TEX30 safeguards sperm morphogenesis and quality consistency required for male fertility

Spermatogenesis, essential for male fertility, requires precise temporal and spatial regulation of gene expression to generate sperm that function robustly in vivo. Here, we show that testis-expressed 30 (Tex30) mRNA expression is induced by the germ-cell-specific transcription factors MEIOSIN and stimulated by retinoic acid 8 during meiotic prophase and is further upregulated in round spermatids. Despite this transcriptional activation, TEX30 protein is detected predominantly in the cytoplasm of step 16 spermatids, where it is highly enriched in the cytoplasmic lobe that is normally discarded as the residual body during spermiation. This strikingly restricted localization suggests that TEX30 safeguards sperm maturation during the final stages of spermiogenesis. Although overall testis morphology and gross spermatogenic progression are largely preserved in Tex30 knockout (KO) mice, epididymal sperm exhibit mild but reproducible abnormalities, including globozoospermia-like head defects and occasional tail deformities, together with variability in acrosome integrity. Importantly, Tex30 KO males display pronounced inter-individual variability in cauda epididymal sperm abundance-a feature not observed in wild-type controls-suggesting that TEX30 contributes to the robustness and consistency of late spermatogenesis rather than to its absolute production. Consistent with this, sperm number and distribution within the uterus are frequently reduced in Tex30 KO males, resulting in inefficient migration into the oviduct during natural mating. Together, these findings demonstrate that TEX30 is dispensable for early spermatogenic progression but is required to maintain the structural integrity, functional competence, and inter-individual robustness of sperm produced during late spermiogenesis, thereby supporting efficient in vivo fertilization.