The Role of Non-Cell Autonomous Wnt Activation in Hair Follicle Growth and Cancer

描述(申请人提供)：组织的动态平衡和再生是由多种细胞类型的协调生长调节的，以产生维持有机体的完整性和功能的组织。这种持久再生组织的能力依赖于成体干细胞 生活在一个称为生态位的专门环境中，这会影响它们的自我更新、成长和分化。未能维持或动员干细胞会导致组织丢失和功能障碍，而这些细胞的不受控制的激活可能会加剧无序生长和癌症。阐明关键分子信号是如何控制干细胞行为的，对于设计治疗人类疾病的靶向疗法具有巨大的意义。研究哺乳动物干细胞是如何被调控的一个主要挑战是，传统的静态分析无法跟踪体内细胞群体随着时间的推移的命运和行为。这项建议旨在解决我们在信号如何与未分化的细胞群接触以产生强劲和有组织的生长方面的一个主要知识缺口。特别是，目前尚不清楚(1)再生过程中关键的形态发生信号是如何调控细胞分裂和移动等细胞行为的，(2)这些信号是如何在一片细胞中传播的，以确保强劲但分隔的生长，以及(3)这些机制如何在肿瘤形成过程中导致无组织和不受控制的生长。毛囊是解决这些问题的理想模型，因为它非常容易获得，并以依赖常驻干细胞的方式经历了良好的周期性再生。通过将该模型与一种新的实时成像技术相结合，我们现在可以独一无二地解决这些悬而未决的问题。在这个项目中，我们研究了毛囊再生所需的关键分子通路Wnt/�-catenin信号是如何在一群未分化的细胞中传播以促进同步和协调生长的。通过实时成像，我们发现只需要一小部分细胞来支持该信号的非细胞自主激活和周围上皮细胞的生长行为，并与可扩散的Wnt配体上调有关。我们的第一个目标是使用体外细胞培养和遗传小鼠模型，在有或没有Wnt分泌的情况下激活�-catenin，以确定在促进毛囊再生过程中对Wnt配体分泌的需求。第二项研究检测基底细胞癌(BCC)上皮细胞Wnt的激活是否需要Wnt分泌，BCC是最常见的皮肤癌，依赖Wnt信号进行生长。我们还将确定持续的上皮性Wnt信号如何影响间充质调节BCC的生长，使用组织移植和遗传方法来调节BCC小鼠模型中的上皮性和真皮Wnt的激活。实现这些目标将为确保适当的组织再生的原理机制提供新的见解，以及它们如何也可以被有害地利用来促进癌症的集体生长。

DESCRIPTION (provided by applicant): Tissue homeostasis and regeneration are mediated by the coordinated growth of multiple cell types to generate tissue that sustains integrity and function of the organism. This ability to durably regenerate tissue relies on adult stem cells that reside in a specialized environment called the niche, which influences their self- renewal, growth and differentiation. Failure to maintain or mobilize stem cells results in tissue loss and dysfunction, while uncontrolled activation of these cells can fuel disorganized growth and cancer. Elucidating how key molecular signals govern stem cell behavior holds tremendous implications for designing targeted therapies to treat human diseases. A major challenge to examining how mammalian stem cells are regulated is the inability of conventional static analysis to follow the fate and behavior of cell populations in vivo over time. This proposal aims to address a major gap in our knowledge of how signals can engage a population of undifferentiated cells to yield robust and organized growth. In particular, is still unclear (1) wht cellular behaviors such as cell divisions and movement are regulated by key morphogenetic signals during regeneration, (2) how these signals are disseminated throughout a field of cells in to ensure robust but compartmentalized growth, and (3) how these mechanisms can contribute to disorganized and uncontrolled growth during tumorigenesis. The hair follicle is the ideal model to address these questions as it is exceptionally accessible and undergoes well-characterized cyclical regeneration in a manner dependent on resident stem cells. By coupling this model to a novel live imaging technique we are now uniquely poised to address these outstanding questions. In this project, we examine how Wnt/�-catenin signaling, a key molecular pathway required for hair follicle regeneration, is propagated throughout a population of undifferentiated cells to promote synchronous and coordinated growth. By live imaging, we have found that only a subset of cells is required to fuel the non-cell autonomous activation of this signal and growth behaviors throughout surrounding epithelial cells and is associated with upregulation of diffusible Wnt ligands. Our first aim uses both in vitro cell culture and genetic mouse models that activate �-catenin in the presence or absence of Wnt secretion to determine the requirement for Wnt ligand secretion in promoting hair follicle regeneration. The second examines if Wnt secretion is required for epithelial Wnt activation in basal cell carcinomas (BCCs), the most common human skin cancer, which is dependent upon Wnt signaling for growth. We will also determine how sustained epithelial Wnt signaling can influence the mesenchyme to regulate BCC growth, using tissue grafting and genetic approaches to modulate epithelial and dermal Wnt activation in a BCC mouse model. Accomplishing these aims will provide novel insight into the principle mechanisms that ensure proper tissue regeneration and how they can also be exploited deleteriously to promote collective growth in cancer.