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

Background: The cystic fibrosis transmembrane conductance regulator gene (C FTR) shows a complex pattern of expression. The regulatory elements conferr ing tissue-specific and temporal regulation are thought to lie mainly outsi de the promoter region. Previously, we identified DNase I hypersensitive si tes (DHS) that may contain regulatory elements associated with the CFTR gen e at -79.5 and at -20.5 kb with respect to the ATG and at 10 kb into the fi rst intron. Materials and Methods: In order to evaluate these regulatory elements in vi vo we examined these DHS in a human CFTR gene that was introduced on a yeas t artificial chromosome (YAC) into transgenic mice. The 310 kb human CFTR Y AC was shown to restore the phenotype of CF-null mice and so is likely to c ontain most of the regulatory elements required for tissue-specific express ion of CFTR. Results: We found that the YAC does not include the -79.5 kb region. The DH S 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 intr on is present in a more restricted set of tissues in the mice, although its presence does not show complete concordance with CFTR expression. The intr on 1 DHS may be important for the higher levels of expression found in huma n pancreatic ducts and in lung submucosal glands. Conclusion: These data support the in vivo importance of these regulatory e lements.