The synaptic availability of GluA1 is reduced in hippocampal neurons of a murine model of dynamin-2 linked autosomal dominant centronuclear myopathy.

Abstract

ObjectiveAutosomal dominant centronuclear myopathy (AD-CNM) is a neuromuscular congenital disease caused by mutations in the DNM2 gene that encodes dynamin-2 (DNM2). The main clinical features of AD-CNM are progressive weakness and atrophy of skeletal muscles. However, cognitive defects have also been reported, suggesting that AD-CNM-causing mutations in DNM2 might also affect central nervous system (CNS). We recently demonstrated that defects in excitatory synaptic transmission occur in the brain of transgenic knock-in (KI) mice harboring the DNM2 p.R465W mutation, the most common causing AD-CNM. As DNM2 regulates the trafficking of glutamate-AMPA receptors (AMPARs), major mediators of excitatory synaptic transmission in mammals, it is feasible that the synaptic availability of AMPAR is affected in the context of AD-CNM. The main objective of this work was to evaluate the impact of the p.R465W DNM2 mutation on the GluA1-AMPAR-subunit synaptic availability in the brain of KI mice.MethodsWe addressed an experimental quantitative study. By using subcellular fractionation and western blot we quantified the expression of GluA1 and synaptic proteins in hippocampal total homogenates and postsynaptic densities (PSDs) in the brain of WT and KI mice. By total internal reflection microscopy (TIRFM) we also analyzed the arrival and residence time of GluA1 into the plasma membrane of hippocampal cultured neurons.ResultsAlthough we did not observe significant differences in the GluA1 expression in hippocampal total homogenates, it was significantly reduced in the PSDs of KI compared to wild-type (WT) brains. Moreover, the residence time of GluA1 in the surface membranes of KI hippocampal neurons was significantly reduced compared to WT neurons.ConclusionThese data strongly suggest that the p.R465W mutation in DNM2 perturbs synaptic GluA1-availability in hippocampal neurons, likely leading to defects in excitatory synaptic transmission.