TEX12

TEX12 is an essential meiosis-specific structural component of the synaptonemal complex (SC) central element that mediates propagation of chromosomal synapsis and the maturation of recombination intermediates into crossovers (PMID:16968740, PMID:18611960). It functions as an obligate partner of SYCE2, with which it forms a highly stable, constitutive hetero-oligomeric complex (SYCE2 tetramer plus two TEX12 dimers) that spontaneously self-assembles into central-element-like filaments (PMID:22870393); crystallographic and biophysical analysis resolves this as 2:2 coiled-coil building blocks that dimerize and associate end-to-end and laterally into micrometer-long, intermediate-filament-like bundled fibers defining the SC midline (PMID:34373646). The C-terminal tip of TEX12 governs both its own dimeric coiled-coil conformation/oligomeric state and the SYCE2-TEX12 fibrous assembly reaction (PMID:36071143). Chromosomal recruitment of the SYCE2-TEX12 complex depends on SYCP1 and is mediated through SYCE3, which remodels the SYCP1 lattice to dock the central element complexes, while TEX12 in turn stabilizes the opposing SYCP1 N-termini at the transverse-filament/central-element junction (PMID:16968740, PMID:27103161, PMID:36635604). SC disassembly at the prophase-to-metaphase I transition is triggered by direct PLK1 phosphorylation of TEX12, which drives its removal from the SC (PMID:22854038). Beyond meiotic chromosomes, TEX12 localizes to centrosomes, where phosphorylation on tyrosine 48 mediates centrosome amplification when TEX12 is aberrantly expressed in somatic and cancer cells (PMID:34880391).

1. 2006 High

   Established TEX12 as a central element protein and defined its position in the SC interaction network, answering where in the SC TEX12 acts and which partners it depends on.

   Evidence Co-IP, immunofluorescence and immunoEM in mouse meiocytes with Sycp1/Syce1/Syce2 knockouts

   PMID:16968740

   Open questions at the time

   • Did not define stoichiometry or the structural basis of the SYCE2-TEX12 interaction
   • Direct vs. indirect nature of the SYCE1 link not resolved
2. 2008 High

   Demonstrated that TEX12 is functionally required not just for SC structure but for synapsis propagation and crossover maturation, linking the central element to recombination outcomes.

   Evidence Tex12 knockout mouse with SC structural analysis and recombination marker readouts

   PMID:18611960

   Open questions at the time

   • Molecular mechanism coupling central element assembly to crossover maturation not defined
   • Whether the recombination defect is direct or secondary to synapsis failure unresolved
3. 2012 High

   Resolved the stoichiometry and self-assembly capacity of the SYCE2-TEX12 complex, showing it is the minimal fiber-forming unit of the central element.

   Evidence Biochemical reconstitution, AUC/gel filtration and EM of human SYCE2-TEX12

   PMID:22870393

   Open questions at the time

   • Atomic-resolution architecture of the building block not yet determined
   • How reconstituted fibers relate to in vivo midline geometry unclear
4. 2012 High

   Identified the regulated disassembly mechanism, showing PLK1 phosphorylation of TEX12 drives central element removal at prophase exit.

   Evidence In vitro PLK1 kinase assay plus PLK1 inhibition (BI 2536) in ex vivo spermatocytes

   PMID:22854038

   Open questions at the time

   • Specific phosphosites on TEX12 not mapped
   • Whether phosphorylation directly destabilizes the SYCE2-TEX12 fiber unknown
5. 2016 Medium

   Placed TEX12 in the interdependent stabilization of opposing SYCP1 N-termini, defining how central element proteins build the transverse-filament junction.

   Evidence ImmunoEM in SYCE2/TEX12-deficient meiocytes

   PMID:27103161

   Open questions at the time

   • Single lab, immunoEM-based; direct TEX12-SYCP1 contact not biochemically demonstrated
6. 2021 High

   Provided the atomic and hierarchical assembly mechanism, defining SYCE2-TEX12 as an intermediate-filament-like fiber that builds the SC midline.

   Evidence X-ray crystallography, SAXS/AUC/SEC-MALS, mutagenesis and EM

   PMID:34373646

   Open questions at the time

   • In vivo fiber dimensions and dynamics not directly imaged
   • Contribution of other CE proteins to native fiber assembly not captured in reconstitution
7. 2021 Medium

   Revealed a meiosis-independent centrosomal role for TEX12 and a pathological function when ectopically expressed, implicating Y48 phosphorylation in centrosome amplification.

   Evidence Immunofluorescence, ectopic expression, Y48 phospho-mutant, siRNA and retinoic acid assays in somatic/cancer cells

   PMID:34880391

   Open questions at the time

   • Kinase responsible for Y48 phosphorylation unidentified
   • Mechanism of centrosome amplification not defined
   • Single lab, requires independent confirmation
8. 2021 Low

   Proposed a direct ZMM-to-central-element link via TEX11-TEX12 interaction, coupling crossover machinery to SC assembly.

   Evidence Protein interaction assay (method not detailed) with comparison to yeast Zip4-Ecm11

   PMID:34969823

   Open questions at the time

   • Mammalian TEX11-TEX12 interaction method undescribed and not independently validated
   • Functional consequence of the interaction not tested
9. 2022 High

   Mapped the TEX12 C-terminal tip as the dual control element governing both TEX12's own oligomeric conformation and SYCE2-TEX12 fiber assembly.

   Evidence X-ray crystallography of TEX12 mutants, SAXS, dynamic light scattering and mutagenesis

   PMID:36071143

   Open questions at the time

   • In vivo consequence of tip mutations on synapsis not tested
   • How conformational switching is regulated in cells unknown
10. 2023 High

    Defined SYCE3 as the recruiter of SYCE2-TEX12, showing it remodels the SYCP1 lattice to dock central element complexes.

    Evidence Biochemistry, separation-of-function mutagenesis in mice, pulldowns and structural analysis

    PMID:36635604

    Open questions at the time

    • Temporal ordering of SYCE3 remodeling relative to TEX12 fiber growth not resolved
    • Direct SYCE3-TEX12 contact surface not defined
11. 2025 Medium

    Validated cross-species conservation of the 2:2 heterocomplex architecture via the yeast Ecm11-Gmc2 ortholog, reinforcing the structural principle underlying SYCE2-TEX12.

    Evidence Reconstitution and biophysics of yeast Ecm11-Gmc2 with in vivo mutagenesis

    PMID:41537827

    Open questions at the time

    • Concerns yeast orthologs and does not directly interrogate mammalian TEX12
    • Sequence-level conservation of TEX12 interfaces not addressed

• How TEX12's centrosomal/oncogenic function mechanistically relates to its SC structural role, and how phosphoregulation (PLK1, Y48) integrates assembly and disassembly, remain open.
• Kinase for Y48 and full PLK1 phosphosite map unknown
• Direct mechanism of centrosome amplification undefined
• No structural model of TEX12 at the centrosome