Circadian oscillations of signaling molecules in mouse peripheral tissues.

Circadian rhythms are biological cycles that occur with a period of about 24 hours in the absence of environmental cues. In mammals, the central circadian clock is found in the hypothalamus of the brain. It is believed that clock components in peripheral tissues regulate local oscillations outside the brain, although most rely on timing cues from the central clock to synchronize to the environment. Many forms of cellular communication rely on G-protein linked signaling pathways to amplify the intracellular effects of certain molecules. Proteins involved in these pathways have been associated with the circadian system. We are particularly interested in the signaling cascade that utilizes the phospholipase C b4 (PLCb4) second messenger system. In Drosophila, a PLCb4 homolog interacts with clock proteins and underlies the mechanism for an oscillation in visual sensitivity. The G-protein, [Ga.sub.11], and regulator of G-protein signaling, RGS16, have been linked to the PLCb4 pathway and are found to associate with receptors involved in the mammalian circadian system. The present study sought to determine the relevance of these proteins in the mammalian signaling system by evaluating oscillations in mouse liver and eye tissues. Liver and eye tissues were collected over the course of the day from 30 mice. Proteins were extracted and the levels were evaluated using standard western blotting techniques. Preliminary data indicate a robust oscillation of PLCb4 in liver and a modest oscillation in the eye. Analysis of RGS16 and [Ga.sub.11] has also revealed mild oscillations in both the eye and the liver. * Supported by the College of Charleston 4th Century Initiative Undergraduate Research & Creative Activities Grants & NIH SCBRIN grant.