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功能，既可以作为中枢神经系统的分化支持细胞，也可以作为常驻干细胞，在产生新的神经元之前经历去分化和增殖。动员胶质细胞成为干细胞样细胞是冷血脊椎动物（变温动物）（如鱼和青蛙）对眼睛生长、受伤或疾病的自然反应。相比之下，包括哺乳动物在内的温血脊椎动物（恒温动物）的神经胶质动员要有限得多。我们研究了小鼠视网膜中的神经胶质细胞活化，其中Muller神经胶质（MG）是干细胞的潜在来源。然而，通过MG自我修复机制的组织再生在恒温动物中并不容易发生。相反，MG对恒温动物损伤的有利反应是反应性胶质瘤，这是一种神经保护反应，可伴随细胞毒性作用。******为了解释哺乳动物MG是如何选择继续作为分化的支持细胞，作为干细胞重新进入细胞周期，或经历反应性胶质瘤的，我们重点研究了锌指转录因子Zac1。我们发现MG在Zac1零突变小鼠中发生了非损伤性胶质瘤。Zac1是一个母体印迹基因，是共调控基因的印迹基因网络（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阻止反应性胶质瘤和可能的干细胞修复。为了验证这一假设，我们将：******目标1。评估Zac1在维持MG分化表型中的正常作用。我们通过描述Zac1突变MG的命运和评估它们对非损伤诱导信号的反应来评估Zac1在维持未损伤眼中分化MG命运中的功能。* * *的目标2。探讨Zac1在MG损伤反应中的作用。为了确定Zac1是否参与损伤依赖性MG反应，我们评估了Zac1在各种应激源下的表达，并询问Zac1过表达是否在MG中具有保护作用。* * *的目标3。确定Zac1是否通过IGN维持成熟的MG表型。为了检验Zac1是否通过IGN维持MG处于分化状态，我们研究了Zac1突变MG和损伤模型中IGN基因的表达，并通过功能丧失和功能获得研究进行IGN功能测试。******影响：该项目将增强我们对MG生物学的基础知识，并将其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，这将使他们在当今的知识经济中具有竞争力

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.**