The Research Of DNA Methylation And Histone Acetylation Affect The Developmental Ability Of Mouse Preimplantation Embryos

The developmental abilities of different preimplantation embryos were various in mouse. Lots of factors were responsible for it, i.e. the quality of sperm, nuclear cells, growth conditions, et al. The related gene transcriptional expression could crucially affect the developmental ability of embryos. The transcription products could be influenced by the gene transcriptional level, which might lead to abnormalities of embryonic epigenetic pattern. DNA methylation and histone acetylation were important epigenetic modes which play a key role in the growth of embryos. The differences in gene expression formed the basis of cell differentiation and biological evolution. Histone acetylation could promote gene transcription, while histone deacetylation suppressed gene transcription. The dynamic balance of AC and DAC levels of embryos were controlled by the emzymes of HAT and HDAC, which could affect chromatin structure, and then gene transcription. The control embryos in vivo and in vitro, parthenogenetic embryos, MEF cloned embryos and iPS cloned embryos were studied in this experiment to explore the developmental abilities, DNA methylation levels and acetylation levels of different groups. At the same time, with the treatment of TSA in vitro embryos, the question whether the acetylation levels of embryos could be improved was investigated. Our results showed that:1. The H3K9 acetylation levels of control group were higher than that of parthenogenetic group at all stages in vivo. Gene promoter could be made in super acetylation by high acetylation levels in parthenogenetic embryos, which might lead to the abnormal expressions of gene and then the decreased developmental potential of embryos.2. With the same strains of mouse, the developmental ability of iPS cloned embryos was higher than that of MEF cloned embryos.3. The developmental abilities of different cloned embryos in C57 and KM mouse were higher than that in iCR mouse. This might be that the iPS cells were derived from the C57 mouse. There were genetic differences in the different strains of mice, which could affect the related gene transcription, and then the development of embryos.4. The development abilities of cloned embryos of the same source were different in different culture systems. The developmental abilities of embryos in CZB/CZBG were lower than that in G1/G2 medium, however that of M2/M16 culture systems were lowest. The higher developmental abilities of embryos in G1/G2 medium might caused by activating the transcription of corresponding gene in embryos.5. H3K9 acetylation levels in different cloned embrys were lower than control groups at pronucleus stage. In addition, at the stage of 2-cell, the cloned embryos had a higher H3K9 acetylation level compared with the parthenogenetic embryos in vivo. This might be caused by maternal gene high expression and few paternal gene expression in the cloned embryos at pronucleus stage. However at 2-cell stage, the paternal genes began to express, which might lead to genetic reprogramming in the embryos and then affect the epigenetic patterns of preimplantation embryos.6. Compared with control embryos, H3K27ace level of the iPS and MEF cloned embryos both had a significant difference at 2-cell stage (P<0.05). The H3K27 acetylation of the iPS cloned embryos was the lowest (0.0967±0.01282), the H3K27ace level of the MEF cloned embryos second. It might be that at 2-cell stage, zygotic genome activation (ZGA) happened in cloned embryos, and a lot of promoting apoptosis genes were accumulated in a short time suppressing the normal development of embryos.7. The abnormal DNA methylation level was harm to embryonic development. The parthenogenetic embryos, the MEF and iPS cloned embryos all had higher levels of DNA methylation at 2-cell stage compared with control groups, which could result in improper development of early implantation embryos. Abnormal gene transcription might be caused by abnormal DNA methylation level by affecting the related enzyme activities.8. The development abilities of parthenogenetic embryos were improved by TSA, which might because the adverse effects of culture in vitro could partly be reduced by TSA. However H3K9 acetylation level in preimplantation embryos might not be entirely affected by TSA.