Molecular and clinical findings in Austrian cystic fibrosis patients with mutations in exon 11 of the CFTR gene.

In order to determine the heterogeneity of mutations in exon 11 of the cystic fibrosis transmembrane conductance regular (CFTR) gene in Austrian cystic fibrosis (CF) patients, we analysed 207 non-delta F508 chromosomes by direct sequencing of PCR-amplified genomic DNA. A total of four previously described point mutations present on 14/207 (6.8%) non-delta F508 chromosomes were detected: G542X, G551D, R553X, and R553Q. The second CF mutation was delta F508 in most patients, W1282X (a nonsense mutation in exon 20) in one and a currently unknown non-delta F508 mutation in another case. One patient was documented to be homozygous for G542X. The proportion of non-delta F508 chromosomes among total CF chromosomes is 45% in Austria and 32% in the world population. In our population the mutations G542X, G551D, and R553X were found on 3.9% (1.7%), 1.9% (0.9%) and 0.5% (0.2%) of non-delta F508 chromosomes (of total CF chromosomes), respectively. The average worldwide frequencies of these mutations are higher: 7.1% (2.4%), 4.8% (1.6%), 2.1% (0.7%) of non-delta F508 chromosomes (of total CF chromosomes screened), respectively. A comparison of the allele frequencies in Austria with those detected in neighbouring countries reveals some notable differences. In a subsequent retrospective analysis we found that all nucleotide changes, identified by direct sequencing, can be detected by denaturing gradient gel electrophoresis (DGGE). The lack of any false positive or false negative result suggests that DGGE is a convenient and reliable screening method for point mutations.