co-localization by confocal microscopy in germ cell line and human spermatogenic cells\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Y2H plus reciprocal Co-IP plus localization, single lab\",\n      \"pmids\": [\"25775403\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"SEPT12 interacts with NDC1 (nuclear pore complex protein) in male germ cell line (co-IP). NDC1 overexpression restricts SEPT12 localization to the nucleus and represses SEPT12 filament formation. In D197N mutant sperm, NDC1 disperses from the sperm neck to manchette region and annulus.\",\n      \"method\": \"Yeast two-hybrid, co-immunoprecipitation, overexpression/localization in germ cell line, knock-in mouse model\",\n      \"journal\": \"International journal of molecular sciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Y2H identification validated by Co-IP, functional overexpression, and in vivo mouse model, single lab\",\n      \"pmids\": [\"27854341\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"SEPT12 phosphorylation on Ser198 by Protein Kinase A (PKA) regulates sperm annulus architecture. A phosphomimetic SEPT12 S198 knock-in mouse shows poor male fertility, weak sperm motility, and loss of the sperm annulus. Phosphorylation at Ser198 interferes with SEPT12 polymerization into complexes and filaments.\",\n      \"method\": \"Knock-in mouse model (phosphomimetic), fertility assays, sperm motility analysis, filament polymerization assay, PKA kinase identification\",\n      \"journal\": \"Cytoskeleton (Hoboken, N.J.)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Moderate — phosphorylation site identified with writer (PKA), phosphomimetic knock-in mouse with functional consequences, multiple readouts\",\n      \"pmids\": [\"30160375\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"CDC42 negatively regulates SEPT12 polymerization. Wild-type CDC42 and constitutively active CDC42Q61L substantially repress SEPT12 polymerization, whereas dominant-negative CDC42T17N does not. CDC42 and SEPT12 co-localize in perinuclear manchette and midpiece regions of spermatids/spermatozoa.\",\n      \"method\": \"Ectopic expression analysis with CDC42 mutants, filament formation assay, scanning electron microscopy, co-localization by immunofluorescence\",\n      \"journal\": \"International journal of molecular sciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — gain/loss-of-function CDC42 mutants with functional filament readout and co-localization, single lab\",\n      \"pmids\": [\"30189608\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"The SEPT12 gene promoter is a 245 bp region upstream of the transcription start site. Androgen receptor (AR) and estrogen receptor α (ERα) directly bind this region (confirmed by chromatin immunoprecipitation). Truncation of AR or ERα binding sites decreases promoter activity; treatment with 17β-estradiol or 5α-dihydrotestosterone enhances promoter activity.\",\n      \"method\": \"Promoter deletion analysis, chromatin immunoprecipitation (ChIP), luciferase reporter assay\",\n      \"journal\": \"Biochimie\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1-2 / Moderate — ChIP plus reporter assay with deletion constructs and hormone treatment, single lab\",\n      \"pmids\": [\"30513371\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"SEPT12 expression alters nuclear membrane localization of SPAG4 (SUN4) and also alters localization of LAMINA/C; this effect is specific to SEPT12 and not observed with SEPT1, SEPT6, SEPT7, or SEPT11.\",\n      \"method\": \"Confocal microscopy after SEPT12 overexpression in testicular cancer cell line, comparison with other septins\",\n      \"journal\": \"International journal of molecular sciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — cell-based localization with specificity controls across multiple septins, single lab\",\n      \"pmids\": [\"30866452\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"SEPT12 forms a complex with SEPT1, SEPT2, SEPT10, and SEPT11 at the sperm neck. The D197N mutation disrupts this complex and causes defective connecting pieces (head-tail junction). SEPT12 interacts and co-localizes with γ-tubulin in elongating spermatids, suggesting SEPT12 and pericentriolar materials jointly form connecting pieces.\",\n      \"method\": \"Co-immunoprecipitation, electron microscopy, immunofluorescence, D197N knock-in mouse model\",\n      \"journal\": \"Molecular human reproduction\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Moderate — Co-IP plus knock-in mouse model plus EM structural analysis plus multiple partner identifications, single lab with multiple orthogonal methods\",\n      \"pmids\": [\"32392324\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Homozygous Septin12 knockout (but not heterozygous) male mice are infertile with reduced sperm counts and abnormal morphology. Loss of PLCζ around the acrosome in Septin12-null sperm is identified as the likely mechanism for fertilization failure, which can be rescued by artificial oocyte activation (AOA).