Molecular phenotypes in early gallbladder and liver disease in the <i>CFTR</i> ^−/− sheep highlight aspects of cystic fibrosis-relevant hepatobiliary disease

The initiating cellular events in cystic fibrosis (CF) hepatobiliary disease are not well characterized, in part due to the lack of accessibility of primary tissues. However, enhanced longevity due to highly effective modulator therapies has generated renewed interest in the key aspects of liver and gallbladder disease, and how these might be treated in people with cystic fibrosis (pwCF). To extend the CF hepatobiliary knowledge base, we performed a transcriptomic analysis of liver and gallbladder development in the wild-type (WT) and <i>CFTR^-/-</i> sheep. Bulk RNA was extracted from each tissue at specific timepoints through gestation (from 50 days to term) and used for RNA sequencing (RNA-seq). Differentially expressed genes between the timepoints within each genotype and between WT and <i>CFTR^-/-</i> sheep at each timepoint were identified and then used in gene ontology process enrichment analysis to reveal altered biological processes. We find that at the molecular level, the gallbladder in the <i>CFTR^-/-</i> animals is both structurally and functionally compromised by midgestation, consistent with the observed microgallbladder phenotype. In the liver, many aspects of differentiation are apparently well-established early in gestation. However, we find functional immaturity in the <i>CFTR^-/-</i> liver at term, where genes associated with many key metabolic processes do not show the upregulation seen at term in the WT liver. We also show that the regulatory mechanisms for the <i>CFTR</i> gene in ovine gallbladder cells are highly conserved with those elucidated at the human <i>CFTR</i> locus, further enhancing the relevance of these data to advance understanding of hepatobiliary disease in pwCF.<b>NEW & NOTEWORTHY</b> We use a physiological genomics approach to further understand the etiology of cystic fibrosis gallbladder and liver disease by using a large animal (sheep) model of organ development. We find that the gallbladder in the <i>CFTR^-/-</i> animals is both structurally and functionally compromised by midgestation. We also observe functional immaturity in the <i>CFTR^-/-</i> liver at term, where genes associated with many key metabolic processes do not show the upregulation seen at term in wild-type liver.