Molecular genetics of morphogenesis of cellular extensions in Drosophila

In this dissertation, I examine how epithelial cells in Drosophila regulate the formation of cellular extensions. The shafts of sensory bristles and epidermal hairs have been used extensively as model cell types for studying morphogenesis at the cellular level. First, I characterized the functions of two genes in these processes. I show that the tricornered (trc) gene (encodes the Drosophila NDR kinase (Geng et al., 2000)) is likely to interact with the actin cytoskeleton in a subtle way (for example, it might function in coordinating the growth of the actin filaments and/or other cellular components). The kinase activity of the Trc protein is required for its function during bristle morphogenesis. I also show that the kojak (koj) gene is likely to encode a large and/or complicated novel regulatory protein, and function in the triggering of hair morphogenesis. Second, I characterized the arista laterals as a third model cell type in Drosophila for studying the morphogenesis of cellular extensions. I show that the morphogenesis of the arista laterals has several advantages over hairs and bristles for in vivo imaging and for inhibitor treatment experiments, and that its developmental plan is evolutionary conserved. I then describe and categorize the arista phenotypes of a collection of known mutations. The results show that the effects of these mutations on arista laterals are largely analogous to that on wing hairs and bristles. My data suggest that these genes (including trc and koj) for the most part function similarly during morphogenesis of all these three cell types in Drosophila.