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.     

Analysis of intragenic polymorphic markers of the CFTR gene in cystic fibrosis patients and health donors from Bashkorostan

The differences in the polymorphic allele frequency distribution patterns of the biallelic (M470 and TUB20) and microsatellite (IVS6aGATT, IVS8CA, and IVS17CA) markers within the CFTR gene between normal and delF508 chromosomes have been established. For most of the marker loci similar distribution of the allele frequencies on normal and mutant chromosomes without delF508 was demonstrated. Certain polymorphic alleles displayed substantial linkage disequilibrium with the delF508 mutation. Analysis of the IVS6aGATT-IVS8CA-M470-IVS17CA-TUB20 haplotypes association on normal and mutant chromosomes provided identification of the delF508 ancestral haplotype. It was suggested that delF508 mutant chromosomes were introduced into the modern Bashkir gene pool as a result of Slavic migrations from the Eastern Europe. The IVS6aGATT-IVS8CA-M470-IVS17CA-TUB20 major haplotype (77272) revealed was statistically significantly most frequently found on the mutant chromosomes without the delF508 mutation. This finding suggests that the Bashkir cystic fibrosis patients, mostly belonging to the Turkic-speaking families, possessed specific CF gene defect associated with the given haplotype.     

XV-2c and KM.19 haplotype analysis in Chilean patients with cystic fibrosis and unknown CFTR gene mutations

Cystic fibrosis (CF) is caused by mutations in the CFTR gene. More than 1600 mutations have been described, with frequencies that differ worldwide according to the ethnic origin of patients. A small group of mutations are recurrent on several populations. It has been shown that they each tend occur on specific chromosome 7 haplotypes, supporting the notion of a single origin for them. Less than 50% of mutations in Chilean patients have been identified to date. To indirectly assess the possible presence of a predominant founder mutation in the remaining unknown alleles, we evaluated 2 polymorphic markers, XV-2c and KM.19, tightly linked to the CFTR locus. The study was done in Chilean CF patients with unknown or deltaF508 (DeltaF508) CFTR mutations and their haplotypes were compared to affected family-based controls. DeltaF508 showed marked linkage disequilibrium with XV-2c/KM.19 haplotype B, with 90% of alleles on that haplotype. There was no difference in haplotype distribution between unknown mutations and normal controls. These results support a European origin for DeltaF508 alleles in Chilean patients, and make unlikely the presence of a predominant founder mutation in the so-far unknown alleles.     

Analysis of the spectra of mutations and polymorphic loci of cystic fibrosis transmembrane conductance regulator in the population of Bashkortostan

The spectra of mutations and polymorphic loci of the gene of cystic fibrosis transmembrane conductance regulator (CFTR) was studied in 60 cystic fibrosis (CF) families from Bashkortostan. Mutations delF508, 394delTT, CFTRdele2,3(21 kb), R334W, and S1196X (33.3, 3.3, 1.7, 0.8, and 0.8%, respectively) were identified. The frequencies of tandem tetranucleotide repeat (TTR) alleles were determined for locus IVS6a-GATT of intron 6 of the CFTR gene and two extragenic loci flanking the CFTR gene, D7S23 and MET (probes CS.7 and MetH) in mutant and normal chromosomes. Allelic and haplotypic associations of these loci with the mutations found were estimated. An absolute linkage between the 6TTR allele of locus IVS6a-GATT and the delF508 mutation was ascertained. A considerable linkage disequilibrium between the delF508 mutation and the C2 allele of locus D7S23 and between this mutation and the A1 allele of locus MET was found. Most of the other mutant chromosomes carried marker alleles 7TTR, C1, and A2. It was demonstrated that 67% of CF chromosomes carrying delF508 had haplotype 6-2-1 for loci IVS6a-GATT/D7S23/MET, respectively. The frequency distribution of haplotypes in CF chromosomes without delF508 had a high variance and did not differ significantly from the distribution in normal chromosomes (chi 2 = 9.415; p > 0.05).     

