The identification of mutations in tubulin beta class IVA (TUBB4A) in hypomyelination with atrophy of the basal ganglia and cerebellum, a type of leukodystrophy, prompted us to elucidate the role of TUBB4A in OLGs (van der Knaap et al., 2002). The gene discussed is TUBB4A; the disease is leukodystrophy.