Cilia are highly conserved structures found from protozoa to mammals where they play essential physiological and developmental functions and cilia dysfunction leads to various syndromes in humans known as ciliopathies. To understand cilia formation and function, I performed functional analysis of two new target genes of the RFX ciliogenic transcription factors. First, I focused on CCDC151 that is evolutionary conserved in motile ciliated species. I showed that CCDC151 is involved in the control of IFT-dependent dynein arm assembly in animals and required for geotaxis behavior of adult flies. In zebrafish, depletion of Ccdc151 leads to left-right asymmetry defects and kidney cysts, two phenotypes resulting from impaired ciliary beating. However, I also showed that CCDC151 is also implicated in other cellular functions in vertebrates as it is involved in proper orientation of cell divisions and implicated in the regulation of primary cilium length in mammalian cells. In a second part, I studied LRRC48 that is also conserved in species with motile cilia. I showed that this protein is essential for motility of flagellar spermatozoids and for motility of the 9+0 sensory cilia as well as in the auditory response in drosophila. In zebrafish, morpholinos induced depletion of this protein leads to hydrocephaly, kidney cysts, inner ear abnormalities and cilia motility defects. Moreover this protein is also required for inner ear biogenesis in the model. In conclusion, these two genes are essential for ciliogenesis and they are new candidate genes potentially implicated in human ciliary diseases
