牛不同供体核克隆囊胚Xist基因DNA甲基化程度的比较研究

利用亚硫酸氢盐测序法分析Holstein奶牛胎儿成纤维细胞(FFB)和输卵管上皮细胞(FOV)来源的克隆囊胚Xist基因DNA甲基化状况,以体外受精囊胚(IVF)和供体细胞作对照.克隆囊胚Xist基因处于较低程度的DNA甲基化状态,其中,FFB来源的克隆囊胚Xist基因DNA甲基化程度为43%,而FOV来源的克隆囊胚仅为17%.在体外受精囊胚中,Xist基因DNA甲基化处于中等状态,为49%.然而,在体细胞中,Xist基因的甲基化程度较高,FFB为66%,FOV为63%.这些结果说明,Xist基因DNA甲基化是可以被重编程的,所检测的CpG岛可能调节Xist基因的表达.结合已发表的实验数据,在同一个体中,FFB来源的克隆囊胚发育率比FOV的低,但其克隆牛胎儿的妊娠率和产犊率比FOV的高,这暗示不同供体核克隆囊胚的重编程是有差异的,并可能影响到胚胎及个体的发育.

Methylation Patterns of The Xist Gene in Cloned Bovine Blastocysts Derived From Different Somatic Donor Cells

Using bisulphate sequencing, methylation patterns of the Xist gene in cloned blastocysts derived from bovine fetal fibroblasts (FFB) or oviduct epithelial cells (FOV) were investigated, as compared to that in donor cells and in vitro fertilized (IVF) blastocysts. Hypomethylation of the Xist gene was observed in the cloned blastocysts (43% and 17% in FFB and FOV derived blastocysts, respectively), while the Xist gene in 49% IVF blastocysts appeared to be methylated. On the contrast, somatic donor cells showed high percentage of methylation (66% and 63% in FFB and FOV cells, respectively). These results suggest that the DNA methylations of the Xist gene were reprogrammable and the detected CpG islands may regulate expression of the Xist gene. Altogether with the previous data, It was shown that development rate of cloned blastocysts derived from FFB is lower than that from FOV of the same origin, while pregnancy and birth rates appear to be opposite. It can be proposed that cloned blastocysts derived from different types of somatic cells differ in DNA reprogramming that may affect embryo and fetal development.