Chronic lentivirus-mediated WT GLB1 overexpression in GM1 gangliosidosis patient fibroblasts coincides with a time-dependent increase in β-gal activity (Fig. 7A) and β-gal protein levels as detected by immunofluorescence in patient cells over 28 days (Fig. 7B; see Fig. 7C for quantification), which coincides with almost complete GM1 ganglioside substrate clearance (Fig. 7D; see Fig. 7E for quantification), suggestive of successful delivery of functional β-gal to lysosomes. The gene discussed is GLB1; the disease is GM1 gangliosidosis.