In vivo analysis of DNase I hypersensitive sites in the human CFTR gene

Background: The cystic fibrosis transmembrane conductance regulator gene (CFTR) shows a complex pattern of expression. The regulatory elements conferring tissue-specific and temporal regulation are thought to lie mainly outside the promoter region. Previously, we identified DNase I hypersensitive sites (DHS) that may contain regulatory elements associated with the CFTR gene at -79.5 and at -20.5 kb with respect to the ATG and at 10 kb into the first intron. Materials and Methods: In order to evaluate these regulatory elements in vivo we examined these DHS in a human CFTR gene that was introduced on a yeast artificial chromosome (YAC) into transgenic mice. The 310 kb human CFTR YAC was shown to restore the phenotype of CF-null mice and so is likely to contain most of the regulatory elements required for tissue-specific expression of CFTR. Results: We found that the YAC does not include the -79.5 kb region. The DHS at -20.5 kb is present in the chromatin of most tissues of the transgenic mice, supporting its non-tissue-specific nature. The DHS in the first intron is present in a more restricted set of tissues in the mice, although its presence does not show complete concordance with CFTR expression. The intron 1 DHS may be important for the higher levels of expression found in human pancreatic ducts and in lung submucosal glands. Conclusion: These data support the in vivo importance of these regulatory elements.