Joan Rutila, Ph.D.
March 6, 1998
Cycle is a New Circadian Rhythm Mutation in Drosophilia
Previous behavioral screens to find genes involved in Drosophila circadian rhythms have identified two major players: period (1) and timeless (2). We are conducting EMS mutagenesis/behavioral screens to identify other clock genes. Our strategy is to find either suppressors or enhancers of perL, on the assumption that it might be easier to uncover important clock components starting from a mutant rather than from a wild-type clock. We have identified a number of candidate mutants, which are in various stages of analysis.
Currently we are characterizing a mutant named cycle which has a semi-dominant phenotype. Flies that are homozygous for the cyc0 mutation are arrhythmic, while heterozygotes have periods that are 1 hour longer than wild-type. Unlike the timSL mutant, a previous mutant obtained from this screen (3), this mutation is insensitive to the per genotype. An interesting feature of these flies is that they make very low, non-cycling levels not only of PER and TIM protein, but of per and tim mRNA as well. The defect appears to be transcriptional, since mutant flies fail to turn on per and tim transcription as shown by nuclear run-on experiments. We are now in the process of cloning this new mutation to determine if, in fact, it codes for a circadian-specific transcription factor.