Mapping age-related dysregulation of in vivo synaptic plasticity to molecular synaptic diversity

突触是高度专业化的结构，由突触前(发送者)和突触后(接收者)站点组成，连接神经细胞并实现通信。在大脑皮层，大多数连接是通过称为树突的小的膜性突起来调节的，树突构成了突触后的位置。突触在功能和蛋白质组成上表现出高度的多样性。此外，蛋白质水平可以动态改变，例如在突触可塑性期间。在突触可塑性过程中，突触强度的调整是学习和记忆过程中新信息编码的基础。为了避免过高或过低的发射率，体内平衡机制已经到位。塑性适应的失调被认为是大脑活动的病理水平不足，在老化的大脑中也观察到了痴呆症的早期阶段。一个根本的挑战是了解脊柱的不同蛋白质组成如何与健康的突触功能和塑料适应有关。最近，巴恩斯实验室在老鼠的视皮层中发现了由塑料和非塑料脊椎组成的离散簇。他们还发现，在衰老的大脑中，树突棘的某些形式的突触可塑性发生了变化。然而，突触功能如何与分子多样性有关仍不清楚。在这个项目中，我假设分子定义的突触的离散群体映射到体内特定类别的突触功能和可塑性。我将确定这些突触簇的失调如何导致老化大脑中的突触功能障碍。我将首先在活体内展示树突棘的不同功能簇。为此，我将在清醒小鼠的正常行为和可塑性诱导后对树突棘进行钙成像实验，以确定功能脊椎簇。为了将功能簇映射到它们的蛋白质组成，我将在脑片中诱导可塑性，并用多重蛋白质组学评估蛋白质水平。最后，为了评估老化大脑中脊柱可塑性的变化，钙成像实验、蛋白质组学和后续的超分辨率显微镜将揭示老年小鼠不同脊椎群体的变化。这项研究将对我们理解大脑老化中的突触功能和脊柱动力学至关重要。特别是，将活体实验中的功能簇与它们在单个突触水平上的分子组成联系起来的可能性使这些发现如此有价值。这项研究对进一步的翻译研究具有重要的启示意义。确定导致老化大脑中突触功能障碍的变化的分子基础，可能会为认知衰退和痴呆症的临床干预开辟新的途径。

Synapses are highly specialised structures consisting of a presynaptic (sender) and postsynaptic (receiver) site to connect neuronal cells and enable communication. In the cortex, most connections are mediated via small membranous protrusions called dendritic spines, which make up the postsynaptic site. Synapses exhibit a high degree of diversity in their function and protein composition. Moreover, protein levels can be dynamically altered, for example during synaptic plasticity. During synaptic plasticity, adjustments in synaptic strength underlie the encoding of new information during learning and memory. To avoid excessive or insufficient firing rates, homeostatic mechanisms are in place. A dysregulation of plastic adaptations is thought to underly pathological levels of brain activity and has also been observed in early stages of dementia in the ageing brain.A fundamental challenge is to understand how different protein compositions of spines relate to healthy synapse function and plastic adaptations. Recently, the Barnes laboratory has found discrete clusters of plastic and non-plastic spines in the visual cortex of mice. They also revealed, that in the aged brain, some forms of synaptic plasticity at dendritic spines are changed. However, how synaptic function relates to molecular diversity remains unclear. In this project I hypothesize that discrete populations of molecularly defined synapses map to specific classes of synaptic function and plasticity in vivo. I will establish how a dysregulation of these synaptic clusters leads to synaptic dysfunction in the ageing brain.I will first demonstrate different functional clusters of dendritic spines in vivo. For this, I will perform calcium imaging experiments of dendritic spines in awake mice during normal behaviour and after the induction of plasticity to determine functional spine clusters. To map functional clusters to their protein composition, I will induce plasticity in brain slices and assess protein levels with multiplexed proteomics. Finally, to assess changes in spine plasticity in the ageing brain, calcium imaging experiments, proteomics and follow-up super resolution microscopy will reveal changes in different spine populations in older mice.This research will be crucial for our understanding of synaptic function and spine dynamics in the ageing brain. Particularly the possibility to correlate functional clusters from in vivo experiments to their molecular composition at the single synapse level makes these findings so valuable. This research is highly relevant with important implications for further translational research. Identifying the molecular basis of changes that drive synaptic dysfunction in the ageing brain may open new avenues for clinical interventions in cognitive decline and dementia.