The neuroendocrine and genetic control of sexual maturation at puberty remains one of the great mysteries of human biology. Recently, the signaling molecule kisspeptin and its receptor GPR54 have been found to have key roles in regulating the reproductive endocrine axis. The experiments in this proposal seek to understand how kisspeptin function is regulated at the transcriptional level using three complementary approaches. 1) An in vivo mouse reporter system will be used to identify cis-acting DMA elements that regulate Kissl expression. DNA constructs containing stretches of the Kissl genomic region fused to GFP will be injected into the hypothalami of live mice. This will allow the identification of specific DNA elements required for Kissl expression. 2) Laser microdissection and gene array analysis will be used to identify trans-acting factors that regulate Kissl expression. Expression of GFP in Kissl-expressing neurons will allow them to be isolated using laser microdissection. RNA will be prepared from neurons that express or do not express Kissl and used for gene array hybridization to create gene expression profiles. Genes expressed in Kissl-expressing neurons but not in non-Kiss1-expressing neurons are likely to be involved in Kissl expression. 3) Human patients with idiopathic hypogonadotropic hypogonadism (IHH) will be screened for mutations in KISS1 regulatory regions. Once key regulatory regions of Kissl are identified in mouse, the analogous regions in human KISS1 region will be screened in our collection of DNA from over 500 patients with IHH. If a likely mutation is identified, the mouse reporter system will be used to test the effect of this mutation on Kissl expression. In this way, identification of human mutations can contribute to the analysis of the mouse Kissl promoter. By using these complementary approaches, I hope to discover how Kissl expression is regulated at the pubertal transition and thereby gain insight into the mechanisms that determine the timing of puberty. These experiments will further our understanding of the precise mechanisms that govern puberty. In addition to providing insight into a fundamental biological process, this work may lead to genetic diagnostic tests for individuals with reproductive disorders. Modulation of the reproductive endocrine axis has important applications for the treatment of precocious and delayed puberty, and also for contraception, infertility, endpmetriosis, and the treatment of sex-hormone dependent tumors such as breast cancer and prostate cancer. [unreadable] [unreadable] [unreadable]