The virtual absence of CFTR in the apical membrane of CF epithelium is corroborated by the absence of any effect of the potentiator ivacaftor (ΔG = 1662 ± 737 μS/cm2, n = 9), whose ΔG value was not statistically different from that of the DMSO control (Figure 1b). The gene discussed is CFTR; the disease is cystic fibrosis.