GRN and Parkinson disease: While qPCR analysis for GRN transcripts showed a significant reduction in PD cells compared to controls (p = 0.01) (Additional file 1: Fig. S3A, Additional file 2), the protein levels were increased in this group of cells compared to HS (p = 0.0425) and gPD-GBA N370S cells (p = 0.0096) (Fig. 2A, B).