Gonadotropin releasing hormone (GnRH) is a decapeptide expressed in hypothalamic neurons where it plays a penultimate role in the control of the hypothalamic-pituitary-gonadal axis and reproduction. In addition, a cDNA coding for GnRH was initially isolated from a placental library and the protein has been demonstrated in the placenta of many species where it may play a role in early hCG production and maintenance of early pregnancy. Although much is known about the secretory dynamics and post- translational regulation of GnRH, little information is available concerning the mechanisms which control its tissue specific expression and how steroid hormones may regulate its production. The clearly defined ontogeny of GnRH secretion across sexual maturation suggests a complex control of developmental as well as tissue specific expression. With the use of two recently derived neuronal cell lines that express GnRH as well as placental cell lines, we have a unique opportunity to address the mechanisms by which tissue specificity, developmental expression, and steroid hormone regulation of GnRH promoter activity occurs. The specific aims of this five year proposal are to: 1. To analyze the specific cis-acting DNA sequences and the trans-acting nuclear protein-DNA interactions that mediate tissue specific and developmental expression of GnRH; and 2. To characterize the cis-acting DNA sequence elements and the protein- DNA or protein-protein interactions that confer steroid hormone regulation to the GnRH promoter. The cis-acting DNA promoter sequences and trans-acting nuclear factors which direct developmental and tissue specific regulation and control by steroid hormones will be characterized by gene transfer studies, DNase I protection, gel retardation assays, methylation interference assays, site directed mutagenesis, and in vitro cell free transcription studies. The results of these studies will impact on our understanding of sexual maturation and hypogonadism, as well as the basic mechanisms which control tissue specific, developmental, and hormonal regulation of neuroendocrine genes.