Correlation between DNA methylation levels of imprinted genes XIST and H19 and developmental efficiency of porcine cloned embryo

Objective  Somatic cell nuclear transfer (SCNT) is widely used in agriculture, biomedicine and other fields, but the low cloning efficiency restricts the application and promotion of this technology. The purpose of this study was to explore the relationship between the DNA methylation levels of imprinted genes (XIST, H19) and cloning efficiency.

Method  Fourteen cell clone groups were obtained by culturing the same pig-derived ear fibroblasts, and were used as the donor cells for SCNT experiments. We statistically compared the blastocyst rates and DNA methylation levels of XIST and H19 gene regulatory regions for each sac of cloned embryos produced with each clone group as donor cells. We analyzed the correlation between the DNA methylation levels of differentially methylated regions for XIST and H19 genes and the blastocyst rates of cloned embryos.

Result  The DNA methylation level of XIST gene of blastocysts obtained from clone group 1 as donor cells was the highest (65.04%) and the blastocyst rate was the lowest (8.6%). The DNA methylation level of XIST gene of blastocysts obtained from clone group 14 as donor cells was the lowest (16.68%) and the blastocyst rate was the highest (38.2%). The correlation analysis showed that there was a strong negative correlation between the XIST gene methylation level and the blastocyst rate (|r|=0.8125>0.8). The highest and lowest DNA methylation levels ofH19 gene A side were 5.12% and 0.61% respectively. Correlation analysis showed that there was only a very weak correlation between the DNA methylation level of H19 gene A side and blastocyst rate (|r|=0.1647< 0.3). The highest and lowest DNA methylation levels on the G side ofH19 gene were 90.92% and 72.69% respectively. Correlation analysis showed that there was only a low correlation between the DNA methylation level on the G side of H19 gene and the blastocyst rate (0.3<|r|=0.3098<0.5).

Conclusion  The lower the DNA methylation level of XIST gene, the higher the blastocyst rate of the clone group. The research results provide a basis for improving the efficiency of pig SCNT embryonic development and improving the existing pig SCNT technology system.