G542X Mutations Research Articles

The 3120 +1G-->A splicing mutation in CFTR is common in Brazilian cystic fibrosis patients.

Cystic fibrosis patients from Rio de Janeiro, Brazil, were screened for mutations in exons 11 and 16 of the cystic fibrosis transmembrane conductance regulator gene (CFTR) by a nonradioactive single-stranded conformational polymorphism (SSCP) analysis technique. This procedure was used to evaluate the undefined mutations in one or both alleles of 64 cystic fibrosis patients. Unusual SSCP profiles were investigated further by sequence analysis. Two patients were shown to carry the G542X mutation (exon 11) and five had the splicing mutation 3120+1G-->A(intron 16), one of them being homozygous for the mutation. This is the first report of the 3120+ IG-->A mutation in Brazil. where it appears to be a frequent disease-associated molecular alteration in the CFTR gene.

Mutational analysis of 30 Slovenian cystic fibrosis patients compared to known Slovenian and European CF mutation spectra

More than 800 mutations have been indentified in the CFTR gene. This vast mutation diversity makes the search for molecular defects in cystic fibrosis difficult. Out of 100 Slovenian CF families, we have screened 30, using DGGE and SSCP as mutation detection techniques, while the remaining 70 have been studied previously. Together our and the previous studies have been able to indentify 18 CF mutations which cover 77.6% of the CF alleles in those families. The relative frequency of deltaF508 is 62.7% which is significantly higher than the average reported for the Mediterranean South European region (51.6%). At the same time, significant differences in mutation frequencies were found for the G542X, R1162X, W1282X, N1303K and 3905insT mutations. Several, otherwise rare mutations have been detected, such as: I148T, Q552X, 457TAT-->G, R1006H, 2907delTT, 3667ins4, A559T and G576A. An interesting fact is that A559T was so far found mostly in CF patients of African-American origin. These results imply that a high heterogeneity of CF mutations occurs within the small population of Slovenia, consisting only of 2 million inhabitants. In view of the spectrum and frequencies of detected mutations, Slovenian population expresses characteristics of Mediterranean and central European countries, and at the same time shows also distinctive differences and unique region specific CF mutations (Q685X, D192G, S4X).

Mutational analysis of 30 Slovenian cystic fibrosis patients compared to known Slovenian and European CF mutation spectra.

More than 800 mutations have been indentified in the CFTR gene. This vast mutation diversity makes the search for molecular defects in cystic fibrosis difficult. Out of 100 Slovenian CF families, we have screened 30, using DGGE and SSCP as mutation detection techniques, while the remaining 70 have been studied previously. Together our and the previous studies have been able to indentify 18 CF mutations which cover 77.6% of the CF alleles in those families. The relative frequency of ΔF508 is 62.7% which is significantly higher than the average reported for the Mediterranean South European region (51.6%). At the same time, significant differences in mutation frequencies were found for the G542X, R1162X, W1282X, N1303K and 3905insT mutations. Several, otherwise rare mutations have been detected, such as: I148T, Q552X, 457TAT→G, R1006H, 2907delTT, 3667ins4, A559T and G576A. An interesting fact is that A559T was so far found mostly in CF patients of African-American origin. These results imply that a high heterogeneity of CF mutations occurs within the small population of Slovenia, consisting only of 2 million inhabitants. In view of the spectrum and frequencies of detected mutations, Slovenian population expresses characteristics of Mediterranean and central European countries, and at the same time shows also distinctive differences and unique region specific CF mutations (Q685X, D192G, S4X).

Relative frequencies of cystic fibrosis mutations in The Netherlands as an illustration of significant regional variation in a small country.

Cystic fibrosis (CF) is one of the most common autosomal recessive disorders in white populations. Significant regional differences in CF mutations among affected individuals have been reported. We have studied the geographic distribution of the relative frequencies of the three most common Dutch CF mutations, deltaF508, A455E, and G542X, by analyzing data on area of residence of CF patients. Significantly higher relative frequencies of the A455E mutation and the G542X mutation were observed in the South-West and the South-East, respectively. A uniform distribution of relative frequencies was found for the deltaF508 mutation. The results of our study show that, even in a small country such as The Netherlands, certain CF mutations may be more common in one region than in another.

