Cystic fibrosis (CF) is caused by mutations in the gene encoding the cystic fibrosis transmembrane conductance regulator (CFTR), which forms a chloride ion (Cl-) transport channel in epithelial cells. But the existence of some CF patients with normal Cl- ion channel activity has puzzled researchers for some time.

In 1 March Nature, Shmuel Muallem and colleagues from the University of Texas Southwestern Medical Center, Dallas report that disruption in the transport of bicarbonate ions (HCO3-) may also be of considerable importance in CF patients (Nature 2001, 410:94-97).

They measured HCO3- and Cl- transport in cells transfected with DNA encoding wild-type or mutant CFTR. In 11 common mutations of CFTR, the transport of HCO3- was more greatly impaired than that of Cl-.

It is lung disease that accounts for most of the mortality in...

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