Changes And Roles Of DNA Methylation In Mouse Model Of Polycustic Ovarian Syndrome And Heat Shock

DNA methylation is an epigenetic modification which plays an important role in gene expression. Using the mouse model, we determined the changes and possible roles of DNA methylation in the stress and diseases.Polycustic ovarian syndrome (PCOS) is one of the reproductive endocrine disorders which usually affects those women who are in the reproductive age. The pathogenesis of this syndrome is not well known so far. The heritability of PCOS is probably more complex, and a PCOS family history appears to be the most informative risk factor for the PCOS development. We used bisulfite sequencing (BSP) and combined bisulfite restrition analysis (COBRA) to examine the DNA methylation status of LHR, AR, FSHR and H19 in mouse model of PCOS induced by dehydroepiandrosterone (DHEA). LHR showed demethylation in mouse model of PCOS, but others had similar methylation level in both groups. The result indicate that demethylation may induce aberrant expression of LHR which results in the changes of signaling pathways activated by the LHR. It is probably one cause of PCOS.To gain a better understanding of the methylation imprinting changes associated with heat stress in early development, we used bisulfite sequencing and combined bisulfite restriction analysis to examine the DNA methylation status of imprinted genes in early embryos (blastocysts). The paternal imprinted genes, H19 and Igf-2r, had lower methylation level in heat-stressed embryos than in control embryos, whereas the maternal imprinted genes, Peg3 and Peg1, had similar methylation pattern in heat-stressed embryos and in control embryos. Our results indicate that heat stress may induce aberrant methylation imprinting, which results in development failure of mouse embryos, and that the effects of heat shock on methylation imprinting may be gene-specific.In addition, we determined the DNA methylation status of Peg3 during preimplantation development of mouse embryos. Peg3 showed completely unmethylated in two cell embryos, and was strongly de novo methylated in morula stages. The results indicate that the process of methylation imprint establishment during preimplantation development is more dynamic than previously thought.In summary, we determined the changes of DNA methylation in mouse model of PCOS and heat shock. These data indicate that DNA methylation is vulnerable to environments condition and is associated with the reproductive endocrine disorders.