Cystic fibrosis transmembrane conductance regulator (CFTR) gene mutations in allergic bronchopulmonary aspergillosis.

The etiology of allergic bronchopulmonary aspergillosis (ABPA) is not well understood. A clinical phenotype resembling the pulmonary disease seen in cystic fibrosis (CF) patients can occur in some individuals with ABPA. Reports of familial occurrence of ABPA and increased incidence in CF patients suggest a possible genetic basis for the disease. To test this possibility, the entire coding region of the cystic fibrosis transmembrane regulator (CFTR) gene was analyzed in 11 individuals who met strict criteria for the diagnosis of ABPA and had normal sweat electrolytes (< or = 40 mmol/liter). One patient carried two CF mutations (deltaF508/R347H), and five were found to carry one CF mutation (four deltaF508; one R117H). The frequency of the deltaF508 mutation in patients with ABPA was significantly higher than in 53 Caucasian patients with chronic bronchitis (P < .0003) and the general population (P < .003). These results suggest that CFTR plays an etiologic role in a subset of ABPA patients.     

Cystic fibrosis mutations in Costa Rica

Using polymerase chain reaction amplification of DNA in dried blood spots and a nonisotopic reverse dot blot hybridization method, we performed molecular genetic analysis for 6 and for 16 of the most common mutations of the cystic fibrosis transmembrane conductance regulator gene (CFTR) in 24 unrelated Costa Rican individuals with cystic fibrosis (CF). While many countries and ethnic groups have been surveyed for CF mutations since the cloning of CFTR, Costa Rica has not heretofore been studied. Moreover, Costa Rica represents an especially intriguing population because of its mixed European-African-Amerindian origins and the existence of a detailed historical record of the founding Spanish families. Thus, such a study may reveal not only the population frequencies of various mutant alleles in this country, but also something about their geographic migrations and ethnic founder effects. The most common CF mutation in Caucasians, deltaF508, was found in only 11 (23%) of the CF chromosomes studied, while the G542X mutation, relatively rare in the general population but more common in southern Europe, was observed in 12 (25%). None of the other mutations tested was found in any of the subjects. We failed to detect the second mutant allele in 17 subjects and could not detect either allele in 4 subjects. The high prevalence of the G542X mutation in our cohort, which exceeds that of both the general Caucasian population and the American Hispanic population, reflects the strong genetic influence of the original Spanish founding families of Costa Rica. These results highlight important differences in Costa Rican CF genotypes as compared both to other North American and European populations and to American Hispanics, raising important implications about isolated founder effects and strategies for population screening in that country.     

Cystic fibrosis mutations in the Hutterite Brethren.

The presence or absence of the major cystic fibrosis (CF) mutation, delta F508, in the general patient population was determined by Kerem et al. using allele-specific oligonucleotides for the mutant and normal sequences in the polymerase chain reaction (PCR). delta F508 was identified by Riordan et al., and it is a 3-bp deletion of the phenylalanine codon at position 508. The Hutterite Brethren are an inbred North American population who have three different DNA marker haplotypes of CF chromosomes. Genomic DNA from both a CF child and one parent from each of 10 Hutterite families was analyzed for the presence or absence of the deletion mutation. delta F508 is associated with one of the three CF haplotypes in the Hutterite population, and this is the most common haplotype in a subset of the linkage family data of Kerem et al. The other two Hutterite CF haplotypes are generally rate in Caucasian populations. Since these two CF haplotypes do not carry the deletion mutation, they must carry a different CF mutation(s). The results of the PCR analysis for the deletion mutation lend additional support to our previous conclusion that there were at least three original carriers of CF mutations among the founders of the Hutterite population and that all copies of the same CF haplotype were identical by descent. One Hutterite CF patient has both of the haplotypes which do not carry delta F508. Analysis of this individual's DNA should allow identification of two additional CF mutations in this population.     