Analysis of cystic fibrosis gene mutations and associated haplotypes in the Croatian population

The aim of this study was to reveal the CFTR gene mutation status in the Croatian population as well as to establish the haplotypes associated with cystic fibrosis (CF) and those associated with specific gene mutations. A total of 48 unrelated CF patients from Croatia were examined. Among 96 tested alleles, we found nine different mutations: DeltaF508, 58.33%; G542X, 3.12%; N1303K, 2.08%; R1162X; 621 + 1G --> T; G85E; Y569C; E585X; and S466X, 1.04%. Analysis of three polymorphic loci revealed 15 different haplotypes. Two of them (21-23-13 and 21-17-13) occurred with a higher frequency (40% and 24%). Both of these haplotypes also carried a CFTR gene mutation (DeltaF508 or G542X) on 27 out of 32 chromosomes. Among 12 (of all together 29) CF alleles on which no mutations were found, we detected 10 different haplotypes. Because there are still no published data on the distribution of polymorphic loci in Croatia, nor haplotypes associated with mutations in the CFTR gene, our results greatly contribute to knowledge regarding the genetic background of CF in this region.     

CFTR haplotypic variability for normal and mutant genes in cystic fibrosis families from southern France

In order to contribute to a better understanding of the dispersion of cystic fibrosis (CF) mutations in the South of France, seven diallelic and three multiallelic markers [three upstream of the cystic fibrosis transmembrane conductance regulator (CFTR) gene (XV-2c, KM.19 and J44) and seven intragenic polymorphisms (IVS6A, IVS8CA, M470V, T854T, IVS17BTA, IVS17BCA and TUB18)] were analyzed for 143 ΔF508 chromosomes, 100 CF chromosomes carrying 85 non-ΔF508 and 15 unknown mutations, and 198 normal CFTR alleles. The study provides haplotypic data for 39 different CF mutations, which should be useful in diagnosis by haplotypic analysis and detection of the associated mutations. A major haplotype [2-1-2-7-16-2-1-(30/31)-13-1] was found in normal chromosomes, which should be the most ancient in the Caucasoid population. The most frequent haplotypes in normal chromosomes were associated with 16 different non-ΔF508 mutations, suggesting that there was no preferential haplotype on which these mutations arose. Several mutations were each associated with more than one haplotype, as the result of slippage at one or two of the three microsatellites (ΔF508, G542X, N1303K, G85E, E585X, K710X and 2184delA) or recombination (1717-1G→A, R334W, L206W, R1162X and Y122X). Haplotypes for the most common CFTR mutations (ΔF508, G542X, N1303K) revealed that a large number of alleles were generated by slippage at the microsatellite loci, suggesting that they are the most ancient CF mutations. Other mutations were associated with haplotypes that were different either at several diallelic sites (R334W) or at both diallelic and microsatellite markers (R1162X and R1158X), which is more suggestive of recurrence. Twenty recombinations were detected among the CF mutant alleles analyzed, 75% of them occurring in the second half of the CFTR gene. The higher mutational heterogeneity and the haplotypic variability reported in this small population from the Mediterranean area are consistent with an earlier appearance of CFTR mutations in southern Europe than in central and northern Europe, and an earlier origin and expansion of this population. Received: 19 February 1996 / Revised: 10 April 1996     

Haplotype distribution of and linkage disequilibrium between four polymorphic markers near the CFTR locus in Brazilian cystic fibrosis patients

To contribute to a better understanding of the origin and distribution of CFTR mutations in the Brazilian population, we have investigated the linkage between four polymorphic markers (XV2c, KM19, GATT, and TUB9) within or near the CFTR locus. The distribution of alleles for each polymorphism for both parental and cystic fibrosis (CF) chromosomes from Rio de Janeiro CF families were ascertained using a maximum-likelihood method. This same method was applied to study the distribution of the haplotypes defined by these markers. There was no significant association between the XV2c and KM19 loci on the parental and CF chromosomes. On the other hand, a strong association between GATT and TUB9 loci was observed on both CF and parental chromosomes, and striking linkage disequilibrium between the GATT-TUB9 pair and deltaF508 was observed (chi2 = 26.48, p < 0.0001). Remarkable linkage disequilibrium between the GATT-TUB9 marker pair and non-deltaF508 was also found (chi2 = 17.05, p < 0.0001). Our finding of a linkage disequilibrium between GATT-TUB9 and the CFTR locus could suggest that gene flow between different ethnic groups, mainly sub-Saharan and Mediterranean populations, with Brazilian populations could have resulted in some CF mutations originating on chromosomes that carried the GATT-TUB9 marker haplotype 7-2 (OR = 1.34 < 2.83 < 6.00; p = 0.0066).     

