GJB1 and hypomyelinating leukodystrophy 2: The more important functional role of Cx47 in the CNS compared with that of Cx32 is also highlighted by the fact that patients with mutations in Cx47 develop the severe hypomyelinating leukodystrophy HLD2 [19], while patients with Cx32 mutations develop only subclinical or transient encephalopathy under conditions of additional metabolic stress (above) [58,62].