One gap junction consists of a cluster of closely packed pairs of transmembrane channels, the connexons, through which materials of low MW diffuse from one cell to a neighboring cell. A connexon is composed of a hexamer of connexins. CNS specific. Expression is restricted to brain, spinal cord, and sciatic nerve. According to PubMed:12881038, expression is abundant in skeletal muscle, liver, and heart, and to a minor degree in pancreas and kidney. Belongs to the connexin family. Gamma-type subfamily.