The transition zone of cilia is composed of several proteins and forms at the boundary between the plasma membrane and the basal body of the cilium. Many human pathologies, such as Meckel Gruber syndrome (MKS), Joubert syndrome (JBT) and nephronophthisis (NPHP), display mutations in genes coding for transition zone proteins. These proteins have been proposed to function in the large MKS complex, and the NPHP and Cep290 modules, and vary between cell types and species with regard to their composition and functional redundancy. On page 3732 in this issue, Helio Roque, Jordan Raff and co-workers take advantage of the absence of NPHP orthologues in flies to elucidate the requirement of the MKS complex in Drosophila. Using super-resolution 3D-structured illumination microscopy, they show that Cep290 and the MKS complex are at distinct locations within the transition zone. The localisation of additional MKS components is dependent on the presence of the MKS subunits MKS1 and B9D1, suggesting a functional complex. Most importantly, by analysing a null mutation for MKS1, they show that the most severe cilia defects are found in two-day-old mutant pupae. However, this effect is alleviated in 72-h-old pupae, and, indeed, adult mutant flies are viable and fertile, with no strong sensory cilia or spermatocyte defects. These findings demonstrate that even in absence of the NPHP complex, flies do not require the MKS complex at the transition zone for functional cilia.
- © 2016. Published by The Company of Biologists Ltd