Proline-Rich Acidic Protein 1 (PRAP1) as a Marker for Established Uterine Receptivity.

Abstract

The proline-rich acidic protein 1 (PRAP1) is mainly expressed in the epithelial cells and has been suggested to play an important role in maintaining normal growth homeostasis in epithelial cells. We have examined the expression and regulation of PRAP1 in mouse uterus. In situ hybridization indicates that PRAP1 mRNA is exclusively expressed in the uterine luminal epithelium (LE). In ovariectomized uterus, PRAP1 expression levels can be upregulated by 17β-estradiol treatment and downregulated by progesterone treatment. PRAP1 mRNA has unique temporal expression pattern in the early pregnant mouse uterus. In normal wild type uterus, PRAP1 mRNA is strongly detected in day 0.5 LE (mating night as day 0), disappears in pre-implantation day 3.5 LE, and then is intensively expressed in day 4.5 LE after implantation has initiated. These data indicate that the temporal expression of PRAP1 is associated with the establishment of uterine receptivity. This indication has been further demonstrated in experimentally-induced delayed implantation wild type mouse uterus and Lpar3(-/-) mouse uterus with delayed implantation. Indeed, PRAP1 mRNA is undetectable in the non-receptive uterus in both delayed implantation mouse models. These results suggest that PRAP1 may serve as a marker for the established uterine receptivity. However, the function of PRAP1 in the LE has not been established. (Supported by startup funding from The University of Georgia and funding from the Interdisciplinary Toxicology Program at The University of Georgia.) (poster)