Analysis of the distinct regulatory functions of DNA methylation in memory-related gene expression

记忆形成的一个重要步骤是基因转录激活。转录调控对于记忆相关基因的正确表达至关重要。DNA的甲基化被认为是这一过程中的关键介质。DNA甲基转移酶蛋白（Dnmts）负责甲基化标记的书写，甲基结合蛋白（如MeCP 2）负责阅读并将该标记翻译成染色质结构的变化和转录的可及性。DNA甲基化在记忆形成过程中调节转录的精确机制还远未被理解。在我以前的工作中，我发现Dnmt 3a 2和Dnmt 3b的水平受神经元活动的调节-Dnmt 3a 2上调，而Dnmt 3b下调-Dnmt 3a 2是记忆形成所必需的，并以积极的方式调节记忆相关基因的表达。此外，我发现，基础和学习诱导的表达Dnmt 3a 2在老化海马受损，这是因果关系与衰老依赖性认知能力下降。我现在提出了一个新的概念，在基因表达的调控DNA甲基化。我推测Dnmt 3b作为一个记忆抑制基因，其表达需要在记忆巩固过程中抑制记忆相关基因的最佳表达。该假设将通过评估记忆形成中Dnmt 3b水平的调节的效果进行实验验证。此外，我提出，微调记忆相关基因的表达是通过一个中间步骤，Dnmt 3a 2的相关miRNA的表达调控。因此，我提供了一种机制，通过这种机制，一个单一的基因可以调节几个mRNA的表达。我的初步工作确定了一系列推定的Dnmt 3a 2靶向miRNA（DTM）。我现在提出了一组实验（分子和行为方法的组合），将允许评估是否调控的DTMs的表达在记忆形成中发挥作用。DNA甲基化标记由Dnmts催化，而甲基化模式的解释由包括MeCP 2的甲基结合蛋白进行。因此，MeCP 2将甲基化标记转化为功能变化。我认为MeCP 2的DNA占有率构成了成熟大脑中基因表达调控的另一个关键水平。根据这一假设，我将测试海马MeCP 2是否需要在成年小鼠的记忆形成和是否MeCP 2基因组占有率的变化与老化和随后的影响基因express.This研究将提供新的，基本的见解记忆形成的基因表达调控的机制。它还将导致识别新的候选人，用于开发与衰老有关的疾病的疗法。

An essential step for memory formation is gene transcription activation. The regulation of transcription is critical for the achievement of proper expression of the memory related genes. The methylation of DNA has been proposed as a key mediator in this process. DNA methyltransferase proteins (Dnmts) are responsible for the writing of methylation marks and the methyl-binding proteins (such as MeCP2) for reading and translating this marks into changes in chromatin structure and accessibility for transcription. The precise mechanism by which DNA methylation regulates transcription during memory formation is far from being understood. This proposal describes a research program that aims at further investigating this question.In my previous work I found that the levels of Dnmt3a2 and Dnmt3b are regulated by neuronal activity - Dnmt3a2 is upregulated, whereas Dnmt3b is downregulated - that Dnmt3a2, is required for memory formation and regulates the expression of memory related genes in a positive manner. Moreover, I showed that the basal and learning-induced expression of Dnmt3a2 is impaired in the aging hippocampus and that this is causally linked with aging-dependent cognitive decline.I now propose a novel concept in the regulation of gene expression by DNA methylation. I hypothesize that Dnmt3b functions as a memory suppressor gene, which expression needs to be repressed during memory consolidation for the optimal expression of memory related genes. This hypothesis will be experimentally validated by assessing the effect of the modulation of Dnmt3b levels in memory formation. Moreover, I propose that the fine-tuning of memory related gene expression is achieved via an intermediate step, the regulation of expression of relevant miRNAs by Dnmt3a2. Thus, I provide a mechanism through which a single gene can modulate the expression of several mRNAs. My preliminary work identified a list of putative Dnmt3a2 target miRNAs (DTMs). I now propose a set of experiments (combination of molecular and behavioral approaches) that will allow assessing whether the regulation of expression of DTMs plays a role in memory formation. The DNA methylation marks are catalyzed by Dnmts whereas the interpretation of the methylation pattern is performed by the methyl binding proteins that include MeCP2. Therefore MeCP2 translates methylation marks into functional changes. I propose that the DNA occupancy by MeCP2 constitutes another level critical for the regulation of gene expression in the mature brain. In line with this hypothesis, I will test whether hippocampal MeCP2 is required for memory formation in adult mice and whether MeCP2 genomic occupancy changes with aging and the subsequent impact on gene expression.This study will provide new, fundamental insights into the mechanism of gene expression regulation in memory formation. It will also lead to the identification of novel candidates for the development of therapies for aging-related diseases.