CFAP53 (cilia and flagella associated protein 53) is a microtubule inner protein essential for motile cilia and flagella function. The protein localizes to axonemal microtubules in cilia where it regulates motility patterns of both 9+0 and 9+2 motile cilia through differential recruitment of axonemal dynein components 1. CFAP53 is required for centriolar satellite integrity, non-motile cilium assembly, and motile cilium formation 2. Through its role in cilia beating, CFAP53 is crucial for establishing left-right organ asymmetry during embryonic development 3. Loss-of-function studies in zebrafish demonstrate that cfap53 is specifically required for cilia rotation in Kupffer's vesicle, the laterality organ, providing a mechanism for proper left-right patterning 3. Additionally, CFAP53 plays an unexpected role in cytokinesis by regulating RhoA protein levels and localizing to the contractile ring during cell division 4. Clinically, homozygous pathogenic variants in CFAP53 cause heterotaxy and visceral laterality defects, including dextrocardia and situs inversus 56. The protein is also essential for sperm flagellum function and male fertility, with altered expression levels observed in asthenozoospermic men 7.