NRG1 and cystic fibrosis: Indeed, we observed that these isolates each harbored a homozygous mutation in a highly conserved region of the CpNRG1 gene (R270K), suggesting that perturbation of Nrg1 function is a conserved mechanism for pathogenic yeast that allows filamentation in the absence of inducing cues in clinical isolates from cystic fibrosis patients (S12 Fig).