JMY蛋白调节Sertoli细胞连接的分子机制研究

Sertoli cells are the unique components interacted with germ cells in seminiferous epithelium and undertake the complex molecular and cellular interactions and regulatory events that together comprise spermatogenesis. On one hand, the cell junctions between Sertoli cells participate in constituting the blood-testis barrier (BTB) that form appropriate niches essential for spermatogenesis. On the other hand, the cell junctions between Sertoli cells and germ cells ensure the adherence and migration of germ cells as well as the sperm head shape and the sperm release. Numerous studies showed that actin related proteins were crucial for maintaining the natural functions of Sertoli cell, particularly in the regulation of cell junction. Interestingly, in our previous research, we firstly found an actin regulatory protein JMY (junction-mediating and regulatory protein) was expressed in Sertoli cell. In order to explore the particular effect of JMY on Sertoli cell, a conditional knockout (CKO) mice model, which specific deleted Jmy gene in the Sertoli cells, was established. Comparing to the healthy males, the Jmy CKO males had poor sperm quality and therefore were subfertility. Histological analysis of the testis showed the germ cells arranged at random and loose in seminiferous epithelium, while some germ cells at late stage of spermatogenesis, mostly the spermatid cell, were detached from the Sertoli cells. Meanwhile, several evidences showed that the Jmy CKO males suffered impaired the BTB and abnormal expression of proteins related to cell junction, endocytosis and vesicular trafficking, based on which linked JMY to endocytosis related vesicular trafficking and future cell junction. Moreover, we identified the proteins experiencing interactions with JMY in Sertoli cell and found a vesicle associated protein VAPA might related to JMY. Therefore, this applying project is focus on the mechanism of JMY in Sertoli cell junction and will further improve the effect of JMY on actin assembly and VAPA interaction, through which regulates junction proteins transport by endocytosis related vesicular trafficking. It will finally contribute to illuminate the mechanism that JMY participates in the maintenance of Sertoli cell junction and spermatogenesis, as well as the male fertility. Additionally, it will also contribute to improving the treatment of male infertility induced by the dysfunction of Sertoli cells.

睾丸Sertoli细胞为精子发生提供了必要的微环境，其细胞连接不仅构成了血睾屏障，还参与了生精细胞黏附、迁移和精子变形等过程。研究表明，细胞内吞和囊泡运输调控了Sertoli细胞连接的动态稳定；其中，actin调节蛋白与Sertoli细胞连接密切相关。前期研究中，我们首次发现actin调节蛋白JMY在小鼠Sertoli细胞表达，且Sertoli细胞Jmy基因敲除将阻碍细胞内吞相关的囊泡运输，破坏Sertoli细胞连接和血睾屏障功能，进而影响精子质量及雄性生育；同时，JMY与囊泡运输相关蛋白VAPA相互作用。因此，本课题将探索JMY调节Sertoli细胞连接的作用机制，明确JMY通过调控actin组装、与VAPA协同作用参与囊泡运输，进而调节Sertoli细胞连接，从而进一步阐明Sertoli细胞连接的调控机制及其对精子发生的影响，并为Sertoli细胞异常所致男性不育的诊治提供理论指导。

睾丸Sertoli细胞为精子发生提供了必要的微环境，其细胞连接不仅构成了血睾屏障，还参与了生精细胞黏附、迁移和精子变形等过程。研究表明，细胞内吞和囊泡运输调控了Sertoli细胞连接的动态稳定；其中，actin调节蛋白与Sertoli细胞连接密切相关。本项目确认一个actin调节蛋白——JMY蛋白在小鼠睾丸支持细胞表达，并成功构建支持细胞特异的Jmy 条件性基因敲除小鼠（Jmy flox/flox; Amh cre+小鼠）。该小鼠雄性生育力下降，具体表现为：（1）生精上皮血睾屏障损伤，生精细胞与支持细胞黏附减弱；（2）畸形精子症，即精子畸形增加；（3）弱精子症，即精子运动力下降。由此可见，在Sertoli细胞中，JMY参与调节血睾屏障进而影响精子质量。为了进一步探索分子机制，利用Jmy条件性基因敲除小鼠和支持细胞原代培养，我们确认Sertoli细胞中JMY通过与actin调节蛋白α-Actinin1和Sorbs2共同作用，调节actin组装影响细胞内吞相关的囊泡运输过程，进而影响连接蛋白的胞内运输，参与调节Sertoli细胞连接和血睾屏障的结构和功能，最终影响精子发生和精子质量。本项目可以为后续的相关研究提供实验思路，同时Jmy条件性基因敲除小鼠模型可以作为一种研究弱精子症发病机制的动物模型，探索病理条件对血睾屏障和精子发生的作用机制。