Abstract
The mRNA expression of GPRC5B, an orphan G protein-coupled receptor, is induced by retinoic acid (RA). Because RA plays critical roles in embryonic development, reproductive functions, metabolism and homeostasis, GPRC5B is also considered crucial in these physiological events. We investigated the changes in expression of GPRC5B and RA receptor (RAR) α mRNAs and immunohistochemical localization of their proteins in the murine placenta and yolk sac at 13.5, 15.5 and 17.5 days post coitus. Stable levels of GPRC5B and RARα mRNAs were detected in the placenta and yolk sac. In the placenta, GPRC5B was present in maternal and fetal vascular endothelial cells, stromal cells, fibroblast-like cells and glycogen cells. A strong reaction to RARα was detected in maternal and fetal vascular endothelial cells and stromal cells. The levels of GPRC5B and RARα proteins in maternal and fetal vascular endothelial cells decreased with gestation. In the yolk sac, GPRC5B and RARα proteins were detected in vascular endothelial cells, but their levels did not change during the gestation period. These findings indicate that GPRC5B is involved in RA-dependent morphogenesis/angiogenesis and regulation of extracellular matrix synthesis in the murine placenta and yolk sac.
