GJA1 and neuromyelitis optica: The main new findings of the current study were as follows: 1) half of MS and NMO/NMOSD cases showed preferential loss of astrocytic Cx43 beyond the demyelinated areas in actively demyelinating and chronic active lesions, where heterotypic Cx43/Cx47 astrocyte-oligodendrocyte (A/O) gap junctions were extensively lost, but not in chronic inactive lesions.