The drug ivacaftor has recently been developed totreat cystic fibrosis in children with the rare G551Dmutant allele of CFTR.a. Do you think that ivacaftor would be effective onlyin patients homozygous for the G551D mutation,or might it work as well in compound heterozygotes in which one copy of chromosome 7 hadG551D and the other copy a different allele ofCFTR, such as the more prevalent allele ΔF508?(The protein encoded by G551D folds up properlyand inserts into the cell membrane, but is inefficient in chloride ion transport. Ivacaftor increasesthe efficiency of G551D’s ion transport. TheΔF508 protein does not fold up properly and therefore does not get inserted into the cell membrane.)b. Why do you think ivacaftor would be more effectivein children than in older cystic fibrosis patients?c. The scientists who developed ivacaftor had a modelfor cystic fibrosis: a line of cells that grow in culture and that are homozygous for G551D. Thesecells accumulate mucus at their surfaces that prevent cilia (tiny hairs on the outside of cells) frombeating. Explain how the scientists could use thisdisease model to screen for drugs that would be effective against G551D-associated cystic fibrosis.
The drug ivacaftor has recently been developed to
treat cystic fibrosis in children with the rare G551D
mutant allele of CFTR.
a. Do you think that ivacaftor would be effective only
in patients homozygous for the G551D mutation,
or might it work as well in compound heterozygotes in which one copy of chromosome 7 had
G551D and the other copy a different allele of
CFTR, such as the more prevalent allele ΔF508?
(The protein encoded by G551D folds up properly
and inserts into the cell membrane, but is inefficient in chloride ion transport. Ivacaftor increases
the efficiency of G551D’s ion transport. The
ΔF508 protein does not fold up properly and therefore does not get inserted into the cell membrane.)
b. Why do you think ivacaftor would be more effective
in children than in older cystic fibrosis patients?
c. The scientists who developed ivacaftor had a model
for cystic fibrosis: a line of cells that grow in culture and that are homozygous for G551D. These
cells accumulate mucus at their surfaces that prevent cilia (tiny hairs on the outside of cells) from
beating. Explain how the scientists could use this
disease model to screen for drugs that would be effective against G551D-associated cystic fibrosis.
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