The secondary NEU1 deficiency occurred in the brains of all analyzed mouse models of neurological MPS (MPS I, II, IIIA, IIIB, IIIC) but not in the models of other LSDs (metachromatic leukodystrophy, ML IV, Tay-Sachs, or NPC1). The gene discussed is NEU1; the disease is metachromatic leukodystrophy.