Specification of Dermal Papilla Cell Fate in the Hair Follicle Stem Cell Niche

干细胞（SC）活化和自我更新的调节是成功的组织发育所必需的， 体内平衡在许多组织中，这是由微环境中支持细胞的信号协调的 称为SC Niche。深入了解哺乳动物SC龛细胞如何被编程， 在发育过程中调节SC的功能是未来组织特异性再生的关键要求。 治疗虽然已经从无脊椎动物的研究中获得了很多知识，但分子理解 哺乳动物SC中的小生境细胞如何在骨髓、脑、肠和毛囊中形成小生境， 由于组织的复杂性和缺乏方法， 分离并表征细胞。我们最近开发了新的遗传工具来研究毛乳头 (DP)毛囊SC龛中的细胞，其被认为指导毛囊SC的命运。我们净化了这些 细胞，确定了它们的分子身份，并建立了研究其命运规格的测定法。这建立 这是一个非常需要的哺乳动物模型，可以研究SC生态位的形成和功能。我们长久以来- 长期目标是了解支配SC生态位命运特化的分子机制，使用 毛囊形态发生和再生的模型系统。我们的工作已经确定了 DP细胞的特征，包括一组信号传导和转录因子（TF）。在本提案中，我们将 检验DP特征TF含有调节SC所必需和足够的活性的假设 激活，毛发诱导DP生态位命运。我们将系统地操纵DP细胞中TF的表达 在体外和体内，以确定指定分子身份的转录控制机制， DP niche细胞的功能活性。我们将进一步建立一个新的可诱导的DP特异性体内基因 针对目前在该领域缺失的小鼠模型。最后，我们将用可用的小鼠进行测试， 针对条件性基因消融，候选DP特征TF对于DP生态位命运的必要性 本说明书中，使用这种新的体内基因消融模型，并与我们建立的体外/体内基因消融模型平行， 杂合敲除测定。我们的工作将确定头发SC生态位命运的核心转录调控 卵泡DP细胞在分离的DP细胞和常规成纤维细胞中激活转录程序， 有望扩大功能齐全的细胞，用于皮肤重建的治疗用途。这些发现将 对其他再生组织具有全局相关性，其中SC小生境起维持组织稳态的作用， 并可能导致3D组织再生疗法的发展。

Regulation of stem cell (SC) activation and self-renewal is necessary for successful tissue development and homeostasis. In many tissues this is orchestrated by signals from supporting cells within the microenvironment called the SC niche. A thorough understanding of how mammalian SC niche cells become programmed and function during development to regulate SCs is a crucial requirement for future tissue-specific regenerative therapies. While much knowledge has been gained from studies in invertebrates, a molecular understanding of how niche cells in mammalian SC niches, such as the bone marrow, brain, intestine and hair follicles, acquire their specialized status is unknown due to the complexity of the tissues and the lack of methods to isolate and characterize the cells. We have recently developed novel genetic tools to study dermal papilla (DP) cells in the hair follicle SC niche, which are thought to direct follicular SC fate. We have purified these cells, defined their molecular identity and established assays to study their fate specification. This establishes a much needed mammalian model where formation and function of the SC niche can be studied. Our long- term goal is to understand the molecular mechanisms that govern SC niche fate specification, using hair follicle morphogenesis and regeneration as a model system. Our work has identified the molecular signature of DP cells, including a battery of signaling and transcription factors (TFs). In this proposal, we will test the hypothesis that the DP signature TFs contain the activity necessary and sufficient to regulate the SC activating, hair inducing DP niche fate. We will systematically manipulate signature TF expression in DP cells in vitro and in vivo to define the transcriptional control mechanisms that specify the molecular identity and functional activity of DP niche cells. We will further establish a novel inducible DP-specific in vivo gene targeting mouse model that is currently missing in the field. Finally, we will test with available mice that are targeted for conditional gene ablation, the necessity of candidate DP signature TFs for DP niche fate specification, using this novel in vivo gene ablation model, and in parallel with our established in vitro/in vivo hybrid knockout assay. Our work will identify the core transcriptional regulation of the SC niche fate of hair follicle DP cells. Activating the transcriptional program in isolated DP cells and in regular fibroblasts bears the promise to expand fully functional cells for therapeutic use in skin reconstructive efforts. These findings will have global relevance for other regenerative tissues, where SC niches operate to maintain tissue homeostasis, and potentially will lead to development of 3D-tissue regenerative therapies.