Epigenetic regulation of skin development and keratinocyte differentiation

 描述(申请人提供)：这个多学科项目的长期目标是了解皮肤上皮干细胞如何在分化为专门细胞系的过程中建立不同的基因激活和沉默模式，以及这些遗传程序在皮肤再生和衰老过程中如何重新组织。最近的数据显示，除了依赖于信号/转录因子的调控机制外，谱系特异的基因表达程序也受到表观遗传的调控，即通过调节共价DNA/组蛋白修饰，以及通过高阶染色质重塑和在3D核空间中建立基因与其增强子元件之间的长距离关联或相互作用。在正常分化的细胞中，谱系特异性的长距离染色质相互作用为细胞特异性转录或沉默提供了结构框架。重要的是，在细胞向恶性转化的过程中，这些相互作用被实质性地重新组织，而位于密切相关的染色质结构域中的基因经常在癌症中充当染色体易位的位置。我们最近的研究表明，在皮肤发育过程中，转录因子依赖的调控机制和表观遗传调控机制通过p63转录因子紧密联系在一起，p63转录因子在染色质重塑基因Satb1和BRG1的表达调控中扮演着以前未知的新角色。在这个提案中，我们将进一步解决一个基本的生物学问题，即表观遗传机制如何与p63转录主控调控因子协同工作，以控制皮肤上皮干细胞在特化(表皮、毛囊)细胞系分化过程中的基因表达。特别是，我们将阐明与基因激活和沉默相关的高阶染色质重塑是如何被控制的，以及在角质形成细胞的终末分化过程中，这些基因与其增强子元件或其他基因之间如何形成功能相互作用。这些问题将通过两个特定的目的来解决：1.确定p63及其靶基因BRG1和Satb1在控制皮肤上皮干细胞及其后代的高阶染色质重塑和系谱特异基因及其增强子元件的拓扑相互作用中的作用。2.确定p63及其靶基因Polycomb Cbx4在控制上皮干细胞及其后代中抑制染色质形成的作用，以沉默非角质形成系基因和选定的细胞周期相关基因。该项目将对我们目前对干细胞在皮肤分化过程中调节基因组重组的表观遗传机制的了解产生根本性的影响，并将推动开发新的表观遗传药物作为治疗皮肤病的新范例。

 DESCRIPTION (provided by applicant): The long-term goal of this multi-disciplinary project is to understand how epithelial stem cells in the skin establish distinct patterns of gene activation and silencing during their differentiation into specialized cell lineages and how these genetic programs are re-organized during skin regeneration and aging. Recent data revealed that in addition to signaling/transcription factor-dependent regulatory mechanisms, lineage-specific gene expression programs are also regulated epigenetically, i.e., via modulation of covalent DNA/histone modifications, as well as through higher-order chromatin remodeling and establishment of long- range associations or interactomes between the genes and their enhancer elements in 3D nuclear space. In normal differentiating cells, lineage-specific long-range chromatin interactions provide structural frameworks for cell-specific transcription or silencing. Importantly, these interactions are substantially re- organized during cell transition towards malignancy, while genes located closely in topologically associated chromatin domains frequently serve as sites for chromosomal translocations in cancers. Our recent studies revealed that during skin development, transcription factor-dependent and epigenetic regulatory mechanisms are intimately linked to each other via p63 transcription factor, which plays a novel, previously unrecognized role in regulation of expression of chromatin remodeling genes Satb1 and Brg1. In this proposal, we will further address a fundamental biological problem on how epigenetic machinery operates in concert with p63 transcription master regulator to control gene expression in skin epithelial stem cells during their differentiation in specialized (epidermal, har follicle) cell lineages. In particular, we will elucidate how higher-order chromatin remodeling associated with gene activation and silencing is controlled and how functional interactomes between the genes and their enhancer elements or other genes are formed in the keratinocytes during terminal differentiation. These questions will be addressed via two Specific Aims: 1. Define a role of p63 and its target genes Brg1 and Satb1 in the control of higher-order chromatin remodeling and topological interactomes of the lineage-specific genes and their enhancer elements in skin epithelial stem cells and their progenies. 2. Identify the role of p63 and its target Polycomb Cbx4 gene in the control of formation of the repressive chromatin compartments to silence non-keratinocyte lineage genes and selected cell cycle- associated genes in epithelial stem cells and their progenies. This project will have a fundamental impact on our current knowledge of epigenetic mechanisms that regulate genome reorganization in stem cells during their differentiation in the skin and will promote the progress towards the development of novel epigenetic drugs as new paradigm for treatment of skin disorders.