Pathogenic TEX14 Variants Disrupt Intercellular Bridge Formation, Causing Meiotic Arrest and Non-Obstructive Azoospermia in Humans and Mice.

BACKGROUND

Non-obstructive azoospermia (NOA) is a major cause of male infertility, frequently associated with congenital factors. Nevertheless, the genetic underpinnings of NOA remain largely unclear.

OBJECTIVES

This study aimed to identify and characterize novel genetic variants contributing to NOA, with a focus on TEX14, a gene critical for intercellular bridge (ICB) formation during meiosis.

MATERIALS/

METHODS

Exome sequencing was performed on genomic DNA from a cohort of 673 patients with NOA, 143 individuals with oligozoospermia, and 100 fertile controls. Potentially pathogenic TEX14 variants were identified and confirmed by Sanger sequencing. Functional analysis, including qPCR and Western blot, was performed to assess TEX14 expression levels in patient and mouse testicular samples and the effects of TEX14 variants on spermatogenesis and ICB formation in both mice and humans.

RESULTS

We identified six novel TEX14 variants in four unrelated infertile Chinese men, including three frameshift mutations (c.2908dupC, p.Arg970Profs5; c.1881dupA, p.Gly628Argfs8; c.1728_1729del, p.Leu577Argfs*58), two missense mutations (c.1121A>G, p.Tyr374Cys; c.865G>A, p.Glu289Lys), and one splicing mutation (c.417+2T>C). To functionally validate the pathogenicity of the frameshift variant c.2908dupC, a mouse model carrying an analogous mutation (Tex14MT1/MT1) was generated. These mice recapitulated the human NOA phenotype, showing a complete loss of TEX14 expression in the testis. Immunofluorescence and histological analyses revealed that spermatogenesis in Tex14MT1/MT1 mice was arrested at the zygotene stage due to a complete failure of the ICB formation. Consistent with this, testicular histology from the patient carrying the c.2908dupC variant also showed meiotic arrest at zygotene and absent ICBs. Furthermore, mass spectrometry analysis of purified ICBs indicated that ICB-associated proteins are predominantly involved in RNA processing and ribonucleoprotein complex biogenesis.

DISCUSSION AND

CONCLUSION

Our results demonstrate that loss-of-function mutations in TEX14 disrupt meiotic ICB formation, leading to zygotene arrest and NOA in both mice and humans, expand the spectrum of pathogenic variants associated with NOA, and establish the essential role of TEX14 in meiotic progression, underscoring the functional importance of TEX14 in male fertility.