Analysis of the Polymorphic Markers within the CFTR Gene in Cystic Fibrosis Patients and Healthy Donors from Bashkortostan

The differences in the polymorphic allele frequency distribution patterns of the biallelic (M470V and TUB20) and microsatellite (IVS6aGATT, IVS8CA, and IVS17CA) markers within the CFTR gene between normal and delF508 chromosomes have been established. For most of the marker loci similar distribution of the allele frequencies on normal and mutant chromosomes without delF508 was demonstrated. Certain polymorphic alleles displayed substantial linkage disequilibrium with the delF508 mutation. Analysis of the IVS6aGATT-IVS8CA-M470V-IVS17CA-TUB20 haplotypes association on normal and mutant chromosomes provided identification of the delF508 ancestral haplotype. It was suggested that delF508 mutant chromosomes were introduced into the modern Bashkir gene pool as a result of Slavic migrations from the Eastern Europe. The IVS6aGATT-IVS8CA-M470V-IVS17CA-TUB20major haplotype (77272) revealed was statistically significantly most frequently found on the mutant chromosomes without the delF508 mutation. This finding suggests that the Bashkir cystic fibrosis patients, mostly belonging to the Turkic-speaking families, possessed specific CFTR gene defect associated with the given haplotype.     

Mutations in the nucleotide binding domain 1 signature motif region rescue processing and functional defects of cystic fibrosis transmembrane conductance regulator delta f508

The gene encoding the cystic fibrosis transmembrane conductance regulator (CFTR), an ATP binding cassette (ABC) transporter that functions as a phosphorylation- and nucleotide-regulated chloride channel, is mutated in cystic fibrosis (CF) patients. Deletion of a phenylalanine at amino acid position 508 (DeltaF508) in the first nucleotide binding domain (NBD1) is the most prevalent CF-causing mutation and results in defective protein processing and reduced CFTR function, leading to chloride impermeability in CF epithelia and heterologous systems. Using a STE6/CFTRDeltaF508 chimera system in yeast, we isolated two novel DeltaF508 revertant mutations, I539T and G550E, proximal to and within the conserved ABC signature motif of NBD1, respectively. Western blot and functional analysis in mammalian cells indicate that mutations I539T and G550E each partially rescue the CFTRDeltaF508 defect. Furthermore, a combination of both revertant mutations resulted in a 38-fold increase in CFTRDeltaF508-mediated chloride current, representing 29% of wild type channel activity. The G550E mutation increased the sensitivity of CFTRDeltaF508 and wild type CFTR to activation by cAMP agonists and blocked the enhancement of CFTRDeltaF508 channel activity by 2 mm 3-isobutyl-1-methylxanthine. The data show that the DeltaF508 defect can be significantly rescued by second-site mutations in the nucleotide binding domain 1 region, that includes the LSGGQ consensus motif.     

Identification of the M1101K mutation in the cystic fibrosis transmembrane conductance regulator (CFTR) gene and complete detection of cystic fibrosis mutations in the Hutterite population.

The Hutterite population is a genetic isolate with an increased incidence of cystic fibrosis (CF). Previously we identified three CF haplotypes defined by polymorphisms flanking the CF transmembrane conductance regulator (CFTR) gene. delta F508 was present on one of the haplotypes in only 35% of CF chromosomes. We hypothesized that the other two CF haplotypes, one of which was the most common and the other of which is rare, each harbored different non-delta F508 mutations. Single-strand conformation polymorphism analysis detected a missense mutation, M1101K, in both chromosomes of a Hutterite patient carrying the two non-delta F508 haplotypes. M1101K appears to have originated on an uncommon CFTR allele and to be infrequent outside the Hutterite population. The presence of M1101K on two haplotypes is likely the result of a CFTR intragenic recombination which occurred since the founding, 10-12 generations ago, of the Hutterite population. The crossover was located between exons 14a and 17b, an interval of approximately 15 kbp. delta F508 and M1101K accounted for all of the CF mutations in patients from 16 CF families representing the three subdivisions of the Hutterite population.     

Applicability of different antibodies for immunohistochemical localization of CFTR in sweat glands from healthy controls and from patients with cystic fibrosis.

