TTBK2 affects sperm quality by regulating the expression of centrosomal proteins and flagellar transporters during spermiogenesis in mice

Sperm plays a crucial role in male reproduction, and only a certain number of normal progressive sperm can achieve oocyte fertilization. Revealing the regulatory mechanism of spermatogenesis will help to clarify the pathogenesis of male infertility. Tau tubulin kinase 2 (TTBK2) is a microtubule-associated protein and a serine/threonine protein kinase, which has been shown to participate in cilia formation. Although the formation of cilia and sperm flagella is similar, the specific role of TTBK2 in the formation of sperm flagella remains to be elucidated. In this study, Ttbk2 was found to be predominantly expressed in the mouse testis, and the protein co-localized with α-tubulin in manchette during spermatogenesis. We inhibited the expression of Ttbk2 by intratesticular injection and found a significant increase in the rate of sperm tail deformity and a significant decrease in sperm forward motility. Transmission electron microscopy results revealed that the microtubule structure in both the midpiece and principal piece of the sperm tail exhibited significant disorganization. Furthermore, the mRNA expression levels of centrosomal protein 164 (Cep164) and centrosomal protein 83 (Cep83), as well as intraflagellar transport 88 (Ift88), were found to be downregulated upon Ttbk2 inhibition. Additionally, the expression of CEP164 and IFT88 was also downregulated at the protein level. In conclusion, by increasing the expression of centrosomal proteins and a flagellar transporter, TTBK2 plays an important role in normal formation and functional maintenance of the sperm tail, laying the foundation for the clinical diagnosis and treatment of male reproductive-related gene mutations.