Geographic distribution and origin of CFTR mutations in Germany

The geographic distribution and origin of CFTR mutations in Germany was evaluated in 658 three-generation families with cystic fibrosis (CF). Fifty different mutations were detected on 1305 parental CF chromosomes from 22 European countries and overseas. The major mutation ΔF508 was identified on 71.5% of all CF chromosomes, followed by R553X (1.8%), N1303K (1.3%), G542X (1.1%), G551D (0.8%) and R347P (0.8%). According to the grandparents’ birthplace, 74% of CF chromosomes had their origin in Germany; the ΔF508 percentage was 77%, 75%, 70% and 62% in northern, southern, western and eastern Germany, respectively. Ten or more mutant alleles in the investigated CF gene pool originated from Austria, the Czech Republic, Poland, Russia, Turkey and the Ukraine. This widespread geographic origin of CFTR mutations in today’s Germany reflects the many demographic changes and migrations in Central Europe during the 20th century. Received: 10 October 1995 / Revised: 9 January 1995     

The spectrum of CFTR mutations in south-west German cystic fibrosis patients

The cystic fibrosis transmembrane conductance regulator (CFTR) gene of 110 cystic fibrosis (CF) patients from the south-west of Germany was screened for 12 different mutations. This analysis resulted in an identification of 79% of all CF mutations and a complete genotype in 66% of the families. The most common mutation found was F508 (67%). Another 5 mutations accounted for a further 12.5% (4% G542X; 3% R553X; 3% N1303K; 2% 1717-1 GA; 0.5% G551D) whereas 6 mutations (R117H, A455E, I507, S549I, S549N, and R1162X) were not found. Fifty-four (49%) patients were AF508 homozygotes and 18 (16.5%) were compound heterozygotes for F508 and one of the rarer mutations. These frequencies differ slightly from those found in the north of Germany and considerably from those reported from the south of Europe, which seems to be consistent with a north to south decline of the relative abundance of F508. Two patients, age 6 and 25 years, were compound heterozygotes for G542X and N1303K. The clinical features of the 6 year old were characterised by severe gastrointestinal and as yet only mild pulmonary complications whereas the 25 year old manifested severe pulmonary and gastrointestinal symptoms indicating that the N1303K mutation of the C-terminal CFTR nucleotide binding fold significantly impairs protein function in both the pancreas and the lungs.     

Cystic fibrosis mutations and associated haplotypes in Turkish cystic fibrosis patients.

Identification of mutations causing cystic fibrosis (CF) in the Turkish population is essential for assessment of the molecular basis of CF in Turkey and the development of strategies for prenatal diagnosis and genetic counseling. Here, we present an updated report of mutations found in the Turkish CF population from an extensive screening study of the entire coding region, including exon-intron boundaries and the promoter region. Cases for which mutations could not be identified were also screened for previously defined large alterations and (TG)mTn-M470V loci. This study revealed a total of 27 different mutations accounting for almost 60% of disease genes in the Turkish population. In this study, we also identified the haplotypes associated with 17 mutations and those associated with unknown mutations. The mutation spectrum of CF in Turkey and its associated haplotypes indicated the presence of a major Mediterranean component in the contemporary Turkish population.     

Cystic fibrosis in a low-incidence population: two major mutations in Finland

The incidence of cystic fibrosis (CF) in Finland, 125 000 newborn, is one of the lowest in Caucasian populations. The F508 mutation accounts for 18/40 (45%) of CF chromosomes in Finland. Other mutations were therefore sought among the remaining 55%. Twelve out of 40 chromosomes (30%) were found to carry 394delTT, whereas G542X and 3732delA were each detected in one chromosome. Eight mutations remained unidentified using a testing panel for 26 mutations. Mutation 394delTT was associated exclusively with haplotype 23-36-13. Five unknown mutations were associated with different haplotypes for microsatellite markers, whereas three shared the same haplotype. Most F508 mutations and all unidentified mutations originated from regions of old and dense settlement in the coastal regions, whereas 394delTT was geographically clustered and enriched in a rural location, consistent with a local founder effect. The remote location of Finland and her population history give a plausible explanation for the rarity of CF in Finland.     

