Amongst the possible regulators, several small GTPases have been associated with the flagellum: ARL-13b is involved in the stabilization of ciliary assembly in C. elegans and its mutations are associated with a ciliopathy named Joubert syndrome (Cantagrel et al., 2008; Cevik et al., 2010; Li et al., 2010). The gene discussed is ARL13B; the disease is Joubert syndrome.