The impact of genomic distance on enhancer-promoter interactions at the CFTR locus

We identified and characterized multiple cell-type selective enhancers of the CFTR gene promoter in previous work and demonstrated active looping of these elements to the promoter. Here we address the impact of genomic spacing on these enhancer:promoter interactions and on CFTR gene expression. Using CRISPR/Cas9, we generated clonal cell lines with deletions between the -35 kb airway enhancer and the CFTR promoter in the 16HBE14o- airway cell line, or between the intron 1 (185 + 10 kb) intestinal enhancer and the promoter in the Caco2 intestinal cell line. The effect of these deletions on CFTR transcript abundance, as well as the 3D looping structure of the locus was investigated in triplicate clones of each modification. Our results indicate that both small and larger deletions upstream of the promoter can perturb CFTR expression and -35 kb enhancer:promoter interactions in the airway cells, though the larger deletions are more impactful. In contrast, the small intronic deletions have no effect on CFTR expression and intron 1 enhancer:promoter interactions in the intestinal cells, whereas larger deletions do. Clonal variation following a specific CFTR modification is a confounding factor particularly in 16HBE14o- cells.

Transcriptomic analysis of lung development in wildtype and CFTR-/- sheep suggests an early inflammatory signature in the CF distal lung

The precise molecular events initiating human lung disease are often poorly characterized. Investigating prenatal events that may underlie lung disease in later life is challenging in man, but insights from the well-characterized sheep model of lung development are valuable. Here, we determine the transcriptomic signature of lung development in wild-type sheep (WT) and use a sheep model of cystic fibrosis (CF) to characterize disease associated changes in gene expression through the pseudoglandular, canalicular, saccular, and alveolar stages of lung growth and differentiation. Using gene ontology process enrichment analysis of differentially expressed genes at each developmental time point, we define changes in biological processes (BP) in proximal and distal lung from WT or CF animals. We also compare divergent BP in WT and CF animals at each time point. Next, we establish the developmental profile of key genes encoding components of ion transport and innate immunity that are pivotal in CF lung disease and validate transcriptomic data by RT-qPCR. Consistent with the known pro-inflammatory phenotype of the CF lung after birth, we observe upregulation of inflammatory response processes in the CF sheep distal lung during the saccular stage of prenatal development. These data suggest early commencement of therapeutic regimens may be beneficial.