Cystic fibrosis mutation ΔF508 in Finland: other mutations predominate

Summary The frequency of mutation ΔF508 was determined in all 20 Finnish cystic fibrosis (CF) families with living affected children (19 with pancreatic insufficiency). ΔF508 was detected in 18 out of 40 CF chromosomes (45%). At least two different mutations associated with pancreatic insufficiently have occurred in a rare haplotype defined by XV2c, CS.7, KM19 alleles 1 2 2. Geographical clustering of ΔF508 and other mutations suggested that a founder effect and genetic drift have influenced the frequency of mutations causing CF in Finland.     

Cystic fibrosis with three mutations in the cystic fibrosis transmembrane conductance regulator gene

Summary Three mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene were discovered in a pancreas-insufficient patient with cystic fibrosis (CF) who displayed an uncommon combination of almost normal chloride concentration in sweat tests and typical symptoms of gastrointestinal and pulmonary disease. The R553Q mutation was found on the maternal F508-CFTR gene. Codon 553 is located within a consensus motif of the ATP-binding cassette transport proteins at a less conserved position. Other members of this protein superfamily contain a glutamine instead of arginine at the homologous position, suggesting a modulating rather than disease-causing role of the R553Q mutation in CFTR. The amplification refractory mutation system did not detect the R553Q mutation in a further 65 normal, 113 F508, and 91 non-F508 CF chromosomes. The index case carried the R553X nonsense mutation on the paternal chromosome. The R553X mutation was present on a further 9 out of 86 German nonF508 CF chromosomes linked with the XV2c-KM19Mp6d9-J44-GATT haplotypes 2-2-2-1-1 and 1-1-2-1-2. The location of R553X on separate haplotypes including both alleles of the intragenic GATT repeat suggests an ancient and/or multiple origins of the R553X mutations. The association of the genotype of the CFTR mutation and the clinical phenotype was assessed for the patients carrying the related genotypes F508/F508 (n = 80), F508/R553X (n = 9) and F508-R553Q/R553X (n = 1). In compound heterozygotes, the median chloride concentration in pilocarpine iontophoresis sweat tests was significantly lower than in the F508 homozygotes (P < 0.01). The patient groups were significantly different with respect to the distributions of the centiles for height (P < 0.001) and weight (P < 0.01) as the most sensitive predictors of the course and prognosis in CF. Growth retardation was more pronounced in the compound heterozygotes.     

Intra- and extragenic marker haplotypes of CFTR mutations in cystic fibrosis families

Summary In order to facilitate the screening for the less common mutations in the cystic fibrosis (CF) gene viz., the CF transmembrane conductance regulator gene (CFTR), marker haplotypes were determined for German nonCF (N) and CF chromosomes by polymerase chain reaction analysis of four polymorphisms upstream of the CF gene (XV-2c, KM.19, MP6-D9, J44) and six intragenic polymorphisms (GATT, TUB9, M470V, T854T, TUB18, TUB20) that span the CFTR gene from exon 6 through exon 21. Novel informative sequence variants of CFTR were detected in front of exons 10 (1525-61 A or G), 19 (3601-65 C or A), and 21 (4006-200 A or G). The CF locus exhibits strong long-range marker-marker linkage disequilibrium with breakpoints of recombination between XV-2c and KM.19, and between exons 10 and 19 of CFTR. Marker alleles of GATT-TUB9 and TUB18-TUB20 were found to be in absolute linkage disequilibrium. Four major haplotypes encompass more than 90% of German N and CF chromosomes. Fifteen CFTR mutations detected on 421 out of 500 CF chromosomes were each identified on one of these four predominant 7-marker haplotypes. Whereas all analysed F508 chromosomes carried the same KM.19-D9-J44-GATT-TUB9-M470V-T854T haplotype, another frequent mutation in Germany, R553X, was identified on two different major haplotypes. Hence, a priori haplotyping cannot exclude a particular CF mutation, but in combination with population genetic data, enables mutations to be ranked by decreasing probability.     

