Infertility represents a significant health concern, with sperm quantity and quality being crucial determinants of male fertility. Oligoasthenoteratozoospermia (OAT) is characterized by reduced sperm motility, lower sperm concentration, and morphological abnormalities in sperm heads and flagella. Although variants in several genes have been implicated in OAT, its genetic etiologies and pathogenetic mechanisms remain inadequately understood. In this study, we identified a homozygous nonsense mutation (c.916C>T, p.Arg306*) in the coiled-coil domain containing 146 ( CCDC146) gene in an infertile male patient with OAT. This mutation resulted in the production of a truncated CCDC146 protein (amino acids 1-305), retaining only two out of five coiled-coil domains. To validate the pathogenicity of the CCDC146 mutation, we generated a mouse model ( Ccdc146 mut/mut ) with a similar mutation to that of the patient. Consistently, the Ccdc146 mut/mut mice exhibited infertility, characterized by significantly reduced sperm counts, diminished motility, and multiple defects in sperm heads and flagella. Furthermore, the levels of axonemal proteins, including DNAH17, DNAH1, and SPAG6, were significantly reduced in the sperm of Ccdc146 mut/mut mice. Additionally, both human and mouse CCDC146 interacted with intraflagellar transport protein 20 (IFT20), but this interaction was lost in the mutated versions, leading to the degradation of IFT20. This study identified a novel deleterious homozygous nonsense mutation in CCDC146 that causes male infertility, potentially by disrupting axonemal protein transportation. These findings offer valuable insights for genetic counseling and understanding the mechanisms underlying CCDC146 mutant-associated infertility in human males.
不孕不育已成为重要的健康问题，其中，影响男性生育能力的关键因素包括精子的数量和质量。少弱畸形精子症（Oligoasthenoteratozoospermia，OAT）以精子数量和运动能力的大幅下降，以及精子头部和鞭毛形态的严重异常为特征。尽管目前已发现多种基因突变与OAT相关，但人们对OAT的遗传病因及其致病机制仍知之甚少。在该研究中，我们在一例OAT男性不育患者中发现了卷曲螺旋结构域蛋白CCDC146（Coiled-Coil Domain Containing 146）编码基因的一处纯合无义突变（c.916C>T，p.Arg306*），此突变导致了由1-305位氨基酸组成的CCDC146截短蛋白的产生，该蛋白仅保留五个卷曲螺旋结构域中的两个。为了验证 CCDC146突变的致病性，我们制作了模拟患者突变的小鼠模型( Ccdc146 mut/mut )，发现 Ccdc146 mut/mut 小鼠雄性不育且表型与患者一致，表现为精子数量和运动能力的显著下降，并伴有多种精子头部和鞭毛形态的缺陷。进一步研究发现，在 Ccdc146 mut/mut 小鼠的精子中，轴丝蛋白如DNAH17、DNAH1和SPAG6的含量显著降低。此外，人类和小鼠的CCDC146蛋白均能与鞭毛内运输蛋白IFT20（intraflagellar transport protein 20）相互作用，但CCDC146截短蛋白失去了与IFT20蛋白相互作用的能力，并导致IFT20降解。综上所述，我们的研究结果表明， CCDC146基因中的这一全新纯合无义突变导致CCDC146蛋白功能受损，可能通过破坏精子鞭毛中轴丝蛋白的运输而导致男性不育。这些发现为 CCDC146突变相关男性不育患者的遗传咨询提供了宝贵的见解。.
Keywords: CCDC146; Human infertility; IFT20; Intraflagellar transport; Oligoasthenoteratozoospermia; Sperm flagellum.