Chloride conductance and genetic background modulate the cystic fibrosis phenotype of Delta F508 homozygous twins and siblings
January 2001
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To investigate the impact of chloride (Cl(-)) permeability, mediated by residual activity of the cystic fibrosis transmembrane conductance regulator (CFTR) or by other Cl(-) channels, on the manifestations of cystic fibrosis (CF), we determined Cl(-) transport properties of the respiratory and intestinal tracts in Delta F508 homozygous twins and siblings. In the majority of patients, cAMP and/or Ca(2+)-regulated Cl(-) conductance was detected in the airways and intestine. Our finding of cAMP-mediated Cl(-) conductance suggests that, in vivo, at least some Delta F508 CFTR can reach the plasma membrane and affect Cl(-) permeability. In respiratory tissue, the expression of basal CFTR-mediated Cl(-) conductance, demonstrated by 30% of Delta F508 homozygotes, was identified as a positive predictor of milder CF disease. In intestinal tissue, 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid-insensitive (DIDS-insensitive) Cl(-) secretion, which is indicative of functional CFTR channels, correlated with a milder phenotype, whereas DIDS-sensitive Cl(-) secretion was observed mainly in more severely affected patients. The more concordant Cl(-) secretory patterns within monozygous twins compared with dizygous pairs imply that genes other than CFTR significantly influence the manifestation of the basic defect.
- Male
- Child
- Adult
- Female
- Research Support, Non-U.S. Gov't
- Phenotype
- Adolescent
- Homozygote
- Cystic Fibrosis Transmembrane Conductance Regulator/*genetics
- *Diseases in Twins
- Chlorides/*metabolism
- Cystic Fibrosis/*genetics/metabolism
- patient
- response
- sibling
- fibrosis
- f 508
- dizygou
- conductance
- conmild
- consevere
- figure
- disease
- tissue
- monozygou
- f 508 cftr
- cl secretion
- table
- secretion
- individual
- measurement
- gluconate