Cilia are widespread eukaryotic subcellular organelles that function in cell motility, movement of extracellular fluids and sensory reception. In C. elegans, the expression of many ciliary genes is regulated by DAF-19, an RFX-type transcription factor that recognizes DNA sequence motifs (X-boxes) in promoters of its targets, which include genes of ciliary structure and transport machinery, receptors and other factors.. Using a genome-wide search approach for X-box containing genes (xbx genes) we identified a list of about 750 xbx genes (candidates). This list comprises some already known ciliary genes as well as new genes, many of which we hypothesize to be important for cilium structure and function, among them the C. elegans gene
xbx-2, which encodes a dynein light chain (DLC) (Tctex-1 family). Previously, we have shown that XBX-2 protein is involved in intraflagellar transport (IFT), an important ciliogenic process. A recently obtained mutant allele for
xbx-2 will allow us to investigate at which point XBX-2 molecules are necessary for proper IFT to occur. To find the possible role of
xbx-2 in IFT, we will apply experimental approaches like cilia length measurements in
xbx-2 mutants, expression of XBX-2::GFP in bbs and in various IFT mutant backgrounds, as well as expression of various other IFT proteins in an
xbx-2 mutant background. In parallel, we are performing global expression analysis of various cilia mutants at different developmental stages. First expression analyses of embryonic stages of cilia versus no-cilia mutants have revealed a list of candidate xbx and ciliary genes that displayed statistically significant down-regulation in their expression patterns. Using the above approaches together with stringent bioinformatic analyses and comparisons with other datasets, we will be able to identify the complete set of genes that is involved in ciliogenesis and functional maintenance of cilia.