Centriole Assembly and Function in Ciliogenesis

Centrioles are cellular organelles best known for their role in forming centrosomes that function in cell division. However, they also play an important and evolutionarily conserved role as basal bodies in the formation of cilia, cellular projections that perform critical sensory and motile functions. Centriole and cilia abnormalities have been linked to aneuploidy and tumorigenesis as well as developmental disorders including ciliopathies and microcephaly. Despite their relevance to human physiology and pathology, centrioles have remained poorly understood at the molecular level, largely due to the technical challenges posed by the small size of this cellular organelle. The goal of this research project is to use a combination of biochemical, cell biological and genetic approaches in the nematode C. elegans to investigate the fundamental and conserved molecular mechanisms underlying centriole assembly and function. The planned research is divided into two aims. The first aim focuses on centriole assembly and specifically the role of the centriolar components SAS-4, -5 and -6 in this process. Experiments proposed in this aim include a molecular characterization of these proteins, their interactions with each other and a/ß-tubulin in formation of the nine-fold symmetric centriole structure. The aim further includes an examination of the in vivo consequences of disease-associated mutations in SAS-4 found in human patients. The second aim seeks to characterize the role of centrioles in initiating ciliogenesis, building on the identification of the hydrolethalus syndrome protein HYLS-1 as a molecular link between the centriole assembly machinery and ciliogenesis. Experiments in this aim include a delineation of the molecular events underlying the conversion of centrioles into basal bodies, focusing on proteins that, like HYLS-1, interact directly with the core centriole structure. The approaches briefly outlined above aim to capitalize on the advantages of C. elegans as an experimental model to further our understanding of centriole assembly and function in ciliogenesis, fundamental cellular activities which are of key relevance to human development and disease. An important part of this work will be to apply our findings to vertebrate and clinical models, in collaboration with experts in the field.