Investigating the Molecular Effects of Superovulation and Embryo Culture on Genomic Imprinting in a Mouse Model System.

Genomic imprinting is a specialized transcriptional mechanism that results in the unequal expression of alleles based on their parent-of-origin. Many imprinted genes have been shown to be critical for proper embryonic and fetal development, and disruption of genomic imprinting at these loci has been associated with many development disorders. Recently, increased frequencies of many imprinting disorders have been correlated with the use of assisted reproductive technologies (ARTs). Rigorous and thorough testing of ARTs is required to determine their influence on processes of genomic imprinting. I hypothesize that the acquisition of genomic imprinting in developing germ cells is disrupted by superovulation, and that imprinting maintenance mechanisms are disrupted during early mouse development by culture media used in human ARTs. We have developed a method to evaluate the methylation and expression patterns of known imprinted genes from individual blastocysts. We utilized this technique to separately address the effects of two different hormone dosages, and six different culture media on imprinted methylation and expression. Superovulation resulted in a loss of imprinted methylation at both hormone concentrations tested, in a dose-dependent manner, and embryo culture resulted in a loss of imprinted methylation in all media tested. We conclude that both imprint acquisition and imprint maintenance can be perturbed by assisted reproductive technologies. Further analysis and use of our novel technique will allow more accurate and comprehensive study of the epigenetic effects of various environmental insults on the preimplantation embryo. (poster)