The protein YWHAE (14‐3‐3 epsilon) in sperm is essential for male fertility

BACKGROUND Spermatogenesis is a complex biological process highlighted by synthesis and activation of proteins that regulate meiosis and cellular differentiation occur during spermatogenesis. 14-3-3 proteins are adaptor proteins that plays critical roles in kinase signaling, especially for regulation of cell cycle and apoptosis in eukaryotic cells. There are seven isoforms of the 14-3-3 family proteins encoded by seven genes (β, e, γ, η, θ/τ, ζ and σ). 14-3-3 isoforms have been shown to have many interacting partners in several tissues including testis. OBJECTIVE While it is known that 14-3-3 proteins are expressed in the functions of testis and sperm, the role for each of the seven isoforms are not known. In this study, we investigated the roles of 14-3-3η and 14-3-3e isoforms in spermatogenesis. MATERIALS AND METHODS To study the in vivo function of 14-3-3η and 14-3-3e in spermatogenesis, we generated testis-specific and global knockout mice for each of 14-3-3η and 14-3-3e isoforms (CKO and GKO, respectively). Computer Assisted Semen Analysis was used to assess sperm motility, while immunohistochemical studies were conducted to check spermatogenesis. RESULTS Although both 14-3-3η and 14-3-3e isoforms were present in mouse testis, only the expression of 14-3-3e, but not 14-3-3η, was detected in sperm. Mice lacking 14-3-3η were normal and fertile while 14-3-3e CKO and GKO males showed infertility. Low sperm count with higher abnormal sperm was seen in 14-3-3e CKO mice. The motility of 14-3-3e knockouts sperm were lower than that of the control. A reduction in the phosphorylation of both glycogen synthase kinase 3 and PP1γ2 were also seen in sperm from 14-3-3e CKO mice, suggesting a specific role of 14-3-3e in spermatogenesis, sperm motility, and fertility. DISCUSSION AND CONCLUSION This is the first demonstration that of the seven 14-3-3 isoforms, 14-3-3e is essential for normal sperm function and male fertility.