Exon 9 of the CFTR gene: splice site haplotypes and cystic fibrosis mutations

The alternatively spliced exon 9 of the cystic fibrosis transmembrane conductance regulator (CFTR) gene codes for the initial part of the amino-terminal nucleotide-binding fold of CFTR. A unique feature of the acceptor splice site preceding this exon is a variable length polymorphism within the polypyrimidine tract influencing the extent of exon 9 skipping in CFTR mRNA. We investigated this repeat for its relationship to CFTR mutations and intragenic markers on 200 chromosomes from German patients with cystic fibrosis (CF). Four frequent length variations were strongly associated with the four predominant haplotypes previously defined by intragenic marker dimorphisms. One of these alleles displayed absolute linkage disequilibrium to the major CF mutation F508. Other frequent CFTR mutations were linked to one particular splice site haplotype indicating that differential exon 9 skipping contributes little to the clinical heterogeneity among CF patients with an identical mutation. We also identified a novel missense mutation (V456F) and a novel nonsense mutation (Q414X) within the coding region of exon 9. The missense mutation V456F adjacent to Walker motif A was present in a pancreas-sufficient CF patient. In contrast, the pancreas-insufficient Q414X/F508 compound heterozygote suffered from a severe form of the disease, indicating that alternative splicing of exon 9 does not overcome the deleterious effect of a stop codon within this exon.     

Cystic fibrosis in the Portuguese population: haplotype distribution and molecular pathology

Summary The aim of this study was to obtain an estimate of the frequency of the ΔF508 mutation in the Portuguese population, and of the tightness of its association with specific haplotypes. Furthermore, the genotype/clinical phenotype relationship and the feasibility of prenatal diagnosis were also investigated. The analysis of 42 cystic fibrosis (CF) families revealed that (1) 52% of CF chromosomes carry the deletion of codon 508; (2) there seems to be a positive correlation between the occurrence of the ΔF508 mutation and the severity of the disease; and (3) fully informative prenatal diagnosis can be offered in 76% of at-risk pregnancies by using both genomic and allele specific oligonucleotide probes.     

CFTR mutations in Turkish and North African cystic fibrosis patients in Europe: implications for screening

AIMS: To obtain more insight into the variability of the CFTR mutations found in immigrant cystic fibrosis (CF) patients who are living in Europe now, and to estimate the test sensitivity of different frequently used methods of DNA analysis to detect CF carriers or patients among these Turkish or North African immigrants. METHODS: A survey among 373 European CF centers asking which CFTR mutations had been found in Turkish and North African CF patients. RESULTS: 31 and 26 different mutations were reported in Turkish and North African patients, identifying 64.2% (113/176) and 87.4% (118/135) alleles, respectively (p < 0.001). The mean sensitivity (detection rate) of three most common CFTR mutation panels to detect these mutations differed between Turkish and North African people, 44.9% (79/176) versus 69.6% (94/135) (p < 0.001), and can be increased to 57.4% (101/176) and 79.3% (107/135) (p < 0.001), respectively, by expanding these panels with 13 mutations which have been found on two or more alleles. CONCLUSION: 35.8% and 12.6%, respectively, of CF alleles in Turkish and North African patients living in Europe now had not been identified. Among these populations, the test sensitivity of common CFTR mutation panels is insufficient for use in screening programs in Europe, even after expansion with frequent Turkish and North African mutations. This raises questions about whether and how to implement CF carrier and neonatal screening in a multiethnic society.     

Cystic fibrosis and innate immunity: how chloride channel mutations provoke lung disease

Innate immunity is essential for prevention of infection in vertebrates and plants and dysfunction of single components of innate immunity may provoke severe disease. Here we describe how mutations in the cystic fibrosis transmembrane conductance regulator gene dysregulate a variety of components of the innate immune system in individuals suffering from the hereditary disease cystic fibrosis. In the airways of these individuals, functions of the mucociliary clearance system, cationic antimicrobial (poly)peptides and neutrophils and macrophages are impaired and inflammatory signal transduction pathways exaggerated. Consequently, chronic airway colonization with opportunistic bacterial pathogens develops and leads to life-threatening lung disease.