CATIP (ciliogenesis associated TTC17 interacting protein) is a conserved protein that plays a critical role in primary ciliogenesis by modulating actin polymerization. CATIP interacts with TTC17 to regulate actin organization; depletion of either protein in human ciliated cells impairs actin polymerization and reduces primary cilia number without affecting cilium length 1. The protein functions through its involvement in the actin cytoskeleton, with the normal protein inhibiting actin repolymerization after disruption, a function impaired by disease-associated mutations 2. Beyond ciliogenesis, CATIP participates in developmental processes; disruption of Catip in embryonic stem cells facilitates conversion to trophoblast stem cells, suggesting a role in cell fate determination during early embryogenesis 3. CATIP mutations cause male infertility: a homozygous missense mutation (p.Phe35Ile) identified in oligoteratoasthenozoospermia patients reduces protein stability and impairs actin polymerization capacity, leading to abnormal sperm axoneme structures and F-actin distribution 2. This mutation represents the first reported recessive CATIP mutation in humans causing spermatogenic failure, consistent with mouse knockout studies demonstrating male infertility as the primary phenotype. These findings establish CATIP as an essential regulator of actin dynamics required for proper ciliogenesis and male reproductive function.