CF2603/4delT,a new frameshift mutation in exon 13 of the cystic fibrosis transmembrane conductance regulator (CFTR) gene

By using temperature gradient gel electrophoresis to screen for mutations in cystic fibrosis (CF) patients, we have found a new mutation in the CF transmembrane conductance regulator gene. It is a frameshift mutation named CF2603/4delT located at the 3-end of exon 13. A thymidine at position 2603 or 2604 is lost. The mutation eliminates an MseI site and, therefore, can be screened by restriction enzyme analysis.     

Two frameshift mutations in the cystic fibrosis gene

Cystic fibrosis (CF) is a recessive disease caused by mutations in the CF transmembrane conductance regulator (CFTR) gene. We have identified in exon 7 two frameshift mutations, one caused by a two-nucleotide insertion and the other caused by a one-nucleotide deletion; these mutations--CF1154insTC and CF1213delT, respectively, are predicted to shift the reading frame of the protein and to introduce UAA(ochre) termination codons at residues 369 and 368.     

The major cystic fibrosis mutation in a British population

Summary We have studied 72 families with at least one child with cystic fibrosis (CF); they were referred because they had requested pre-natal diagnosis in a future pregnancy. The F508 mutation was found in 108/140 CF chromosomes (77%). In 41/72 families (57%), both parents carried a deleted chromosome and the child was doubly deleted. In only 4 families, 2 of them being consanguineous, did neither parent carry a deleted chromosome. Meconium ileus was associated with children who were F508/F508, F508/non-deleted and non-deleted/ non-deleted.This paper should have been published in Human Genetics, Vol.85, No.4, 1990, together with the other European data on Population analysis of the major mutation in cystic fibrosis. Its publication was delayed for technical reasons     

394delTT: a Nordic cystic fibrosis mutation

In a systematic screening for mutations in the gene encoding the cystic fibrosis transmembrane regulator among Danish cystic fibrosis (CF) patients, we identified a mutation in exon 3 (394delTT); this mutation was found to be relatively common in Denmark. We therefore screened for 394delTT in Sweden and Norway, where it turned out to be the second most frequent mutation, accounting for 4% of all CF mutations. It also occurs with a high frequency in Finland, but has not been found in larger surveys of mutations in the CFTR gene. Thus, 394delTT seems to be a specific Nordic CF mutation.     

Detection of three rare frameshift mutations in the cystic fibrosis gene in an African-American (CF444delA), an Italian (CF2522insC), and a Soviet (CF3821delT).

We have identified three new frameshift mutations in the CFTR gene in patients with cystic fibrosis (CF). The first one involves the deletion of an adenine nucleotide in exon 4 in an African-American patient (CF444delA), the second involves the insertion of a cytosine nucleotide in exon 13 in an Italian patient (CF2522insC), and the third results from the deletion of a thymidine nucleotide in exon 19 in a Soviet patient (CF3821delT). Each mutation is predicted to result in premature termination of the CFTR protein.     

Ethnic heterogeneity and cystic fibrosis transmembrane regulator (CFTR) mutation frequencies in Chicago-area CF families.

The identification of a common mutation, delta F508, in the CFTR gene allowed, for the first time, the detection of cystic fibrosis (CF) carriers in the general population. Further genetic studies revealed > 100 additional disease-causing mutations in this gene, few of which occur on > 1% of CF chromosomes in any ethnic group. Prior to establishing counseling guidelines and carrier risk assessments, we sought to establish the frequencies of the CFTR mutations that are present in CF families living in the Chicago area, a region notable for its ethnic heterogeneity. Our sample included 283 unrelated CF carriers, with the following ethnic composition: 78% non-Ashkenazi Caucasians, 5% Ashkenazi, 9% African-American, 3% Mexican, 0.3% Native American, and 5% mixed ancestry. When a panel of 10 mutations (delta F508, delta I507, G542X, G551D, R553X, S549N, R1162X, W1282X, N1303K, and 1717-1G-->A) was used, detection rates ranged from 75% in non-Ashkenazi Caucasians to 40% in African-Americans. These data suggest that the goal of screening for 90%-95% of CF mutations may be unrealistic in this and other, similar U.S. populations.     

Detection of a de novo R1066H mutation in an Italian patient affected by cystic fibrosis

Search for mutations in a cystic fibrosis patient, compound heterozygous for 1717–1G→A and another uncharacterized molecular defect, revealed the presence of a de novo R1066H mutation on the affected chromosome of paternal origin. Three additional rare mutations (R1066C, R1066S and R1066L), occurring at the CpG dinucleotide at position 3328–3329 of the cystic fibrosis transmembrane conductance regulator gene, have so far been reported. The identification of a R1066H de novo mutation further suggests that this dinucleotide may constitute a mutational hotspot. Received: 10 November 1995 / Revised: 18 January 1996     

Functional characterization of a novel CFTR mutation P67S identified in a patient with atypical cystic fibrosis.

