Early pioneering investigations showed that mice bearing combinations of different alleles that included an Mbp encoding transgene, the Mbp null shiverer and myelin deficiency (mld) alleles accumulated Mbp mRNA in the CNS over a wide range that correlated closely with MBP protein levels in the brain (Popko et al., 1987; Shine et al., 1992). Here, MBP is linked to metachromatic leukodystrophy.