Sweat electrolyte and cystic fibrosis mutation analysis allows early diagnosis in Brazilian children with clinical signs compatible with cystic fibrosis

A total of 540 individuals with clinical signs suggestive of cystic fibrosis (CF) was studied. The sweat chloride was measured and the DF508, G542X, R553X, and W1282X mutations of the CF gene were screened by polymerase chain reaction (PCR). With this approach the diagnosis of CF was confirmed in 12 children, while 7 additional cases, who are heterozygous for the DF508 mutation, have had minor clinical signs. The frequency of the DF508 allele among the 540 individuals was approximately 3%. The mean age of children diagnosed with CF was 1.81 years, which is significantly earlier than in other studies of the Brazilian population. We also demonstrated that this approach has important clinical implications for earlier and adequate treatment, which was shown to be fundamental for increasing significantly the quality of life and life expectancy. This is particularly true in countries such as Brazil where most CF cases remain undiagnosed, mainly in families of low socio-economical status.

Severe liver impairment in a cystic fibrosis-affected child homozygous for the G542X mutation

The clinical and laboratory findings of a cystic fibrosis (CF) patient homozygous for the G542X mutation are described. This is the first case, among the 7 G542X homozygous CF subjects described so far who shows severe liver involvement, associated pancreatic insufficiency, and moderate pulmonary expression of the disease, as demonstrated by laboratory and imaging data. This case adds to the conclusion that genotype/phenotype correlation in cystic fibrosis is more complex than formerly suspected.

Complete detection of mutations in cystic fibrosis patients of Native American origin.

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.

Mutation analysis for cystic fibrosis to determine carrier status in 167 sperm donors from the Nebraska Genetic Semen Bank.

Cystic fibrosis is the most common autosomal recessive disorder in Caucasian populations, with an approximate frequency of 1/2500 live births and a carrier frequency of 1/25. Due to the high rate of predicted carriers (> 63,000) in the Nebraska population (1990 U.S. Census = 1,578,358), we analyzed sperm DNA obtained from semen donors at the University of Nebraska Genetic Semen Bank for eight of the more common mutations to determine the frequency and diversity in our population. The subjects included 167 semen donors (31 normal healthy donors, 56 infertility patients, 21 prevasectomy patients, and 59 prechemotherapy or preradiation cancer patients). The mutations analyzed included delta F508, R117H, G542X, S549R/N, G551D, R553X, R560T, and W1282X. Analyses were performed using PCR amplified products that were analyzed using polyacrylamide gel electrophoresis, slot blot, and restriction endonuclease digestion. These results were correlated with results from the clinical semen analyses and selected clinical parameters. Results for the total donor population studied showed that the delta F508 mutation was present in 8/167 (4.8%) donors, the R117H mutation was present in 4/167 (2.4%) donors and the G542X mutation was present in 1/167 (0.6%) donors. The observed number of carriers from this population, 13/167 (7.8%), was significantly greater (P = 0.02) than that expected assuming a carrier frequency of 1/25. The excess of carriers was restricted to the subgroup of infertility patients. This suggests that CF carriers may be at higher risk for infertility than the general population.

Mutation analysis and haplotype correlation for 139 cystic fibrosis patients from the Nebraska Regional Cystic Fibrosis Center.

Cystic fibrosis (CF) is the most common autosomal recessive disorder in Caucasian populations with an approximate frequency of one in 2,500 live births and a carrier frequency of one in 25. We studied 400 individuals seen at The Nebraska Regional Cystic Fibrosis Center that included 139 CF patients, 206 parents, and 55 unaffected siblings to determine the frequency of the delta F508, R117H, G542X, S549R/N, G551D, R553X, R560T, and W1282X mutations. In addition, we determined haplotypes on each of these individual's chromosomes using four markers that included XV-2c, KM-19, pMP6d.9, and G2. Results from this study showed that the delta F508 mutation was present in 70% of CF chromosomes. Of the 139 CF patients 74 (53%) were homozygous for the delta F508 deletion, 47 (34%) were heterozygous for the delta F508 deletion and an unknown mutation, and 18 (13%) carried two unknown mutations. Four additional mutations were also found in our population and included G542X (6%), G551D (5%), R553X (4%), and R560T (1%). One patient was documented to be a compound heterozygote for G542X/G551D. A polymorphism, F508C, that has previously been reported in several families was also present in our study. The most common haplotype associated with the delta F508 deletion in our CF patients was the E haplotype (CF Consortium B) while other mutations were associated with a variety of haplotypes.

