Singh Arun J, Gross Michael K, Filtz Theresa M, Kioussi Chrissa
Department of Pharmaceutical Sciences, College of Pharmacy, Oregon State University, Corvallis, OR 97331, USA.
Gene Rep. 2016 Jun;3:5-13. doi: 10.1016/j.genrep.2016.01.003. Epub 2016 Feb 1.
Genome-wide mapping reveals chromatin landscapes unique to cell states. Histone marks of regulatory genes involved in cell specification and organ development provide a powerful tool to map regulatory sequences. H3K4me3 marks promoter regions; H3K27me3 marks repressed regions, and Pol II presence indicates active transcription. The presence of both H3K4me3 and H3K27me3 characterize poised sequences, a common characteristic of genes involved in pattern formation during organogenesis.
We used genome-wide profiling for H3K27me3, H3K4me3, and Pol II to map chromatin states in mouse embryonic day 12 forelimbs in wild type (control) and -null mutant mice. We compared these data with previous gene expression studies from forelimb Lbx1 migratory myoblasts and correlated -dependent expression profiles and chromatin states. During forelimb development, several lineages including myoblast, osteoblast, neurons, angioblasts etc., require synchronized growth to form a functional limb. We identified 125 genes in the developing forelimb that are -dependent. Genes involved in muscle specification and cytoskeleton architecture were positively regulated, while genes involved in axonal path finding were poised.
Our results have established histone modification profiles as a useful tool for identifying gene regulatory states in muscle development, and identified the role of Pitx2 in extending the time of myoblast progression, promoting formation of sarcomeric structures, and suppressing attachment of neuronal axons.
全基因组图谱揭示了细胞状态特有的染色质景观。参与细胞特化和器官发育的调控基因的组蛋白标记为绘制调控序列提供了有力工具。H3K4me3标记启动子区域；H3K27me3标记抑制区域，而Pol II的存在表明活跃转录。H3K4me3和H3K27me3同时存在表征了 poised 序列，这是器官发生过程中参与模式形成的基因的共同特征。
我们使用全基因组分析H3K27me3、H3K4me3和Pol II来绘制野生型（对照）和 Pitx2 基因敲除突变小鼠胚胎第12天前肢的染色质状态。我们将这些数据与先前来自前肢Lbx1迁移成肌细胞的基因表达研究进行比较，并关联Pitx2依赖性表达谱和染色质状态。在前肢发育过程中，包括成肌细胞、成骨细胞、神经元、血管母细胞等在内的几个谱系需要同步生长以形成功能正常的肢体。我们在发育中的前肢中鉴定出125个依赖于Pitx2的基因。参与肌肉特化和细胞骨架结构的基因受到正向调控，而参与轴突路径寻找的基因则处于 poised 状态。
我们的结果已将组蛋白修饰谱确立为识别肌肉发育中基因调控状态的有用工具，并确定了Pitx2在延长成肌细胞进展时间、促进肌节结构形成以及抑制神经元轴突附着方面的作用。
