Is the TEX11-.652del237bp Exonic In-Frame Deletion Variant Associated with Azoospermia? The Results of an In Vitro...

Background: In 2015, it was discovered that mutations in the TEX11 gene are associated with azoospermia in general and meiotic maturation arrest in particular. TEX11 is a component of the ZZS complex (comprising Zip2-, Zip4- and Spo16 and originally described in Saccharomyces cerevisiae). During meiosis, this complex is required for the promotion of double-strand break (DSB) repair and thus the maintenance of genomic integrity. Since the initial discovery, several variants and deletions in TEX11 have been reported in patients with spermatogenesis defects. However, many of these new variants have not been functionally validated, which makes it difficult to confirm their direct impact on meiosis. The exonic in-frame deletion TEX11-c.652del237bp has been recurrently identified in infertile men. However, mice models carrying this deletion remain fertile-suggesting that these models may not faithfully replicate human meiotic phenotypes. To address this discrepancy, we functionally validated the TEX11-c.652del237bp variant in vitro. Methods: After amplification in Escherichia Coli DH5α, the pIRES2-EGFP plasmid containing either the wild-type TEX11 sequence or the TEX11-c.652del237bp sequence was transfected into the HEK293 human embryonic kidney cell line. qPCR and Western blot analyses were then used to evaluate the presence and expression levels of TEX11 mRNA and TEX11 protein. Results: The qPCR and Western blot analyses showed that truncated mRNA and protein were produced in cells transfected with the c.652del237bp variant. Hence, the deletion probably leads to the transcription and translation of TEX11 in human testis. Furthermore, in silico modeling suggested that the deletion does not have a significant impact on the ZZS complex. Conclusions: Our in vitro and in silico data demonstrate that the c.652del237bp in-frame deletion results in a truncated TEX11 protein and thus question the deletion's pathogenic role in human meiosis. However, the absence of a meiotic phenotype in the corresponding mouse model is suggestive of species-specific differences in TEX11 endogenous function. Further studies (such as co-immunoprecipitation experiments with other ZZS complex proteins) are needed to fully assess the functional impact of TEX11-c.652del237bp. These experiments might also provide novel insights into the specific role of the TEX11 SPO22 domain in human spermatogenesis.