CFTR and cystic fibrosis: First, we showed that the pharmacological rescue of F508del-CFTR could be measured using the membrane potential sensitive FLIPR® dye in a well-studied CF bronchial epithelial cell line (CFBE41o−)37 that was modified to overexpress F508del-CFTR.38 In these studies, the cells were grown to 5 days post-confluency at low temperature (27 °C for 48 h) to ensure partial rescue of the primary trafficking defect exhibited by F508del-CFTR.39 In Supplementary Fig. 2, we show F508del-CFTR protein expression in these rescued cells.