The cut locus is a large Drosophila gene that controls differentiation of a variety of tissues. Mutations of the gene transform the external sensory organs into chordotonal organs and prevent differentiation of particular wing margin bristles as well as the insect kidneys. Expression is also required in the head for the occurrence of cuticle expansion, a programmed behavior. Mutations upstream of the transcribed portion of the gene interfere with proper regulation. Many of the upstream mutations are insertions of the retrotransposon gypsy, which may interrupt expression by acting as a barrier between the promoter and enhancer elements. The interactions of cut with other genes and gene products in the process of regulation that leads to differentiation of cell type will be examined. The cut regulatory elements will be identified by their ability to regulate a reporter gene, and experiments will be carried out to test specific genes to discover what genes are required for cut expression in particular tissues and which ones encode proteins that bind directly to the cut regulatory elements. The localization of the cut regulatory elements will also demonstrate clearly whether the gypsy transposable element acts as a barrier between enhancers and promoters.
