Integrating developmental pathways and chromatin structure during lineage specifcation

为了使受精卵发育成活的动物，控制细胞再生能力、身份和命运的基因必须在适当的时间和地点开启和关闭。DNA序列与蛋白质包装的方式发生变化，形成一种叫做染色质的结构，这在基因表达的调节中很重要。然而，迄今为止，这主要是在人工细胞培养系统中进行的研究，对于在与胚胎发育更相关的情况下发生在特定基因上的染色质结构的变化知之甚少。我们建议使用一种新开发的细胞培养系统，使小鼠胚胎干细胞能够定向发育成通常会形成肌肉和骨骼（中胚层）或肠、肺、肝和胰腺（内胚层）的细胞类型。有了这个系统，我们就可以产生大量与胚胎中的细胞非常相似的细胞，并用已知对胚胎发育很重要的特定化学信号挑战这些细胞。该系统将用于研究染色质结构是如何在全球范围内以及在一组特定基因（Hox基因）上发生变化的，Hox基因是发育的关键调节因子。我们的全局分析将帮助我们理解细胞逐渐局限于中胚层和内胚层谱系的方式，而在Hox集群中，我们将能够提出具体的问题，了解这是如何发生的。这项工作将有助于更好地理解干细胞如何在再生医学中用于靶向来自这些细胞类型的器官。

In order for the fertilized egg to develop into a live-borne animal, genes that control the regenerative capacity, identity and fate of cells must be switched on and off at the right time and place. Changes in the way that the DNA sequence is packaged up with proteins, to form a structure called chromatin, are important in this regulation of gene expression. However, to date this has mainly been studied in artificial cell culture systems and little is known about the changes in chromatin structure that happen at specific genes in a situation that is more relevant to the development of the embryo. We propose to use a newly developed cell culture system that enables mouse embryonic stem cells to be directed to undergo development towards cell types that usually go on to form muscle and bone (mesoderm) or gut, lung, liver and pancreas (endoderm). With this system we can produce large quantities of cells that closely resemble their equivalents in an embryo and challenge these cells with specific chemical signals that are known to be important for embryonic development. This system will be used to study how chromatin structure is changed both globally and at a particular set of genes, the Hox genes, which are key regulators of development. Our global analysis will help us to understand the way in which cells are progressively restricted to the mesoderm and endoderm lineages, while at the Hox cluster in particular we will be able to ask specific questions about how this happens. This work will help to better understand how stem cells can be used to target organs derived from these cell types in regenerative medicine.