Role of Per and Tim mRNA Cycling in the Drosophila Circadian Oscillator

University Of Houston, Houston TX

Investigators

Abstract

NSF 9982942 - Hardin Lay Abstract Circadian rhythms are fluctuations in behavioral and physiological activities over a ~24hr period. Three core properties define such rhythms: 1) They are entrained by environmental cues such as light and temperature, 2) They persist (or free-run) under constant environmental conditions, and 3) They run at a rate that is relatively temperature insensitive. Although circadian rhythms parallel environmental cycles of light and dark, they are not simply a reaction to environmental fluctuations, but are generated by an endogenous timekeeping system termed the circadian clock. The importance of the circadian clock is underscored by its ubiquity; clocks are present in organisms ranging from microbes to plants, insects and mammals. In every organisms tested to far, the lock is comprised of a circadian feedback loop in gene expression, where the rhythmic expression of core clock genes is controlled by the action of their own protein products. We would like to know whether rhythmic expression of these core clock genes is needed to synchronize the clock to light and dark cycles or to maintain clock function in constant darkness. We are using fruit flies to answer these questions because much is known about the core clock genes in this organism, the expression of these genes can be easily manipulated and clock function can be assessed by measuring rhythmic behavior. Our plan is to express these core clock gees at constant levels and determine 1) if the flies can properly synchronize to light dark cycles and 2) whether they are rhythmic in constant darkness. If the flies are arrhythmic or can't properly synchronize to light-dark cycles then rhythmic gene expression is an integral part of the circadian clock, but if synchronization and rhythmically are unaffected expression of core clock genes is dispensable for clock function.