Molecular and Functional Investigations of Gonadotropin and Gonadotropin Releasing Hormone in Lamprey Reproduction

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9722765 Condon This proposal will investigate the control of reproduction by the brain and pituitary in an ancient fish, the lamprey. Lampreys are important because they are members of the oldest lineage of vertebrates, the Agnathans or jawless fish, and raise interesting questions on evolution. This laboratory has focused on the structure and function of two brain hormones involved in the brain- pituitary gonadal axis in lampreys. The primary structures of two brain hormones, gonadotropin-releasing hormone (GnRH- I and GnRH-III) have been determined in lampreys. This information combined with immunocytochemical and physiological studies provides strong evidence for the regulatory influence of the brain on the pituitary-gonadal axis in lampreys. In addition, lampreys are the first vertebrates to clearly demonstrate a dual role for GnRH molecules as neurohormones mediating the pituitary-gonadal axis. However, the investigations on the role of GnRHs in reproductive processes have been impeded by the lack of an identified gonadotropin that could be used in assays as a measure of pituitary responsiveness to GnRH. The purification and identification of lamprey pituitary gonadotropin, GTH, is critical to examine the hypothalamic- pituitary-gonadal relations in lampreys. Thus identification of GTH and verification of the ways in which the hypothalamus affects the pituitary gonadal axis are needed in the lamprey, and are part of this project. The experiments will incorporate a variety of approaches to further define the relationship of the brain and pituitary in Agnathans. The ongoing and proposed studies are focused on molecular, biochemical and functional studies of GnRHs in lampreys to test the hypothesis that multiple forms of GnRH released from the brain influence the synthesis and secretion of a gonadotropin-like molecule which regulated the function of the gonads. Results fsrom these studies in lampreys will provide better understanding of the molecular evolution from invertebrates to later evolved vertebrates. %%% This research is looking to see if there is regulation from the hypothalamus to the pituitary and the gonads in the lamprey. The lamprey belongs to one of the oldest lineage's of vertebrates and is used to look at the origin of various vertebrate signaling systems. This laboratory has identified and sequenced the gonadotropin releasing hormone from the hypothalamus of the lamprey, and now wants to identify the hormone released from the pituitary in response to GnRH. Also the effects of environmental factors on this hormonal pathway will be determined. This research will provide a better understanding of molecular evolution of the reproductive system. ***