TEKT2

TEKT2 is a tektin family structural protein of the sperm flagellum that organizes the cytoarchitecture of the middle piece by bridging the outer dense fiber to the surrounding mitochondrial sheath. It localizes to the periphery of the outer dense fiber and physically interacts with TEKT2BP1/Ccdc172, which resides at the mitochondrial sheath, positioning the TEKT2-TEKT2BP1 complex as a structural link between these two compartments (PMID:24394471). A distinct head-associated pool of TEKT2 is present at the acrosome cap of spermatozoa (PMID:27883267). Its expression is controlled by tissue-specific transcriptional inputs: TULP1 activates the tekt2 promoter to support photoreceptor cilium length (PMID:36396940), TBX5 binds the TEKT2 promoter and drives its transcription in cardiomyocytes (PMID:36936432), and Oog1 suppresses Tekt2 in female germ cells (PMID:29731491). Beyond ciliary and flagellar contexts, TEKT2 regulates podocyte cytoskeletal dynamics downstream of high-glucose stimulation, where its loss preserves NPHS1 levels and prevents cytoskeletal remodeling (PMID:36251411). TEKT2 protein is reduced in human non-obstructive azoospermia and teratozoospermia in the absence of coding or regulatory-region mutations, indicating epigenetic or post-transcriptional downregulation (PMID:42133143).

1. 2014 Medium

   Established the structural role of TEKT2 in the sperm middle piece by identifying its physical partner and the spatial logic of their interaction.

   Evidence Yeast two-hybrid screening with immunocytochemical localization in sperm flagella

   PMID:24394471

   Open questions at the time

   • No reciprocal co-IP or in vitro reconstitution of the TEKT2-TEKT2BP1 complex
   • Functional consequence of disrupting the bridge not tested
   • Filament assembly mechanism not addressed
2. 2016 Low

   Revealed that TEKT2 has a head-localized pool at the acrosome cap distinct from its flagellar distribution, broadening its possible roles in sperm.

   Evidence Immunofluorescence on bull spermatozoa

   PMID:27883267

   Open questions at the time

   • Single immunolocalization method without functional test
   • Role of the acrosomal pool unknown
   • Not confirmed in other species
3. 2018 Medium

   Showed that TEKT2 expression is actively repressed in female germ cells, identifying Oog1 as a negative transcriptional regulator and explaining its germline sex specificity.

   Evidence RNAi transgenic mouse with qRT-PCR readout in ovaries

   PMID:29731491

   Open questions at the time

   • Direct versus indirect repression not distinguished
   • Single qRT-PCR readout
   • No protein-level confirmation
4. 2022 Medium

   Placed TEKT2 downstream of TULP1 in a transcriptional pathway governing photoreceptor cilium structure, extending its role beyond sperm to sensory cilia.

   Evidence CRISPR knockout zebrafish, RNA-seq, and dual-luciferase reporter assay

   PMID:36396940

   Open questions at the time

   • Whether TEKT2 acts as a structural cilium component in photoreceptors not directly shown
   • No rescue of cilium length by TEKT2
   • Mechanism linking promoter activation to ciliary phenotype unresolved
5. 2022 Medium

   Demonstrated a non-ciliary function for TEKT2 in regulating podocyte cytoskeletal dynamics, linking it to glucose-induced remodeling and slit-diaphragm protein levels.

   Evidence siRNA knockdown in cultured podocytes with cytoskeletal imaging and NPHS1 Western blot

   PMID:36251411

   Open questions at the time

   • Molecular mechanism connecting TEKT2 to NPHS1 not defined
   • In vitro culture only, no in vivo confirmation
   • Whether effect is direct cytoskeletal or transcriptional unclear
6. 2023 Medium

   Identified TBX5 as a direct transcriptional activator of TEKT2 in cardiomyocytes, defining a tissue-specific regulatory input distinct from germline control.

   Evidence ChIP and qPCR after TBX5 knockdown in HL-1 cardiomyocytes

   PMID:36936432

   Open questions at the time

   • Functional role of TEKT2 in cardiomyocytes not established
   • No structural or phenotypic consequence tested
   • Single cell line
7. 2026 Medium

   Connected TEKT2 to human male infertility phenotypes and showed that downregulation is not driven by sequence variants, pointing toward epigenetic/post-transcriptional control.

   Evidence Western blotting on human NoA and teratozoospermia samples plus Sanger sequencing of the regulatory region

   PMID:42133143

   Open questions at the time

   • Specific epigenetic or post-transcriptional mechanism not identified
   • Causality versus correlation with infertility not established
   • Small clinical cohort

• How TEKT2 assembles into tektin filaments and mechanically couples the outer dense fiber to the mitochondrial sheath, and what unifies its roles across flagella, sensory cilia, and podocytes, remains unresolved.
• No structural model of TEKT2 filament assembly
• No knockout fertility phenotype in the corpus
• Mechanistic basis of non-ciliary podocyte function undefined