- skittles, a Drosophila phosphatidylinositol 4-phosphate 5-kinase, is required for cell viability, germline development and bristle morphology, but not for neurotransmitter release. Hassan, B.A., Prokopenko, S.N., Breuer, S., Zhang, B., Paululat, A., Bellen, H.J. Genetics (1998)