Affinage

SEPTIN12

Septin-12 · UniProt Q8IYM1

Length
358 aa
Mass
40.7 kDa
Annotated
2026-06-10
27 papers in source corpus 17 papers cited in narrative 17 extracted findings
Cross-family judge vs UniProt: Affinage preferred faithfulness: 7/7 claims corpus-supported (100%)

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

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).

Mechanistic history

Synthesis pass · year-by-year structured walk · 12 steps
  1. 2007 Medium

    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

    PMID:17685441 PMID:18047794

    Open questions at the time
    • Did not resolve the in vivo filament composition
    • Reported midbody/cytokinesis localization in cell lines was not reconciled with the testis-specific role
  2. 2008 High

    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

    PMID:18443421

    Open questions at the time
    • GTP hydrolysis kinetics not measured
    • Did not address whether hydrolysis versus binding drives filament dynamics
  3. 2012 High

    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

    PMID:22275165 PMID:22479503

    Open questions at the time
    • Dominant-negative mechanism shown in cell lines, not yet in vivo at this stage
    • Effect on annulus shown indirectly
  4. 2013 Medium

    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

    PMID:24213608

    Open questions at the time
    • Direct versus indirect tubulin binding not resolved
    • Mechanism of tubulin organization unknown
  5. 2015 High

    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

    PMID:25588830 PMID:25775403

    Open questions at the time
    • How the GTP-binding domain selects SEPT7 structurally not solved
    • Functional consequence of nuclear-envelope linkage not yet tested in vivo
  6. 2016 Medium

    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

    PMID:27854341

    Open questions at the time
    • Physiological trigger for NDC1-mediated sequestration unknown
    • Reciprocal regulation not quantified
  7. 2018 High

    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

    PMID:30160375 PMID:30189608 PMID:30513371

    Open questions at the time
    • How PKA and CDC42 inputs are integrated in time/space unknown
    • Endogenous Ser198 phosphorylation dynamics during spermiogenesis not mapped
  8. 2019 Medium

    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

    PMID:30866452

    Open questions at the time
    • Overexpression artifact versus physiological effect not excluded
    • Direct versus indirect remodeling not resolved
  9. 2020 High

    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

    PMID:32392324

    Open questions at the time
    • Assembly order of the neck complex unknown
    • Relationship between annulus and neck filament pools not defined
  10. 2022 Medium

    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

    PMID:35547809

    Open questions at the time
    • Mechanistic link between SEPT12 and PLCζ retention not established
    • Whether PLCζ loss is direct or secondary to morphological defects unclear
  11. 2024 High

    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

    PMID:38870534

    Open questions at the time
    • Direct binding interface between SUN5 and SEPT12 not mapped
    • Stoichiometry of the LaminB1/SUN5/SEPT12 complex unknown
  12. 2025 Medium

    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

    PMID:39850804

    Open questions at the time
    • Effect on SEPT7 shown by overexpression rather than endogenous assay
    • Quantitative impact on GTP binding/hydrolysis for T96I not measured

Open questions

Synthesis pass · forward-looking unresolved questions
  • The mechanism by which SEPT12 filaments retain or position acrosomal PLCζ, and the structural basis of partner-septin selection, remain unresolved.
  • 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

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0003924 GTPase activity 2 GO:0005198 structural molecule activity 2 GO:0008092 cytoskeletal protein binding 2 GO:0008289 lipid binding 1
Localization
GO:0005635 nuclear envelope 3 GO:0005856 cytoskeleton 2
Pathway
R-HSA-1266738 Developmental Biology 2 R-HSA-1474165 Reproduction 2
Complex memberships
LaminB1/SUN5/SEPT12 nuclear-envelope complexsperm annulus septin octamer (SEPT12-SEPT7-SEPT6-SEPT2/SEPT4)sperm neck septin complex (SEPT12-SEPT1-SEPT2-SEPT10-SEPT11)

Evidence

Reading pass · 17 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
2007 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. Yeast two-hybrid screen, nucleotide binding assay, phosphoinositide binding assay, co-expression/co-localization in CHO cells, RT-PCR, Northern blot, Western blot Cell motility and the cytoskeleton Medium 17685441
2007 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. Co-immunoprecipitation (in vitro and in vivo), co-expression in HeLa cells, immunocytochemistry Journal of biochemistry and molecular biology Medium 18047794
2008 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. In vitro GTP-binding assay, site-directed mutagenesis, immunocytochemistry in HeLa cells Molecules and cells High 18443421
2012 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. GTP hydrolysis assay, GTP binding assay, filament formation assay, in silico structural modeling Human mutation High 22275165
2012 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. DNA sequencing, RT-PCR splice assay, filament formation assay (ex vivo), immunocytochemistry PloS one Medium 22479503
2013 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. Co-immunoprecipitation, SEPTIN12-transgenic mouse model, shRNA knockdown, confocal microscopy International journal of molecular sciences Medium 24213608
2015 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. Co-immunoprecipitation, deletion/domain mapping, knock-in mouse model (D197N), electron microscopy, immunofluorescence Journal of cell science High 25588830
2015 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. Yeast two-hybrid, co-immunoprecipitation, co-localization by confocal microscopy in germ cell line and human spermatogenic cells PloS one Medium 25775403
2016 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. Yeast two-hybrid, co-immunoprecipitation, overexpression/localization in germ cell line, knock-in mouse model International journal of molecular sciences Medium 27854341
2018 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. Knock-in mouse model (phosphomimetic), fertility assays, sperm motility analysis, filament polymerization assay, PKA kinase identification Cytoskeleton (Hoboken, N.J.) High 30160375
2018 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. Ectopic expression analysis with CDC42 mutants, filament formation assay, scanning electron microscopy, co-localization by immunofluorescence International journal of molecular sciences Medium 30189608
2018 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. Promoter deletion analysis, chromatin immunoprecipitation (ChIP), luciferase reporter assay Biochimie Medium 30513371
2019 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. Confocal microscopy after SEPT12 overexpression in testicular cancer cell line, comparison with other septins International journal of molecular sciences Medium 30866452
2020 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. Co-immunoprecipitation, electron microscopy, immunofluorescence, D197N knock-in mouse model Molecular human reproduction High 32392324
2022 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). Septin12 knockout mouse model, ICSI with AOA, immunofluorescence for PLCζ localization Frontiers in cell and developmental biology Medium 35547809
2024 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. Immunoprecipitation-mass spectrometry, co-immunoprecipitation, immunofluorescence, Sun5 knockout mouse model Molecular human reproduction High 38870534
2025 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. Immunofluorescence, transmission electron microscopy, overexpression in NT2/D1 cells Frontiers in cell and developmental biology Medium 39850804

