Microtubule-associated protein 1B (MAP1B) is required for dendritic spine development and synaptic maturation

Abstract

Microtubule-associated protein 1B (MAP1B) is prominently expressed during early stages of neuronal development, and it has been implicated in axonal growth and guidance. MAP1B expression is also found in the adult brain in areas of significant synaptic plasticity. Here, we demonstrate that MAP1B is present in dendritic spines, and we describe a decrease in the density of mature dendritic spines in neurons of MAP1B-deficient mice that was accompanied by an increase in the number of immature filopodia-like protrusions. Although these neurons exhibited normal passive membrane properties and action potential firing, AMPA receptor-mediated synaptic currents were significantly diminished. Moreover, we observed a significant decrease in Rac1 activity and an increase in RhoA activity in the postsynaptic densities of adult MAP1B +/- mice when compared with wild type controls. MAP1B +/- fractions also exhibited a decrease in phosphorylated cofilin. Taken together, these results indicate a new an