A study for the detection of known and novel mutations in the cystic fibrosis transmembrane conductance regulator gene

Abstract

Cystic fibrosis (CF) is one of the most common and severe autosomal recessive genetic disorders worldwide. It results from mutations in the gene encoding the cystic fibrosis transmembrane conductance regulator (CFTR). The gene has 27 exons which encode a 1480 amino acid transmembrane ion channel protein. The major CF mutation F508 accounts for about 67% of the 30000 CF Caucasian chromosomes screened worldwide. Moreover, more than 600 other mutations have been identified, each with a frequency of at the most a few percent. The mutations responsible for CF in the Turkish population are not yet known. In the Turkish patients, F508 is found at a significantly lower frequency (13%), which indicates that CF is caused predominantly by other mutations. A systematic study was initiated to characterize the CF mutations. First, we screened for four mutations which are frequent in neighboring geographical areas, and found them to be infrequent. It became obvious that, an efficient, quick and reliable mutation screening method which would cover all of the coding region was needed. We applied to 124 CF chromosomes the DGGE technique to analyze all of the gene except for the first and last exons with the purpose of detecting any variants in the gene. These variants would later be subjected to DNA sequence analysis to determine mutations or polymorphisms which they represent. Our previous hypothesis that the profile of CF mutations in the Turkish population shows great heterogeneity is consistent with the data obtained. As expected, several mutations and variants were identified which were distributed randomly throughout 14 exons in the coding regions of the CFTR gene, each of which would account for a relatively small fraction of the CF mutations.