You get cystic fibrosis because one protein that's made by your lung epithelium is not expressed properly.

得囊胞性纤维症的病因是,肺上皮细胞产生的一种蛋白,表达不正常

耶鲁公开课 - 生物医学工程探索课程节选

You're able to make the protein but the protein doesn't function properly.

肺上皮细胞可以表达这种蛋白,但其并不具有正常功能

耶鲁公开课 - 生物医学工程探索课程节选