Epigenetic transcriptional control of intestinal epithelial regionality

不同的细胞特性对于组织功能是必不可少的，但是维持成体细胞特异性转录程序的分子机制知之甚少。在哺乳动物消化道中，小肠和大肠的不同区域保持非常稳定，而区域特性（化生）的畸变与疾病相关。在这里，我建议确定表观遗传和转录决定因素的前-后肠上皮区域性。我还将研究这些规则在小鼠模型中是如何被违反的，在小鼠模型中，成年结肠上皮突然获得了小肠的所有特性。通过分析区域特异性染色质可及性（ATAC-seq）、组蛋白修饰（ChIP-seq）和基因表达（RNA-seq），我将首先描述与从野生型小鼠小肠（十二指肠、空肠和回肠）和大肠（盲肠和结肠）纯化的肠干细胞相关的增强子和转录因子（TF）。使用肠干细胞衍生的类器官，然后我将检查候选TF在维持区域性方面的功能。这些研究集中在TF在产生和维持稳定的染色质状态中的作用。第二，宿主实验室已经发现，单个结肠限制性TF（SATB 2）的缺失导致结肠上皮向回肠上皮的表型和转录转化。我的初步数据表明，这种转变涉及广泛的重布线可访问的染色质。通过绘制染色质可及性和全基因组SATB 2结合随时间的变化，在急性SATB 2损失和被迫表达，我将调查表观遗传事件的序列，以解释SATB 2如何驱动后验身份。这些发现对于理解表观遗传机制如何维持可能在人类疾病中受到干扰的稳定细胞身份具有意义。

Diverse cellular identities are essential for tissue functions, but the molecular mechanisms that maintain adult cell-specific transcriptional programs are poorly understood. In the mammalian digestive tract, distinct regions of the small and large intestines remain remarkably stable, whilst aberrations in regional identity (metaplasia) are associated with disease. Here, I propose to identify epigenetic and transcriptional determinants of anterior-posterior gut epithelial regionality. I will also investigate how exactly these rules are violated in a mouse model where adult colonic epithelium abruptly acquires all properties of the small intestine. By profiling region-specific chromatin accessibility (ATAC-seq), histone modifications (ChIP-seq), and gene expression (RNA-seq), I will first delineate the enhancers and transcription factors (TFs) associated with intestinal stem cells purified from wild-type mouse small (duodenum, jejunum and ileum) and large (cecum and colon) intestines. Using intestinal stem cell-derived organoids, I will then examine the functions of candidate TFs in maintaining regionality. These studies centre on TF roles in producing and maintaining stable chromatin states. Second, the host laboratory has found that loss of a single colon-restricted TF, SATB2, causes phenotypic and transcriptional conversion of colonic into ileal epithelium. My preliminary data indicate that this transformation involves extensive rewiring of accessible chromatin. By mapping chromatin accessibility and genome-wide SATB2-binding over time, in response to acute SATB2 loss and forced expression, I will investigate the sequence of epigenetic events to explain how SATB2 drives posterior identity. These findings have implications for understanding how epigenetic mechanism maintain stable cell identities that may be perturbed in human disease.