CFTR and cystic fibrosis: To test the effect of ASO-induced exon 23 skipping on mRNA from CFTR mutations commonly found with CFTR-W1282X in compound heterozygotes, we treated primary hBE cells isolated from a CF patient, with the CFTR-W1282X and CFTR-F508del mutations, with ASO-23AB and measured chloride secretion (Fig. 5A).