MSRA and cystic fibrosis: Mice heterozygous for the Cftr null (Cftr+/−) or p.Arg117His allele (Cftr+/R117H) were crossed to mice with one or two Msra null alleles to produce CF mice (Cftr−/− or CftrR117H/R117H) with wild-type (+/+), heterozygous (+/−), and null (−/−) Msra genotypes.