Identification of estrogen-regulated genes in the mouse uterus using a delayed-implantation model

Gonadal steroid hormones are known to modulate the implantation of the blastocyst, but how the controlling genetics are regulated remains largely unknown. Using a delayed-implantation model, we examined estrogen-regulated genes (ERGs) in the mouse uterus using the differential-display reverse transcription-polymerase chain reaction (DD RT-PCR). Pregnant mice were ovariectomized and injected daily with progesterone (P, 1 mg/mouse), followed by a single injection of estrogen (E, 200 ng/mouse); 24 or 48 hr later, total RNA was extracted from the uterus. Reverse Northern analysis verified the expression patterns of 36 clones out of thousands of RNA species. Only five clones had mRNA levels that were modified, whereas other mRNAs were unchanged or not detectable. Sequence analysis of these, using the Basic Local Alignment Search Tool (BLAST) service, revealed that four of these clones were novel; one clone, designated ERG10, was found to be the mouse homologue of that deleted in oral cancer DOC-1. DOC-1 mRNA was detected all tissues examined, but only in the uterus and cervix was markedly increased 12 hr after E administration, it returned to basal level by 48 hr. One of the novel genes, designated ERG8, had three different forms of mRNAs and was expressed ubiquitously in all examined tissues. In the uterus, the mRNA level of ERG8 also increased 12 hr after E administration. These results suggest that during the implantation process, E differentially regulates several genes depending on cell type. Uterine-specific induction of newly found genes, such as ERG8 and 10, by E appears to be important for the early implantation process.