The hereditary disease cystic fibrosis (CF) is caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene. Understanding of the consequences of CFTR gene mutations is derived chiefly from in vitro studies on heterologous cell cultures and on cells hyperexpressing CFTR. Data from ex vivo studies on human tissue are scarce and contradictory, a fact which is in part explained by secondary tissue destruction in most affected organs. The purpose of this study was to establish conditions under which wild-type and mutated CFTR can be studied in affected human tissue. Sweat glands carry the basic defect underlying CF and are not affected by tissue destruction and inflammation. Therefore, we used this tissue to test a panel of eight different CFTR antibodies under various fixation techniques. The antibodies were tested on skin biopsy sections from healthy controls, from CF patients homozygous for the most common mutation, DeltaF508, and from patients carrying two nonsense mutations. Of the eight CFTR antibodies, only three-M3A7, MATG 1104, and cc24-met the criteria necessary for immunolocalization of CFTR in sweat glands. The labeling pattern in the CF sweat glands was consistent with the postulated processing defect of DeltaF508 CFTR. The antibodies exhibited different sensitivities for detecting DeltaF508 CFTR.     

Increased functional cell surface expression of CFTR and DeltaF508-CFTR by the anthracycline doxorubicin

Cystic fibrosis (CF) is a disease that is caused by mutations within the cystic fibrosis transmembrane conductance regulator (CFTR) gene. The most common mutation, DeltaF508, accounts for 70% of all CF alleles and results in a protein that is defective in folding and trafficking to the cell surface. However, DeltaF508-CFTR is functional when properly localized. We report that a single, noncytotoxic dose of the anthracycline doxorubicin (Dox, 0.25 microM) significantly increased total cellular CFTR protein expression, cell surface CFTR protein expression, and CFTR-associated chloride secretion in cultured T84 epithelial cells. Dox treatment also increased DeltaF508-CFTR cell surface expression and DeltaF508-CFTR-associated chloride secretion in stably transfected Madin-Darby canine kidney cells. These results suggest that anthracycline analogs may be useful for the clinical treatment of CF.     

Beta-oestradiol rescues DeltaF508CFTR functional expression in human cystic fibrosis airway CFBE41o- cells through the up-regulation of NHERF1.

BACKGROUND INFORMATION: CF (cystic fibrosis) is a disease caused by mutations within the CFTR (CF transmembrane conductance regulator) gene. The most common mutation, DeltaF508 (deletion of Phe-508), results in a protein that is defective in folding and trafficking to the cell surface but is functional if properly localized in the plasma membrane. We have recently demonstrated that overexpression of the PDZ protein NHERF1 (Na(+)/H(+)-exchanger regulatory factor 1) in CF airway cells induced both a redistribution of DeltaF508CFTR from the cytoplasm to the apical membrane and the PKA (protein kinase A)-dependent activation of DeltaF508CFTR-dependent chloride secretion. In view of the potential importance of the targeted up-regulation of NHERF1 in a therapeutic context, and since it has been demonstrated that oestrogen treatment increases endogenous NHERF1 expression, we tested the hypothesis that oestrogen treatment can increase NHERF1 expression in a human bronchiolar epithelial CF cell line, CFBE41o(-), with subsequent rescue of apical DeltaF508CFTR chloride transport activity. RESULTS: We found that CFBE41o(-) cells do express ERs (oestrogen receptors) in the nuclear fraction and that beta-oestradiol treatment was able to significantly rescue DeltaF508CFTR-dependent chloride secretion in CFBE41o(-) cell monolayers with a peak between 6 and 12 h of treatment, demonstrating that the DeltaF508CFTR translocated to the apical membrane can function as a cAMP-responsive channel, with a significant increase in chloride secretion noted at 1 nM beta-oestradiol and a maximal effect observed at 10 nM. Importantly, knock-down of NHERF1 expression by transfection with siRNA (small interfering RNA) for NHERF1 inhibited the beta-oestradiol-dependent increase in DeltaF508CFTR protein expression levels and completely prevented the beta-oestradiol-dependent rescue of DeltaF508CFTR transport activity. CONCLUSIONS: These results demonstrate that beta-oestradiol-dependent up-regulation of NHERF1 significantly increases DeltaF508CFTR functional expression in CFBE41o(-) cells.     

