Physiological role of actin regulation in male fertility: Insight into actin capping proteins in spermatogenic cells

BACKGROUND: During spermatogenesis, cytoskeletal elements are essential for spermatogenic cells to change morphologically and translocate in the seminiferous tubule. Actin filaments have been revealed to be concentrated in specific regions of spermatogenic cells and are regulated by a large number of actin‐binding proteins. Actin capping protein is one of the essential actin regulatory proteins, and a recent study showed that testis‐specific actin capping protein may affect male infertility. METHODS: The roles of actin during spermatogenesis and testis‐specific actin capping protein were reviewed by referring to the previous literature. MAIN FINDINGS (RESULTS): Actin filaments are involved in several crucial phases of spermatogenesis including acrosome biogenesis, flagellum formation, and nuclear processes such as the formation of synaptonemal complex. Besides, an implication for capacitation and acrosome reaction was also suggested. Testis‐specific actin capping proteins are suggested to be associated with the removal of excess cytoplasm in mice. By the use of high‐throughput sperm proteomics, lower protein expression of testis‐specific actin capping protein in infertile men was also reported. CONCLUSION: Actin is involved in the crucial phases of spermatogenesis, and the altered expression of testis‐specific actin capping proteins is suggested to be a cause of male infertility in humans.