CCDC13 is a coiled-coil domain-containing centriolar satellite protein essential for primary cilia formation and genome stability. 1 It localizes to centriolar satellites and the basal body, where it interacts with PCM1, Cep290, and pericentrin to regulate microtubule organization and promote BBS4 localization to centriolar satellites and cilia. 1 CCDC13 prevents DNA damage accumulation during mitotic transit, distinct from its role in satellite integrity. 1 The protein is highly evolutionarily conserved across flagellated species and plays a critical tissue-specific role in sperm flagellum biogenesis through interactions with intraflagellar transport (IFT) proteins and flagellar components. 2 CCDC13 deficiency causes male infertility with multiple morphological abnormalities of sperm flagella (MMAF)-like phenotype, whereas PCM1 knockout only reduces motility. 2 Beyond reproductive function, CCDC13 has been implicated in immune homeostasis, with mutations associated with type 1 diabetes susceptibility in NOD mice, 3 and altered expression detected in chr3 endometritis and glioblastoma. 4 5 Rare variants in CCDC13 have also been associated with blood pressure variation in African ancestry populations. 6