CFAP52 is a microtubule inner protein component of dynein-decorated doublet microtubules in the axoneme of motile cilia and flagella 1. It localizes to centrosomes, basal bodies, the manchette in spermatids, and sperm flagella, functioning beyond motile cilia-bearing cells 2. CFAP52 is essential for proper ciliary and flagellar beating by orchestrating interactions with CFAP45 and dynein ATPases to regulate microtubule sliding and adenine nucleotide homeostasis 34. In spermatogenesis, CFAP52 stabilizes the head-tail coupling protein SPATA6 and maintains axonemal structure, including the 9+2 microtubule arrangement and radial spoke proteins 5. Biallelic CFAP52 mutations cause male infertility characterized by asthenozoospermia, defective sperm head-tail connections, and flagellar morphological abnormalities 35. CFAP52 mutations also associate with situs inversus totalis and heterotaxy without primary ciliary dyskinesia 6. While sperm from CFAP52-mutant patients cannot swim effectively, male infertility caused by CFAP52 deficiency can be overcome through intracytoplasmic sperm injection, indicating preserved nuclear quality 5. CFAP52 represents an emerging diagnostic target for male infertility with flagellar development defects 7.