Atrial natriuretic peptide (ANP), binds to guanylyl cyclase/natriuretic peptide receptor-A (NPRA/GC-A) and elicits natriuretic, diuretic, vasorelaxant, and antiproliferative responses, important factors in the control of blood pressure and blood volume. However, the molecular basis of these activities and the functional expression and regulation of Nprl gene (coding for NPRA) remain incompletely understood. To further understand the functional significance of Nprt gene, we will study its transcriptional regulation using genomic clones, which we have isolated and sequenced, and physiological function(s) using the gene-targeted mutant mouse models, which we have established at our facility. Our fundamental hypothesis is that the regulated activity of Nprl gene requires cooperative interactions among ubiquitous and tissue-specific transcription factors that respond to extra-and intracellular signals, and that the absence of Nprl gene expression in intact animals in vivo renders unopposed powerful sodium retaining, vasoconstrictive, and proliferative systems, whereas, overexpression of Nprl gene exerts a gene-dose-dependent action that is natriuretic, vasodilatory, and antiproliferative in nature. To accomplish the objective of this proposal, we will integrate genetic information at the molecular level, with biochemical information at protein level, and physiological information at the whole animal level, resulting in a vertically integrated molecular-physiological strategy. We will exploit the power of molecular genetic techniques to answer cellular, biochemical, and pathophysiological questions in intact animals in vivo and isolated cultured cells in vitro so as to arrive at conclusions that are definitive and physiologically relevant. The information obtained from the above lines of investigation will provide the means to test directly the efficacy of Nprl genomic regulatory elements and the impact of Nprl gene dosage and null mutation in ANP/cGMP-mediated biological responses. Overall, this project is expected to produce important new insights into the molecular mechanisms that underlie NPRA-dependent blood pressure regulation, kidney function, and cardiovascular pathophysiology in general.