Gap junctions (GJs) are specialized intercellular channels that directly connect cytoplasms of adjacent cells, enabling direct exchanges of small molecules (less than 1200 Da). Gap junctions are composed by two docked hemichannels (HCs), also named connexons, one on each cell. Hemichannels are hexamers of homotypic or heterotypic connexins (Cxs), which are the transmembrane proteins encoded by a multigene family of approximately 20 members in mammals 20, 21, 22, 23, 24, 25 that form respectively homotypic or heterotypic GJs.