Shedding of cilia occurs from unicellular organisms to metazoans. Although essential during the cell cycle and during neurogenesis, the process remains poorly understood. In all cellular models, this phenomenon occurs distal to the transition zone (TZ), suggesting the underlying molecular mechanisms might be conserved. TZ module proteins are known to cooperate to establish TZ formation and function; to determine whether they also control deciliation, Gogendeau et al. studied the function of five TZ module proteins in the ciliate Paramecium tetraurelia. They found that all proteins are recruited to the TZ of growing cilia and localize with 9-fold symmetry at the level of the most distal part of the TZ. Depletion of some of these proteins induces constant deciliation of some cilia, while depletion of the others prevents calcium/ethanol-induced deciliation. This constitutes the first evidence for a role of conserved TZ proteins in deciliation and opens up new directions for understanding the physiology of motile cilia. The image shows the ciliary pattern of paramecia treated with control RNAi (top left) or RNAi for three different TZ proteins. Cells were stained for mono-glycylated tubulin (magenta) to show cilia tips and poly-glutamylated tubulin (green) to show basal bodies and cilia.

Image Credit: pbio.3000640