Golebiewska Anna, Atkinson Stuart P, Lako Majlinda, Armstrong Lyle
Institute of Human Genetics, University of Newcastle Upon Tyne, International Centre for Life, United Kingdom.
Stem Cells. 2009 Jun;27(6):1298-308. doi: 10.1002/stem.59.
The molecular mechanisms underlying pluripotency and lineage specification from embryonic stem cells (ESCs) are still largely unclear. To address the role of chromatin structure in maintenance of pluripotency in human ESCs (hESCs) and establishment of lineage commitment, we analyzed a panel of histone modifications at promoter sequences of genes involved in maintenance of pluripotency, self-renewal, and in early stages of differentiation. To understand the changes occurring at lineage-specific gene regulatory sequences, we have established an efficient purification system that permits the examination of two distinct populations of lineage committed cells; fluorescence activated cell sorted CD133(+) CD45(-)CD34(-) neural stem cells and beta-III-tubulin(+) putative neurons. Here we report the importance of other permissive marks supporting trimethylation of Lysine 4 H3 at the active stem cell promoters as well as poised bivalent and nonbivalent lineage-specific gene promoters in hESCs. Methylation of lysine 9 H3 was found to play a role in repression of pluripotency-associated and lineage-specific genes on differentiation. Moreover, presence of newly formed bivalent domains was observed at the neural progenitor stage. However, they differ significantly from the bivalent domains observed in hESCs, with a possible role of dimethylation of lysine 9 H3 in repressing the poised genes.
胚胎干细胞（ESC）多能性和谱系特化的分子机制仍不清楚。为了研究染色质结构在维持人类胚胎干细胞（hESC）多能性和建立谱系定向中的作用，我们分析了一组参与维持多能性、自我更新和分化早期阶段的基因启动子序列上的组蛋白修饰。为了了解谱系特异性基因调控序列上发生的变化，我们建立了一个高效的纯化系统，该系统允许检测两个不同的谱系定向细胞群体；荧光激活细胞分选的CD133(+) CD45(-)CD34(-)神经干细胞和β-III-微管蛋白(+)假定神经元。在此，我们报道了其他许可标记在hESC中支持活性干细胞启动子处H3赖氨酸4三甲基化以及平衡的二价和非二价谱系特异性基因启动子的重要性。发现H3赖氨酸9甲基化在分化时抑制多能性相关基因和谱系特异性基因中起作用。此外，在神经祖细胞阶段观察到新形成的二价结构域的存在。然而，它们与在hESC中观察到的二价结构域有显著差异，H3赖氨酸9二甲基化可能在抑制平衡基因中起作用。
