The regulation of melanocyte stem cells by Wnt signaling

总结 皮肤黑素细胞（MCs）的缺失可导致许多皮肤色素沉着疾病，包括 高/低皮肤色素沉着，以及最具侵略性的皮肤癌，黑色素瘤，仍然缺乏一个 疗方在开发黑色素瘤以及许多其他肿瘤的有效治疗方法中的主要障碍之一是， 色素性疾病是我们对Mc干细胞（McSC）的组织和调节的理解不足。 到目前为止，仅在毛囊中鉴定了McSCs，并且不知道McSCs是否存在于毛囊中。 皮肤表皮。此外，人们对McSC如何受到分子调节知之甚少。这是在斯塔克 与上皮干细胞相反，上皮干细胞的身份和特征一直是质疑这一点的关键。 群体并确定上皮干细胞在组织再生期间以及在组织再生期间如何受到调节 致癌作用在上一个授予期间，我们有两个重要发现：第一，我们发现Wnt 信号转导调节McSCs的自我更新和分化以及它们的黑色素瘤转化， 建立的黑色素瘤小鼠模型。其次，我们发现表皮中的MC亚群也 显示活跃的Wnt信号传导，并且这些表皮MC在表皮内长期存在。我们 假设Wnt-活性表皮Mcs代表维持并 再生皮肤表皮中的MC并可转化为黑素瘤细胞。我们将检验这一假设 三个具体目标。在Aim 1下，我们将在正常稳态下进行体内遗传谱系分析 以及在UV暴露后Mc增殖期间与离体皮肤/毛发重建测定平行， 确定Wnt-活性表皮MC是否自我更新和分化以持久维持表皮或毛发 麦克在目标2下，我们将研究Wnt信号如何调节正常条件下表皮MC的行为。 体内平衡和紫外线暴露后。为此，我们将进行Wnt功能丧失和获得实验， 采用已建立的遗传小鼠模型的Mcs。在目标3下，我们将测试表皮MC的能力， 在移植模型中表达黑素瘤诱导突变后形成黑素瘤。总之，这 这项研究将是第一个明确解决皮肤表皮内存在McSCs的问题，并开始 定义表皮McSCs是如何被调节的。我们的研究结果将在Mc领域产生重大影响， 黑素瘤生物学新鉴定的皮肤表皮内的McSCs和调节它们的Wnt通路 行为将为预防和治疗黑色素瘤以及各种 色素沉着疾病

SUMMARY Abnormalities of skin melanocytes (Mcs) can cause a number of skin pigmentation diseases including hyper/hypo skin pigmentation, as well as the most aggressive form of skin cancer, melanoma, that still lacks a cure. One of the major obstacles in developing effective treatments for melanoma as well as many other pigmentary disorders is our poor understanding of the organization and regulation of Mc stem cells (McSCs). Thus far, McSCs have been only identified in the hair follicle, and it is not known whether McSCs are present in the skin epidermis. Moreover, little is known about how McSCs are molecularly regulated. This is in stark contrast to epithelial stem cells whose identity and characterization have been key to interrogating this population and determining how epithelial stem cells are regulated during tissue regeneration as well as during carcinogenesis. During the last granting period, we made two important discoveries: First, we found that Wnt signaling regulates the self-renewal and differentiation of McSCs as well as their melanoma-transformation in an established melanoma mouse model. Second, we found that a subpopulation of Mcs in the epidermis also displays active Wnt signaling, and these epidermal Mcs persist for long-term within the epidermis. We hypothesize that Wnt-active epidermal Mcs represent a McSC population that maintains and regenerates Mcs in the skin epidermis and can transform into melanoma cells. We will test this hypothesis in three Specific Aims. Under Aim1, we will perform in vivo genetic lineage analysis under normal homeostasis and during Mc proliferation following UV exposure in parallel with ex vivo skin/hair reconstitution assays to determine whether Wnt-active epidermal Mcs self-renew and differentiate to durably maintain epidermal or hair Mcs. Under Aim 2, we will examine how Wnt signaling regulates the behavior of epidermal Mcs under normal homeostasis and following UV exposure. For this, we will perform Wnt loss- and gain-of-function experiments in Mcs employing established genetic mouse models. Under Aim3, we will test the ability of epidermal Mcs to form melanoma upon expression of melanoma-inducing mutations in a transplantation model. In summary, this study will be the first to definitively address the presence of McSCs within the skin epidermis and to begin to define how epidermal McSCs are regulated. Our findings will have a major impact in the field of Mc and melanoma biology. Newly identified McSCs within the skin epidermis and the Wnt pathway that regulates their behavior will provide novel targets for the prevention and treatment of melanoma as well as various pigmentation diseases.