\",\n      \"method\": \"Septin12 knockout mouse model, ICSI with AOA, immunofluorescence for PLCζ localization\",\n      \"journal\": \"Frontiers in cell and developmental biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — knockout mouse plus functional ICSI/AOA rescue plus immunofluorescence mechanistic marker, single lab\",\n      \"pmids\": [\"35547809\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"SUN5 interacts with SEPT12 (and LAMINB1) in mouse testis, identified by immunoprecipitation-mass spectrometry and validated by further studies. The SUN5-SEPT12 interaction promotes their co-aggregation at the sperm neck; Sun5 deficiency disrupts the LaminB1/SUN5/SEPT12 complex, causing separation of the SEPT12-proximal centriole from the nucleus and breakage of the head-to-tail junction.\",\n      \"method\": \"Immunoprecipitation-mass spectrometry, co-immunoprecipitation, immunofluorescence, Sun5 knockout mouse model\",\n      \"journal\": \"Molecular human reproduction\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Moderate — IP-MS identification, validated by Co-IP, functional knockout mouse showing complex disruption and structural consequence, multiple orthogonal methods\",\n      \"pmids\": [\"38870534\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"A novel SEPT12 T96I mutation causes male infertility; overexpression of SEPT12 T96I in NT2/D1 cells impairs SEPT7 filament formation, demonstrating that SEPT12 filament integrity is required for proper SEPT7 filament organization. Sperm from T96I carriers show obliquely positioned annulus with SEPT12/SEPT7 co-localization defects, large nuclear vacuoles, and acrosomal decondensation.\",\n      \"method\": \"Immunofluorescence, transmission electron microscopy, overexpression in NT2/D1 cells\",\n      \"journal\": \"Frontiers in cell and developmental biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 / Moderate — cell-based overexpression with functional filament readout, TEM structural analysis, and patient sperm phenotype, single lab\",\n      \"pmids\": [\"39850804\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"SEPTIN12 (SEPT12) is a testis-specific GTP-binding cytoskeletal protein that forms octameric heterofilaments with SEPT2, SEPT4, SEPT6, and SEPT7 at the sperm annulus, and with SEPT1, SEPT2, SEPT10, and SEPT11 at the sperm neck; its GTP-binding domain drives interaction with partner septins (especially SEPT7), while its N- and C-termini mediate self-polymerization into filaments that provide mechanical support for sperm motility and head-tail junction integrity. SEPT12 also links the cytoskeleton to the nuclear envelope by interacting with the SUN-domain proteins SPAG4/SUN4 and SUN5, and with LAMINB1, maintaining nuclear envelope integrity in postmeiotic germ cells; it additionally interacts with α/β-tubulins to coordinate sperm head morphogenesis and tail elongation, and its polymerization is negatively regulated by CDC42 and by PKA-mediated phosphorylation on Ser198. Disease mutations (T89M, D197N, T96I) impair GTP hydrolysis or binding, disrupt filament formation in a dominant-negative manner, and cause teratozoospermia/oligozoospermia in men, while homozygous knockout in mice causes infertility partly through loss of PLCζ and fertilization failure.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"SEPTIN12 (SEPT12) is a testis-enriched GTP-binding septin that polymerizes into cytoskeletal heterofilaments essential for sperm morphogenesis and male fertility [#0, #6]. It binds GTP and hydrolyzes it, and this nucleotide state governs its behavior: GTP binding is required for filament formation and for interaction with partner septins such as SEPT11, while self-interaction is GTP-independent [#2]. SEPT12 assembles into octameric filaments with SEPT7, SEPT6, SEPT2, and SEPT4 at the sperm annulus, with its GTP-binding domain mediating the SEPT7 interaction and its N- and C-termini driving self-polymerization [#6]; at the sperm neck it forms a distinct complex with SEPT1, SEPT2, SEPT10, and SEPT11 that, together with γ-tubulin, builds the head-to-tail connecting piece [#13]. Beyond septin networks, SEPT12 interacts with α/β-tubulins to organize the microtubule cytoskeleton during sperm head morphogenesis and tail elongation [#5], and it tethers the cytoskeleton to the nuclear envelope through the SUN-domain proteins SPAG4/SUN4 and SUN5 together with LAMINB1, an