KAVANAUGH, S.K.*; GORBMAN, A.; SOWER, S.A.; University of New Hampshire, Durham; University of Washington, Seattle; University of New Hampshire, Durham: The distribution of gonadotropin releasing hormone in the urochordate Ciona intestinalis.

The tunicate Ciona intestinalis, a urochordate, is in a unique position in the chordate lineage to ask important questions about how animals have evolved from a basal chordate to more derived lineages such as cephalochordata and vertebrata. A key characteristic to the directional development of an organism is reproduction. Gonadotropin releasing hormone (GnRH) is the key neurohormone that is important in the role of reproduction for all vertebrates. Research during the last several years has established that there is considerable species diversity in the structure of GnRH�s among protochordates and vertebrates. In invertebrates, the primary structure of nine forms have been identified and shown to stimulate gamete release. However, the distribution and function of GnRH in C.i. have not been fully determined. Therefore, the objective of this study is to determine tissue specific expression of Ci-GnRH-1 and Ci-GnRH-2 in adult C.i. using reverse transcriptase- PCR (RT-PCR) and in situ hybridization. To examine the expression of the two GnRH genes total RNA and genomic DNA were isolated from whole animals. Total RNA from neural tissue (cerebral ganglion and neural gland), testis, ovary, heart, and hepatic organ was also isolated. Results from RT-PCR indicated both forms are only expressed in the neural tissue. Based on this, sense and antisense riboprobes were synthesized and freshly prepared cryostat tissue sections of neural tissue were prepared for in situ hybridization. Results indicate the presence of expression in the cerebral ganglion bordering the neural gland. The current results along with previous studies provide key information on the evolution of GnRH in protochordates. (Supported by NSF 0090852 to Stacia Sower)