Drosophila myb plays roles in maintaining genomic integrity and regulating cell proliferation and differentiation during development. A.L. Katzen , S-M. Fung , C.A. Fitzpatrick , N.V. Sharkov , G.S. Scaria , K.L. Artiles , G. Ramsay. Dept Molecular Genetics, Univ Illinois Col Medicine, Chicago, IL.

   The studies in our laboratory focus on the function of the Drosophila myb (Dm myb) gene during development. Dm myb is related to the vertebrate proto-oncogene c-myb, which represents a small family of genes that encode transcription factors. By studying two temperature sensitive mutations, myb¹ and myb², we have previously shown that Dm myb is required for progression through the G₂/M transition and for suppression of endoreduplication in wing cells. Recently, we have been investigating the cellular basis of the abdominal phenotype in Dm myb mutants. These studies have revealed that in proliferating abdominal epidermal cells, Dm myb is required to sustain the appropriate rate of proliferation, to suppress formation of supernumerary centrosomes, and to maintain genomic integrity. We have also taken advantage of the Gal4/UAS binary system to express either wild type or activated versions (similar to the oncogene) of Dm myb. Ectopic expression of Dm myb within the developing animal can have potent consequences, including lethality; disruption of cell cycle regulation and patterning in the wing; and suppression of endoreduplication. Finally, we are currently analyzing the distribution and intracellular localization of the DMyb protein during embryogenesis, and we are performing temperature shift experiments to study the role that Dm myb plays during oogenesis and early embryogenesis. Preliminary observations reveal an asymmetric disruption of cellular proliferation that may reflect an interaction between Dm myb and the pattern formation genes that establish polarity. Taken together, our findings indicate that in addition to being required for cell proliferation, Dm myb may play an important role in regulating some differentiation and pattern formation pathways during development.