arrangement required to keep the proximal centriole anchored to the nucleus [#7, #15, #12]. SEPT12 polymerization is negatively regulated by CDC42 in its active state and by PKA-mediated phosphorylation on Ser198, both of which suppress filament assembly [#10, #9]. Transcription of the gene is hormonally controlled by direct androgen receptor and estrogen receptor α binding to its promoter [#11]. Dominant-negative GTPase-domain mutations (T89M, D197N, T96I) and a splice variant impair GTP hydrolysis or binding, block filament formation, and cause teratozoospermia/oligozoospermia in men [#3, #4, #16], while homozygous Septin12 knockout in mice causes infertility associated with loss of PLCζ and fertilization failure [#14].\",\n  \"teleology\": [\n    {\n      \"year\": 2007,\n      \"claim\": \"Establishing SEPT12 as a bona fide septin required showing it had the biochemical hallmarks of the family and a defined cellular home, which placed it at the sperm annulus as a nucleotide- and lipid-binding filament protein.\",\n      \"evidence\": \"Yeast two-hybrid (SEPT5 bait), nucleotide and phosphoinositide binding assays, co-expression with SEPT4 in CHO cells\",\n      \"pmids\": [\"17685441\", \"18047794\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Did not resolve the in vivo filament composition\", \"Reported midbody/cytokinesis localization in cell lines was not reconciled with the testis-specific role\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Determining how nucleotide state controls SEPT12 assembly distinguished GTP-dependent functions (filament formation, partner-septin binding) from GTP-independent self-interaction.\",\n      \"evidence\": \"In vitro GTP-binding assay with G56N GTP-motif mutant and immunocytochemistry in HeLa cells\",\n      \"pmids\": [\"18443421\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"GTP hydrolysis kinetics not measured\", \"Did not address whether hydrolysis versus binding drives filament dynamics\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Linking SEPT12 to human disease showed that GTPase-domain mutations act dominant-negatively to poison wild-type filament assembly, explaining infertility phenotypes.\",\n      \"evidence\": \"GTP hydrolysis/binding assays and dose-dependent filament assays for T89M and D197N; splice variant causing exon 5 skipping with ex vivo filament assay\",\n      \"pmids\": [\"22275165\", \"22479503\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Dominant-negative mechanism shown in cell lines, not yet in vivo at this stage\", \"Effect on annulus shown indirectly\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Connecting SEPT12 to the microtubule cytoskeleton revealed a role beyond septin filaments in organizing tubulin during sperm head and tail shaping.\",\n      \"evidence\": \"Co-IP with α/β-tubulin, transgenic mouse co-localization, shRNA knockdown with confocal microscopy\",\n      \"pmids\": [\"24213608\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct versus indirect tubulin binding not resolved\", \"Mechanism of tubulin organization unknown\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Defining the native filament architecture and a parallel nuclear-envelope role established both the octameric annulus filament stoichiometry and a SEPT12-SUN/LAMIN linkage in postmeiotic germ cells.\",\n      \"evidence\": \"Domain mapping, Co-IP, D197N knock-in mouse with EM for annulus filaments; Y2H and Co-IP for SPAG4/SUN4-LAMINB1 complexes\",\n      \"pmids\": [\"25588830\", \"25775403\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How the GTP-binding domain selects SEPT7 structurally not solved\", \"Functional consequence of nuclear-envelope linkage not yet tested in vivo\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Identifying NDC1 as a partner provided a mechanism that can sequester SEPT12 to the nucleus and repress its filament assembly, adding spatial regulation.\",\n      \"evidence\": \"Y2H, Co-IP, NDC1 overexpression/localization, D197N knock-in mouse\",\n      \"pmids\": [\"27854341\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Physiological trigger for NDC1-mediated sequestration unknown\", \"Reciprocal regulation not quantified\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Two regulatory inputs onto SEPT12 polymerization were defined—PKA phosphorylation at Ser198 and active CDC42—both suppressing filament assembly, and the SEPT12 gene was placed under direct hormonal transcriptional control.