Institute for Neuro- and Sensory Physiology, University Medical Center Göttingen, Göttingen, 37073, Germany
Cluster of Excellence "Multiscale Bioimaging: from Molecular Machines to Networks of Excitable Cells" (MBExC), University of Göttingen, Göttingen 37073, Germany.
J Neurosci. 2021 Feb 10;41(6):1157-1173. doi: 10.1523/JNEUROSCI.0921-20.2020. Epub 2020 Dec 11.
The activity and the metabolism of the brain change rhythmically during the day/night cycle. Such rhythmicity is also observed in cultured neurons from the suprachiasmatic nucleus, which is a critical center in rhythm maintenance. However, this issue has not been extensively studied in cultures from areas less involved in timekeeping, as the hippocampus. Using neurons cultured from the hippocampi of newborn rats (both male and female), we observed significant time-dependent changes in global activity, in synaptic vesicle dynamics, in synapse size, and in synaptic mRNA amounts. A transcriptome analysis of the neurons, performed at different times over 24 h, revealed significant changes only for RNA-binding motif 3 (Rbm3). RBM3 amounts changed, especially in synapses. RBM3 knockdown altered synaptic vesicle dynamics and changed the neuronal activity patterns. This procedure also altered local translation in synapses, albeit it left the global cellular translation unaffected. We conclude that hippocampal cultured neurons can exhibit strong changes in their activity levels over 24 h, in an RBM3-dependent fashion. This work is important in several ways. First, the discovery of relatively regular activity patterns in hippocampal cultures implies that future studies using this common model will need to take the time parameter into account, to avoid misinterpretation. Second, our work links these changes in activity strongly to RBM3, in a fashion that is independent of the canonical clock mechanisms, which is a very surprising observation. Third, we describe here probably the first molecule (RBM3) whose manipulation affects translation specifically in synapses, and not at the whole-cell level. This is a key finding for the rapidly growing field of local synaptic translation.
大脑的活动和代谢在日夜周期中呈节律性变化。这种节律性也在视交叉上核培养神经元中观察到，视交叉上核是维持节律的关键中心。然而，在涉及时间保持的较少区域（如海马体）的培养物中，这一问题尚未得到广泛研究。我们使用来自新生大鼠（雄性和雌性）海马体的培养神经元进行研究，观察到全局活动、突触小泡动力学、突触大小和突触 mRNA 含量均存在显著的时间依赖性变化。在 24 小时的不同时间对神经元进行转录组分析，仅发现 RNA 结合基序 3（Rbm3）发生显著变化。RBM3 含量发生变化，尤其是在突触中。RBM3 敲低改变了突触小泡动力学，并改变了神经元活动模式。该程序还改变了突触中的局部翻译，但不影响全局细胞翻译。我们得出结论，海马体培养神经元在 24 小时内可以表现出强烈的活动水平变化，这种变化依赖于 Rbm3。这项工作在几个方面都很重要。首先，在海马体培养物中发现相对规则的活动模式表明，未来使用这种常见模型的研究将需要考虑时间参数，以避免误解。其次，我们的工作将这些活动变化与 Rbm3 紧密联系起来，这种方式独立于经典时钟机制，这是一个非常令人惊讶的观察结果。第三，我们在这里描述了第一个分子（Rbm3），其操纵特异性地影响突触中的翻译，而不是整个细胞水平。这是局部突触翻译这一日益发展的领域的一个关键发现。
