The Research Of Histone H3K27Trimethylation And Acetylation Regulate The Development Of Mouse Embryos

The trimethylation on lysine27of histone3(H3K27me3) is considered as a marker of inactive transcription,whereas the acetylation on lysine27of histone3(H3K27ace) can promote the transcription. The different effects of the two types of epigenetic modification on the same locus play important roles in embryonic development. In vivo and parthenogenetic embryos which are obtained from activating the MⅡ oocytes were collected and used as a model to study the difference of H3K27trimethylation and acetylation. Then the parthenogenetic embryos were treated with two inhibitors(Trichostatin and5-azacytidine) to address the effects the two inhibitors on the mentioned above epigenetic modification patterns, further confirming the developmental ability of different periods of parthenogenetic embryos and the later implantation ability. In this study,4-6weeks old female Kunming mice were injected with pregnant mare serum gonadotrophin (PMSG) and human chorionic gonadotropin (hCG), and then mate with the mature male. Different stages of in vivo preimplantation and parthenogenetic embryos were collected according to a book named manipulating the mouse embryo:a laboratory manual. Indirect immunofluorescence histochemistry was performed to study the H3K27me3and H3K27ace patterns of various types of embryos. The different epigenetic patterns of different stages of the parthenogenetic embryos, as well as TSA and5-azaC treated embryos, were compared with the normal group embryos. The detailed results are listed as follows:1. During the1-cell to blastocyst stage, the fluorescence intensity of H3K27ace were decreased at the2-cell stage (0.04±0.002) and increased onwards, peaking at the blastocyst stage (0.25±0.005). H3K27acetylation patterns in parthenogenetic embryos showed a distinguishing pattern when compared with the in vivo group. The fluorescence intensities from1-to8-cell of parthenogenetic groups were higher and the intensity in the last two stages embroys is lower than those of the normal group, respectively. It’s worth noting that the pattern of H3K27ace in the two types of embryos showed an asymmetric pattern from1-cell to morula, while the obviously difference occurred at the blastocyst stage. Besides the two periods of1-cell and morula have no significant difference, the other periods of parthenogenetic group have the significant differences with the normal group (P<0.05), especially the stages of2-cells (0.12± 0.007vs0.04±0.002) and blastocyst (0.12±0.006vs0.25±0.005).2.The level of H3K27me3is low in MⅡ oocytes. The patterns of H3K27me3showed a gradually decreased trend in each period during pre-implantation embryonic development in the normal groups, reaching the minimum at the blastocyst stage (0.021±0.004). When compared with the in vivo groups, the patterns of H3K27me3in parthenogenetic embryos showed a distinguishing pattern. The trend of the H3K27me3patterns in parthenogenetic embryos is absolutely opposite, peaking at the blastocyst stage (0.015±0.002). The overall level of transcription is much lower in parthenogenetic embryos than those of in vivo groups. Beside the blastocyst stage, the other periods of parthenogenetic group have a significant difference with the normal group (P<0.05).3. TSA treatment caused some impact on the patterns of H3K27me3in parthenogenetic embryos. Although there is no significant difference between the treated and the control groups in the first three periods from2-cell to8-to16-cell, the overall level of H3K27me3has increased in the treated group. The period of blastocyst stage has a significant difference with the treated group. The in vitro culture environment treated by TSA has been improved with a certain degree. The level of H3K27ace in parthenogenetic embryos can be increased by5-AzaC treatment in every period, especially the blastocyst stage. Abnormal level of H3K27ace can be repaired partly in parthenogenetic embryos. It is possible to promote the transcription of placenta development related gene. There is some significance on improving the development ability and implantation capacity. The differences of the mentioned above epigenetic modification patterns in parthenogenetic embryos derived from the culture conditions and environmental changes play an important role in pre-implantation embryo development, especially accompanying assisted reproductive technology. Systematic study the impact of culture conditions in preimplantation embryo development and the epigenetic risks related to assisted reproductive technologies is warranted.