The flagellum is essential for sperm motility and fertilization in vivo. The axoneme is the main component of the flagella, extending through its entire length. An axoneme is comprised of two central microtubules surrounded by nine doublets, the nexin-dynein regulatory complex, radial spokes, and dynein arms. Failure to properly assemble components of the axoneme in a sperm flagellum, leads to fertility alterations. To understand this process in detail, we have defined the function of an uncharacterized gene, Cfap97 domain containing 1 (Cfap97d1). This gene is evolutionarily conserved in mammals and multiple other species, including Chlamydomonas. We have used two independently generated Cfap97d1 knockout mouse models to study the gene function in vivo. Cfap97d1 is exclusively expressed in testes starting from post-natal day 20 and continuing throughout adulthood. Deletion of the Cfap97d1 gene in both mouse models leads to sperm motility defects (asthenozoospermia) and male subfertility. In vitro fertilization (IVF) of cumulus-intact oocytes with Cfap97d1 deficient sperm yielded few embryos whereas IVF with zona pellucida-free oocytes resulted in embryo numbers comparable to that of the control. Knockout spermatozoa showed abnormal motility characterized by frequent stalling in the anti-hook position. Uniquely, Cfap97d1 loss caused a phenotype associated with axonemal doublet heterogeneity linked with frequent loss of the fourth doublet in the sperm stored in the epididymis. This study demonstrates that Cfap97d1 is required for sperm flagellum ultra-structure maintenance, thereby playing a critical role in sperm function and male fertility in mice.

鞭毛对于精子的活力和体内受精至关重要。轴突是鞭毛的主要成分，延伸到它的整个长度。轴突由两个中央微管组成，两个微管被九个双峰所包围，分别是nexin-dynein调节复合物，放射状辐条和dynein臂。未能正确组装精子鞭毛中轴突成分，会导致生育能力改变。为了详细了解此过程，我们定义了一个未表征的基因Cfap97结构域的功能，该结构域包含1（Cfap97d1）。该基因在哺乳动物和包括衣藻（Chlamydomonas）在内的多种其他物种中是进化保守的。我们使用了两个独立生成的Cfap97d1基因敲除小鼠模型研究体内基因功能。Cfap97d1从出生后第20天开始一直在睾丸中表达，并一直持续到整个成年期。两种小鼠模型中Cfap97d1基因的缺失都会导致精子活动力缺陷（无精子症）和男性不育。Cfap97d1缺陷精子的卵丘完整卵母细胞的体外受精（IVF）产生的胚胎很少，而无透明带卵母细胞的IVF产生的胚胎数量与对照组相当。精子敲除表现出异常的运动性，其特征是在反钩位置经常失速。唯一地，Cfap97d1丧失导致表型与轴突双重结构异质性有关，后者与附睾中存储的精子的第四双重结构的频繁丧失有关。这项研究表明，Cfap97d1是精子鞭毛超微结构维持所必需的，因此在小鼠精子功能和雄性育性中起着至关重要的作用。