Key Laboratory of Stem Cell Biology, Institute of Health Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences/Shanghai JiaoTong University School of Medicine, Shanghai, China.
J Cell Physiol. 2011 Dec;226(12):3190-6. doi: 10.1002/jcp.22679.
The identity of embryonic stem cells (ESCs) is controlled by a set of pluripotency genes, including Oct4, Sox2, Nanog, and Fgf4. How their expression is repressed during differentiation and reactivated during reprogramming is largely unknown. Here, using mouse ESCs as well as F9 and P19 cells (mouse embryonal carcinoma cell lines, P19 being considered further differentiated than F9 cells) as models, we found that HDAC inhibitors elevated Fgf4 expression in P19 cells, but reduced it in F9 cells. We also observed that HDAC inhibitors enhanced the expression of Fgf4 and a subset of pluripotency genes in differentiated ESCs, but reduced their expression in undifferentiated and less differentiated ESCs. Mechanistically, we observed more HDAC1 recruitment and a weaker association of histone 4 lysine 5 acetylation at the Fgf4 enhancer in P19 cells compared to F9 cells. Additionally, we demonstrated the interaction between Sox2 and HDAC1 both in vitro and in vivo, implicating a possible role for Sox2 in the recruitment of HDAC1 to the Fgf4 enhancer. We also found that Nanog bound to the Fgf4 enhancer, and this binding was stronger in F9 cells, indicating the involvement of Nanog in the regulation of Fgf4 expression in undifferentiated and less differentiated pluripotent stem cells. This study uncovers an important role of HDAC1 and histone modifications in the repression of Fgf4 and perhaps other pluripotency genes during ESC differentiation. Our results also suggest that HDAC inhibitors may promote reprogramming partially through activating pluripotency genes at some intermediate stages.
胚胎干细胞（ESCs）的特性由一组多能性基因控制，包括 Oct4、Sox2、Nanog 和 Fgf4。其在分化过程中如何被抑制以及在重编程过程中如何被重新激活在很大程度上是未知的。在这里，我们使用小鼠 ESCs 以及 F9 和 P19 细胞（小鼠胚胎癌细胞系，P19 细胞被认为比 F9 细胞进一步分化）作为模型，发现 HDAC 抑制剂在 P19 细胞中上调了 Fgf4 的表达，但在 F9 细胞中降低了其表达。我们还观察到 HDAC 抑制剂增强了分化的 ESCs 中 Fgf4 和一组多能性基因的表达，但降低了未分化和分化程度较低的 ESCs 中这些基因的表达。从机制上讲，我们观察到与 F9 细胞相比，P19 细胞中 HDAC1 的募集更多，组蛋白 4 赖氨酸 5 乙酰化的结合较弱。此外，我们在体外和体内证明了 Sox2 和 HDAC1 之间的相互作用，暗示 Sox2 可能在将 HDAC1 募集到 Fgf4 增强子中发挥作用。我们还发现 Nanog 结合到 Fgf4 增强子上，并且在 F9 细胞中结合更强，表明 Nanog 参与了未分化和分化程度较低的多能干细胞中 Fgf4 表达的调控。这项研究揭示了 HDAC1 和组蛋白修饰在 ESC 分化过程中抑制 Fgf4 乃至其他多能性基因的重要作用。我们的结果还表明，HDAC 抑制剂可能通过在某些中间阶段激活多能性基因来部分促进重编程。