Source papers

Stage 0 corpus · 27 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
2012 SEPT12 mutations cause male infertility with defective sperm annulus. Human mutation 102 22275165
2015 SEPT12 orchestrates the formation of mammalian sperm annulus by organizing core octameric complexes with other SEPT proteins. Journal of cell science 68 25588830
2007 Sept12 is a component of the mammalian sperm tail annulus. Cell motility and the cytoskeleton 59 17685441
2015 SEPT12/SPAG4/LAMINB1 complexes are required for maintaining the integrity of the nuclear envelope in postmeiotic male germ cells. PloS one 48 25775403
2012 SEPTIN12 genetic variants confer susceptibility to teratozoospermia. PloS one 41 22479503
2011 SEPT12 deficiency causes sperm nucleus damage and developmental arrest of preimplantation embryos. Fertility and sterility 34 20801438
2013 SEPT12-microtubule complexes are required for sperm head and tail formation. International journal of molecular sciences 23 24213608
2016 SEPT12-NDC1 Complexes Are Required for Mammalian Spermiogenesis. International journal of molecular sciences 21 27854341
2011 Single-nucleotide polymorphisms in the SEPTIN12 gene may be a genetic risk factor for Japanese patients with Sertoli cell-only syndrome. Journal of andrology 20 21636737
2020 The SEPT12 complex is required for the establishment of a functional sperm head-tail junction. Molecular human reproduction 18 32392324
2018 CDC42 Negatively Regulates Testis-Specific SEPT12 Polymerization. International journal of molecular sciences 17 30189608
2019 Testis-Specific SEPT12 Expression Affects SUN Protein Localization and is Involved in Mammalian Spermiogenesis. International journal of molecular sciences 15 30866452
2018 Regulation of septin phosphorylation: SEPT12 phosphorylation in sperm septin assembly. Cytoskeleton (Hoboken, N.J.) 14 30160375
2007 SEPT12 interacts with SEPT6 and this interaction alters the filament structure of SEPT6 in Hela cells. Journal of biochemistry and molecular biology 14 18047794
2008 GTP binding is required for SEPT12 to form filaments and to interact with SEPT11. Molecules and cells 12 18443421
2019 Single-nucleotide polymorphism c.474G>A in the SEPT12 gene is a predisposing factor in male infertility. Molecular reproduction and development 11 31880374
2022 Homozygous Loss of Septin12, but not its Haploinsufficiency, Leads to Male Infertility and Fertilization Failure. Frontiers in cell and developmental biology 9 35547809
2024 SUN5 interacts with nuclear membrane LaminB1 and cytoskeletal GTPase Septin12 mediating the sperm head-and-tail junction. Molecular human reproduction 8 38870534
2011 Single nucleotide polymorphisms in the SEPTIN12 gene may be associated with azoospermia by meiotic arrest in Japanese men. Journal of assisted reproduction and genetics 7 22116646
2018 Association of single nucleotide polymorphism c.673C>A/p.Gln225Lys in SEPT12 gene with spermatogenesis failure in male idiopathic infertility in Northeast China. The Journal of international medical research 5 30488758
2015 New single nucleotide polymorphism G5508A in the SEPT12 gene may be associated with idiopathic male infertility in Iranian men. Iranian journal of reproductive medicine 3 26568753
2025 A novel SEPT12 mutation, T96I, is associated with sperm head and annulus defects. Frontiers in cell and developmental biology 2 39850804
2024 Sept10 and sept12 are expressed in specific proliferating cells in zebrafish brain. Gene expression patterns : GEP 1 39672481
2018 Identification of SEPTIN12 as a novel target of the androgen and estrogen receptors in human testicular cells. Biochimie 1 30513371
2026 Functional characterization of porcine septin12 and its role in male reproduction. Animal bioscience 0 41927050
2024 [SEPT12 in male infertility: Advances in studies]. Zhonghua nan ke xue = National journal of andrology 0 40783874
2021 SEPTIN12 c.474 G > A polymorphism as a risk factor in teratozoospermic patients. Molecular biology reports 0 34057684

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