Tetrahymena Poc5 is a transient basal body component that is important for basal body maturation

Basal bodies (BBs) are microtubule-based organelles that act as a template for and stabilize cilia at the cell surface. Centrins ubiquitously associate with BBs and function in BB assembly, maturation and stability. Human POC5 (hPOC5) is a highly conserved centrin-binding protein that binds centrins through Sfi1p-like repeats and is required for building full-length, mature centrioles. Here, we use the BB-rich cytoskeleton of to characterize Poc5 BB functions. Poc5 (TtPoc5) uniquely incorporates into assembling BBs and is then removed from mature BBs prior to ciliogenesis. Complete genomic knockout of leads to a significantly increased production of BBs, yet a markedly reduced ciliary density, both of which are rescued by reintroduction of TtPoc5. A second -like gene, , is similarly implicated in modulating BB production. When and are co-deleted, cell viability is compromised and BB overproduction is exacerbated. Overproduced BBs display defective transition zone formation and a diminished capacity for ciliogenesis. This study uncovers a requirement for Poc5 in building mature BBs, providing a possible functional link between mutations and impaired cilia.This article has an associated First Person interview with the first author of the paper.