Control of reproductive aging by germline stem cells

项目总结/摘要 成体干细胞衰竭是衰老的标志。然而，衰老过程中干细胞衰竭的机制 在很大程度上是未知的，也没有可以延缓人类干细胞衰老的疗法。C. elegans是一个 研究衰老的首要模式生物;成年动物寿命短，只含有一个干细胞库， 产生卵子和精子的生殖干细胞。广泛的发展研究提供了丰富的 描述了控制年轻动物中这些干细胞的分子和细胞事件。我的目标是 理解干细胞衰竭，我的策略是利用C的实验能力。优雅和 干细胞发育的详细知识，以阐明干细胞衰老。体细胞远端细胞（DTC） 通过表达Notch途径配体LAG-2和APX-1作为干细胞小生境，LAG-2和APX-1结合并激活 干细胞中的GLP-1/Notch受体。Notch信号通路在进化过程中是保守的， 反复参与调节哺乳动物的干细胞，这表明蠕虫中的小生境/干细胞系统是 可能具有广泛的相关性。阐明该系统的监管逻辑将推动以下领域的发展： 生殖老化和干细胞衰竭我们实验室的初步结果表明， 生殖系干细胞的活性随着年龄的增长而迅速和进行性地下降。基于这些结果，我建议 两个创新的假设(1)年龄相关的DTC小生境Notch信号转导下降导致干细胞 疲惫不堪(2)神经元TGF-β信号传导介导DTC小生境的活性，并有助于年龄- 与生殖系中成体干细胞的减少有关。为了验证这些假设，我提出了两个具体目标。目的 1：阐明生殖系中成体干细胞老化过程中Notch通路调控的机制。我会 监测老化过程中DTC龛中LAG-2配体的表达，并分析LAG-2配体和Notch受体 功能这些结果将通过确定LAG-2配体的表达是如何被调节的来严格检验我的假设 以及LAG-2配体和/或GLP-1/Notch受体是否足以维持干细胞活性 在老化过程中。目的2：确定感觉神经元如何调节DTC龛介导生殖干细胞 细胞老化我将分析在lag-2启动子中的p53 -3结合位点，以及p53 -3和p53 -5转录 这些因子是TGF-β信号传导的效应因子。我将研究包括蛋白质在内的多层次组织 表达、干细胞动力学和后代产生。这些结果将确定神经元信号如何控制 衰老过程中的生态位和干细胞。干细胞衰竭的机制仍然是个谜， 实验将通过确定神经元、小生境和干细胞的贡献来推进这一领域 自己结果将建立一个知识基础，可能会刺激创新的方法， 保持干细胞功能，促进人类健康衰老。

Project Summary/Abstract Adult stem cell exhaustion is a hallmark of aging. However, mechanisms of stem cell exhaustion during aging are largely unknown, and there are no therapies that can delay stem cell aging in humans. C. elegans is a premier model organism for studying aging; adult animals are short lived and only contain one stem cell pool, the germline stem cells that generate eggs and sperm. Extensive developmental studies have provided a rich description of the molecular and cellular events that control these stem cells in young animals. My goal is to understand stem cell exhaustion, and my strategy is to exploit the experimental power of C. elegans and the detailed knowledge of stem cell development to elucidate stem cell aging. The somatic distal tip cell (DTC) serves as the stem cell niche by expressing the Notch pathway ligands LAG-2 and APX-1, which bind and activate the GLP-1/Notch receptor in the stem cells. Notch signaling pathways are conserved during evolution and have been repeatedly implicated in regulating stem cells in mammals, suggesting the niche/stem cell system in worms is likely to be broadly relevant. Elucidating the regulatory logic of this system will advance the fields of reproductive aging and stem cell exhaustion. Preliminary results from our lab demonstrate that the number and activity of germline stem cells decline rapidly and progressively with age. Based on these results, I propose two innovative hypotheses. (1) An age-related decline in Notch signaling from the DTC niche causes stem cell exhaustion. (2) Neuronal TGF-β signaling mediates the activity of the DTC niche and contributes to the age- related decline of adult stem cells in the germline. To test these hypotheses, I propose two specific aims. Aim 1: Elucidate mechanisms of Notch pathway regulation during adult stem cell aging in the germline. I will monitor LAG-2 ligand expression in the DTC niche during aging and analyze LAG-2 ligand and Notch receptor function. The results will rigorously test my hypothesis by establishing how LAG-2 ligand expression is regulated during aging and whether LAG-2 ligand and/or GLP-1/Notch receptor are sufficient to sustain stem cell activity during aging. Aim 2: Determine how sensory neurons regulate the DTC niche to mediate germline stem cell aging. I will analyze the DAF-3 binding site in the lag-2 promoter, and the DAF-3 and DAF-5 transcription factors that are the effectors of TGF-β signaling. I will examine multiple levels of organization including protein expression, stem cell dynamics, and progeny production. The results will establish how neuronal signals control the niche and stem cells during aging. The mechanisms of stem cell exhaustion remain mysterious, and these experiments will advance the field by determining the contributions of neurons, the niche, and the stem cells themselves. The results will establish a foundation of knowledge that may stimulate innovative approaches to preserve stem cell function and promote healthy aging in humans.