Drosophilasensory cilia lacking MKS-proteins exhibit striking defects during development but only subtle defects in adults

Cilia are conserved organelles that have important motility, sensory and signalling roles. The transition zone (TZ) at the base of the cilium is critical for cilia function, and defects in several TZ proteins are associated with human congenital ciliopathies such as Nephronophthisis (NPHP) and Meckel Gruber syndrome (MKS). In several species, MKS and NPHP proteins form separate complexes that cooperate with Cep290 to assemble the TZ, but flies lack an obvious NPHP complex. We show that MKS proteins in flies are spatially separated from Cep290 at the TZ, and that flies mutant for individual MKS genes fail to recruit other MKS proteins to the TZ, while Cep290 appears to be recruited normally. Although there are abnormalities in microtubule and membrane organisation in developing MKS mutant cilia, these defects are less apparent in adults, where sensory cilia and sperm flagella function quite normally. Thus, surprisingly, MKS proteins are not essential for cilia or flagella function in flies.