Chromatin architectural protein CTCF and regulation of skin development and tumorigenesis

项目摘要 该项目的长期目标是了解皮肤中的上皮干细胞是如何建立独特的 基因激活和沉默的模式，在他们分化成专门的细胞谱系，以及如何这些 基因程序在皮肤再生和肿瘤发生期间被重组。 现在广泛接受的是，除了信号传导/转录因子介导的机制，谱系- 特定的基因表达程序也受到表观遗传学的调节，即，通过共价DNA/组蛋白 修饰，以及通过基因及其增强子元件在细胞核中的空间排列。 增强子-启动子相互作用是提供功能和结构框架的关键决定因素 由谱系特异性转录因子控制的细胞特异性转录。然而，增强子-启动子 调节网络在细胞向恶性转化期间基本上重新组织，其包括 基因启动子异常暴露于不适当的调控元件，导致前 癌基因，以及肿瘤抑制基因的沉默。 CCCTC结合因子（CCCTC binding factor，CTCF）是一种核心结构蛋白，在细胞凋亡中起关键作用。 控制增强子/启动子相互作用的建立和维持。CTCF基因频繁突变 在癌症中，其肿瘤抑制活性的消除有助于癌症的发展和进展。 我们的初步数据表明，CTCF在小鼠和人表皮中表达， Krt 14驱动的Ctcf基因消融导致皮肤发育、表皮屏障 维持和肿瘤发生。在这个多PI提案中，我们将测试CTCF作为关键的假设， 决定因素，控制建立和维持的增强子-启动子调控网络， 皮肤上皮干细胞及其后代在发育和出生后的稳态，而改变 导致皮肤肿瘤发生。我们将通过两个具体目标来解决这个假设： 1.定义CTCF在建立和维护谱系特异性高阶 染色质结构，增强子-启动子调控网络和基因表达在不同的 在发育和毛发周期相关的皮肤再生过程中的皮肤上皮细胞群。 2.描述Ctcf在基因表达调控、3D染色质组织和 肿瘤发生过程中皮肤上皮细胞中的增强子-启动子相互作用。 该项目将对我们目前对表观遗传机制的认识产生根本性的影响， 在干细胞分化和肿瘤发生过程中调节干细胞的基因组重组，并将促进 在开发新型表观遗传药物作为治疗皮肤病的新范例方面取得了进展。

PROJECT SUMMARY The long-term goal of this 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 tumorigenesis. It is now widely accepted that in addition to signaling/transcription factor-mediated mechanisms, lineage- specific gene expression programs are also regulated epigenetically, i.e., via covalent DNA/histone modifications, as well as via spatial arrangements of the genes and their enhancer elements in the nucleus. Enhancer-promoter interactions serve as key determinants providing functional and structural frameworks for cell-specific transcription controlled by lineage-specific transcription factors. However, enhancer-promoter regulatory networks are substantially re-organized during cell transition towards malignancy, which include an aberrant exposure of gene promoters to inappropriate regulatory elements resulting in activation of pro- oncogenes, as well as in silencing of the tumor suppressor genes. CCCTC-binding factor (CTCF) serves as one of the core architectural proteins that plays a key role in the control the establishment and maintenance of enhancer/promoter interactions. CTCF gene is frequently mutated in cancers, and abrogation of its tumor-suppressor activity contributes to cancer development and progression. Our preliminary data demonstrate that CTCF is expressed in both mouse and human epidermis, while Krt14-driven Ctcf genetic ablation results in severe alterations in skin development, epidermal barrier maintenance, and tumorigenesis. In this multi-PI proposal, we will test a hypothesis that CTCF serves as critical determinant that control the establishment and maintenance of the enhancer-promoter regulatory networks in skin epithelial stem cells and their progenies during development and postnatal homeostasis, while alterations in such networks result in skin tumorigenesis. We will address this hypothesis via two Specific Aims: 1. Define the roles of CTCF in the establishment and maintenance of lineage-specific higher-order chromatin structure, enhancer-promoter regulatory networks and gene expression in distinct populations of skin epithelial cells during development and hair cycle-associated skin regeneration. 2. Delineate the roles for Ctcf in regulation of gene expression, 3D chromatin organization and enhancer-promoter interactions in the skin epithelial cells during tumorigenesis. This project will have a fundamental impact on our current knowledge of epigenetic mechanisms that regulate genome reorganization in stem cells during their differentiation and tumorigenesis and will promote the progress towards the development of novel epigenetic drugs as a new paradigm for treatment of skin disorders.