POLR1C and leukodystrophy: Both missense variants found at POLR1C—a gene that encodes a subunit common to RNA polymerases I (POLR1) and III (POLR3)—affect amino acids that are conserved through species, and have been known to be associated with Treacher Collins syndrome (TCS) [31] and hypomyelinating leukodystrophies [19,20,21,22].