Fluorescent Marker of a Plasticity-Related Change in Dendritic Spines

The F-actin capping protein CapZ accumulates more in dendritic spines within regions where a long-term potentiation (LTP)-inducing stimulus has been applied. With the goal of developing an in vivo synaptic plasticity marker, we produced a transgenic mouse line, called AiCE-Tg, in which CapZ tagged with enhanced green fluorescence protein (EGFP-CapZ) is expressed in some spines. Twenty minutes after unilateral visual or somatosensory stimulation in AiCE-Tg mice, EGFP-CapZ signals were intensified in a subset of dendritic spines in stimulated cortices, and that difference was abolished by NMDA receptor blockade. Immunolabeling of α-actinin, a PSD-95 binding protein that can recruit AMPA receptors to postsynaptic sites, showed that α-actinin localization was more frequent/more accumulated in the brightest EGFP-CapZ spines (top 100) than in less bright spines (top 1000). This input-dependent redistribution of EGFP-CapZ may reflect LTP-like changes in vivo and thus may provide a useful tool for synaptic plasticity research.