A new approach to homeostatic maintenance of dendritic epidermal T cells

描述(申请人提供)：维持身体组织的动态平衡通常需要用祖细胞或躯体干细胞产生的年轻细胞来替换受损或老化的细胞。然而，并不是所有的组织类型都以这种方式保持。树突状表皮T细胞是一种皮肤γδT细胞，由胎儿胸腺通过T细胞抗原受体基因的V(D)J重组而获得，但在出生后的整个生命过程中维持在皮肤上皮细胞中表达典型的γδT细胞受体。DETC在上皮屏障监测、肿瘤监测和伤口愈合中发挥重要作用。整个DETC种群在整个生命过程中都是自我维持的，然而个体DETC的寿命和再生行为仍然难以捉摸。为了便于γδT细胞的遗传解剖，我们的实验室现在生产了第一个γδ谱系特异性Cre株。通过三苯氧胺治疗，可以时间和空间控制的方式实现谱系特异性条件性基因的激活或缺失。这一新建立的遗传工具为我们提供了一个前所未有的机会，在出生后的生活中追踪和遗传操纵DETC。我们将利用这一遗传工具来探索与成人皮肤中DETC的动态平衡维持有关的两个基本问题：1)DETC在动态平衡维持期间是否均匀扩张和/或再生；2)TCR信号在DETC的长期维持或伤口愈合等常规功能中的必要性。首先，我们将把可诱导的Cre与多色荧光报告结合起来标记DETC，并跟踪它们在活体小鼠中的克隆行为。其次，我们将使用可诱导的Cre系统通过条件性基因敲除来扰乱TCR信号通路。DETC TCR的同质性支持抗原在DETC的初始选择中起重要作用的观点。目前尚不清楚DETC的长期内稳态维持是否需要TCR信号。这项拟议的研究将为遗传分析支持DETC在成年生活中维持体内平衡的调控途径奠定基础。DETC的研究也是理解成人生活中组织维持的基本规则的一个极好的模型，特别是在组织维持独立于祖细胞或体细胞的情况下。

DESCRIPTION (provided by applicant): Homeostatic maintenance of somatic tissues typically requires replacement of damaged or aged cells by young cells generated from progenitors or somatic stem cells. However, not all tissue types are maintained in such a way. Dendritic Epidermal T Cells (DETC) are skin resident γδ T cells, which are exclusively derived from fetal thymus through V(D)J recombination of the T cell antigen receptor (TCR) genes but are maintained as a homogeneous population expressing a canonical γδTCR in the skin epithelium throughout postnatal life. DETC play important roles in epithelium barrier surveillance, tumor surveillance, and wound healing. The entire DETC population is self-sustained throughout life, yet the lifespan and regenerative behavior of individual DETC remain elusive. To facilitate genetic dissection of γδ T cells, our lab now produced the first γδ lineage specific Cre strain. Lineage specific conditional gene activation or deletion can be achieved in a temporally and spatially controlled manner through tamoxifen treatment. This newly established genetic tool provides an unprecedented opportunity for us to track and genetically manipulate DETC during postnatal life. We will use this genetic tool to explore two fundamental issues concerning homeostatic maintenance of DETC in the adult skin: 1) do DETC expand and/or regenerate uniformly during homeostatic maintenance and 2) the necessity of TCR signaling in either long-term maintenance of DETC or routine function such as wound healing. First, we will combine the inducible Cre with a multi-color fluorescent reporter to label DETC and track their clonal behavior in live mice. Second, we will use the inducible Cre system to disrupt the TCR signaling pathway through conditional gene knockout. The homogeneity of DETC TCR supports the idea that antigens play an important role in the initial selection of DETC. Whether TCR signaling is needed for long-term homeostatic maintenance of DETC is not known. The proposed study will lay the groundwork for genetic analysis of regulatory pathways underpinning homeostatic maintenance of DETC in adult life. The study of DETC also serves as an excellent model for understanding the fundamental rules of tissue maintenance in adult life, particularly in the case where tissue maintenance is independent of progenitor or somatic stem cells.