Rare mutations in the complement regulatory gene CSMD1 are associated with male and female infertility

Infertility in men and women is a common and complex genetic trait with shared biological bases between the sexes. We performed a series of rare variant analyses across 73,185 women and men to identify genes that contribute to primary gonadal dysfunction and identified CSMD1 as a strong candidate in both sexes. CSMD1 is a complement regulatory protein on chromosome 8p23. In order to interpret and support our genetic findings, we performed detailed transcriptomic and protein-based experiments which found CSMD1 enriched at the germ-cell/somatic-cell interface in both male and female gonads. We then performed a battery of tests on Csmd1 knockout mice. Knockout males show increased rates of infertility, and present testes with severe histological degeneration and significantly increased deposition of complement C3 protein. Knockout females show significant reduction in ovarian quality and breeding success, as well as impaired branching of the mammary glands. Furthermore, double knockout of Csmd1 and C3 leads to an unexpected and non-additive reduction in breeding success, suggesting that CSMD1 and the complement pathway play an important role in the normal postnatal development of the gonads in both sexes. RNA-seq of mouse whole ovaries, whole testes, and FACS purified germ cell subpopulations男女不孕不育是一类常见且复杂的遗传性状，且两性间共享相关生物学基础。本研究纳入73185名男性与女性，开展了一系列罕见变异分析，以筛选与原发性性腺功能障碍相关的致病基因，并鉴定出CSMD1为两性共有的强势候选基因。CSMD1是定位于8号染色体8p23区域的补体调控蛋白。为阐释并佐证本研究的遗传学发现，我们开展了详尽的转录组学与蛋白质组学实验，结果显示CSMD1在两性性腺的生殖细胞-体细胞界面处富集表达。随后，我们对Csmd1敲除小鼠开展了系统性测试。敲除雄性小鼠的不孕率显著升高，睾丸呈现严重的组织学变性，且补体C3蛋白的沉积量明显增加。敲除雌性小鼠的卵巢质量与繁殖成功率均显著下降，同时乳腺分支发育受损。此外，Csmd1与C3的双敲除会导致繁殖成功率出现意料之外的非加性下降，提示CSMD1与补体通路在两性性腺的正常产后发育过程中发挥关键作用。本研究同时对小鼠完整卵巢、完整睾丸以及荧光激活细胞分选术（FACS）纯化的生殖细胞亚群开展了RNA测序（RNA-seq）。