Isolation and characterization of new PLC-g mutations. J.R. Thackeray , J. Hastings , T. Abbeyquaye , R. Mankidy. Biology Department, Clark University, Worcester, MA.
Phospholipase C-g (PLC-g) is activated upon growth factor stimulation by interaction with receptor or non-receptor tyrosine kinases. PLC-g catalyzes the hydrolysis of phosphatidylinositol (4,5) bisphosphate (PIP2) into two second messenger molecules: diacylglycerol (DAG) and inositol trisphosphate (IP3); IP3 stimulates the release of calcium from internal stores, whereas DAG is an activator of protein kinase C. We have recently shown that a Drosophila PLC-g homolog is encoded by small wing (sl), a gene first identified by Bridges in 1915. Characterization of the three surviving sl alleles (sl,1, 2 and 3) suggested that all three are nulls by genetic criteria, consistent with molecular defects that predict a truncated protein product. All three alleles are homozygous viable, giving adults with extra R7 photoreceptors and ectopic wing veins. These mild effects, produced via effects on Ras/Raf/MAPK signaling via DER/EGFR and/or Sev, are in stark contrast to the embryonic lethal phenotype observed in the mouse PLC-g1 knockout. To further our understanding of the role of PLC-g in RTK signaling we have undertaken an F1 screen for new sl alleles. Seven new EMS-induced sl mutations have been recovered from ~20,000 X chromosomes screened to date. All appear to be phenotypically indistinguishable from sl,1, 2 and 3 and have molecular defects throughout the protein. Molecular and genetic characterization of the new alleles will be presented.