Laboratory of Structural Physiology, Center for Disease Biology and Integrative Medicine, Graduate School of Medicine, The University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan.
Department of Neurosurgery, Graduate School of Medicine, The University of Tokyo, Bunkyo-ku Tokyo 113-0033, Japan.
eNeuro. 2018 Nov 8;5(5). doi: 10.1523/ENEURO.0282-18.2018. eCollection 2018 Sep-Oct.
Excitatory synapses are often formed at small protrusions of dendrite, called dendritic spines, in most projection neurons, and the spine-head volumes show strong correlations with synaptic connectivity. We examined the dynamics of spine volume in the adult mouse visual cortex using time-lapse two-photon imaging with a resonant Galvano scanner. Contrary to expectations, we found that the spines in the adult neocortex showed fluctuations to a similar degree as that observed in young hippocampal preparations, but there were systematic differences in how the dynamics were dependent on spine volumes, thus allowing for fewer fluctuations in small spines, which could account for the relatively low turnover rates of neocortical spines . We found that spine volumes fluctuated to a greater extent in a mouse model ( knockout) of fragile X mental retardation than in wild-type mice, and the spine turnover rates were also higher in knock-out mice. Such features of spine dynamics in knock-out mice could be represented by a single slope factor in our model. Our data and model indicate a small but significant change in the average spine volume and more eminent differences in the statistical distribution in knock-out mice even in adulthood, which reflects the abnormal dynamics of spine volumes.
兴奋性突触通常形成于大多数投射神经元的树突小突起，称为树突棘，而棘头体积与突触连接性呈强相关性。我们使用共振式振镜扫描体式显微镜对成年小鼠视觉皮层进行延时双光子成像，检测了成年期树突棘体积的动力学变化。出乎意料的是，我们发现成年新皮层中的树突棘与在幼年海马组织中观察到的程度相似，也存在波动，但树突棘体积的动力学变化依赖方式存在系统差异，从而允许在小棘突中产生更少的波动，这可以解释为什么新皮层棘突的周转率相对较低。我们发现，脆性 X 智力低下症（fragile X mental retardation）的小鼠模型（knock-out）中的棘突体积波动比野生型小鼠更大，并且在 knockout 小鼠中，棘突周转率也更高。我们的模型可以用一个斜率因子来表示 knockout 小鼠中棘突动力学的这些特征。我们的数据和模型表明，即使在成年期，knock-out 小鼠的平均棘突体积也会发生微小但显著的变化，而且在统计学分布上也会出现更为明显的差异，这反映了棘突体积的异常动力学。