Novel short chain fatty acids restore chloride secretion in cystic fibrosis

Phenylalanine deletion at position 508 of the cystic fibrosis transmembrane conductance regulator (DeltaF508-CFTR), the most common mutation in cystic fibrosis (CF), causes a misfolded protein exhibiting partial chloride conductance and impaired trafficking to the plasma membrane. 4-Phenylbutyrate corrects defective DeltaF508-CFTR trafficking in vitro, but is not clinically efficacious. From a panel of short chain fatty acid derivatives, we showed that 2,2-dimethyl-butyrate (ST20) and alpha-methylhydrocinnamic acid (ST7), exhibiting high oral bioavailability and sustained plasma levels, correct the DeltaF508-CFTR defect. Pre-incubation (>or=6h) of CF IB3-1 airway cells with >or=1mM ST7 or ST20 restored the ability of 100microM forskolin to stimulate an (125)I(-) efflux. This efflux was fully inhibited by NPPB, DPC, or glibenclamide, suggesting mediation through CFTR. Partial inhibition by DIDS suggests possible contribution from an additional Cl(-) channel regulated by CFTR. Thus, ST7 and ST20 offer treatment potential for CF caused by the DeltaF508 mutation.     

Analysis of the Spectra of Mutations and Polymorphic Loci of Cystic Fibrosis Transmembrane Conductance Regulator in the Population of Bashkortostan

The spectra of mutations and polymorphic loci of the gene of cystic fibrosis transmembrane conductance regulator (CFTR) was studied in 60 cystic fibrosis (CF) families from Bashkortostan. Mutations delF508, 394delTT, CFTRdele2,3(21 kb), R334W, and S1196X (33.3, 3.3, 1.7, 0.8, and 0.8%, respectively) were identified. The frequencies of tandem tetranucleotide repeat (TTR) alleles were determined for locus IVS6a-GATT of intron 6 of the CFTR gene and two extragenic loci flanking the CFTR gene, D7S23and MET(probes CS.7 and MetH) in mutant and normal chromosomes. Allelic and haplotypic associations of these loci with the mutations found were estimated. An absolute linkage between the 6TTR allele of locus IVS6a-GATT and the delF508 mutation was ascertained. A considerable linkage disequilibrium between thedelF508mutation and the C2 allele of locus D7S23and between this mutation and the A1 allele of locus MET was found. Most of the other mutant chromosomes carried marker alleles 7TTR, C1, and A2. It was demonstrated that 67% of CF chromosomes carrying delF508 had haplotype 6–2–1 for loci IVS6a-GATT/D7S23/MET, respectively. The frequency distribution of haplotypes in CF chromosomes without delF508had a high variance and did not differ significantly from the distribution in normal chromosomes (² = 9.415; p > 0.05)).     

Cystic fibrosis in Lebanon: distribution of CFTR mutations among Arab communities

Cystic fibrosis (CF) is thought to be rare among the Arab populations from the Middle East and little data have been reported so far. We have studied a sample of 20 families living in Lebanon for several generations and who have at least one child with CF. These families are mainly from the Maronite, Greek Catholic, Greek Orthodox, Shiite or Sunnite groups. We found a 50% rate of consanguineous marriage, independent of the community of origin. The distribution of CF genotypes was determined through the screening of all exons of the CFTR (cystic fibrosis transmembrane conductance regulator) gene by the technique of denaturing gradient gel electrophoresis combined with asymmetric amplification DNA sequencing. A total of ten different mutations accounting for 87.5% of 32 unrelated CF alleles was identified, including two novel putative mutations (E672del and IVS21-28G→A). Three mutations, ΔF508 (37.5%), W1282X (15.6%), and N1303K (9.4%) accounted for 62.5% of CF alleles. Interestingly, in the Maronite group, 66.7% of the ΔF508 chromosomes were found to be associated with allele 7 of the IVS8(T)tract, contrasting with the absolute linkage disequilibrium between European ΔF508 chromosomes and allele 9. During this study, two previously undescribed polymorphisms (IVS14a + 17del5 and 2691T/C) were also identified. Received: 2 January 1997 / Accepted: 16 March 1997     

Effects of cystic fibrosis transmembrane conductance regulator and DeltaF508CFTR on inflammatory response, ER stress, and Ca2+ of airway epithelia

