Table 1.

The seven classes of CFTR defects, with examples.

Class	Explanation	Example
I	defective synthesis of the protein	G542X
II	defective trafficking to the cell membrane	F508del
III	decreased ability to open, even though it is present at the cell surface	G551D
IV	decreased ability to conduct ions, even though the gate can open	R347P
V	decreased amount of post-translationally processed, fully active CFTR	A455E
VI	decreased stability at the surface	N287Y
VII	absence of mRNA	del2,3(21kb)