CCDC183 is essential for cytoplasmic invagination around the flagellum during spermiogenesis and male fertility.

Sperm flagellum plays a critical role in male fertility. Here, we generated Ccdc183 knockout (KO) mice using the CRISPR/Cas9 system to reveal the protein function of CCDC183 in spermiogenesis. We demonstrated that the absence of CCDC183 causes male infertility with morphological and motility defects in spermatozoa. Due to the lack of CCDC183, centrioles after elongation of axonemal microtubules do not connect the cell surface and nucleus during spermiogenesis, which causes subsequent loss of cytoplasmic invagination around the flagellum. As a result, the flagellar compartment does not form properly and cytosol-exposed axonemal microtubules collapse during spermiogenesis. In addition, ectopic localization of accessory structures such as the fibrous sheath and outer dense fibers, and abnormal head shape due to abnormal sculpting by the manchette are observed in Ccdc183 KO spermatids. Our results indicate that CCDC183 plays an essential role in cytoplasmic invagination around the flagellum to form functional spermatozoa during spermiogenesis.