Tissue Size and Precision Control in Growing Hair Follicles

项目总结 生物组织似乎“知道”它们想要的最终尺寸，并准确而有力地实现它们。而与此同时， 原则上，一个简单的负面信号反馈应该足以解释一个特定的干细胞谱系是如何 调节它的细胞输出，实际上它不能工作，因为大多数组织在物理上都很大，有干细胞 它们的后代分布在厘米级的距离内。组织是如何克服微观腐烂的 可扩散的分子信号在空间尺度上突破距离数量级的限制仍然难以捉摸。 这个应用程序的灵感来自于我们的偶然发现，即成纤维细胞生长因子和骨形态发生蛋白突变小鼠能够生长 超长和高度不精确的毛发，可以超过正常老鼠毛发长度的7倍。我们的血统 分析表明，毛发干细胞在空间上持续补充短命的转运放大(TA)细胞 位于距干细胞近1厘米的地方。有趣的是，我们的单细胞RNA测序分析显示 物理上位于中间上皮祖细胞之间的中间上皮祖细胞以前未被发现的异质性 干细胞和TA细胞。 通过综合的数学和实验方法，这一应用程序将专注于测试 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 细胞间的通信使反馈信息能够在大空间尺度上从TA细胞传播到干细胞 调节新的祖细胞生产的细胞，以控制头发的大小。拟议研究的第一个目的是 是描绘和量化中间上皮祖细胞的异质性，并通过计算和 通过实验确定毛囊中特定中间前体状态之间的功能联系 以及头发的长度和精度。第二个目标是定义小区间通信网络 上皮性毛囊谱系，并通过计算和实验确定多个短程 信号活动相互协调，形成一个远程反馈机制，控制祖细胞之间的流量 远距离的干细胞室和TA细胞室为头发的正常生长提供帮助。第三个目标是确定信号的影响 毛囊周围的间充质壁龛细胞在上皮细胞系上控制毛发大小。 研究的前提是基于新颖和广泛的初步实验和计算数据。这个 拟议的研究具有重要意义，因为它们将建立新的远程信号机制和 揭示中间细胞状态在组织大小控制中的新作用。建议的研究具有创新性。 因为他们将建立新的实验模型来研究组织大小调节使用超长和 超短毛突变小鼠，并将产生许多用于上皮干细胞研究的新的小鼠遗传工具。 它们还将产生几种新的数学和计算工具，用于分析单细胞RNA- 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.