However, combined cell and gene therapy using AAVs, lentiviruses or CRISPR-based approaches has also been extensively investigated in the setting of cystic fibrosis, a disease that is caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene (reviewed in Berical et al., 2019). The gene discussed is CFTR; the disease is cystic fibrosis.