An investigation of two novel genes associated with Wnt signalling in Drosophila melanogaster

Important segmentation and patterning processes are studied extensively in *Drosophila melanogaster*, the fruitfly, a model organism in developmental biology. These events are mediated by pathways conserved between invertebrates and vertebrates. The Wnt signal transduction pathway is of major importance in these studies. Furthermore it is related to human diseases like colon cancer, Alzheimer’s and diabetes. The bristles of *Drosophila* are external sensory organs in the peripheral nervous system, linking the environment and the behaviour dictated by this environment. The stereo-typed pattern in which the bristles occur is conserved within the *Drosophilidae*. The ge-netic mechanisms underlying bristle patterning in *Drosophila* can be used as a model to investigate the Wnt pathway. This dissertation describes work undertaken to elucidate the nature of two previously unknown putative members of the pathway. *l(2)56B-W* is a gene of which two alleles with an interesting phenotype were retrieved from a large-scale mutation screen. P[ED17] is an enhancer trap line with a proneural-like expression pattern, recovered from a small-scale insertion screen. This thesis reports the results from an RNAi-approach to investigate the *l(2)56B-W*-locus. The mechanics of RNAi itself are also discussed. Both available alleles were par-tially sequenced. I have confirmed the expression pattern of the P[ED17] construct using both confocal imaging and X-gal staining. I discuss possible genetic models that might form the basis for this expression pattern. Molecular analysis of the genomic DNA flanking the inser-tion site localised this site in the genome and the two nearest transcripts were used to perform *in situ* hybridisation to test for proneural-like expression. Finally, I report the generation of homozygous ED17 revertant lines and discuss initial steps in their genetic and molecular characterisation.