Excess Expression of Uterine Ribosomal Protein Genes P2 and S25 During the “Implantation Window” in the Rat

Abstract

Objective: The present study describes the siolation of “implantation-related” uterine cDNA clones. It further describes their temporal and spatial expression and their identification as the messengers for two ribosomal proteins: RP2 and RS25.

Methods: Libraries of cDNA, representing spayed rats treated with progresterone for 3 consecutive days and with estrogen for either 12 or 36 hours, were screened using homologous and heterologous probes. Two cDNA clones showing differential intensity of the signal were sequenced, the timing of their expression was analyzed by Northern analysis, and their spatial expression was visualized by in situ hybridization.

Results: The steady-state level of RP2 mRNA was temporally and spatially controlled by estrogen and progesterone. Whereas estrogen, alone or in combination with progesterone, stimulated this gene, the spatial distribution of the activation was different. Estradiol alone directed RP2 expression to the endometrial-myometrial border, whereas combined treatment increased epithelial staining and directed heavy expression to the stratum vasculare. In normal pregnancy, during the implantation-window period, RP2 was mainly expressed on the mesometrial side, with much less staining on the antimesometrial side. The steady-state levels of the RS25 messenger were elevated by estrogen alone or in combination with progesterone and were confined to the uterine epithelium, RS25 mRNA was evenly distributed throughout the uterine stroma during implantation.

Conclusion: A developmental pattern of expression of RP2 is reported that corresponds temporally with the primary decidual response but is spatially expressed at the site of the secondary response.