Abstract
BACKGROUND: Sperm motility is essential for male fertility, and its regulation is dependent on the structural integrity of the axoneme. The axoneme consists of a conserved "9+2" microtubule arrangement and is supported by microtubule inner proteins. However, the functional significance of many microtubule inner proteins remains unclear. Cilia- and flagella-associated protein 77 (CFAP77) has been identified as a microtubule inner protein in various species, but its role in mammalian sperm function has not been fully elucidated. OBJECTIVES: This study aims to investigate the function of CFAP77 in sperm motility and male fertility using a Cfap77 knockout mouse model. MATERIALS AND METHODS: Cfap77 knockout mice were generated using the CRISPR-Cas9 system. Male fertility was assessed by mating tests, and sperm motility was analyzed using computer-assisted sperm analysis. Immunoblotting and immunoprecipitation-mass spectrometry were performed to determine CFAP77's localization and interaction with other microtubule inner proteins. RESULTS: We found that CFAP77 localized to the sperm flagella in mice. Moreover, Cfap77 knockout males exhibited significantly reduced fertility, with impaired sperm motility despite normal morphology. Immunoprecipitation-mass spectrometry analysis revealed that CFAP77 interacts with TEKTL1, and CFAP77 loss leads to a reduced amount of TEKTL1 in spermatozoa. DISCUSSION AND CONCLUSION: We demonstrate that CFAP77 is crucial for sperm motility and male fertility. The interaction between CFAP77 and other microtubule inner proteins suggests a role in stabilizing other microtubule inner proteins and regulating flagellar function. These results provide insights into the molecular mechanisms of sperm motility regulation.