To investigate the functions of PWS-genes in β-cells, we used CRISPR/Cas9 genome-editing to target 3.16 Mb deletions encompassing the PWS-genes (Figs 1A and S1A) in rat INS-1(832/13)::mCherry insulinoma cells (hereafter termed INS-1) that secrete rat and human insulin [34] and express a mouse Ins2 C-peptide-mCherry biosensor in insulin secretory granules [42]. Here, INS is linked to pancreatic insulinoma.