Ana1/Cep295 regulates centriole elongation via Cep135 and microtubules

Centrioles are essential for centrosome and cilium formation. In fly spermatocytes, they undergo dramatic elongation to form giant centrioles that support sperm development. The conserved centriole protein Ana1/Cep295 is known to promote this elongation, yet the underlying mechanism remains poorly understood. Here, we show that Ana1 regulates centriole length through two distinct mechanisms. It directly interacts with Cep135 to promote centriole elongation and to recruit Cep135 into the proximal centriole-like structure. Ana1 also binds and bundles microtubules in vitro, and this activity is required for centriole elongation in vivo. Importantly, these two interactions are not mutually exclusive and both contribute to Ana1-induced centriole overelongation. Together, our findings reveal that Ana1 is involved in centriole elongation through interactions with distinct centriolar components during fly spermatogenesis.