Tssk4 belongs to the Testis Specific Serine/threonine protein Kinase (TSSK) family, members of which play an important role in spermatogenesis and/or spermiogenesis. Several Tssk family proteins have extensively been studied. However, the exact function of Tssk4 remains unclear. A Tssk4 knockout mouse model was generated and the males were subfertile due to seriously decreased sperm motility. The ultrastructure of the Tssk4(-/-)sperm tail is disorganized at the midpiece-principal piece junction, leading to a severe bend in the sperm flagellum. One or more axonemal microtubule doublets are absent and the midpiece is fused with the principal piece. Furthermore, we identified the association between Tssk4 and Odf2, a prominent cytoskeletal protein of the outer dense fiber (ODF) in sperm flagellum. Tssk4 can change the phosphorylation state of Odf2 and conversely Odf2 potentiates the autophosphorylation activity of Tssk4. These findings reveal that Tssk4 is required for maintaining the structural integrity of sperm flagellum and male fertility.
Keywords: Odf2; Tssk4; male fertility; sperm motility; structural integrity.
© The Author 2014. Published by Oxford University Press on behalf of the European Society of Human Reproduction and Embryology. All rights reserved. For Permissions, please email: journals.permissions@oup.com.