Regulation of histone H3 lysine 9 methylation in oocytes and early pre-implantation embryos
Regulation of histone H3 lysine 9 methylation in oocytes and early pre-implantation embryos
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DOI：
10.1242/dev.01116
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发表时间：
2004-05-01
期刊：
影响因子：
4.6
通讯作者：
Aoki, F
中科院分区：
文献类型：
--
作者：
Liu, HL;Kim, JM;Aoki, F
基因组的表观遗传修饰，如组蛋白残基的共价修饰，确保了植入前发育过程中适当的基因激活，并可能参与受精后亲本基因组的不对称重编程。我们研究了组蛋白H3赖氨酸9(H3/K9)的甲基化模式，以及在小鼠植入前发育早期参与双亲基因组不对称重塑的调控机制。用特异性识别甲基化H3/K9的抗体进行免疫细胞化学，在男性原核中发现非常弱的甲基化信号或没有甲基化信号，而在女性原核中检测到明显的甲基化信号。这种不对称的H3/K9甲基化模式在不同亲本基因组中一直持续到两细胞阶段。然而，在四细胞阶段，H3/K9发生了从头甲基化，不对称性消失了。未甲基化的雄性原核在转移到去核的GV期或中期卵母细胞时发生了从头开始的甲基化，这表明组蛋白H3甲基酶在受精前是活跃的，但在受精后则不是如此，而不对称甲基化模式是受精后细胞质中甲基酶活性的这种变化所产生的。因此，组蛋白H3只在母系染色体中甲基化，而在受精前存在于卵母细胞中，而在父系染色体中不甲基化，而父系染色体中没有甲基化。早期胚胎中不对称H3/K9甲基化模式的维持是一个依赖于蛋白质合成和合子转录的活跃过程，因为男性原核中的从头甲基化发生在蛋白质合成或基因表达分别被环己亚胺或Alphad-Amanitin抑制时。此外，当雄性原核移植到去核的GV卵母细胞时，H3/K9和DNA发生了相应的从头甲基化。我们的结果表明，在植入前发育的早期，H3/K9甲基化是亲本基因组起源的表观遗传学标记。
Epigenetic modifications of the genome, such as covalent modification of histone residues, ensure appropriate gene activation during pre-implantation development, and are probably involved in the asymmetric reprogramming of the parental genomes after fertilization. We investigated the methylation patterns of histone H3 at lysine 9 (H3/k9), and the regulatory mechanism involved in the asymmetric remodeling of parental genomes during early preimplantation development in mice. Immunocytochemistry with an antibody that specifically recognizes methylated H3/K9 showed a very weak or absent methylation signal in the male pronucleus, whereas a distinct methylation signal was detected in the female pronucleus. This asymmetric H3/K9 methylation pattern in the different parental genomes persisted until the two-cell stage. However, de novo methylation of H3/K9 occurred and the asymmetry was lost during the four-cell stage. The unmethylated male pronucleus underwent de novo methylation when it was transferred into enucleated GV- or MII-stage oocytes, which suggests that histone H3 methylase is active before fertilization, but not afterwards, and that the asymmetric methylation pattern is generated by this change in methylase activity in the cytoplasm after fertilization. Thus, histone H3 is methylated only in the maternal chromosomes, which are present in the oocytes before fertilization, and is not methylated in the paternal chromosomes, which are absent. The maintenance of asymmetric H3/K9 methylation patterns in early embryos is an active process that depends on protein synthesis and zygotic transcription, as de novo methylation in the male pronucleus occurred when either protein synthesis or gene expression was inhibited by cycloheximide or alphad-amanitin, respectively. In addition, corresponding de novo methylation of H3/K9 and DNA occurred when the male pronucleus was transferred to an enucleated GV oocyte. Our results suggest that H3/K9 methylation is an epigenetic marker of parental genome origin during early preimplantation development.