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

描述（由申请人提供）：许多脊椎动物在胚胎和幼体时期具有强大的组织再生能力，但这种能力在发育和衰老过程中逐渐消失。与年龄相关的再生能力下降的机制是未知的，这是一个需要新的方法和模型系统的领域。本研究以被囊动物为研究对象，研究衰老对组织再生的影响。虽然以前没有被用作衰老模型，但Ciona具有许多有利的属性：它具有强大的再生能力，但随着年龄的增长，再生能力会下降；基因组测序，cDNA和ESTs集合覆盖了总基因的80%；稳定的转基因系，在特定组织中标记了基因表达；作为脊索类无脊椎动物的一员，被认为是脊椎动物的姐妹分类群，关于被囊动物衰老和再生之间关系的信息可能与人类有关。本提案的五个具体目标是为了获得在衰老过程中有缺陷的口腔虹吸再生的分子和细胞理解。我们将重点关注口腔虹吸管的感觉色素器官，可能在年轻和中年动物中以高保真度再生的光感受器，但在老年动物中表现出特定的缺陷。前三个目标将集中在色素器官再生中涉及产生年龄相关缺陷的细胞事件。第一个目的是研究衰老对色素器官前体干细胞/祖细胞生态位维持和前体细胞在再生过程中向伤口部位迁移的影响。第二个目标将集中在虹吸伤口部位、干/前体生态位和再生过程中色素器官的细胞死亡和增殖的年龄相关变化。第三个目标探索虹吸神经和中枢神经系统在再生衰老中的作用，使用消蚀技术和转基因系在整个神经系统中进行GFP染色。第四和第五个目的是研究色素器官再生中年龄相关缺陷的分子机制。第四个目标将识别和确定再生过程中涉及的基因表达模式，包括Notch信号系统的组成部分，初步研究表明其与再生过程有关。第五个目标将使用RNAi基因沉默来确定再生基因的功能变化如何参与前三个目标中揭示的细胞衰老过程。这项研究有望填补一个主要的空白，以了解再生能力如何随着年龄的增长而下降，在一个模式脊索动物代表最接近的脊椎动物的亲属。

DESCRIPTION (provided by applicant): Many vertebrates have robust capacities for tissue regeneration as embryos and juveniles but this power fades during development and aging. The mechanisms of age-related decline in regenerative capacity are unknown and an area in which new approaches and model systems are necessary. This proposal develops the tunicate Ciona intestinalis as a chordate model for studying the effects of aging on tissue regeneration. Although not previously used as an aging model, Ciona has many favorable attributes for this purpose: it has powerful capacities for regeneration, which decline during aging, a sequenced genome, a collection of cDNA and ESTs covering 80% of the total genes, stable transgenic lines with tagged gene expression in specific tissues, and a short life history in which age is directly related to size. As a member of a chordate invertebrate group that is inferred to be the sister taxon of vertebrates, information obtained about the relationship between aging and regeneration in tunicates may be relevant to humans. The five specific aims of this proposal are designed to obtain a molecular and cellular understanding of defective oral siphon regeneration during aging. We will focus on the sensory pigment organs of the oral siphon, possible photoreceptors that regenerate with high fidelity in young and middle age animals, but show specific defects in old animals. The first three aims will focus on the cellular events involved in producing age-related defects in pigment organ regeneration. The first aim will investigate the effects of aging on maintenance of the stem/progenitor cell niche for pigment organ precursors and precursor cell migration to the wound site during regeneration. The second aim will focus on age-related changes in cell death and proliferation in the siphon wound site, the stem/precursor niche, and the reforming pigment organs during regeneration. The third aim explores the role of siphon nerves and the CNS in regenerative aging using ablation techniques and a transgenic line with GFP staining throughout the nervous system. The fourth and fifth aims investigate the molecular mechanisms responsible for age-related defects in pigment organ regeneration. The fourth aim will identify and determine the expression patterns of genes involved in regeneration, including components of the Notch signaling system, which preliminary studies have implicated in the regenerative process. The fifth aim will use RNAi gene silencing to establish how functional changes in regeneration genes are involved in the cellular aging processes revealed in the first three aims. This research is expected to fill a major gap in understanding how regenerative capacity declines with aging in a model chordate representing the closest living relative of vertebrates. PUBLIC HEALTH RELEVANCE: The ability to replace injured tissues fades with aging in most vertebrates, including humans. This study will develop the tunicate Ciona intestinalis, a vertebrate relative with powerful regeneration abilities that also recede with age, as a model to study the relationship between aging and tissue regeneration.