New Neurons in the Retina

描述(申请人提供)：这项正在进行的研究计划的总体目标是了解在发育和再生过程中调节视网膜神经发生的细胞-细胞相互作用的分子基础。来自体内、体外和许多不同脊椎动物物种的实验室积累的证据表明，调控视网膜前体细胞分化的外部信号随着发育年龄和视网膜位置的不同而不同，视网膜前体细胞对外部提示的反应能力在视网膜发育过程中逐渐改变，反映了不同年龄视网膜前体细胞的内在变化。然而，在硬骨鱼中，视网膜神经发生贯穿成体生活，所有类型的新神经元都是从位于远外围视网膜睫状缘区(CMZ)的多能视网膜前体细胞产生的，这表明即使是“早期出生”的视网膜细胞类型(如视网膜神经节细胞)也被视网膜前体细胞保留在成年硬骨视网膜的CMZ中。这些多能祖细胞表现出自我更新，可以生成所有类型的视网膜细胞，并在损伤时被有丝分裂激活；因此，它们具有视网膜干细胞的所有特征。此外，散布在成年硬骨鱼分化的中央视网膜上，与Muller神经胶质细胞相关的是偶尔缓慢增殖的前体细胞，这些前体细胞产生快速增殖的、血统受限的杆状前体细胞，这些前体迁移到外核层并产生新的杆状感光细胞。鱼类视网膜中正在进行的神经发生的能力与强大的再生能力有关：当硬骨视网膜中的神经元被破坏时，在特定条件下它们会被取代。中央视网膜再生神经元的来源似乎是穆勒相关的视网膜前体细胞，因此也是视网膜干细胞。 本研究的目的是：1)定义和表征胚胎和成年斑马鱼(Danio Rerio)视网膜中视网膜干细胞和视网膜前体细胞的分子图谱，并建立分子/遗传层次结构；2)检测视网膜损伤后Muller神经胶质细胞的表型可塑性，并检验它们作为视网膜干细胞的假设；3)确定定义视网膜干细胞的视网膜形成潜力所必需的和充分的内在和外在因素。 了解控制视网膜祖细胞增殖和分化的分子机制对于未来视网膜退行性疾病或视网膜损伤患者治疗性视网膜移植的发展具有重要价值。更多地了解成年鱼视网膜中视网膜干细胞的特征和能力，可能会为实现这一目标提供重要的见解。

DESCRIPTION (provided by applicant): The overall objective of this ongoing research program is to understand the molecular basis of cell-cell interactions that regulate retinal neurogenesis during development and regeneration. The accumulated evidence from many laboratories working both in vivo and in vitro and with a number of different vertebrate species suggests that extrinsic signals regulating the differentiation of retinal progenitor cells vary with developmental age and retinal location, and that the competence of retinal progenitors to respond to extrinsic cues is progressively altered during retinal development, reflecting intrinsic changes in retinal progenitors at different ages. However, in teleost fish, retinal neurogenesis continues throughout adult life, and new neurons of all types are generated from multipotent retinal progenitor cells located in the ciliary marginal zone (cmz) at the far peripheral retina, suggesting that the capacity to generate even the 'early born' retinal cells types (e.g., retinal ganglion cells) is retained by retinal progenitors in the cmz of the adult teleost retina. These multipotent progenitors exhibit self-renewal, can generate all retinal cell types, and are mitotically activated in response to injury; therefore, they have all the characteristics of retinal stem cells. In addition, scattered across the differentiated, central retina in adult teleost fish, and associated with Muller glial cells, are occasional, slowly proliferating progenitors, which give rise to clusters of rapidly proliferating, lineage-restricted rod precursors that migrate into the outer nuclear layer and generate new rod photoreceptors. The capacity for ongoing neurogenesis in the fish retina is associated with a robust ability to regenerate: when neurons in the teleost retina are destroyed, under certain conditions they are replaced. The source of regenerated neurons in central retina appears to be the Muller-associated retinal progenitors, which therefore are also retinal stem cells. The objectives of the proposed research are to: 1) define and characterize the molecular profiles of retinal stem cells and retinal progenitor cells in the embryonic and adult zebrafish (Danio rerio) retina, and establish the molecular/genetic hierarchy, 2) examine the phenotypic plasticity of Muller glial cells in response to retinal injury, and test the hypothesis that they function as retinal stem cells, and 3) identify the intrinsic and extrinsic factors that are necessary and sufficient to define the retinogenic potential of retinal stem cells. Understanding the molecular mechanisms controlling the proliferation and differentiation of retinal progenitors will have important value for the future development of therapeutic retinal transplantation in patients with retinal degenerative diseases or retinal injuries. Learning more about the characteristics and capabilities of retinal stem cells in the adult fish retina may provide important insights to help reach that goal.