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The transition zone (TZ) of eukaryotic cilia and flagella is a structural intermediate between the basal body and the axoneme that regulates ciliary traffic. Mutations in genes encoding TZ proteins (TZPs) cause human inherited diseases (ciliopathies). Here, we use the trypanosome to identify TZ components and localize them to TZ subdomains, showing that the Bardet-Biedl syndrome complex (BBSome) is more distal in the TZ than the Meckel syndrome (MKS) complex. Several of the TZPs identified here have human orthologs. Functional analysis shows essential roles for TZPs in motility, in building the axoneme central pair apparatus and in flagellum biogenesis. Analysis using RNAi and HaloTag fusion protein approaches reveals that most TZPs (including the MKS ciliopathy complex) show long-term stable association with the TZ, whereas the BBSome is dynamic. We propose that some Bardet-Biedl syndrome and MKS pleiotropy may be caused by mutations that impact TZP complex dynamics.

Original publication




Journal article


Proc Natl Acad Sci U S A

Publication Date





E5135 - E5143


BBSome, MKS/B9 complex, cilium/flagellum, transition zone, trypanosome, Bardet-Biedl Syndrome, Basal Bodies, Cell Compartmentation, Cilia, Ciliary Motility Disorders, Ciliopathies, Cytoskeleton, Encephalocele, Flagella, Humans, Microscopy, Electron, Transmission, Microscopy, Fluorescence, Mutation, Polycystic Kidney Diseases, Proteome, Protozoan Proteins, RNA Interference, Trypanosoma