Tssk6 is essential for the regulation of male zebrafish fertility.

Protein kinases are critical regulators of cellular functions and play a pivotal role in male reproduction. In this study, we investigated the role and regulatory mechanisms of the testis-specific serine/threonine kinase 6 (tssk6) in zebrafish. We found that tssk6 gene is highly expressed in the testis of adult male zebrafish, with its protein sequence showing high homology to those of mice and humans, highlighting its evolutionary conservation across vertebrates and suggesting an ancient, critical role in male reproduction. By constructing tssk6 mutants, we demonstrated that deletion of this gene leads to impaired testis development, reduced sperm quality, and decreased fertilization capacity in male zebrafish, directly linking tssk6 to the regulation of male fertility. In addition, transcriptome analysis of testis from tssk6 mutants further revealed significant changes in the expression of genes essential for spermatogenesis, sperm-egg recognition and fusion, shedding light on the molecular mechanisms underlying these reproductive defects. Collectively, these findings highlight the critical regulatory role of tssk6 in male zebrafish fertility. Our study not only advances our understanding of the molecular mechanisms underlying male reproduction but also provides valuable insights into conserved reproductive pathways in vertebrates.