A subset of evolutionarily conserved centriolar satellite core components is crucial for sperm flagellum biogenesis.

Rationale: Centriolar satellites are non-membranous cytoplasmic granules that cluster around centrosomes, with pericentriolar material 1 (PCM1) serving as the molecular marker for these structures. Although significant progress has been made in understanding their composition, cellular, and organismal functions over the past decades, the tissue-specific roles of centriolar satellite proteins in sperm flagellum biogenesis and male fertility are still not well understood.

Methods

We utilize publicly available data and conduct phylogenetic analysis to explore the tissue distribution and conservation of centriole satellite components across flagellated species. Knockout mouse models for Ccdc13 and Pcm1 were constructed to investigate their physiological roles. Sperm morphology and functionality were analyzed using immunofluorescence, transmission electron microscopy, and sperm motility analysis. Immunofluorescence, immunoblotting, co-immunoprecipitation, and proteomics analyses were carried out to elucidate the molecular mechanisms by which CCDC13 regulates sperm flagellum biogenesis.

Results

We show that most satellite components are expressed in the testis and associated with ciliary function. Comparative analysis of ciliary-related satellite components across 11 flagellated and non-flagellated species revealed six highly conserved satellite proteins in flagellated species. PCM1, a well-known centriolar satellite scaffolding protein, was found to be less conserved. Based on these findings, we selected CCDC13, a highly conserved satellite protein, and PCM1, a less conserved component, for functional comparison in sperm flagellum biogenesis. Using knockout mouse models, we demonstrated that Ccdc13 deficiency led to male infertility with multiple morphological abnormalities of the sperm flagella (MMAF)-like phenotype due to defects in sperm flagellum biogenesis. While Pcm1 knockout only resulted in decreased sperm motility without affecting flagellum biogenesis. Molecularly, CCDC13 interacts with IMT, IFT-associated proteins, and flagellar components to regulate transport of cargo to proper positions for flagellum biogenesis.

Conclusion

This study identifies a subset of highly conserved centriolar satellite proteins essential for sperm flagellum biogenesis. The identification of these proteins provides valuable insights into the genetic mechanisms underlying flagellum function and their evolutionary development. Additionally, defects in these proteins may be associated with male infertility in humans.