Yi Liu, Ph.D. Associate Professor  Voice (214) 645-6033 Fax (214) 645-6049 Room ND13.214AA Yi.Liu@UTSouthwestern.edu The University of Texas Southwestern Medical Center at Dallas Department of Physiology 5323 Harry Hines Boulevard Dallas, TX  75390-9040

Molecular Mechanisms of Circadian Clocks

Circadian clocks have been described in almost all organisms ranging in complexity from single cells to mammals and function to control daily rhythms in a variety of biochemical, cellular, physiological and behavioral events.  These rhythms have a period close to 24 hours (circadian) and persist in the absence of external time cues.  One of the most important characteristics of circadian rhythms is that they can be synchronized or entrained by environmental signals, the strongest of which are light and temperature.   In humans and mammals, circadian clocks control  events such as sleep-wake and activity cycles, body temperature cycles, endocrine functions, and gene expression.  Clinical consequences in humans including sleep disorders and depression can be observed when the clock malfunctions.  The influence of a functional clock on temporal regulation is evident from the decreased performance of shift workers and the jet lag felt by long distance travelers.

Our lab is using filamentous fungus Neurospora crassa, one of the best studied model organisms for circadian clocks, to understand the molecular mechanisms of the circadian clock.  In Neurospora, the circadian clock acts to control a variety of processes, and previous studies have shown that the Neurospora circadian clock is an auto-regulated negative feedback loop in which the frequency (frq) gene is an essential component.  My laboratory is using molecular, biochemical, and genetic approaches to answer three general questions: 1) What are the components of the input pathways to the clock and how do environmental signals entrain the clock; 2) What are the genes that make up the oscillator and how are they regulated to generate rhythms and 3) How does the clock control rhythmic output events? In the long term, these studies will enable us to compare clock mechanisms of fungi with those of other eukaryotes and to help guide research in other organisms.

Publications