Molecular Biology of the Cell I, German Cancer Research Center, D-69120 Heidelberg, Germany.
J Neurosci. 2010 Nov 3;30(44):14835-42. doi: 10.1523/JNEUROSCI.3030-10.2010.
Dicer-dependent noncoding RNAs, including microRNAs (miRNAs), play an important role in a modulation of translation of mRNA transcripts necessary for differentiation in many cell types. In vivo experiments using cell type-specific Dicer1 gene inactivation in neurons showed its essential role for neuronal development and survival. However, little is known about the consequences of a loss of miRNAs in adult, fully differentiated neurons. To address this question, we used an inducible variant of the Cre recombinase (tamoxifen-inducible CreERT2) under control of Camk2a gene regulatory elements. After induction of Dicer1 gene deletion in adult mouse forebrain, we observed a progressive loss of a whole set of brain-specific miRNAs. Animals were tested in a battery of both aversively and appetitively motivated cognitive tasks, such as Morris water maze, IntelliCage system, or trace fear conditioning. Compatible with rather long half-life of miRNAs in hippocampal neurons, we observed an enhancement of memory strength of mutant mice 12 weeks after the Dicer1 gene mutation, before the onset of neurodegenerative process. In acute brain slices, immediately after high-frequency stimulation of the Schaffer collaterals, the efficacy at CA3-to-CA1 synapses was higher in mutant than in control mice, whereas long-term potentiation was comparable between genotypes. This phenotype was reflected at the subcellular and molecular level by the elongated filopodia-like shaped dendritic spines and an increased translation of synaptic plasticity-related proteins, such as BDNF and MMP-9 in mutant animals. The presented work shows miRNAs as key players in the learning and memory process of mammals.
依赖于 Dicer 的非编码 RNA，包括 microRNAs (miRNAs)，在许多细胞类型中对 mRNA 转录物翻译的调节中发挥重要作用，这些调节对于分化是必需的。在体内实验中，使用神经元中特定细胞类型的 Dicer1 基因失活，结果表明其对神经元发育和存活具有重要作用。然而，对于成年、完全分化的神经元中 miRNA 的缺失的后果知之甚少。为了解决这个问题，我们使用了一种在 Camk2a 基因调控元件控制下的诱导型 Cre 重组酶（他莫昔芬诱导型 CreERT2）。在成年小鼠前脑中诱导 Dicer1 基因缺失后，我们观察到一整套大脑特异性 miRNA 的逐渐丧失。动物在一系列厌恶和食欲动机认知任务中进行测试，例如 Morris 水迷宫、IntelliCage 系统或痕迹恐惧条件反射。与 miRNA 在海马神经元中的半衰期相当长相一致，我们观察到突变小鼠在 Dicer1 基因突变后 12 周，即在神经退行性过程发生之前，记忆强度增强。在急性脑切片中，在 Schaffer 侧支的高频刺激后立即，突变小鼠的 CA3 到 CA1 突触的效能比对照小鼠更高，而长时程增强在两种基因型之间是可比的。这种表型在亚细胞和分子水平上反映为突变动物中树突棘的伸长丝状样形状和突触可塑性相关蛋白的翻译增加，例如 BDNF 和 MMP-9。本研究表明 miRNA 是哺乳动物学习和记忆过程中的关键参与者。
