Role of Chromatin Regulators in Skin Control

描述(申请人提供)：皮肤是保护身体免受感染和脱水的重要屏障。它也是动物感知触摸、疼痛和温度的重要感觉器官。位于基底层的一层多能胚胎表皮祖细胞形成了皮肤谱系：提供屏障功能的表皮，对热保护至关重要的毛囊，以及介导机械转导的默克尔细胞。虽然控制表皮和毛囊发育的分子机制已经被广泛研究，但控制默克尔细胞命运的过程完全未知。转录图谱显示，关键染色质调节因子在表皮祖细胞和默克尔细胞中的表达存在差异。其中包括Polycomb抑制物复合体的几个亚单位，它们在表皮祖细胞中表达，但在Merkel细胞中下调。利用体内功能丧失研究，我们发现Polycomb复合体控制着Merkel细胞谱系的发育。如果没有Polycomb抑制，分化会加速，默克尔细胞会早熟获得。为了深入了解Polycomb控制Merkel细胞发育的机制，我们在表皮祖细胞中鉴定了Polycomb复合体抑制的基因。其中最突出的是Sox2，它编码一种在默克尔细胞中高表达的转录因子。条件消融皮肤中的Sox2后，Merkel细胞数量显著减少，表明Sox2对Merkel细胞发育的重要性。总体而言，上述结果建议了一种工作模型，在该模型中，Polycomb复合体通过抑制默克尔细胞系的关键发育调节因子(如Sox2)来控制表皮前体细胞的分化。这项资助的主要重点是确定Polycomb复合体控制默克尔细胞命运决定的分子机制。在Aim1中，我们将分析Polycomb介导的Sox2抑制在控制Merkel细胞谱系中的意义。在AIM2中，我们将描述在表皮祖细胞向Merkel细胞分化过程中，Polycomb复合体、活性染色质修饰和转录机制组件如何协同调节Sox2基因的激活。最后，在Aim3中，我们将探索其他染色质调节因子在控制默克尔谱系发育中的作用。事实上，转录图谱显示，除了Polycomb复合体，五个关键的染色质调节因子在表皮祖细胞和默克尔细胞中有差异表达。利用体内功能丧失、分子和生化研究，我们将揭示这些染色质调节因子对默克尔细胞发育的意义。总之，这些研究将确定染色质调节剂在皮肤发育和命运决定中的作用。)

DESCRIPTION (provided by applicant): Skin is an essential barrier that protects the body from infection and dehydration. It is also an important sensory organ that allows animals to perceive touch, pain, and temperature. A single layer of multipotent embryonic epidermal progenitors located in the basal layer gives rise to skin lineages: the epidermis that provides barrier function, hair follicles that are important for thermal protection, and Merkel cells that mediate mechanotransduction. While the molecular mechanisms controlling development of the epidermis and hair follicles have been extensively studied, the processes controlling Merkel cell fate determination are completely unknown. Transcriptional profiling revealed differential expression of key chromatin regulators in epidermal progenitors and Merkel cells. Among them were several subunits of the Polycomb repressor complex, which were expressed in epidermal progenitors but were downregulated in Merkel cells. Using in vivo loss-of-function studies, we uncovered that the Polycomb complex controls Merkel cell lineage development. Without Polycomb repression, differentiation is accelerated and Merkel cells are precociously acquired. To get insight into the mechanisms of Polycomb control of Merkel cell development, we have identified genes repressed by the Polycomb complex in epidermal progenitors. The most prominent among them was Sox2, which encodes a transcription factor that is highly expressed in Merkel cells. Conditional ablation of Sox2 in skin revealed a dramatic decrease in Merkel cell number, indicating the importance of Sox2 for Merkel cell development. Overall, the above-mentioned results suggest a working model wherein the Polycomb complex controls differentiation in epidermal progenitors by repressing key developmental regulators of the Merkel cell lineage, such as Sox2. The main focus of this grant is to determine the molecular mechanisms by which the Polycomb complex controls Merkel cell fate determination. In Aim1, we will analyze the significance of Polycomb-mediated Sox2 repression in control of the Merkel cell lineage. In Aim2, we will delineate how the Polycomb complex, active chromatin modifications, and components of the transcriptional machinery cooperate to regulate Sox2 gene activation during differentiation of epidermal progenitors to Merkel cells. Finally, in Aim3 we will explore the role of other chromatin regulators in control of Merkel lineage development. Indeed, transcriptional profiling revealed that aside from the Polycomb complex, five key chromatin regulators are differentially expressed in epidermal progenitors and Merkel cells. Using in vivo loss-of-function, molecular and biochemical studies, we will uncover the significance of these chromatin regulators with respect to Merkel cell development. In summary, these studies will define the role of chromatin regulators in skin development and fate determination.)