Spermatogenesis is a complex developmental process that involves the proliferation of diploid cells, meiotic division, and haploid differentiation. Many genes are shown to be essential for male fertility using knockout (KO) mice; however, there still remain genes to be analyzed to elucidate their molecular mechanism and their roles in spermatogenesis. Calcium- and integrin-binding protein 1 (CIB1) is a ubiquitously expressed protein that possesses three paralogs: CIB2, CIB3, and CIB4. It is reported that Cib1 KO male mice are sterile due to impaired haploid differentiation. In this study, we discovered that Cib4 is expressed strongly in mouse and human testis and begins expression during the haploid phase of spermatogenesis in mice. To analyze the function of CIB4 in vivo, we generated Cib4 KO mice using the CRISPR/Cas9 system. Cib4 KO male mice are sterile due to impaired haploid differentiation, phenocopying Cib1 KO male mice. Spermatogenic cells isolated from seminiferous tubules demonstrate an essential function of CIB4 in the formation of the apical region of the sperm head. Further analysis of CIB4 function may shed light on the etiology of male infertility caused by spermatogenesis defects, and CIB4 could be a target for male contraceptives because of its dominant expression in the testis.

中文翻译：

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CIB4 对于小鼠精子发生的单倍体阶段是必不可少的†。

精子发生是一个复杂的发育过程，涉及二倍体细胞的增殖、减数分裂和单倍体分化。使用敲除 (KO) 小鼠显示，许多基因对雄性生育能力至关重要；然而，仍有待分析基因以阐明它们的分子机制和它们在精子发生中的作用。钙和整联蛋白结合蛋白 1 (CIB1) 是一种普遍表达的蛋白质，具有三个旁系同源物：CIB2、CIB3 和 CIB4。据报道，由于单倍体分化受损，Cib1 KO 雄性小鼠是不育的。在这项研究中，我们发现Cib4在小鼠和人类睾丸中强烈表达，并在小鼠精子发生的单倍体阶段开始表达。为了在体内分析 CIB4 的功能，我们使用 CRISPR/Cas9 系统生成了Cib4 KO 小鼠。由于单倍体分化受损，Cib4 KO 雄性小鼠不育，表型复制Cib1 KO 雄性小鼠。从生精小管中分离的生精细胞证明了 CIB4 在精子头部顶端区域的形成中的基本功能。对 CIB4 功能的进一步分析可能有助于阐明由精子发生缺陷引起的男性不育症的病因，而 CIB4 因其在睾丸中的主要表达而可能成为男性避孕药的靶点。