Cystic fibrosis (CF) is caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene. CFTR serves as a cAMP-stimulated chloride channel in a wide range of epithelial tissues and its dysfunction is a hallmark of CF. Over 1400 mutations in the CFTR gene are known, but functional data exist only for a minority of the mutant channels. The aim of the present study was to functionally characterize a novel CFTR mutation identified in a patient with atypical CF. Full length sequencing of the patient's CFTR gene revealed a homozygous C to T transition at nucleotide position 331 (CCT>TCT), which results in a P67S amino acid substitution. Mutant and wild-type CFTR were heterologously expressed in Xenopus laevis oocytes. CFTR whole-cell currents were studied using the two-electrode voltage-clamp technique. Channel surface expression was assessed by a chemiluminescence assay. Expression of P67S-CFTR resulted in functional CFTR chloride channels. However, the CFTR chloride conductance observed in oocytes expressing the mutant channel averaged only 24% of that in oocytes expressing wild-type CFTR. Similarly, surface expression of the mutant channel was reduced. In contrast, the mutation did not alter the anion selectivity of the channel, and Western blot analysis indicated a similar protein expression level of mutant and wild-type CFTR. Our findings indicate that the P67S mutation reduces CFTR chloride channel function by reducing channel surface expression. The mild disease phenotype of the patient indicates that the residual function of the mutant channel is sufficient to prevent the development of severe CF symptoms.     

Unusually common cystic fibrosis mutation in Portugal encodes a misprocessed protein

A561E, a novel cystic fibrosis (CF) associated mutation in the first nucleotide binding domain of CFTR, is the second most common CF mutation in Portugal. Properties of the A561E-CFTR protein were studied by immunoblotting, pulse-chase, immunocytochemistry, and MQAE halide-efflux assay in stably transfected BHK cells. Altogether, results presented here suggest that A561E causes protein mislocalization in the endoplasmic reticulum where the mutant protein must be trapped by the quality control mechanism. We conclude that A561E originates a protein trafficking defect, thus belonging to class II of CFTR mutations. As it is the case for F508del-CFTR (the most common CF mutant), low temperature treatment partially rescues a functional A561E-CFTR channel, suggesting that substitution of glutamic acid for alanine at position 561 does not completely abolish CFTR function. Pharmacological strategies previously reported for treatment of CF patients with the F508del mutation could thus be also effective in CF patients bearing the A561E mutation.     

Haplotypes associated with the cystic fibrosis gene (CF)

The linkage relationships between the cystic fibrosis locus and six marker loci allowed us to build 122 haplotypes bearing the CF gene and to compare them to the 122 normal haplotypes. We obtained 13 different marker haplotypes associated with the CF chromosomes and 22 with the normals in our population. To examine the possibility of a correlation between the clinical and the genetical polymorphism of the disease haplotype analysis was carried out taking in account age at diagnosis, severity of the disease and a particular clinical subgroup such as meconium ileus or pancreatic sufficiency. The results showed that a particular haplotype (121) is predominant in the severe form of the disease. This may have implication in diagnosis and prognosis of the disease.     

Two novel mutations in a cystic fibrosis patient of Chinese origin

Cystic fibrosis is rare in non-Caucasian populations, and in such populations little is known about the spectrum of mutations and polymorphisms in the CFTR gene. We studied a 23-year-old patient of Chinese ethnicity with sweat chloride values of 104 mM/l, pancreatic sufficiency, an FEV₁ 60% of normal, sputum cultures positive for Staphylococcus aureus and Burkholderia cepacia, and a history of allergic bronchopulmonary aspergillosis. Genetic screening for 31 common CFTR mutations was negative, leading us to search for unknown mutations using single-strand conformation polymorphism and heteroduplex analysis (SSCP/HA). Two novel mutations were detected. In exon 4, a deletion of 8 bp (451–458, ΔGCTTCCTA) causes a frameshift and immediately creates a stop codon. In exon 16, mutation 3041G→A causes the missense change G970D. Functional analysis using an isotopic flux assay indicated that the G970D mutation retains partial function; western blotting indicated that the protein is glycosylated. The patient is heterozygous for the common polymorphisms (2694T/G) in exon 14a and (GATT)_6/7 in intron 6a, indicating that these variants arose in ancestors common to Caucasians and Chinese. Received: 29 January 1999 / Accepted: 18 March 1999     

Terminal glycosylation in cystic fibrosis (CF): a review emphasizing the airway epithelial cell

Altered terminal glycosylation, with increased fucosylation and decreased sialylation is a hallmark of the cystic fibrosis (CF) glycosylation phenotype. Oligosaccharides purified from the surface membrane glycoconjugates of CF airway epithelial cells have the Lewis x, selectin ligand in terminal positions. This review is focused on the investigations of the glycoconjugates of the CF airway epithelial cell surface. Two of the major bacterial pathogens in CF, Pseudomonas aeruginosa and Haemophilus influenzae, have binding proteins which recognize fucose in -1,3 linkage and asialoglycoconjugates. Therefore, consideration has been given to the possibility that the altered terminal glycosylation of airway epithelial glycoproteins in CF contributes to both the chronic infection and the robust, but ineffective, inflammatory response in the CF lung. Since the glycosylation phenotype of CF airway epithelial cells have been modulated by the expression of wtCFTR, the hypotheses which have been proposed to relate altered function of CFTR to the regulation of the glycosyltransferases are discussed. Understanding the effects of mutant CFTR on glycosylation may provide further insight into the regulation of glycoconjugate processing as well as new approaches to the therapy of CF.     

Rare genotype del2,3/2184insA in a cystic fibrosis patient

In this paper we present an interesting case of cystic fibrosis patient with rare genotype de12,3/2184insA and atypical clinical image including: mild symptoms in an early phase of disease, quick progress of lung disease, complicated with pneumothorax after Bordetella pertussis infection and very good response to systemic and inhaled steroid therapy.