The molecular basis of planarian regeneration

描述（由申请人提供）：我们的目标是鉴定和功能表征支持后生动物再生的基因和遗传途径。我们建议使用地中海施米德涡虫作为模型系统来解决这个问题，因为它是最简单的头侧动物之一，具有复杂的器官系统，显示出广泛的再生能力：一个被斩首的动物可以在一周内再生并将一个新的头部与原有的组织结合起来。此外，这种显著的发育可塑性是由一个丰富的和实验上可获得的被称为新母细胞的全能性干细胞群体驱动的。在最后一段时间里，研究基因功能和测量再生反应的研究取得了进展，再加上地中海S. mediterranea基因组的测序和最近的注释，为从分子和功能基因组的角度研究动物再生问题创造了前所未有的机会。我们建议充分利用涡虫的吞吐能力和生物可塑性来建立一个详细的再生分子景观。我们建议：1)利用高密度DNA阵列进行全基因组、高时间分辨率的再生分析；2)测试关键的、进化上保守的胚胎信号通路在组织稳态和再生的成人背景下的功能，为解释微阵列实验提供功能基础；3)对器官特异性再生进行筛选，确定一般再生事件中存在的分子专门化调控程度和程度。综合起来，这些研究应该为我们提供迄今为止进行的最全面的再生机制研究，并且应该作为正式测试动物之间再生的进化分歧或趋同的平台，这是一个阻碍在哺乳动物等再生能力差的动物中实施合理再生治疗的中心未解决的问题。公共卫生相关性：该项目的首要目标是确定动物再生过程的机制基础。本项目利用地中海施米德涡虫（Schmidtea mediterranea）的基因组测序，以及在上一个资助期内取得的方法学进展和发现：1)定义一个高时间分辨率、全基因组范围的再生表达谱；2)询问已知的胚胎信号通路在组织再生和体内平衡的成人背景下的功能；3)发现与截肢后成人器官再生有关的基因。这三条研究线相互协同，它们的整合将为我们提供一套高分辨率的调节再生和再生能力的分子过程。事实上，我们的项目已经开始发现已知基因在成人环境中的新功能，并定义许多功能未知的保守动物基因的功能。鉴于涡虫和脊椎动物之间存在高度的进化保守性，涡虫基因功能的表征将促进人类干细胞功能、再生和伤口愈合的研究，有效地推进人类健康的这些前沿。

DESCRIPTION (provided by applicant): Our objective is to identify and functionally characterize the genes and genetic pathways underpinning metazoan regeneration. We propose to use the planarian Schmidtea mediterranea as a model system to address this problem because it is among the simplest cephalized bilaterians with complex organ systems that display extensive regenerative capacities: a decapitated animal will regenerate and functionally integrate a new head to the pre-existing tissues in under a week. In addition, such remarkable developmental plasticity is driven by an abundant and experimentally accessible population of totipotent stem cells known as neoblasts. The advances made during the last period of funding to interrogate gene function and measure regenerative responses, combined with the sequencing and recent annotation of the S. mediterranea genome create an unprecedented opportunity to frame the problem of animal regeneration in molecular and functional genomic terms. We propose to take full advantage of the throughput capacity and biological plasticity afforded by planarians to establish a detailed molecular landscape of regeneration. We propose to: 1) carry out genome- wide, high temporal resolution analyses of regeneration using high density DNA arrays; 2) test the functions of key, evolutionarily conserved embryonic signaling pathways in the adult contexts of tissue homeostasis and regeneration to provide a functional basis for interpreting the microarray experiments; and 3) to carry out screens of organ-specific regeneration to determine the regulatory extent and degree of molecular specialization that exists in general regenerative events. Combined, these studies should provide us with the most comprehensive mechanistic study of regeneration performed to date, and should serve as a platform to formally test the evolutionary divergence or convergence of regeneration among animals, a central unresolved aspect hindering the implementation of rational regenerative therapeutics in poor regenerators such as mammals. PUBLIC HEALTH RELEVANCE: The overarching goal of this project is to define a mechanistic basis for the process of animal regeneration. This project takes advantage of the sequenced genome of the planarian Schmidtea mediterranea, and of the methodological advances and findings obtained during the last funding period to: 1) define a high temporal resolution, genome- wide, expression profile of regeneration; 2) interrogate the functions of known embryonic signaling pathways in the adult contexts of tissue regeneration and homeostasis; and 3) uncover genes involved in the regeneration of adult organs after amputation. All three lines of investigation synergize with each other and their integration should provide us with a high resolution set of molecular processes regulating regeneration and regenerative capacities. In fact, our project has begun to uncover novel functions in adult contexts of known genes, and to define functions for the many conserved animal genes for which functions are still unknown. Given the high degree of evolutionary conservation that exists between planarians and vertebrates, the characterization of gene functions in planarians will advance efforts to study human stem-cell function, regeneration and wound healing, effectively advancing these frontiers of human health.