In order to identify a possible hereditary predisposition to the development of obstructive pulmonary disease of unknown origin, we have looked for the presence of Cystic Fibrosis Transmembrane Regulator (CFTR) gene mutations in unrelated patients with no signs of Cystic Fibrosis (CF). We screened for 70 common mutations, and also for rare mutations by denaturing gradient gel electrophoresis analysis. In this search, different CFTR gene mutations (R75Q, delta F508, R1066C, M1137V and 3667ins4) were found in five out of 16 adult Italian patients with disseminated bronchiectasis, a significant increase over the expected frequency of carriers. Moreover, three rare CFTR gene DNA polymorphisms (G576A, R668C, and 2736 A-->G), not deemed to be the cause of CF, were found in two patients, one of which was a compound heterozygote with R1066C. These results indicate that CFTR gene mutations, and perhaps also DNA polymorphisms, may be involved in the etiopathogenesis of at least some cases of bronchiectasis.

A complete coding-region analysis on 225 cystic fibrosis (CF) chromosomes from a cohort that includes all the affected subjects born in two North-Eastern Italian regions over eight years was performed. In a previous study, we identified mutations on 166/225 (73.8%) CF chromosomes after screening for 62 mutations. To characterise the remaining 59 CF chromosomes, we carried out automated direct DNA sequencing (exons 9 and 13), RNA single-strand conformation polymorphism (exons 1-8 and 10-12) and denaturing gradient gel electrophoresis (exons 14a-24) of the 27 exons and flanking regions of the CF transmembrane conductance regulator gene. We identified 22 mutations, four of which are novel, viz. 711 + 5G-->A, R709X, 3132delTG and 2790-2A-->G, and we characterised 90.2% (203/225) of the CF chromosomes. Taking advantage of the homogeneity of the sample, an evaluation of the most important clinical parameters, assessed at the age of 12 years, is presented. We confirm some previously reported genotype-phenotype correlations and we report a new nonsense mutation (R709X) associated with a pancreatic sufficient phenotype.

An increased incidence of cystic fibrosis (CF) has been reported in some populations of Native Americans of the Southwest such as the Pueblo, which is a genetic isolate. As the most common mutation found in Caucasians (delta F508) was absent and only one chromosome carried the G542X mutation, we decided to analyze the entire coding sequence of the CFTR gene in eight Pueblo CF patients. We have identified four different mutations: G542X, R1162X, 3849+10kbC-->T, and D648V that account for these 16 haplotypes. The R1162X was found on 11 chromosomes. Using intragenic microsatellites, we have compared the haplotypes of those chromosomes to those of Italian origin where the R1162X mutation was initially reported. These haplotypes turned out to be identical, suggesting a common origin and an admixture with Italian or Spanish settlers, followed by typical founder effect. In contrast the 3849+10kbC-->T mutation, which was found on three chromosomes, is associated with different haplotypes than those on chromosomes carrying the same mutation in Caucasians. A novel mutation, D648V, observed on one chromosome has not been found outside the Pueblo population.

The frequency of 62 different CFTR mutations in 225 chromosomes from a CF birth cohort, which includes all the affected subjects born in northeast Italy during a 10-year period of time, was investigated. New mutations were also searched by the analysis of 15 different exons. The total proportion of CF chromosomes with detectable mutations is 73.78%. Therefore although a considerable improvement in CF mutation detection in our population has been achieved, the search for other common and uncommon mutations should be continued. Moreover a carrier screening program should be postponed until reaching a cumulative proportion of known CF alleles of at least 90%. The correlations between the genotypes which have been identified and the main clinical features added some new information to the classification of CF mutations as pancreatically severe or mild ones.

No abstract