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. 2018 Apr 13;27(148):170124. doi: 10.1183/16000617.0124-2017

TABLE 1.

Classification of gene mutations that cause cystic fibrosis (CF)

Class Mutation examples Mutation mechanism
I G542X, W1282X No functional CFTR protein is synthesised due to the presence of premature termination codons
II F508del CFTR protein is synthesised but misfolded, keeping it from reaching the apical cell surface
III G551D, G1349D Full-length CFTR protein reaching the apical cell surface exhibits abnormal gating (channel persists in the closed state)
IV R117H, R334W, R347P Full-length CFTR protein reaches the apical cell surface but transport of chloride ions is reduced due to channel pore defect
V 2789+5G>A, 3849+10kbC>T Reduced number of CFTR transcripts due to promoter or splicing abnormalities
VI 4326delTC, 4279insA Defective CFTR stability at the cell surface; C-terminus mutations result in accelerated turnover

CFTR: CF transmembrane conductance regulator.