EXPRESSION OF RAS GTPASE-ACTIVATING PROTEIN (GAP) IN HUMAN NORMAL CHORIONIC VILLI AND HYDATIDIFORM MOLE

Pas GTPase-activating protein (GAP), an important downregulator of Ras activity, has previously been shown to be abundant in human placenta. The expression of p120 and p100 isoforms of GAP in human normal chori onic villi (n=5) and hydatidiform mole (n=5) was investigated to clari fy the involvement of Ras GAP in the growth of chorionic villi in the first trimester of pregnancy. Immunablot analysis revealed that bath p 120- and p100-GAP isoforms were remarkably less expressed in mole vill i than in normal chorionic villi. The expression of p100-GAP significa ntly reduced in comparison with that of p120-GAP in mole villi. Northe rn blot analysis showed that the amount of GAP mRNA reduced in hydatid iform mole less than one-third of that in normal chorionic villi. The GAP activity, measured by the effect of tissue extract on the hydrolys is of Ras-hound GTP, was significantly lower in hydatidiform mole than in normal chorionic villi. These results suggest that Ras GAP may pla y an important role in the normal growth and differentiation of human chorionic villi in the first trimester. (C) 1997 W. B. Saunders Compan y Ltd.