Whole genome sequencing identifies a homozygous splicing variant in TDRKH segregating with non-obstructive azoospermia in an Iranian family.

Abstract

Non-obstructive azoospermia (NOA) resulting from primary spermatogenic failure represents one of the most severe forms of male infertility, largely because therapeutic options are very limited. Beyond their diagnostic value, genetic tests for NOA also hold prognostic potential. Specifically, genetic diagnosis enables the establishment of genotype-testicular phenotype correlations, which, in some cases, provide a negative predictive value for testicular sperm extraction (TESE), thereby preventing unnecessary surgical procedures. In this study, we employed whole-genome sequencing (WGS) to investigate two generations of an Iranian family with NOA and identified a homozygous splicing variant in TDRKH (NM_001083965.2: c.562-2A>T). TDRKH encodes a conserved mitochondrial membrane-anchored factor essential for piRNA biogenesis in germ cells. In Tdrkh knockout mice, de-repression of retrotransposons in germ cells leads to spermatogenic arrest and male infertility. Previously, our team reported TDRKH involvement in human NOA cases through the investigation of a North African cohort. This current study marks the second report of TDRKH's role in NOA and human male infertility, underscoring the significance of the piRNA pathway in spermatogenesis. Furthermore, across both studies, we demonstrated that men carrying TDRKH variants, similar to knockout mice, exhibit complete spermatogenic arrest, correlating with failed testicular sperm retrieval.