Our Unit is interested in the molecular mechanisms underlying regulated patterns of gene expression, both in time and space. Our model systems include the rodent retina and the suprachiasmatic nucleus (SCN), which contain self-sustaining molecular clocks, and the pineal gland, a slave oscillator in rodents. Currently, the program is mainly focused on the use of the arylalkylamine N-acetyltransferase (AA-NAT) gene as a model for tissue and time of day specific gene expression. This gene encodes the key regulated enzyme in the melatonin biosynthetic pathway. Because AA-NAT is expressed in both the pineal and retina, it represents a single rhythmic output of two different kinds of oscillator. Rat and mouse transgenic technology and transient transfections of primary retinal/pineal cultures are being used to probe the different regions and elements that contribute to the observed patterns of gene expression in both systems. This project has generated two major developments. First, a rat NAT promoter fragment was characterized that can drive highly specific gene expression in transgenic rats. In these rats, transgene expression can only be detected in the pineal gland and retina, and only at night. Second, the promoter fragment mentioned above was used to successfully target expression of a dominant negative form of the transcription factor Fra-2 to the rat pineal gland at night. We are currently assessing the effect of this perturbation upon pineal gene reprogramming at night. In addition, we have recently isolated and partially characterized a novel gene, from a mouse brain library, which can interact with the period 1 (Per 1) gene product. We are in the process of assessing the function of this new protein and its possible role in clock-related events. - gene expression, circadian, SCN, retina, pineal