A gain-of-function screen for genes that affect the development of the Drosophila adult external sensory organ

The Drosophila adult external sensory organ, comprising a neuron and its su pport cells, is derived fi om a single precursor cell via several asymmetri c cell divisions. To identify molecules involved in sensory organ developme nt, we conducted a tissue-specific gain-of-function screen. We screened 229 3 independent P-element lines established by P. Rorth and identified 105 li nes, carrying insertions at 78 distinct loci, that produced misexpression p henotypes with changes in number, fate, or morphology of cells of the adult external sensory organ. On the basis of the gain-of-function phenotypes of both internal and external support cells, we subdivided the candidate line s into three classes. The first class (52 lines, 40 loci) exhibits partial or complete loss of adult external sensory organs. The second class (38 lin es, 28 loci) is associated with increased numbers of entire adult external sensory organs or subsets of sensory organ cells. The third class (15 lines , 10 loci) results in potential cell fate transformations. Genetic and mole cular characterization of these candidate lines reveals that some loci iden tified in this screen correspond to genes known to function in the formatio n of the peripheral nervous system, such as big brain, extra macrochaetae, and numb. Also emerging from the screen are a large group of previously unc haracterized genes and several known genes that have not yet been implicate d in the development of the peripheral nervous system.