Maalouf Walid E, Alberio Ramiro, Campbell Keith H S
Animal Development and Biotechnology Group, School of Biosciences, Division of Animal Physiology, Sutton Bonington Campus, University of Nottingham, Loughborough, Leicestershire, UK.
Epigenetics. 2008 Jul-Aug;3(4):199-209. doi: 10.4161/epi.3.4.6497. Epub 2008 Jul 24.
The oocyte is remarkable in its ability to remodel parental genomes following fertilization and to reprogram somatic nuclei after nuclear transfer (NT). To characterize the patterns of histone H4 acetylation and DNA methylation during development of bovine gametogenesis and embryogenesis, specific antibodies for histone H4 acetylated at lysine 5 (K5), K8, K12 and K16 residues and for methylated cytosine of CpG dinucleotides were used. Oocytes and sperm lacked the staining for histone acetylation, when DNA methylation staining was intense. In IVF zygotes, both pronuclei were transiently hyper-acetylated. However, the male pronucleus was faster in acquiring acetylated histones, and concurrently it was rapidly demethylated. Both pronuclei were equally acetylated during the S to G(2)-phase transition, while methylation staining was only still observed in the female pronucleus. In parthenogenetically activated oocytes, acetylation of the female pronucleus was enriched faster, while DNA remained methylated. A transient de-acetylation was observed in NT embryos reconstructed using a non-activated ooplast of a metaphase second arrested oocyte. Remarkably, the intensity of acetylation staining of most H4 lysine residues peaked at the 8-cell stage in IVF embryos, which coincided with zygotic genome activation and with lowest DNA methylation staining. At the blastocyst stage, trophectodermal cells of IVF and parthenogenetic embryos generally demonstrated more intense staining for most acetylated H4 lysine, whilst ICM cells stained very weakly. In contrast methylation of the DNA stained more intensely in ICM. NT blastocysts showed differential acetylation of blastomeres but not methylation. The inverse association of histone lysine acetylation and DNA methylation at different vital embryo stages suggests a mechanistically significant relationship. The complexities of these epigenetic interactions are discussed.
卵母细胞在受精后重塑亲本基因组以及核移植（NT）后重编程体细胞核的能力十分显著。为了表征牛配子发生和胚胎发生过程中组蛋白H4乙酰化和DNA甲基化模式，使用了针对赖氨酸5（K5）、K8、K12和K16残基乙酰化的组蛋白H4以及CpG二核苷酸甲基化胞嘧啶的特异性抗体。当DNA甲基化染色强烈时，卵母细胞和精子缺乏组蛋白乙酰化染色。在体外受精（IVF）合子中，两个原核均短暂过度乙酰化。然而，雄性原核获取乙酰化组蛋白的速度更快，同时其迅速去甲基化。在S期到G（2）期过渡期间，两个原核乙酰化程度相同，而甲基化染色仅在雌性原核中仍可观察到。在孤雌激活的卵母细胞中，雌性原核的乙酰化富集更快，而DNA保持甲基化。在使用中期第二次减数分裂阻滞卵母细胞的未激活卵质体构建的核移植胚胎中观察到短暂的去乙酰化。值得注意的是，在IVF胚胎的8细胞阶段，大多数H4赖氨酸残基的乙酰化染色强度达到峰值，这与合子基因组激活以及最低的DNA甲基化染色一致。在囊胚阶段，IVF和孤雌胚胎的滋养外胚层细胞通常对大多数乙酰化H4赖氨酸表现出更强的染色，而内细胞团（ICM）细胞染色非常弱。相比之下，ICM中DNA的甲基化染色更强。核移植囊胚显示出卵裂球的乙酰化差异，但没有甲基化差异。不同重要胚胎阶段组蛋白赖氨酸乙酰化与DNA甲基化的反向关联表明存在具有重要机制意义的关系。讨论了这些表观遗传相互作用的复杂性。
