Neurogenic plasticity and brain development

神经源性可塑性和大脑发育

• 批准号: RGPIN-2022-04784
• 负责人: Tropepe, Vincent
• 金额: $ 2.91万
• 依托单位: University of Toronto
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2022
• 资助国家: 加拿大
• 起止时间: 2022-01-01 至 2023-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=746538
• 关键词: Neurogenic; plasticity; brain; development

A long-term goal of my research program is to understand how an animal's experience in the environment influences brain development. NSERC-funded research from my lab showed that sensorimotor experience, such as movement or vision, maintains high levels of neurogenesis in the zebrafish larval brain. Larvae that swim the most in normal ambient light cycles exhibit increased brain growth over subsequent days of development. In contrast, movement restraint or dim light cycles lead to reduced brain growth. We observed that sensorimotor deprivation resulted in neural stem cells (NSCs) undergoing premature neuronal differentiation, with fewer neurons generated over time. Thus, NSCs appear to change their fate in response to altered sensorimotor stimuli, but the intrinsic mechanism underlying this neurogenic plasticity is unresolved and is the focus of this proposal. Cell fate decisions in NSCs are strongly influenced by epigenetic modifications such as chromatin methylation, and the enzyme Ehmt2 is a key regulator of this process by turning NSC genes off so that stem cells can differentiate into neurons. We generated an Ehmt2 loss of function mutant using CRISPR/Cas9 gene editing and asked whether this gene is required to mediate experience-dependent neurogenic plasticity responses of NSCs. Preliminary data indicates that neurogenesis is not altered in the Ehmt2 mutant in response to movement restraint, suggesting that loss of Ehmt2 prevents the plasticity response in the brain normally elicited by sensorimotor deprivation. Our novel mutant model provides a paradigm for testing hypotheses regarding the regulation of NSC cell fate and likewise for linking neurogenic plasticity to patterns of epigenetic modification within NSCs. The objective of this proposal is to investigate whether an altered movement experience causes NSCs in the postembryonic zebrafish pallium to change their fate due to epigenetic silencing of NSC genes. The following three specific research aims are designed to address this objective: Aim 1: To examine how Ehmt2 loss of function alters experience-dependent neurogenic plasticity. Genetic lineage tracing will test whether mutant NSCs fail to provide a normal plasticity response to movement restraint, by enhancing self-renewal instead of promoting differentiation. Aim 2: To evaluate the degree to which neurogenic plasticity requires Ehmt2-dependent silencing of NSC gene expression. We will interrogate how loss of Ehmt2 leads to transcriptome changes in NSCs under normal or movement restrained conditions. Aim 3: To determine the impact of enhanced Ehmt2 expression on neurogenic plasticity. Increased Ehmt2 activity will test if enhanced chromatin methylation prevents expansion of NSCs when movement is increased, and instead promotes differentiation. This research will help to elucidate mechanisms of experience-dependent neurogenic plasticity for a deeper understanding of gene-by-environment interactions in brain development.

我的研究计划的一个长期目标是了解动物在环境中的经历如何影响大脑发育。NSERC资助的我实验室的研究表明，感觉运动体验，如运动或视觉，在斑马鱼幼虫大脑中保持高水平的神经发生。在正常环境光周期中游泳最多的仔鱼在随后的发育中表现出大脑生长的增加。相比之下，运动限制或昏暗的光线周期会导致大脑发育减少。我们观察到，感觉运动剥夺导致神经干细胞（NSC）经历过早的神经元分化，随着时间的推移产生较少的神经元。因此，神经干细胞似乎改变了他们的命运，以响应改变感觉运动刺激，但这种神经源性可塑性的内在机制尚未得到解决，是这个建议的重点。NSC中的细胞命运决定受到染色质甲基化等表观遗传修饰的强烈影响，而Ehmt 2酶是这一过程的关键调节因子，它关闭NSC基因，使干细胞分化为神经元。我们使用CRISPR/Cas9基因编辑产生了Ehmt 2功能缺失突变体，并询问该基因是否需要介导NSC的经验依赖性神经源性可塑性反应。初步数据表明，神经发生不改变Ehmt 2突变体在运动限制，这表明Ehmt 2的损失，防止在大脑中的可塑性反应通常引起的感觉运动剥夺。 我们的新的突变体模型提供了一个范例，用于测试关于NSC细胞命运调控的假设，并同样用于将神经源性可塑性与NSC内的表观遗传修饰模式联系起来。这项建议的目的是调查是否改变运动的经验，导致神经干细胞在胚胎后斑马鱼paleurs改变他们的命运，由于表观遗传沉默的NSC基因。以下三个具体的研究目的是为了解决这个目标：目的1：检查Ehmt 2功能的丧失如何改变经验依赖性神经可塑性。遗传谱系追踪将测试突变的神经干细胞是否无法通过增强自我更新而不是促进分化来提供对运动限制的正常可塑性反应。 目的2：评估神经源性可塑性需要Ehmt 2依赖性NSC基因表达沉默的程度。我们将探讨Ehmt 2的丢失如何导致正常或运动限制条件下神经干细胞的转录组变化。 目的3：确定Ehmt 2表达增强对神经源性可塑性的影响。Ehmt 2活性的增加将测试当运动增加时，增强的染色质甲基化是否阻止NSC的扩增，而是促进分化。这项研究将有助于阐明经验依赖性神经可塑性的机制，以更深入地了解大脑发育中的基因与环境的相互作用。