Non-radioactive detection of the most common mutations in the cystic fibrosis transmembrane conductance regulator gene by multiplex allele-specific polymerase chain reaction.

A rapid, simple, nonradioactive method for detection of four common mutations causing cystic fibrosis (CF) has been developed combining multiplexing with allele-specific polymerase chain reaction amplification. This approach (MASPCR) provides an easy assay for direct genotyping of normal and mutant CF alleles in homozygotes and heterozygotes. The strategy involves multiplex PCR of exons 10, 11, and 21 within the cystic fibrosis transmembrane conductance regulator (CFTR) gene in a single reaction containing three common oligoprimers and either the four normal or four mutant oligos corresponding to the delta F508, G551D, G542X, and N1303K mutations. Primers are chosen so that the size of the four PCR products differ, thereby facilitating detection on agarose gels following amplification in the same reaction. Patient samples are primed with either four normal or four mutant oligo mixtures, and PCR products run in parallel on gels to detect band presence or absence. This approach provides a simple and potentially automated method for cost-effective population screening.

Frequency of the delta F508 deletion and G551D, R553X and G542X mutations in Yugoslav CF patients.

A study was undertaken to find the frequency of the delta F508 deletion and those of the G551D, R553X and G524X mutations among the mainly Slavic population of Serbia, Bosnia, Herzegovina, and Montenegro and compare the frequencies determined with those in other European populations. The delta F508 mutation was found to account for about 70% of CF genes in central Jugoslavia, where its frequency is significantly higher than elsewhere in Southern European populations.

Cystic fibrosis mutations delta F508 and G542X in Jewish patients.

We have screened our CF patients for mutations in exons 10 and 11 of the CFTR gene. Two mutations, delta F508 and G542X, have been found in 66 Jewish CF patients. The average frequency of the delta F508 mutation in the Jewish population is 33.8%. The G542X mutation accounts for 13% of the Ashkenazi CF mutations and has been found in three out of seven chromosomes of Jewish patients from Turkey (probably descended from Ashkenazi immigrants). The G542X mutation was not found in any of the other non-Ashkenazi patients. All the G542X bearing chromosomes have the same haplotype. Based on these observations it is concluded that the G542X mutation was introduced into the Jewish people after the split into Ashkenazi and non-Ashkenazi.

Methods for analysis of multiple cystic fibrosis mutations

A large number of mutations causing cystic fibrosis (CF) have been reported. In an attempt to improve methods for genetic diagnosis and for heterozygote screening, we evaluated methods for efficient analysis of the delta F508, G542X, G551D, R553X, and N1303K mutations. We found that multiple mutations can be analyzed simultaneously using hybridization with allele-specific oligonucleotides. Alternatively all of these mutations can be detected by amplification of DNA followed by restriction enzyme digestion and analysis on polyacrylamide gels. A previously reported method for use of modified primers for DNA amplification to allow detection of virtually any single-base change by restriction enzyme analysis proved particularly useful. The common delta F508 mutation and three mutations in exon 11 were analyzed using a multiplex amplification reaction followed by double digestion with restriction enzymes and electrophoresis in a single lane on a polyacrylamide gel. In a sample of 439 CF chromosomes from North American Caucasians, the frequencies of various mutations were as follows: delta F508 = 75.8%, G542X = 2.7%, G551D = 3.2%, R553X = 1.4%, and N1303K = 1.4% for a total of 84.5% detection of CF chromosomes by analysis for these five mutations.

A child, homozygous for a stop codon in exon 11, shows milder cystic fibrosis symptoms than her heterozygous nephew

The clinical and molecular findings in an infant with mild manifestations of cystic fibrosis, who is homozygous for the G542X mutation, and her heterozygous nephew, who is severely affected, are described.