GBA1 and Parkinson disease: Both the imaging (Figure 7a–e) and the biochemical assays (Figure 7i–j) performed in MEF cells (and in HEK293 cells, see below) recapitulate experiments performed in other cell lines and models (e.g., in fly models of GD and PD) [9] in demonstrating defective lysosomal delivery of the GCaseLeu444Pro protein, which is associated with severe disease phenotypes linked to GBA1 variants.