Regulation of catagen regression and progenitor pruning by the dermal sheath

项目摘要 头发周期涉及显着重塑生长毛囊（HF）在重复阶段的祖细胞 死亡和毛囊退化，休息和新的头发生长。因此，它是研究回归的一个很好的模型 以及由上皮干细胞（SC）和祖细胞执行并由 生态位微环境来自毛乳头（DP）的信号调节祖细胞增殖和分化 在生长的HFs的球中，并在休息到生长的过渡期间诱导毛胚中的SC再生 完全生长的HF。最近，来自DP的信号也被牵连到在退化期诱导祖细胞死亡 回归分析在退化过程中，DP本身需要从生长鳞茎的基部重新定位到SC水库 在上HF。这是如何实现的，几十年来一直不为人知。我们之前鉴定了 鞘（DS）作为功能性平滑肌，收缩以物理地重新定位DP以到达其基本SC， 相邻位置。在这里，我们将测试DS是否是调节祖细胞的潜在信号源， 死亡，一个同样重要的过程，推动退化期的回归。我们发现DS 动态产生许多信号分子，包括转化生长因子β（TGF β）， 先前通过来自DP的TGF β 1信号参与祖细胞死亡。根据初步数据， 然而，发现DP是修剪祖细胞数量的关键，DS是重要的信号 调节卵泡退化的来源。在我们的研究中，我们将严格检验DS 构成了一个信号生态位，通过TGF β信号控制头发周期的退化。我们将有选择地 并在毛发生长期间诱导消融DS和DP，并明确确定它们对退行期的需求 启动和祖细胞死亡。我们将探讨TGFβ通路组分在DS和TGFβ 1中的表达。 在祖细胞中的信号传导，建立DS衍生的TGFβ信号传导在TGFβ1修剪祖细胞中的关键作用， 用组合pSmad 2染色质消融和鉴定下游转录靶点 免疫沉淀和转座酶可及染色质测序分析。最后，我们将确定 通过smFISH和IF检测祖细胞-DS界面处TGFβ活化复合物的分子组分，以及 在全卵泡收缩试验中，解读DS收缩介导的力如何激活TGFβ信号传导。 总之，这项工作将确定卵泡鞘调节祖细胞命运的关键生理功能， 可能有助于开发HF再生方法，包括操纵退化期修剪， 祖先

Project Summary The hair cycle involves remarkable remodeling of growing hair follicles (HF) in repeated phases of progenitor death and follicle regression, rest and new hair growth. It is therefore an excellent model for studying regression and regeneration processes that are executed by epithelial stem cells (SC) and progenitors and regulated by the niche microenvironment. Signals from the dermal papilla (DP) regulate progenitor proliferation and differentiation in the bulb of growing HFs, and induce SCs in the hair germ during the rest-to-growth transition to regenerate fully growing HFs. Recently, signals from the DP were implicated to induce also progenitor death during catagen regression. During regression, the DP itself needs to relocate from the base of growing bulbs to the SC reservoir in the upper HF. How this is accomplished has been unknown for decades. We previously identified the dermal sheath (DS) as a functional smooth muscle that contracts to physically relocate the DP to reach its essential SC- adjacent position. Here, we will test whether the DS is a potential signaling source that regulates progenitor death, a process equally essential for propelling catagen regression. We have discovered that the DS dynamically produces many signaling molecules including transforming growth factor beta (TGF), which was previously implicated in progenitor death by TGF signals from the DP. With additional preliminary data we found, however, that the DP is dispensable for pruning progenitor numbers and that the DS is the essential signal source for regulating follicle regression. In our studies, we will rigorously test the hypothesis that the DS constitutes a signaling niche that through TGF signaling controls regression in the hair cycle. We will selectively and inducibly ablate the DS and DP during hair growth and unequivocally determine their requirement for catagen initiation and progenitor death. We will explore expression of TGFβ pathway components in the DS and TGFβ signaling in the progenitors, establish a key role of DS-derived TGFβ signaling in progenitor pruning by Tgfβ1 ablations and identify downstream transcriptional targets with combinatorial pSmad2 chromatin immunoprecipitation and transposase-accessible chromatin sequencing analyses. Finally, we will determine the molecular components of the TGFβ activation complex at the progenitor-DS interface by smFISH and IF, and decipher how DS contraction-mediated forces activate TGFβ signaling in whole-follicle contraction assays. Overall, this work will define key physiological functions of the follicle sheath for regulating progenitor fate, which may be useful for developing HF regenerative approaches, including manipulating catagen pruning of progenitors.