A Sensitized Screen for Genes that Interact with Bag-of-marbles During Definitive Hematopoiesis. Erin A.T. Boyle, Dawn W. Hopkins, Robert A. Schulz. University of Notre Dame, Notre Dame, IN.

   Homozygous mutation of bag-of-marbles (bam) causes an overproliferation of differentiated blood cells in the lymph gland of Drosophila at the expense of the progenitor population. Using lamellocyte induction as an indication of aberrant differentiation, a sensitized screen of the second and third chromosomes was performed in order to identify genes that interact with bam. I have identified four regions that cause significant induction of lamellocytes. Deficiency 8074 induced lamellocytes in 22% of the bam-deficient trans-heterozygote animals compared to 12% for animals that contained the deficiency alone. The gene likely responsible for this induction is CG9384, which induces lamellocytes at a frequency of 30% in the trans-heterozygote and 21% in the mutant alone. Region 8957 induced lamellocytes at a frequency of 25% in the trans-heterozygotes and 66% for animals that contained the deficiency alone. Preliminary data suggests that the genes responsible for this phenotype are Tctp and CG4820. A third region 27346 induces lamellocytes independent of bam at a frequency of 30%. Smaller deficiencies in this region are currently being screened. The fourth deficiency region 7659 contains a set of two genes Cha and VACht, which induce lamellocytes in 54% of larva, independent of bam. Furthermore there is a reduction of the medullary zone in heterozygous Cha and VACht mutants, which indicates they may play a role in progenitor maintenance. When the genes responsible for lamellocyte induction in the four deficiency regions are confirmed, complete mutant phenotype analysis will be completed to determine their likely role in larval hematopoeisis.