Regulation of non-classical major histocompatability complex class I mRNA expression in bovine embryos.

Regulation of expression of the class I major histocompatability complex (MHC class I) at the maternal fetal interface may play a critical role in embryo survival and the establishment of pregnancy in cattle. However, information concerning immunoregulation of implantation in cattle remains quite limited. Therefore, our current research is concerned with characterizing the expression and regulatory effect of a number of immune factors in the developing bovine embryo. We have analysed the effect of embryo culture in vitro (IVC) in medium supplemented with progesterone (P4): leukemia inhibitory factor (LIF), interferon gamma (IFNG), interleukin (IL)-1B, IL3, IL4, IL10 and granulocyte-colony stimulating factor (G-CSF) on in vitro embryo development and expression of the bovine non-classical MHC class I genes NC2, NC3 and N4 in blastocysts. Cytokine supplementation during IVC did not affect cleavage rate or blastocyst development. However, embryo mRNA expression of NC2, NC3 and NC4 was significantly (p≤0.05) modified in a gene- and cytokine-specific manner. Sequence analysis of the promoter regions of these genes confirmed the presence of appropriate binding sites through which the cytokine signalling could be mediated. In contrast to the lack of effect on in vitro blastocyst development, the non-classical MHC-I expression data suggests a preferential immunomodulatory role of these cytokines during preimplantation embryo development.

Genomic imprinting and reproduction.

Genomic imprinting is the parent-of-origin specific gene expression which is a vital mechanism through both development and adult life. One of the key elements of the imprinting mechanism is DNA methylation, controlled by DNA methyltransferase enzymes. Germ cells undergo reprogramming to ensure that sex-specific genomic imprinting is initiated, thus allowing normal embryo development to progress after fertilisation. In some cases, errors in genomic imprinting are embryo lethal while in others they lead to developmental disorders and disease. Recent studies have suggested a link between the use of assisted reproductive techniques and an increase in normally rare imprinting disorders. A greater understanding of the mechanisms of genomic imprinting and the factors that influence them are important in assessing the safety of these techniques.