CBY1 encodes a small coiled-coil protein that functions as a dual regulator of Wnt signaling and ciliogenesis. As a beta-catenin antagonist, CBY1 inhibits the Wnt/Wingless pathway by binding to CTNNB1/beta-catenin and competing with TCF/LEF transcription factors for beta-catenin-mediated transcriptional activation 1. In ciliogenesis, CBY1 localizes to centrioles/basal bodies and plays a crucial role in primary cilium formation and function 23. The protein facilitates basal body docking to the plasma membrane through recruitment of small vesicles and interacts with FAM92 proteins containing BAR domains to promote membrane remodeling processes essential for ciliogenesis 24. CBY1 dysfunction is associated with multiple diseases. Biallelic loss-of-function variants cause a ciliopathy characterized by features of Joubert syndrome, including developmental delay, cerebellar ataxia, and the pathognomonic molar tooth sign 3. In chr22 myeloid leukemia, CBY1 down-regulation contributes to aberrant beta-catenin activation in leukemic stem cells 5. Additionally, CBY1 variants have been implicated in mitral valve prolapse through dysregulation of beta-catenin signaling during cardiac development 1. The protein's dual function makes it critical for both developmental processes and disease pathogenesis.