Department of Internal Medicine, University of Iowa, Iowa City, IA 52242, USA.
Blood. 2012 May 10;119(19):e139-47. doi: 10.1182/blood-2011-12-396754. Epub 2012 Mar 21.
Efficient in vitro generation of hematopoietic stem cells (HSCs) from embryonic stem cells (ESCs) holds great promise for cell-based therapies to treat hematologic diseases. To date, HoxB4 remains the most effective transcription factor (TF) the overexpression of which in ESCs confers long-term repopulating ability to ESC-derived HSCs. Despite its importance, the components and dynamics of the HoxB4 transcriptional regulatory network is poorly understood, hindering efforts to develop more efficient protocols for in vitro derivation of HSCs. In the present study, we performed global gene-expression profiling and ChIP coupled with deep sequencing at 4 stages of the HoxB4-mediated ESC differentiation toward HSCs. Joint analyses of ChIP/deep sequencing and gene-expression profiling unveiled several global features of the HoxB4 regulatory network. First, it is highly dynamic and gradually expands during the differentiation process. Second, HoxB4 functions as a master regulator of hematopoiesis by regulating multiple hematopoietic TFs and chromatin-modification enzymes. Third, HoxB4 acts in different combinations with 4 other hematopoietic TFs (Fli1, Meis1, Runx1, and Scl) to regulate distinct sets of pathways. Finally, the results of our study suggest that down-regulation of mitochondria and lysosomal genes by HoxB4 plays a role in the impaired lymphoid lineage development from ESC-derived HSCs.
高效地从胚胎干细胞（ESCs）体外生成造血干细胞（HSCs），为基于细胞的疗法治疗血液疾病提供了巨大的希望。迄今为止，HoxB4 仍然是最有效的转录因子（TF），其在 ESCs 中的过表达赋予 ESC 衍生的 HSCs 长期重编程能力。尽管它很重要，但 HoxB4 转录调控网络的组成和动态仍知之甚少，这阻碍了开发更有效的体外衍生 HSCs 方法的努力。在本研究中，我们在 HoxB4 介导的 ESCs 向 HSCs 分化的 4 个阶段进行了全基因表达谱分析和 ChIP 与深度测序。ChIP/深度测序和基因表达谱分析的联合分析揭示了 HoxB4 调控网络的几个全局特征。首先，它具有高度动态性，并在分化过程中逐渐扩展。其次，HoxB4 通过调节多个造血 TF 和染色质修饰酶，作为造血的主调控因子发挥作用。第三，HoxB4 与其他 4 个造血 TF（Fli1、Meis1、Runx1 和 Scl）以不同的组合方式作用，调节不同的途径集。最后，我们的研究结果表明，HoxB4 下调线粒体和溶酶体基因在 ESC 衍生的 HSCs 中淋巴谱系发育受损中发挥作用。
