Defining the heterogeneity of cell lineages in the inter-follicular epidermis

摘要 尽管毛囊间表皮(IFE)对于基本的身体屏障功能至关重要， 基底层内的干细胞(SCs)的分子特征尚未实现。这有损于 我们有能力研究特定控制IFE SCs的机制，以实现适当的动态平衡和创伤 并了解这些机制在皮肤病和衰老中可能受到的影响。IFE SC 在体内传统上被鉴定为DNA标记保留细胞(LRC)，而转运扩增(TA)或 祖细胞被认为是非LRCs。然而，LRC和非LRC标记明确地测试了这一点 一直缺乏活体模型。使用我们的H_2B-GFP脉冲追赶转基因小鼠系统，我们标记了IFE LRCs和非LRCs，定义了mRNA表达谱，并发现这些细胞在分子上是不同的。在我们的 第一组初步数据，我们证明，与预期的SC经常分裂相反 细胞，LRC(标记为Dlx1Creer)和非LRC(标记为Slc1a3Creer)的IFE细胞子集 在长期血统追踪中充当两个独立的SC。总体而言，我们的数据支持一种模型，在该模型中 IFE是一个异质组织，由分子上不同的区域或区域组成，这些区域或区域是 相对于彼此和皮肤地标在空间上形成图案。这些地区富含LRC和 非LRC，以不同的速率再生，包含不同的SCs和分化的细胞，可以定义为 分子离散的IFE细胞亚群。我们提供LRC和非LRC丰富的标记和基因 定义新的IFE细胞子集的标记工具，这将使我们能够严格检查新的 揭示了生活的异质性。具体目标是：(1)审查非正规教育领土的组织 整个生命周期，并确定新发现的IFE细胞亚群的相对SC潜力；(Ii)验证和 从我们新发现的未分化和分化的IFE细胞中提炼IFE异质性的标记 以及(Iii)通过我们鉴定的两个转录因子来揭示IFE异质性的机制 在LRC和非LRC IFE子集中。总而言之，我们的数据将成为了解 IFE中以前未被识别的细胞和分子异质性，并提供了一个新的切入点 SC在这个基本的，但知之甚少的皮肤间隔中的调节。

Abstract Despite the crucial importance of the inter-follicular epidermis (IFE) for the essential body barrier function, molecular characterization of the stem cells (SCs) within the basal layer has not been achieved. This impairs our ability to study the mechanisms that specifically control IFE SCs for proper homeostasis and wound healing and to understand how these mechanisms may be affected in skin disease and aging. The IFE SCs have been traditionally identified in vivo as DNA label retaining cells (LRCs) while transit amplifying (TA) or progenitor cells were considered non-LRCs. However, LRC and non-LRC markers to unambiguously test this model in vivo had been lacking. Using our H2B-GFP pulse-chase transgenic mouse system, we label IFE LRCs and non-LRCs, define mRNA expression profiles, and find that these cells are molecularly distinct. In our first set of preliminary data, we demonstrate that, contrary to the expectation that SC are frequently dividing cells, both of our IFE cellular subsets of LRCs (marked by Dlx1CreER) and of non-LRCs (marked by Slc1a3CreER) act as two independent SCs in long-term lineage tracing. Collectively, our data support a model in which the IFE is a heterogeneous tissue, being composed of molecularly distinct domains or territories, which are spatially patterned relative to each other and to skin landmarks. These territories are enriched in LRCs and non-LRCs, regenerate at different rates, and contain distinct SCs and differentiated cells that can be defined as molecularly discrete IFE cellular subsets. We provide LRC and non-LRC-enriched markers and genetic labeling tools that define novel IFE cellular subsets, which will enable us to rigorously examine the newly uncovered IFE heterogeneity. The specific objectives are to: (i) examine the organization of IFE territories throughout life, and determine relative SC potential of newly uncovered IFE cellular subsets; (ii) validate and refine markers of IFE heterogeneity from our newly uncovered undifferentiated and differentiated IFE cellular subsets; and (iii) unravel mechanism of IFE heterogeneity by focusing on two transcription factors we identified in our LRC versus non-LRC IFE subsets. Collectively, our data will constitute a key for understanding previously un-recognized cellular and molecular heterogeneity within the IFE and provide a new entry point into SC regulation in this essential, yet poorly understood skin compartment.