Tissue Size and Precision Control in Growing Hair Follicles

项目摘要 生物组织似乎“知道”它们预期的最终尺寸，并精确而稳健地实现它们。同时， 原则上，一个简单的负信号反馈应该足以解释一个给定的干细胞谱系 调节其细胞输出，实际上它不能工作，因为大多数组织在物理上很大， 它们的后代会分散在厘米级的距离上。组织如何克服微观衰变 可扩散分子信号突破空间尺度上数量级的距离的限制仍然是难以捉摸的。 这个应用程序的灵感来自于我们的偶然发现，FGF和BMP突变小鼠能够生长 超长且高度不精确的毛发，其长度可超过正常小鼠毛发的7倍。我们这一谱系 分析表明，毛发干细胞在空间上不断补充短寿命的转运放大（TA）细胞， 位于离干细胞近1厘米处。有趣的是，我们的单细胞RNA测序分析显示， 先前未被认识到的中间上皮祖细胞的异质性， 干细胞和TA细胞 通过一个综合的数学和实验的方法，这个应用程序将侧重于测试 我们的新假设是，两个或多个中间细胞状态之间的动态平衡及其相关的 细胞-细胞通信使得反馈信息能够在大的空间尺度上从TA细胞传播到干细胞 细胞来调节新的祖细胞的生产，以控制头发的大小。拟议研究的第一个目标是 是描绘和量化中间上皮祖细胞的异质性， 通过实验确定毛囊中特定中间祖细胞状态之间的功能联系 头发的长度和精确度第二个目标是定义通信网络内的小区-小区通信网络。 上皮毛囊谱系，并通过计算和实验建立多个短程 信号传导活动协调形成一个远程反馈机制，控制祖细胞之间的流量， 远距离干细胞和TA细胞隔室的适当头发生长。第三个目标是确定信号影响 毛囊周围的间充质小生境细胞对上皮细胞系细胞的作用，以控制头发的大小。 研究前提是基于新颖和广泛的初步实验和计算数据。的 拟议的研究是重要的，因为它们将建立新的远程信号机制， 揭示了中间细胞状态在组织尺寸控制中的新作用。拟议的研究是创新的 因为他们将建立新的实验模型，用于研究组织大小调节， 超短毛突变小鼠，并将为上皮干细胞研究带来许多新的遗传小鼠工具。 它们还将产生几种用于分析单细胞RNA的新型数学和计算工具， 测序数据和复杂细胞谱系的新空间模型，如毛囊。

PROJECT SUMMARY Biological tissues appear to “know” their intended final sizes and achieve them precisely and robustly. While, in principle, a simple negative signaling feedback should be sufficient to explain how a given stem cell lineage regulates its cellular outputs, in reality it cannot work because most tissues are physically large, with stem cells and their progeny spread out over centimeter-scale distances. How tissues overcome the microscopic decay limits of diffusible molecular signals to breach distances orders-of-magnitude in spatial scale remains elusive. This application is inspired by our serendipitous discovery that FGF and BMP mutant mice are able to grow super-long and highly imprecise hairs that can exceed the length of normal mouse hairs by 7-fold. Our lineage analyses suggest that hair stem cells continuously replenish short-lived transit-amplifying (TA) cells spatially located nearly 1 cm away from the stem cells. Interestingly, our single-cell RNA-sequencing analyses reveal previously unappreciated heterogeneity of the intermediate epithelial progenitor cells physically located between the stem and TA cells. Through an integrated mathematical and experimental approach, this application will focus on testing our new hypothesis that dynamic equilibrium between two or more intermediate cell states and their associated cell-cell communications enable feedback information propagation over large spatial scale from TA cells to stem cells to regulate the new progenitor cell production for hair size control. The first aim of the proposed research is to profile and quantify the heterogeneity of intermediate epithelial progenitors, and computationally and experimentally determine the functional link between specific intermediate progenitor states in the hair follicle and the hair length and its precision. The second aim is to define the cell-cell communication networks within the epithelial hair follicle lineage, and computationally and experimentally establish how multiple short-range signaling activities coordinate to form a long-range feedback mechanism that controls progenitor flux between distant stem and TA cell compartments for proper hair growth. The third aim is to determine the signaling impact of mesenchymal niche cells, which surround the hair follicle, on the epithelial lineage cells for hair size control. The study premise is based on novel and extensive preliminary experimental and computational data. The proposed studies are significant because they will establish new long-range signaling mechanisms and uncover novel roles of intermediate cell states in tissue size control. The proposed studies are innovative because they will establish new experimental models for studying tissue size regulation using super-long and extra-short hair mutant mice and will result in numerous new genetic mouse tools for epithelial stem cell research. They will also result in several novel mathematical and computational tools for analyzing single-cell RNA- sequencing data and new spatial models for complex cell lineages, such as in the hair follicle.