A New Genetic Tool for Lineage Tracing of Mitotic Cells in Mice

摘要有丝分裂是体细胞干细胞和祖细胞最重要的特征之一。这些细胞的增殖活性对于支持组织功能、替换受损或老化的组织和维持组织稳态至关重要。由于谱系追踪工具的限制，我们对体细胞干细胞或祖细胞如何以及在多大程度上促进体细胞组织的功能和稳态仍然知之甚少。适应性免疫系统为研究祖细胞增殖爆发与组织稳态之间的动态关系提供了最好的例子之一。在对病原体的免疫反应中，抗原特异性淋巴细胞经历猛烈的克隆扩增。这些新产生的效应细胞在病原体清除后通过细胞凋亡迅速被清除。一小部分经历过抗原的细胞会发展成记忆细胞，这些细胞寿命很长，并且在随后暴露于同一抗原时能够进一步扩增。记忆淋巴细胞的产生和体内平衡的维持对持久的免疫至关重要。迄今为止，记忆淋巴细胞的起源和命运仍未完全了解。我们正在开发一种独特的Cre/lox介导的小鼠有丝分裂重组系统。使用该报告系统，成年小鼠中的任何增殖细胞都可以用可见标记物脉冲标记，以便对这些细胞及其后代进行长期追踪。我们计划使用这种遗传标记系统来标记和追踪来自病原体免疫反应的记忆T细胞。我们将检查在原发性和继发性病原体暴露后记忆T细胞的发育、定位和维持。由于该实验系统旨在标记任何分裂细胞的后代，因此该系统也可用于追踪和分析淋巴系统以外组织类型中的祖细胞或干细胞的克隆行为。我们期待该标记系统在组织再生、衰老和免疫记忆等领域的广泛应用。

DESCRIPTION (provided by applicant): A New Genetic Tool for Lineage Tracing of Mitotic Cells in Mice Abstract Mitosis represents one of the most important signatures of somatic stem cells and progenitor cells. The proliferative activity of these cells is essential for supporting tissue functions, replacing damaged or aged tissues, and maintaining tissue homeostasis. Due to the limitations of lineage tracing tools, we still know little about how and to what extent somatic stem or progenitor cells contribute to the function and homeostasis of somatic tissues. The adaptive immune system provides one of the best examples to study the dynamic relationship between the proliferative burst of progenitors and tissue homeostasis. During an immune response to pathogens antigen-specific lymphocytes undergo vigorous clonal expansion. These newly generated effector cells are quickly removed through apoptosis following pathogen clearance. A small fraction of antigen-experienced cells develops into memory cells, which are long lived and are capable of further expansion during subsequent exposure to the same antigen. The generation and homeostatic maintenance of memory lymphocytes are critical for long lasting immunity. Thus far, the origin and fate of memory lymphocytes are still not completely understood. We are developing a unique Cre/lox mediated mitotic recombination system in mice. Using this reporter system, any proliferating cells in adult mice may be pulse labeled with a visible marker for long term tracing of these cells and their descendants. We plan to use this genetic marking system to label and trace memory T cells derived from an immune response to pathogens. We will examine the development, location, and maintenance of memory T cells after primary and secondary pathogen exposure. Because the experimental system is designed to mark the descendants of any dividing cells, the system should also be useful for tracing and analyzing clonal behavior of progenitors or stem cells in tissue types beyond the lymphoid system. We anticipate a broad application of this marking system in the fields such as tissue regeneration, aging, and immunological memory. PUBLIC HEALTH RELEVANCE: The proposed research will provide a new research tool for experimental analysis of immune cells and stem cells in animal models. The outcome will impact our understanding of immune memory and stem cell behaviors.