Two major components of the cytoskeletal system, filamentous actin (F-actin) and microtubules (MTs), have been shown to be involved in postsynaptic functions. Actin network has prominent roles in determining dendritic spine morphology and in anchoring postsynaptic proteins. A sub-population of the dynamic MTs transiently invades into dendritic spines, and may contribute to critical events in synapse development. Previous results suggest that F-actin and MTs interact within spines. However, molecular mechanisms that mediate MT-actin interaction within spines have not been fully understood.

ACF7/MACF1 is a mammalian spectraplakin able to bind both MTs and F-actin directly. ACF7 is essential for proper neuronal migration and axonal projection in developing mouse brain, and it is previously-identified as a candidate postsynaptic component by proteomic analyses of biochemically purified PSD fractions. However its role in post synaptic function has not been investigated. Here, we showed that ACF7 accumulates at a subset of dendritic spines. Fluorescence recover after photobleaching (FRAP) analysis revealed that ACF7 relative stably associates with spine cytoplasm rather than simply binding to F-actin. To clarify molecular mechanisms underlying ACF7 dependent synapse regulation, we are currently observing dynamics of MTs invading into spines.