Department of Medical Laboratories Technology, College of Applied Medical Sciences, Taibah University, Madina, Saudi Arabia.
Biology Department, Kent State University, Kent, OH, USA.
Andrology. 2021 Jan;9(1):312-328. doi: 10.1111/andr.12865. Epub 2020 Aug 5.
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 play 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, ε, γ, η, θ/τ, ζ and σ). 14-3-3 isoforms have been shown to have many interacting partners in several tissues including testis.
While it is known that 14-3-3 proteins are expressed in the functions of testis and spermatozoon, the role for each of the seven isoforms is not known. In this study, we investigated the roles of 14-3-3η and 14-3-3ε isoforms in spermatogenesis.
To study the in vivo function of 14-3-3η and 14-3-3ε in spermatogenesis, we generated testis-specific and global knockout mice for each of 14-3-3η and 14-3-3ε isoforms (CKO and GKO, respectively). Computer-assisted semen analysis was used to assess sperm motility, while immunohistochemical studies were conducted to check spermatogenesis.
Although both 14-3-3η and 14-3-3ε isoforms were present in mouse testis, only the expression of 14-3-3ε, but not 14-3-3η, was detected in spermatozoa. Mice lacking 14-3-3η were normal and fertile while 14-3-3ε CKO and GKO males showed infertility. Low sperm count with higher abnormal spermatozoa was seen in 14-3-3ε CKO mice. The motility of 14-3-3ε knockout spermatozoa was lower than that of the control. A reduction in the phosphorylation of both glycogen synthase kinase 3 and PP1γ2 was also seen in spermatozoa from 14-3-3ε CKO mice, suggesting a specific role of 14-3-3ε in spermatogenesis, sperm motility, and fertility.
This is the first demonstration that of the seven 14-3-3 isoforms, 14-3-3ε is essential for normal sperm function and male fertility.
精子发生是一个复杂的生物学过程，在此过程中会合成和激活多种蛋白质，这些蛋白质在减数分裂和细胞分化中发挥重要作用。14-3-3 蛋白是衔接蛋白，在激酶信号转导中发挥关键作用，尤其是在真核细胞的细胞周期和细胞凋亡调控中。14-3-3 蛋白家族由七个基因（β、ε、γ、η、θ/τ、ζ 和 σ）编码，有七种同工型。在多种组织中，包括睾丸，已经发现 14-3-3 同工型有许多相互作用的伴侣。
虽然已知 14-3-3 蛋白在睾丸和精子的功能中表达，但七种同工型中的每一种的作用尚不清楚。在这项研究中，我们研究了 14-3-3η 和 14-3-3ε 同工型在精子发生中的作用。
为了研究 14-3-3η 和 14-3-3ε 在精子发生中的体内功能，我们分别生成了 14-3-3η 和 14-3-3ε 同工型的睾丸特异性和全局敲除小鼠（CKO 和 GKO）。利用计算机辅助精液分析评估精子的运动能力，同时进行免疫组织化学研究以检查精子发生情况。
虽然 14-3-3η 和 14-3-3ε 同工型都存在于小鼠睾丸中，但只有 14-3-3ε 同工型，而不是 14-3-3η 同工型，在精子中被检测到。缺乏 14-3-3η 的小鼠正常且具有生育能力，而 14-3-3ε CKO 和 GKO 雄性表现出不育。14-3-3ε CKO 小鼠的精子计数较低，异常精子较多。14-3-3ε 敲除精子的运动能力低于对照。还观察到 14-3-3ε CKO 小鼠精子中糖原合酶激酶 3 和 PP1γ2 的磷酸化减少，这表明 14-3-3ε 在精子发生、精子运动和生育力中具有特定作用。
这是首次证明在七种 14-3-3 同工型中，14-3-3ε 对于正常精子功能和男性生育能力是必需的。
