POLR3A and leukodystrophy: BC200 RNA was the most downregulated Pol III transcript in several datasets of POLR3A p.M852V mutant cells; moreover, BC200 RNA was also decreased in fibroblasts from patients with POLR3-HLD and in the MO3.13 cell line of oligodendrocytes carrying the POLR3A c.2554A > G (p.M852V) mutation20.