DNA hydroxymethylation and Tet-enzymes in the control of the skin development and hair growth

项目总结 这个项目的长期目标是了解皮肤上皮干细胞是如何建立独特的 分化为特化细胞系过程中的基因表达模式，以及这些基因是如何 在与细胞分化受损相关的病理性皮肤状况下，程序会发生变化。 对基因组和染色质生物学的研究表明，除了信号/转录因子- 依赖于调控机制，谱系特异的基因表达程序也受到调控 在表观遗传学上，即通过调节共价DNA/组蛋白修饰和高阶染色质重塑。 DNA甲基化和5-甲基胞嘧啶随后氧化为5-羟甲基胞嘧啶(5HmC)是 调控哺乳动物发育和干细胞分化的关键表观遗传学事件。5-羟基-4-羟基-4-羟基-4-羟基-4-羟基-4-酮的氧化 甲基胞嘧啶是由TET1/2/3家族酶催化的，是DNA中的重要步骤 去甲基化。最近的数据显示，Tet蛋白在许多生物学过程中发挥着重要的作用，包括 发展、癌症和细胞重编程，而所有三个Tet基因的遗传消融都是致命的。 然而，Tet介导的DNA羟甲基化在控制基因表达中的作用 角质形成细胞在表皮和毛囊的终末分化过程中仍然模糊。我们的预赛 数据显示，5hmC修饰的DNA在毛囊隆起中丰富，在分化表皮方面也是如此。 和毛发基质角质形成细胞。此外，遗传性Tet3消融会导致表皮屏障的改变 在胚胎发育过程中形成，而Shh-Cre介导了头发中所有三个Tet基因的消融 基质角质形成细胞导致毛干结构和毛发角蛋白基因表达的改变。 在这个提案中，我们将检验Tet蛋白作为调节基因的关键决定因素的假设 DNA去甲基化诱导表皮和毛囊角质形成细胞分化的表达程序 家族特异性基因的启动子和增强子，以及控制表皮屏障的关键基因的启动子和增强子 形成和毛囊循环。这一假设将通过两个具体目标加以阐述： 1)确定Tet1、TET2和Tet3在控制表皮发育、末端 角质形成细胞分化和表皮屏障的维持。 2)明确不同的Tet基因对自我更新的共同特征和差异影响 生理性毛囊上皮干细胞及其后代的分化潜能 依赖毛发周期的皮肤再生。 这个项目将对我们目前对表观遗传机制的了解产生根本性的影响 干细胞分化过程中的基因组重组，将促进向 通过靶向Tet酶和表观基因组治疗皮肤病的新范例的开发。

PROJECT SUMMARY The long-term goal of this project is to understand how epithelial stem cells in the skin establish distinct patterns of gene expression during their differentiation into specialized cell lineages and how these genetic programs are altered in pathological skin conditions associated with impaired cell differentiation. Research into genome and chromatin biology has revealed that in addition to signaling/transcription factor- dependent regulatory mechanisms, lineage-specific gene expression programs are also regulated epigenetically, i.e., via regulation of covalent DNA/histone modifications and higher-order chromatin remodeling. DNA methylation and subsequent oxidation of 5-methylcytosine into 5-hydroxymethylcytosine (5hmC) are key epigenetic events regulating development and stem cell differentiation in mammals. Oxidation of 5- methylcytosine is catalyzed by the TET1/2/3 family enzymes and serve as an important step in DNA demethylation. Recent data reveal that Tet proteins plays essential roles in many biological processes including development, cancer and cellular reprogramming, while genetic ablation of all three Tet genes is lethal. However, the role of Tet-mediated DNA hydroxymethylation in the control of gene expression in keratinocytes during terminal differentiation in the epidermis and hair follicle remain obscured. Our preliminary data reveal that 5hmC-modified DNA is abundant in the hair follicle bulge, as well as in differentiating epidermal and hair matrix keratinocytes. Furthermore, genetic Tet3 ablation results in alterations of epidermal barrier formation during embryonic development, while Shh-Cre mediated ablation of all three Tet genes in the hair matrix keratinocytes results in alterations of the hair shaft structure and hair keratin gene expression. In this proposal, we will test the hypothesis that Tet proteins serve as critical determinants that regulate gene expression programmes in differentiating epidermal and hair follicle keratinocytes via DNA demethylation at the promoters and enhancers of lineage-specific genes, as well as of key genes that control epidermal barrier formation and hair follicle cycling. This hypothesis will be addressed via two Specific Aims: 1) Define the roles of Tet1, Tet2 and Tet3 in the control of epidermal development, terminal keratinocyte differentiation and epidermal barrier maintenance. 2) Define the common features and differential impact of the distinct Tet genes on self-renewing and differentiation potentials of the hair follicle epithelial stem cells and their progenies during physiological hair cycle-dependent skin regeneration. 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 will promote the progress towards the development of novel paradigms for treatment of skin disorders via targeting Tet enzymes and epigenome.