Epigenetic regulation of skin development and keratinocyte differentiation

 描述（由申请人提供）：这个多学科项目的长期目标是了解皮肤中的上皮干细胞如何在分化成专门的细胞谱系期间建立不同的基因激活和沉默模式，以及这些遗传程序如何在皮肤再生和老化期间重新组织。 最近的数据显示，除了信号传导/转录因子依赖的调控机制外，谱系特异性基因表达程序也受到表观遗传学的调控，即，通过共价DNA/组蛋白修饰的调节，以及通过更高级的染色质重塑和在3D核空间中基因及其增强子元件之间的长程关联或相互作用组的建立。 在正常分化的细胞中，谱系特异性的长程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，这些相互作用在细胞向恶性转化期间基本上被重新组织，而紧密位于拓扑相关的染色质结构域中的基因经常充当癌症中染色体易位的位点。 我们最近的研究表明，在皮肤发育过程中，转录因子依赖性和表观遗传调控机制通过p63转录因子密切相关，p63转录因子在染色质重塑基因Satb 1和Brg 1的表达调控中起着一种新的、以前未被认识的作用。 在这个提议中，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转录主调节因子协同作用，在皮肤上皮干细胞分化为专门的（表皮，毛囊）细胞系期间控制其基因表达。特别是，我们将阐明如何控制与基因激活和沉默相关的高阶染色质重塑，以及如何在终末分化过程中在角质形成细胞中形成基因及其增强子元件或其他基因之间的功能性相互作用。这些问题将通过两个具体目标来解决：1。定义p63及其靶基因Brg 1和Satb 1在控制皮肤上皮干细胞及其后代中的谱系特异性基因及其增强子元件的高阶染色质重塑和拓扑相互作用中的作用。 2.确定p63及其靶点Polycomb Cbx 4基因在控制抑制性染色质区室形成中的作用，以沉默上皮干细胞及其后代中的非角质形成细胞谱系基因和选定的细胞周期相关基因。 该项目将对我们目前关于在皮肤分化过程中调节干细胞基因组重组的表观遗传机制的知识产生根本性影响，并将促进新型表观遗传药物作为治疗皮肤疾病的新范式的发展。

 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.