Abstract: 2

TRANSCRIPTIONAL REGULATION OF HUMAN GONADOTROPIN-RELEASING HORMONE RECEPTOR (GnRHR) IN HUMAN PLACENTAL CELLS.

Kwai Wa Cheng¹ , Sung Keun Kang¹ , Chen Jei Tai¹ , Parimal S. Nathwani¹ , Peter C.K. Leung^{1 *}
Department of Obstetrics and Gynaecology, The Univeristy of British Columbia, Vancouver, B.C. Canada. ¹

The correlation between dynamic changes in GnRHR and human chorionic gonadotropin secretion suggest that the regulation of GnRHR gene expression is an important determinant of the gonadotropin-releasing hormone (GnRH) action in the placenta. In order to understand the placental transcriptional regulation of the GnRHR gene, three GnRHR promoter-luciferase constructs were transiently transfected into two human placental cell-lines, human choriocarcinoma cells (JEG-3) and immortalized human extravillous trophoblasts (IEVT), and mouse gonadotroph T3-1 cells. Using reverse transcription polymerase chain reaction, GnRHR mRNA has been identified in both JEG-3 and IEVT, suggesting the feasibility of using these cells in studying the placenta-specific expression of GnRHR. The transfection results indicated that an up-stream promoter was utilized in placental cells whereas both up- and down-stream promoters were required in T3-1 cells. Further sequential deletion of the 5' flanking region (5'FR), revealed 3 suppressor and 2 enhancer regions which control the GnRHR promoter activity in the placental cells. In an early attempt to study the possible role of GnRH in regulating GnRHR gene expression in the placenta, the full length 5'FR luciferase construct was transiently transfected into IEVT and T3-1 cells. Prolonged GnRH agonist (GnRHa) treatment (24h) resulted in an average 75% decrease (P<0.001) of the GnRHR promoter activity in T3-1 cells. This decrease was mimicked by phorbol ester (TPA) administration. Interestingly, no inhibition of GnRHR promoter activity was observed in IEVT after GnRHa and TPA treatments. These results suggest that a different promoter and control mechanism are used in placental cells to control the human GnRH receptor gene expression.

    This abstract is being presented on Saturday, July 31 at 1:45 PM at Todd 116.