We tested whether cystic fibrosis (CF) airway epithelia have larger innate immune responses than non-CF or cystic fibrosis transmembrane conductance regulator (CFTR)-corrected cells, perhaps resulting from ER stress due to retention of DeltaF508CFTR in the endoplasmic reticulum (ER) and activation of cytosolic Ca(2+) (Ca(i)) and nuclear factor (NF)-kappaB signaling. Adenovirus infections of a human CF (DeltaF508/DeltaF508) nasal cell line (CF15) provided isogenic comparisons of wild-type (wt) CFTR and DeltaF508CFTR. In the absence of bacteria, there were no or only small differences among CF15, CF15-lacZ (beta-galactosidase-expressing), CF15-wtCFTR (wtCFTR-corrected), and CF15-DeltaF508CFTR (to test ER retention of DeltaF508CFTR) cells in NF-kappaB activity, interleukin (IL)-8 secretion, Ca(i) responses, and ER stress. Non-CF and CF primary cultures of human bronchial epithelial cells (HBE) secreted IL-8 equivalently. Upon infection with Pseudomonas aeruginosa (PA) or flagellin (key activator for airway epithelia), CF15, CF15-lacZ, CF15-wtCFTR, and CF15DeltaF508CFTR cells exhibited equal PA binding, NF-kappaB activity, and IL-8 secretion; cells also responded similarly to flagellin when both CFTR (forskolin) and Ca(i) signaling (ATP) were activated. CF and non-CF HBE responded similarly to flagellin + ATP. Thapsigargin (Tg, releases ER Ca(2+)) increased flagellin-stimulated NF-kappaB and ER stress similarly in all cells. We conclude that ER stress, Ca(i), and NF-kappaB signaling and IL-8 secretion were unaffected by wt- or DeltaF508CFTR in control and during exposure to PA, flagellin, flagellin + ATP, or flagellin + ATP + forskolin. Tg, but not wt- or DeltaF508CFTR, triggered ER stress. Previous measurements showing hyperinflammatory responses in CF airway epithelia may have resulted from cell-specific, rather than CFTR- or DeltaF508CFTR-specific effects.     

Distribution patterns of the ΔF508 mutation in the CFTR gene on CF-linked marker haplotypes in the German population

Summary We have measured the frequency of the ΔF508 mutation in the cystic fibrosis transmembrane conductance regulator (CFTR) gene and its association with cystic fibrosis (CF)-linked marker haplotypes in the German population. Based on the analysis of 400 CF chromosomes, the frequency of the ΔF508 mutation is estimated to be 77.3%, the vast majority being associated with marker haplotype KM19-XV2c 2 1. Our data further suggest the presence of another frequent CF mutation associated with this marker haplotype.     

Frequency of the F508 deletion in the CFTR gene in Turkish cystic fibrosis patients

Summary The F508 deletion in the cystic fibrosis transmembrane conductance regulator (CFTR) gene was found in 8 out of 30 Turkish cystic fibrosis (CF) chromosomes (27%). Five Turkish ΔF508 CF chromosomes were associated with the risk haplotype B in KM19 (2 allele)/XV2c (1 allele). In the Turkish population, cystic fibrosis is predominantly caused by mutations other than the F508 deletion.     

XV-2c/KM19 haplotypes analysis of cystic fibrosis patients from western Mexico

The analysis of polymorphic markers within or closely linked to the cystic fibrosis transmembrane regulator (CFTR) gene is useful as a molecular tool for carrier detection of known and unknown mutations. To establish the association between mutations in the CFTR gene in western Mexican cystic fibrosis (CF) patients, the distribution of XV2c/KM19 haplotypes was analyzed by PCR and restriction enzyme digestion in 384 chromosomes from 74 CF patients, their unaffected parents, and normal subjects. The haplotype analysis revealed that haplotype B was present in 71.9% of CF chromosomes compared to 0% of non-CF chromosomes. The F508del and G542X mutations were strongly associated with haplotype B (96.7% and 100% of chromosomes, respectively). The haplotype distribution of the CF chromosomes carrying other CFTR mutations had a more heterogeneous background. Our results show that haplotype B is associated with CFTR mutations. Therefore, haplotype analysis is a suitable alternate strategy for screening CF patients with a heterogeneous clinical picture from populations with a high molecular heterogeneity where carrier detection programs are not available. In addition, it may be a helpful diagnostic tool for genetic counseling and carrier detection in the relatives of CF patients and in couples who are planning to have children.