\",\n      \"evidence\": \"Phosphomimetic S198 knock-in mouse with fertility/motility assays; CDC42 mutant expression with filament assays; ChIP and luciferase reporter for AR/ERα promoter binding\",\n      \"pmids\": [\"30160375\", \"30189608\", \"30513371\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How PKA and CDC42 inputs are integrated in time/space unknown\", \"Endogenous Ser198 phosphorylation dynamics during spermiogenesis not mapped\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"A specificity test showed that SEPT12, uniquely among tested septins, remodels nuclear-membrane localization of SUN4 and LAMIN A/C, reinforcing its dedicated nuclear-envelope-tethering role.\",\n      \"evidence\": \"SEPT12 overexpression in a testicular cancer cell line with comparison against SEPT1/6/7/11\",\n      \"pmids\": [\"30866452\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Overexpression artifact versus physiological effect not excluded\", \"Direct versus indirect remodeling not resolved\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Resolving a second, neck-localized SEPT12 complex and its tie to pericentriolar γ-tubulin explained how SEPT12 contributes to the head-tail connecting piece, with the D197N mutation breaking this junction.\",\n      \"evidence\": \"Co-IP (SEPT1/2/10/11 and γ-tubulin), EM, immunofluorescence, D197N knock-in mouse\",\n      \"pmids\": [\"32392324\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Assembly order of the neck complex unknown\", \"Relationship between annulus and neck filament pools not defined\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"A definitive loss-of-function model showed homozygous Septin12 knockout causes infertility and linked the fertilization defect to loss of acrosomal PLCζ, rescuable by artificial oocyte activation.\",\n      \"evidence\": \"Septin12 knockout mouse, ICSI with AOA, PLCζ immunofluorescence\",\n      \"pmids\": [\"35547809\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanistic link between SEPT12 and PLCζ retention not established\", \"Whether PLCζ loss is direct or secondary to morphological defects unclear\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Identifying SUN5 as a SEPT12/LAMINB1 partner defined the molecular tether anchoring the proximal centriole to the nucleus, whose loss breaks the head-to-tail junction.\",\n      \"evidence\": \"IP-mass spectrometry, Co-IP, immunofluorescence, Sun5 knockout mouse\",\n      \"pmids\": [\"38870534\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct binding interface between SUN5 and SEPT12 not mapped\", \"Stoichiometry of the LaminB1/SUN5/SEPT12 complex unknown\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"A new patient mutation (T96I) demonstrated that SEPT12 filament integrity is required for proper SEPT7 filament organization, tying a specific GTPase-domain lesion to annulus and acrosome defects.\",\n      \"evidence\": \"Overexpression in NT2/D1 cells, immunofluorescence, TEM, patient sperm phenotyping\",\n      \"pmids\": [\"39850804\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Effect on SEPT7 shown by overexpression rather than endogenous assay\", \"Quantitative impact on GTP binding/hydrolysis for T96I not measured\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"The mechanism by which SEPT12 filaments retain or position acrosomal PLCζ, and the structural basis of partner-septin selection, remain unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No high-resolution structure of SEPT12-containing filaments\", \"Direct biochemical link from SEPT12 to PLCζ not established\", \"Integration of CDC42, PKA, and NDC1 regulation during spermiogenesis unmapped\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0003924\", \"supporting_discovery_ids\": [2, 3]},\n      {\"term_id\": \"GO:0005198\", \"supporting_discovery_ids\": [0, 6]},\n      {\"term_id\": \"GO:0008092\", \"supporting_discovery_ids\": [5, 13]},\n      {\"term_id\": \"GO:0008289\", \"supporting_discovery_ids\": [0]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005856\", \"supporting_discovery_ids\": [0, 6]},\n      {\"term_id\": \"GO:0005635\", \"supporting_discovery_ids\": [7, 12, 15]},\n      {\"term_id\": \"GO:0015630\", \"supporting_discovery_ids\": [5]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-1474165\", \"supporting_discovery_ids\": [6, 14]},\n      {\"term_id\": \"R-HSA-1266738\", \"supporting_discovery_ids\": [5, 13]}\n    ],\n    \"complexes\": [\n      \"sperm annulus septin octamer (SEPT12-SEPT7-SEPT6-SEPT2/SEPT4)\",\n      \"sperm neck septin complex (SEPT12-SEPT1-SEPT2-SEPT10-SEPT11)\",\n      \"LaminB1/SUN5/SEPT12 nuclear-envelope complex\"\n    ],\n    \"partners\": [\n      \"SEPT7\",\n      \"SEPT6\",\n      \"SEPT11\",\n      \"SPAG4\",\n      \"SUN5\",\n      \"LAMINB1\",\n      \"NDC1\",\n      \"CDC42\"\n    ],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":7,"faith_total":7,"faith_pct":100.0}}