DIVERSE GENETIC REGULATORY MOTIFS REQUIRED FOR MURINE ADENOSINE-DEAMINASE GENE-EXPRESSION IN THE PLACENTA

Murine adenosine deaminase (ADA) is a ubiquitous purine catabolic enzy me whose expression is subject to developmental and tissue-specific re gulation. ADA is enriched in trophoblast cells of the chorioallantoic placenta and is essential for embryonic and fetal development. To begi n to understand the genetic pathway controlling Ada gene expression in the placenta, we have identified and characterized a 770-base pair fr agment located 5.4 kilobase pairs upstream of the Ada transcription in itiation site, which directs reporter gene expression to the placenta of transgenic mice. The expression pattern of the reporter gene reflec ted that of the endogenous Ada gene in the placenta. Sequence analysis revealed potential binding sites for bHLH and GATA transcription fact ors. DNase I footprinting defined three protein binding regions, one o f which was placenta-specific. Mutations in the potential protein bind ing sites and footprinting regions resulted in loss of placental expre ssion in transgenic mice. These findings indicate that multiple protei n binding motifs are necessary for Ada expression in the placenta.