Elucidating the molecular mechanisms that control Muller glia activation in the retina

概述：神经胶质细胞具有非凡的能力，既可以作为中枢神经系统中的分化支持细胞，也可以作为常驻干细胞，在产生新神经元之前经历去分化和增殖。在鱼类和青蛙等冷血脊椎动物中，动员神经胶质细胞成为干细胞样细胞是对眼睛生长、损伤或疾病的自然反应。相比之下，神经胶质细胞的动员在温血脊椎动物(恒温动物)中要有限得多，包括哺乳动物。我们研究了小鼠视网膜中胶质细胞的激活，穆勒胶质细胞(MG)是干细胞的潜在来源。然而，通过MG自愈修复机制的组织再生在吸热状态下并不容易发生。相反，MG对恒温损伤的有利反应是反应性胶质增生，这是一种神经保护反应，可能具有伴随的细胞毒效应。 为了解释哺乳动物MG是如何做出选择的，要么继续作为分化的支持细胞，要么作为干细胞重新进入细胞周期，或者经历反应性胶质增生，我们关注锌指转录因子Zac1。我们发现，在Zac1缺失突变小鼠中，MG经历了非损伤的胶质细胞增殖症。Zac1是母系印记基因，是共同调控基因印记基因网络(IGN)的一部分。因此，我们假设Zac1维持MG处于静止、分化状态，通过IGN发挥作用，防止反应性胶质细胞增生，并可能进行干细胞修复。为了检验这一假设，我们将： 目的1.评估Zac1在维持分化的MG表型中的正常作用。我们通过表征Zac1突变MG的命运和评估它们对非损伤诱导线索的反应，来评估Zac1在维持未受伤眼睛中分化的MG命运中的作用。 目的2.研究Zac1在MG损伤反应中的作用。为了确定Zac1是否参与了损伤依赖型MG的反应，我们评估了Zac1在不同应激源下的表达，并询问Zac1的过度表达在MG中是否具有保护作用。 目的3.确定Zac1是否通过IGN维持成熟的MG表型。为了测试Zac1是否通过IGN维持MG的分化状态，我们研究了Zac1突变型MG和损伤模型中IGN基因的表达，并进行了IGN功能测试和功能丧失和获得的研究。 影响：该项目将加强我们对MG生物学的基础知识，应用于干细胞生物学和组织再生的一般领域。HQP将接触到创新的、最先进的技术，使他们在当今以知识为基础的经济中具有竞争力。

Overview: Glial cells have an extraordinary ability to function either as differentiated support cells in the central nervous system, or as resident stem cells, undergoing de-differentiation and proliferation before giving rise to new neurons. Mobilization of glial cells to become stem cell-like is a natural response to eye growth, injury or disease in cold-blooded vertebrates (ectotherms), such as fish and frogs. In contrast, glial mobilization is much more limited in warm-blooded vertebrates (endotherms), including mammals. We study glial cell activation in the murine retina, where Muller glia (MG) are a potential source of stem cells. However, tissue regeneration via a MG self-healing repair mechanism does not occur readily in endotherms. Instead, the favored response of MG to injury in endotherms is reactive gliosis, a neuroprotective response that can have accompanying cytotoxic effects. To decipher how mammalian MG make the choice to either remain as differentiated support cells, re-enter the cell cycle as stem cells, or undergo reactive gliosis, we focus on the zinc finger transcription factor Zac1. We found that MG undergo injury-independent gliosis in Zac1 null mutant mice. Zac1 is a maternally imprinted gene and part of an imprinted gene network (IGN) of co-regulated genes. We thus hypothesize that Zac1 maintains MG in a quiescent, differentiated state, acting via the IGN to prevent reactive gliosis and possibly stem cell-repair. To test this hypothesis we will: Aim 1. Assess the normal role of Zac1 in maintaining a differentiated MG phenotype. We assess Zac1 function in maintaining a differentiated MG fate in the uninjured eye by characterizing the fate of Zac1 mutant MG and by assessing their responsiveness to non-injury inductive cues. Aim 2. Examine the role of Zac1 in the MG injury response. To determine whether Zac1 participates in injury-dependent MG responses, we assess Zac1 expression in response to various stressors, and ask whether Zac1 overexpression is protective in MG. Aim 3. Determine whether Zac1 acts through the IGN to maintain a mature MG phenotype. To test whether Zac1 acts through the IGN to maintain MG in a differentiated state, we study the expression of IGN genes in Zac1 mutant MG and injury models, and perform IGN functional tests with loss- and gain-of-function studies. Impact: This project will enhance our fundamental knowledge of MG biology, with applications to the general field of stem cell biology and tissue regeneration. HQP will be exposed to innovative, state-of-the-art techniques that will allow them to be competitive in today's knowledge-based economy.