The lack of a complete recapitulation of the clinical and pathological MLD phenotype led to the generation of the Arsa(–/–) mice with the addition of neural cells overexpressing the sulfatide synthesizing enzymes, including UDP-galactose: ceramide galactosyltransferase (CGT) and cerebroside sulfotransferase (CST). The gene discussed is UGT8; the disease is metachromatic leukodystrophy.