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

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 基因表达模式在他们分化成专门的细胞谱系，以及这些基因是如何表达的。 程序在与受损的细胞分化相关的病理性皮肤状况中改变。 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，谱系特异性基因表达程序也受到调控， 表观遗传学，即，通过调节共价DNA/组蛋白修饰和高级染色质重塑。 DNA甲基化和随后的5-甲基胞嘧啶氧化成5-羟甲基胞嘧啶（5 hmC）是 调节哺乳动物发育和干细胞分化的关键表观遗传事件。氧化5- 甲基胞嘧啶由TET 1/2/3家族酶催化，并作为DNA合成的重要步骤 去甲基化最近的数据显示，泰特蛋白在许多生物过程中起着重要作用，包括 发育、癌症和细胞重编程，而所有三个泰特基因的基因切除是致命的。 然而，Tet介导的DNA羟甲基化在控制基因表达中的作用， 在表皮和毛囊的终末分化期间，角质形成细胞保持模糊。我们的初步 数据显示，5 hmC修饰的DNA在毛囊隆突中以及在分化的表皮中丰富， 和毛发基质角质形成细胞。此外，遗传Tet 3消融导致表皮屏障的改变， 而Shh-Cre介导了毛发中所有三个泰特基因的消融 基质角质形成细胞导致毛干结构和毛角蛋白基因表达的改变。 在这个建议中，我们将测试的假设，泰特蛋白作为关键的决定因素，调节基因 通过DNA去甲基化在分化表皮和毛囊角质形成细胞中的表达程序 谱系特异性基因以及控制表皮屏障的关键基因的启动子和增强子 形成和毛囊周期。这一假设将通过两个具体目标来解决： 1)定义Tet 1、Tet 2和Tet 3在控制表皮发育、终末 角质形成细胞分化和表皮屏障维持。 2)定义不同的泰特基因对自我更新的共同特征和差异影响， 毛囊上皮干细胞及其后代在生理过程中的分化潜能 毛发周期依赖的皮肤再生。 这个项目将对我们目前对调节基因表达的表观遗传机制的认识产生根本性的影响。 干细胞分化过程中的基因组重组，并将促进向 开发通过靶向泰特酶和表观基因组治疗皮肤病的新范例。

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.