TRANSCRIPTION FACTOR AP-2-GAMMA REGULATES MURINE ADENOSINE-DEAMINASE GENE-EXPRESSION DURING PLACENTAL DEVELOPMENT

Trophoblast cells are specialized extra-embryonic cells present only i n eutherian mammals. They play a major role in the implantation and pl acentation processes. To understand better the molecular mechanisms th at control the development and function of trophoblast cells, we sough t to identify the transcription factors that regulate murine adenosine deaminase (ADA) gene expression in the placenta. Here we report a det ailed characterization of a placenta-specific footprinting region (FP1 ) in the Ada placental regulatory element. The sequence of FP1 was map ped by DNase I footprinting and was found to match a consensus AP-2 tr anscription factor-binding site. Electrophoretic mobility shift assays demonstrated that FP1 interacted with AP-a-like proteins. Further ana lysis using AP-2 antibody confirmed that AP-2 protein was indeed prese nt in the placenta and bound to FP1. Mutation at the AP-2 site in FP1 abolished the ability of the Ada placental regulatory element to bind AP-2 proteins and failed to target chloramphenicol acetyltransferase r eporter gene expression to placentas in transgenic mice, indicating th at AP-2 is required for Ada expression in the placenta. In addition, R Nase protection assays demonstrated that AP-S gamma was the predominan t AP-2 family member expressed in the placenta. In situ hybridization analysis revealed that AP-S gamma expression was enriched in the troph oblast lineage throughout development, suggesting that AP-2 gamma may be critical for trophoblast development and differentiation.