Division of Animal Sciences, University of Missouri, Columbia, MO 65211, USA.
Biol Reprod. 2013 Feb 28;88(2):48. doi: 10.1095/biolreprod.112.104471. Print 2013 Feb.
During early mammalian embryogenesis, there is a wave of DNA demethylation postfertilization and de novo methylation around implantation. The paternal genome undergoes active DNA demethylation, whereas the maternal genome is passively demethylated after fertilization in most mammals except for sheep and rabbits. However, the emerging genome-wide DNA methylation landscape has revealed a regulatory and locus-specific DNA methylation reprogramming pattern in mammalian preimplantation embryos. Here we optimized a bisulfite sequencing protocol to draw base-resolution DNA methylation profiles of several selected genes in gametes, early embryos, and somatic tissue. We observed locus-specific DNA methylation reprogramming in early porcine embryos. First, some pluripotency genes (POU5F1 and NANOG) followed a typical wave of DNA demethylation and remethylation, whereas CpG-rich regions of SOX2 and CDX2 loci were hypomethylated throughout development. Second, a differentially methylated region of an imprint control region in the IGF2/H19 locus exhibited differential DNA methylation which was maintained in porcine early embryos. Third, a centromeric repeat element retained a moderate DNA methylation level in gametes, early embryos, and somatic tissue. The diverse DNA methylation reprogramming during early embryogenesis is thought to be possibly associated with the multiple functions of DNA methylation in transcriptional regulation, genome stability and genomic imprinting. The latest technology such as oxidative bisulfite sequencing to identify 5-hydroxymethylcytosine will further clarify the DNA methylation reprogramming during porcine embryonic development.
在哺乳动物胚胎早期发育过程中,受精后会出现一波 DNA 去甲基化和植入前后的新甲基化。在大多数哺乳动物中,父本基因组经历活跃的 DNA 去甲基化,而母本基因组在受精后是被动去甲基化的,但除了绵羊和兔子之外。然而,新兴的全基因组 DNA 甲基化景观揭示了哺乳动物胚胎前植入过程中一种调节和特定基因座的 DNA 甲基化重编程模式。在这里,我们优化了亚硫酸氢盐测序方案,以绘制配子、早期胚胎和体细胞中几个选定基因的碱基分辨率 DNA 甲基化图谱。我们观察到早期猪胚胎中的基因座特异性 DNA 甲基化重编程。首先,一些多能性基因(POU5F1 和 NANOG)遵循典型的 DNA 去甲基化和再甲基化波,而 SOX2 和 CDX2 基因座的 CpG 丰富区域在整个发育过程中呈低甲基化状态。其次,IGF2/H19 基因座中的印迹控制区的差异甲基化区域表现出不同的 DNA 甲基化,这种差异在猪早期胚胎中得以维持。第三,着丝粒重复元件在配子、早期胚胎和体细胞中保持中等的 DNA 甲基化水平。早期胚胎发育过程中的多样化 DNA 甲基化重编程可能与 DNA 甲基化在转录调控、基因组稳定性和基因组印记中的多种功能有关。最新的技术,如氧化亚硫酸氢盐测序来识别 5-羟甲基胞嘧啶,将进一步阐明猪胚胎发育过程中的 DNA 甲基化重编程。