The Tunicate Ciona: A New Model for the Effects of Aging on Tissue Regeneration

总结 衰老过程中再生能力的丧失是生物学和生物医学中尚未解决的主要问题。 在这里，我们继续开发被囊玻璃海鞘作为再生衰老研究的模型。乔纳 具有许多有利的属性，包括小的测序基因组，广泛的工具包， 基因操纵，寿命短，随着年龄的增长而消失的强大再生能力， 干细胞龛参与再生，一批稳定的绿色荧光蛋白转基因株系 在特定组织中表达，以及产生含有年轻和年老身体部位的嵌合动物的能力。 最重要的是，玻璃海鞘属于一个无脊椎脊索动物群体，被认为是最接近的生活亲属， 脊椎动物，这表明对这种生物的研究通常与脊椎动物有关，包括 人类这项建议的三个具体目标旨在逐步推进我们的理解 干细胞龛、芽基和周围组织环境在再生过程中的相对作用 以玻璃海鞘的口部虹吸管为模型，研究了玻璃海鞘的衰老过程及其分子机制。 第一个目标将使用一种新的嵌合体检测方法，在这种方法中，干细胞的小生境在年轻人和老年人之间交换 动物和分离的干细胞被注射到老年动物中以确定干细胞的相对作用 干细胞本身、再生芽基和周围组织环境， 再生老化这一目标将利用我们以前的鳃囊（咽）干细胞的鉴定 作为祖细胞来源的小生境迁移到虹吸截肢部位并分化成多个 再生过程中的组织。第二个目标是识别、表征和定位关键的表达 负责年轻动物中强大的虹吸再生和这种能力的丧失的调节基因 古老的动物。这一目标将使用一组预先存在的候选基因，这些基因在细胞中以高水平表达， 年轻动物的再生虹吸以及一组新的下调和上调的调控基因 在成体生命的不同阶段，在干细胞龛中表达， 周期第三个目的是确定职能、层级关系，以及恢复失去的能力 通过RNAi介导的基因敲低和改善测定的关键再生基因的再生能力 在年老的动物身上使用嵌合体的方法。这项研究旨在揭示遗传机制 在无脊椎脊索动物模型中，衰老过程中再生能力的丧失是潜在的， 阐明我们对脊椎动物再生性衰老的进化历史和原因的理解。

Summary The loss of regenerative capacity during aging is a major unsolved problem in biology and biomedicine. Here we continue to develop the tunicate Ciona intestinalis as a model for regenerative aging research. Ciona has many favorable attributes for this purpose, including a small sequenced genome, an extensive tool kit for genetic manipulations, a short life span, powerful regeneration capacities that disappear with age, an identified stem cell niche involved in regeneration, a collection of stable transgenic lines with green fluorescent protein expressed in specific tissues, and the ability to produce chimeric animals containing young and old body parts. Most importantly, Ciona belongs to an invertebrate chordate group recognized as the closest living relative of vertebrates, suggesting that research on this organism will be generally relevant to vertebrates, including humans. The three specific aims of this proposal are designed to incrementally advance our understanding the relative roles of the stem cell niche, the blastema, and the surrounding tissue environment in regenerative aging and the molecular mechanisms governing this process using the Ciona oral siphon (mouth) as a model. The first aim will use a novel chimera assay in which stem cell niches are swapped between young and old animals and isolated stem cells are injected into old animals to determine the relative roles of the stem cell niche, the stem cells themselves, the regeneration blastema, and the surrounding tissue environment in regenerative aging. This aim will exploit our previous identification of the branchial sac (pharynx) stem cell niche as the source of progenitor cells that migrate the site of siphon amputation and differentiate into multiple tissues during regeneration. The second aim is to identify, characterize, and localize the expression of key regulatory genes that are responsible for robust siphon regeneration in young animals and loss of this capacity in old animals. This aim will use both a set of pre-existing candidate genes expressed at high levels in the regenerating siphon of young animals as well as a new set of downregulated and upregulated regulatory genes expressed in the stem cell niche to be identified by transcriptome sequencing at different stages of the adult life cycle. The third aim is to determine the functions, hierarchical relationships, and ability to restore lost regenerative capacity of key regeneration genes by RNAi mediated gene knockdown and amelioration assays using the chimera approach in old animals. This research is designed to reveal the genetic mechanisms underlying the loss of regenerative capacity during aging in an invertebrate chordate model with the potential to clarify our understanding of the evolutionary history and causes of regenerative aging in vertebrates.