Ivacaftor Reverses Airway Mucus Abnormalities in a Rat Model Harboring a Humanized G551D-CFTR

Abstract

Rationale: Animal models have been highly informative for understanding the characteristics, onset, and progression of cystic fibrosis (CF) lung disease. In particular, the CFTR 2/2 rat has revealed insights into the airway mucus defect characteristic of CF but does not replicate a human-relevant CFTR (cystic fibrosis transmembrane conductance regulator) variant.Objectives: We hypothesized that a rat expressing a humanized version of CFTR and harboring the ivacaftor-sensitive variant G551D could be used to test the impact of CFTR modulators on pathophysiologic development and correction.Methods: In this study, we describe a humanized-CFTR rat expressing the G551D variant obtained by zinc finger nuclease editing of a human complementary DNA superexon, spanning exon 2-27, with a 59 insertion site into the rat gene just beyond intron 1. This targeted insertion takes advantage of the endogenous rat promoter, resulting in appropriate expression compared with wildtype animals.Measurements and Main Results: The bioelectric phenotype of the epithelia recapitulates the expected absence of CFTR activity, which was restored with ivacaftor. Large airway defects, including depleted airway surface liquid and periciliary layers, delayed mucus transport rates, and increased mucus viscosity, were normalized after the administration of ivacaftor.Conclusions: This model is useful to understand the mechanisms of disease and the extent of pathology reversal with CFTR modulators.

Advances in Genome Editing and Application to the Generation of Genetically Modified Rat Models

“…Humanized animal models are of great value to better study human diseases by insertion of the human gene into the animal genome (Figure 4C, right panel). For some projects, cDNA of the gene of interest is enough and can be used to generate humanized models, as it was done for a humanized model of cystic fibrosis (Birket et al, 2020).…”

“…Cftr KO rats showed a very severe digestive phenotype and lung lesions in surviving older animals, and reduced weight and life expectancy, although milder in DF508 rats. Very recently, a humanized model of cystic fibrosis was created by inserting the human CFTR cDNA sequence harboring a G551D mutation by KI into the rat genome, downstream of the endogenous Cftr promoter (Birket et al, 2020).…”

On the Corner of Models and Cure: Gene Editing in Cystic Fibrosis

“…Recently, a humanized transgenic G551D rat model was generated ( Birket et al, 2020 ), the rationale being that pharmacological responses are often species-specific, such as the differential Ivacaftor response of mouse vs. human F508del-CFTR ( Bose et al, 2019 ). A hCFTR cDNA super-exon, spanning exon 2–27 was inserted using ZFNs with a 5′ insertion site into the rat Cftr gene just beyond intron 1.…”

A Novel G542X CFTR Rat Model of Cystic Fibrosis Is Sensitive to Nonsense Mediated Decay

“…Previously, we developed a CF knockout rat model that enables the longitudinal study of muco-obstructive lung disease characteristic of CF patients ( Guilbault et al, 2007 ; Rogers et al, 2008 ; Birket et al, 2018 ), providing some advantages over other available species. More recently, the G551D gating mutation has been introduced into CF rats, permitting pharmacological research ( Birket et al, 2020 ). For the present study, we generated a knockin CF rat expressing the CFTR G542X mutation within its native locus.…”