STK33 is required for the differentiation of spermatocytes and spermatids in male mice by maintaining mitochondrial homeostasis

Spermatogenesis is a highly intricate and tightly regulated cell development process, involving mitosis, meiosis and spermiogenesis. STK33, a member of the serine/threonine kinase family, is prominently expressed in testicular tissue, particularly in spermatocytes. In male mice, STK33 is essential for the spermatid differentiation and male infertility. However, the role of STK33 in spermatocyte cell development in males has remained unexplored. To further elucidate the exact role of STK33 in mouse reproduction, we generated STK33 -/- mice using CRISPR/Cas9 technology. Deletion of STK33 resulted in complete infertility in male mice, and STK33 -/- mice displayed reduced sperm count compared to wild-type (WT) mice. Single-cell cytometry results of testes show that the differences between STK33 -/- and WT mice mainly concentrate at the spermatocyte stage, with differentially expressed genes primarily focusing on metabolic pathways. STK33 -/- mice manifested mitochondrial abnormalities and heightened apoptosis compared to WT mice. Furthermore, there were notable irregularities in the expression of proteins associated with apoptosis and mitochondrial function.In conclusion, our findings unveil a novel role for STK33 in germ cell development in male mice, whereby knockout of the STK33 gene leads to disruption of mitochondrial homeostasis and increased cell apoptosis in mouse spermatocytes and spermtids.