Expression of Cx31.3 in small myelinated fibers. These are images of sections of human cortex, immunostained with a rabbit antiserum against Cx31.3 (726) and a mouse monoclonal antibody against myelin basic protein (MBP), myelin-associated glycoprotein (MAG), Caspr, or neurofilament light (NFL) as indicated. Cx31.3 (red arrows) is co-localizated along thin fibers with MBP and MAG, which are components of the myelin sheath, as well as with NFL, an axonal marker (green arrows). In some myelinated fibers, Cx31.3 appears to be enriched at paranodes flanking the nodes, as it overlaps with Caspr. Scale bar: 10 μm.