Differential expression of transcripts encoding retinoid binding proteins and retinoic acid receptors during placentation of the mouse

Abstract

We report the distribution of transcripts from genes encoding the retinol binding protein (RBP), the cellular retinol binding proteins (CRBP I, II) and retinoic acid binding proteins (CRABP I, II), the retinaldehyde dehydrogenase type 2 (RALDH-2), the retinoic acid receptors (RARs), and the retinoid X receptors (RXRs) in mouse placental tissues from 6.5 to 19.5 days postcoitum (dpc). During early placentation, RBP and RALDH-2 gene expression are restricted to the endoderm of the visceral yolk sac and the outer uterine epithelium, respectively, whereas CRBP I transcripts are detected in the visceral yolk sac and in the presumptive chorioallantoic placenta. By 15.5 dpc, CRBP I expression is down-regulated in the yolk sac where CRBP II becomes strongly expressed. Expression of CRBP II is also detected in the trophoblastic giant cells. Throughout placentation, the expression patterns of the CRABP I and II genes partly overlap in the decidual tissue and the vacuolar zones of the decidua, suggesting a role for these binding proteins in sequestering free retinoic acid from maternal blood, thus regulating its availability to the embryo. RARα is ubiquitously expressed in all placental tissues, except in trophoblastic giant cells, at all stages studied. During early placentation, RARβ and RARγ are co-expressed in the decidua but differentially expressed in the chorionic region (RARβ, 10.5 to 12.5 dpc) and the presumptive labyrinth (RARγ, 7.5 to 12.5 dpc). During the same stages, RXRα is strongly expressed in the presumptive placenta. HARγ remains weakly expressed in the labyrinth until 15.5 dpc, whereas RXPα exhibits a strong expression in this zone until birth, suggesting a role for these receptors in the development and function of the definitive placenta.