POLR3K and leukodystrophy: Mutations in genes encoding subunits of the transcription complex RNA polymerase III (POLR3), namely POLR3A, POLR3B, POLR1C, POLR3K and POLR3GL might cause a particular type of hypomyelinating leukodystrophies known as Pol III-related leukodystrophies [19,35,36,37,38,39].