Synaptic status differentially regulates neurofilaments in dendritic spines

Abstract Neurofilaments are one of the main cytoskeletal components in neurons and they can be found in the form of oligomers at pre- and postsynapses. How their presence is regulated at the postsynapse remains widely unclear. Here we systematically quantified by immunolabeling the occurrence of the neurofilament isoform triplet neurofilament light (NFL), medium (NFM), and heavy (NFH) at the postsynapse with STED nanoscopy together with markers of synaptic strength and activity. Our data shows that within dendritic spines neurofilament isoforms rarely colocalize with each other and that they are present to different extents, with NFL being the most abundant isoform. The amount of the three isoforms correlates with markers of postsynaptic strength and presynaptic activity to varying degrees: while NFL shows moderate correlation to both synaptic traits suggesting its involvement in synaptic response, NFM and NFH were only correlated on a low level. By quantifying the presence of neurofilaments at the postsynapse within the context of the synaptic status, this work sheds new light on the regulation of synaptic neurofilaments and their possible contribution to psychiatric disorders.