Chromatin Dynamics During Epithelial Commitment

项目摘要 诱导多能干细胞（iPS）和组织工程的最新进展开启了 隐性营养不良性表皮松解症患者获得基于角质形成细胞的组织替代的大门 大疱病（RDEB）。虽然我们的实验室已经表明，骨形态发生蛋白（BMP）和视黄酸 (RA)形态发生素可以诱导ES/iPS衍生的可移植的人角质形成细胞，详细的机制 对角质形成细胞分化的深入了解仍然是有效组织制造的主要障碍 也是NIH再生医学创新项目的目标。无RA/BMP，主调节器 p63结合，但表现出很少的转录变化，突出了形态发生谱系的重要性 选择器相互作用。HiChIP分析显示RA/BMP诱导染色质构象变化， 将染色质结合的p63连接到连接的增强子/启动子的变化， 每个基因的转录特异性。通过我们新的网络转录因子（TF）推理， 我们发现，一个单一的转录因子TFAP 2C的强制表达可以诱导 在不存在RA/BMP的情况下的功能性角质形成细胞。我们随后确定了一个两步 TFAP 2C启动简单上皮景观并诱导表达的机制 并为p63打开额外的结合位点。反过来，p63使TFAP 2C模式的 表观遗传景观导致p63阳性自动调节和TFAP 2C亚群的关闭 结合位点，将景观转移到以p63为中心的角质形成细胞TF网络。这些数据支持 RA/BMP通过TFAP 2家族成员启动表观遗传变化的有趣假设 最终导致p63驱动的表观遗传成熟的景观角质形成细胞。在这 我们的建议旨在通过以下方式解决我们知识中的关键差距：TFAP 2的功能验证- 通过确认TFAP 2对RA/BMP的必要性， 介导的表观遗传景观变化，决定了早期TF的TFAP 2C功能需求 网络，并定义形态发生诱导型TFAP 2C相互作用组;阐明p63如何成熟 通过确定TFAP 2和p63在角质形成细胞产生过程中 共同允许p63阳性自动调节，确定角质形成细胞成熟是否需要p63- 依赖性TFAP 2抑制，并完成和验证角质形成细胞的推断TF模型 分化成功完成这一提案将提供深入的机械见解， 组织分化的染色质动力学，并建立详细的表观遗传特征， 使我们能够开发新的细胞疗法，用于治疗以前无法治疗的遗传性皮肤病。

Project Summary Recent advances with induced pluripotent stem (iPS) cells and tissue engineering have opened the door to keratinocyte-based tissue replacement for patients with Recessive Dystrophic Epidermolysis bullosa (RDEB). While our lab has shown that bone morphogenic protein (BMP) and retinoic acid (RA) morphogens can induce ES/iPS-derived graftable human keratinocytes, detailed mechanistic insights into keratinocyte differentiation remain a major roadblock to efficient tissue manufacturing and a goal of the NIH Regenerative Medicine Innovation Project. Without RA/BMP, master regulator p63 binds but exhibits few transcriptional changes, highlighting the importance of morphogen-lineage selector interactions. HiChIP analysis shows that RA/BMP induces chromatin conformational changes that connect chromatin-bound p63 to linked enhancers/promoters and determine transcriptional specificity at each gene. Through our novel network transcription factor (TF) inference model we discovered that forced expression of a single transcription factor, TFAP2C, can induce functional keratinocytes in the absence of RA/BMP. We subsequently identified a two-step mechanism where the TFAP2C initiates the simple epithelial landscape, and induces expression of and opens additional binding sites for the p63. In turn, p63 matures the TFAP2C-patterned epigenetic landscape resulting in p63 positive autoregulation and the closing of a subset of TFAP2C binding sites, shifting the landscape to a p63-centric keratinocyte TF network. These data support the intriguing hypothesis that RA/BMP initiates epigenetic changes through TFAP2 family members that ultimately result in p63-driven epigenetic maturation of the landscape to keratinocytes. In this proposal we aim to address key gaps in our knowledge through: Functional validation of the TFAP2- centric network in epigenetic landscape initiation by confirming TFAP2 necessity for RA/BMP- mediated epigenetic landscape change, determining TFAP2C functional requirement for the early TF network, and defining the morphogen-inducible TFAP2C interactome; Elucidation how p63 matures the chromatin landscape during keratinocyte production by determining how TFAP2 and p63 cooperate to allow p63 positive autoregulation, determining if keratinocyte maturation requires p63- dependent TFAP2 repression, and completing and validating an inference TF model of keratinocyte differentiation. Successful completion of this proposal will provide deep mechanistic insights into the chromatin dynamics of tissue differentiation and establish a detailed epigenetic characterization that enables development of our novel cell therapy for a previously untreatable genetic skin disorder.