Imprinted and DNA methyltransferase gene expression in the endometrium during the pre- and peri-implantation period...

The endometrium plays a key role in providing an optimal environment for attachment of the preimplantation embryo during the early stages of pregnancy. Investigations over the past 2 decades have demonstrated that vital epigenetic processes occur in the embryo during the preimplantation stages of development. However, few studies have investigated the potential role of imprinted genes and their associated modulators, the DNA methyltransferases (DNMTs), in the bovine endometrium during the pre- and peri-implantation period. Therefore, in the present study we examined the expression profiles of the DNMT genes (3A, 3A2 and 3B) and a panel of the most comprehensively studied imprinted genes in the endometrium of cyclic and pregnant animals. Intercaruncular (Days 5, 7, 13, 16 and 20) and caruncular (Days 16 and 20) regions were analysed for gene expression changes, with protein analysis also performed for DNMT3A, DNMT3A2 and DNMT3B on Days 16 and 20. An overall effect of day was observed for expression of several of the imprinted genes. Tissue-dependent gene expression was detected for all genes at Day 20. Differences in DNMT protein abundance were mostly observed in the intercaruncular regions of pregnant heifers at Day 16 when DNMT3A, DNMT3A2 and DNMT3B were all lower when compared with cyclic controls. At Day 20, DNMT3A2 expression was lower in the pregnant caruncular samples compared with cyclic animals. This study provides evidence that epigenetic mechanisms in the endometrium may be involved with implantation of the embryo during the early stages of pregnancy in cattle.