Histone variant H3.3 maintains a decondensed chromatin state essential for mouse preimplantation development
Histone variant H3.3 maintains a decondensed chromatin state essential for mouse preimplantation development
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DOI：
10.1242/dev.095513
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发表时间：
2013-09-01
期刊：
影响因子：
4.6
通讯作者：
Ramalho-Santos, Miguel
中科院分区：
文献类型：
--
作者：
Lin, Chih-Jen;Conti, Marco;Ramalho-Santos, Miguel
组蛋白变体可以取代核小体中的典型组蛋白并改变染色质结构和基因表达。组蛋白变体 H3.3 优先与活性染色质结合，并参与多种发育过程的调节。然而，H3.3 调节基因活性的机制尚不清楚，并且基因重复阻碍了对小鼠中 H3.3 功能的分析。在这里，我们报道了受精小鼠受精卵中 H3.3 的特异性敲低导致桑葚胚阶段的发育停滞。这种表型可以通过外源 H3.3 来挽救，但不能通过规范的 H3.1 mRNA 来挽救。 H3.3的缺失早在两细胞阶段就导致染色体过度浓缩和错误分离，并相应产生高水平的非整倍性，但似乎并不影响两细胞阶段的合子基因激活或桑葚胚阶段的谱系基因转录。 H3.3 缺陷胚胎的开放染色质标记物（例如 H3K36me2 和 H4K16Ac）的水平显着降低。重要的是，H3.3K36 中破坏 H3K36 甲基化 (H3.3K36R) 的突变并不能挽救 H3.3 敲低 (KD) 表型。此外，H3.3 KD 胚胎增加了接头 H1 的掺入。 Mof (Kat8)（一种 H4K16 特异性乙酰转移酶）的敲低同样会导致 H1 过量掺入。值得注意的是，泛 H1 RNA 干扰 (RNAi) 部分挽救了 H3.3 KD 胚胎的染色体浓缩，并允许发育至囊胚阶段。这些结果表明，H3.3 介导开放染色质和浓缩染色质之间的平衡，这对于小鼠早期发育过程中染色体分离的保真度至关重要。
Histone variants can replace canonical histones in the nucleosome and modify chromatin structure and gene expression. The histone variant H3.3 preferentially associates with active chromatin and has been implicated in the regulation of a diverse range of developmental processes. However, the mechanisms by which H3.3 may regulate gene activity are unclear and gene duplication has hampered an analysis of H3.3 function in mouse. Here, we report that the specific knockdown of H3.3 in fertilized mouse zygotes leads to developmental arrest at the morula stage. This phenotype can be rescued by exogenous H3.3 but not by canonical H3.1 mRNA. Loss of H3.3 leads to over-condensation and mis-segregation of chromosomes as early as the two-cell stage, with corresponding high levels of aneuploidy, but does not appear to affect zygotic gene activation at the two-cell stage or lineage gene transcription at the morula stage. H3.3-deficient embryos have significantly reduced levels of markers of open chromatin, such as H3K36me2 and H4K16Ac. Importantly, a mutation in H3.3K36 that disrupts H3K36 methylation (H3.3K36R) does not rescue the H3.3 knockdown (KD) phenotype. In addition, H3.3 KD embryos have increased incorporation of linker H1. Knockdown of Mof (Kat8), an acetyltransferase specific for H4K16, similarly leads to excessive H1 incorporation. Remarkably, pan-H1 RNA interference (RNAi) partially rescues the chromosome condensation of H3.3 KD embryos and allows development to the blastocyst stage. These results reveal that H3.3 mediates a balance between open and condensed chromatin that is crucial for the fidelity of chromosome segregation during early mouse development.