Analysis of drongo, a new Drosophila zinc finger gene expressed during oogenesis and neurogenesis
This thesis is an investigation into the function of the drongo, a novel gene with a zinc finger motif, orignally isolated via enhancer trapping from its expresssion in the embryonic neuroectoderm. Drongo has previously been shown to be expressed during oogenesis, neurogenesis and eye development. In this project, sequencing of a Drongo cDNA clone, shows homology to human nucleoporin protein hRIP; and a lesser extent to other proteins including the mammalian ARF-l GTPase activating protein (ARF-l GAP), a protein involved in vesicular transport across the cell; and family of yeast zinc finger genes GTSI/GCSI/GL03, members of which have also recently been shown to have GAP activity. Overexpression of drongo during early oogenesis results in egg chambers with supernumary nurse cells, probably as a result of a delay in follicle cell migration; a phenotype similar to that of braniac mutants. Overexpression during late oogenesis causes a mislocalisation of Oskar, producing embryos which lacked denticle belts and which often had posterior defects, suggesting that ectopic expression of the gene at different times in development can have different consequences. A mutagenesis screen carried out generated a number of potential mutant alleles, although none as yet have identified a mutation in the drongo gene. The use of an peptide antibody to the protein on S2 cells and western blots has identified a possible localisation of the Drongo protein to the endoplasmic reticulum, suggesting a role in vesicle transport. Drongo has also been shown to be developmentally expressed and the gene appears to encode two proteins which may or may not be functionally distinct. The role of Drongo as a possible ARF GAP, are discussed.