ΔF508 frequency and associated haplotypes near the cystic fibrosis locus in the Yugoslav population

Summary Chromosomes from 19 unrelated Southern Yugoslav families in which cystic fibrosis (CF) occurs were analysed for the presence of the ΔF508 mutation, using polymerase chain reaction amplification followed by dot blot and polyacrylamide gel analysis. Of the 38 CF chromosomes, 15 (39.5%) carry the ΔF508 deletion. Restriction fragment length polymorphism haplotypes for KM19/PstI, XV2c/TaqI and J3.11/PstI marker loci were determined and are compared for a total of 34 N and 37 CF chromosomes.     

Linkage disequilibrium and CF allele segregation analysis in cystic fibrosis families in Northern Ireland

Summary Linkage disequilibrium and cystic fibrosis (CF) allele segregation were analysed in 46 CF families in Northern Ireland. The smaller (+) allele of the KM19/PstI polymorphism and the larger (-) allele of the XV-2c/TaqI polymorphism showed marked linkage disequilibrium with CF. This information can be used to alter the risk of an individual being a carrier of CF away from the expected population risk of 1 in 20. The high-risk genotypes K+K+ or X-X- have a risk of 1 in 10 and the low-risk genotypes K-K- or X+X+ have a risk of 1 in 50. A study of the segregation of CF alleles in the 46 families, using KM19 and Xv-2c, showed preferential inheritance of the paternal (79%), as opposed to the maternal (21%), CF allele by the heterozygous carriers. A mechanism that might explain this observation is discussed.     

Frequency of the ΔF508 mutation and XV2c,KM19 haplotypes in cystic fibrosis families from The Netherlands: haplotypes without ΔF508 still in disequilibrium

Summary We have determined the frequency of the major cystic fibrosis (CF) three base pair deletion (ΔF508) mutation in 152 CF chromosomes from patients originating from the northern part of The Netherlands. In these patients, the deletion represents approximately 76% of CF mutations. Meconium ileus is strongly associated with homozygosity for the ΔF508 mutation. The XV2c,KM19 haplotypes on the CF chromosomes without the ΔF508 mutation are in disequilibrium with the population frequency, although showing an increased frequency of the 1 2 haplotype. The surplus of this haplotype is almost entirely made up by the pancreatic insufficient patients.     

Cystic fibrosis haplotype association and the ΔF508 mutation in adult British CF patients

Summary The ΔF508 mutation and cystic fibrosis (CF) haplotypes with the markers KM19, pMP6d-9 and J3.11 are described in 54 adult British CF patients. ΔF508 was found on 70% of all CF chromosomes, on none of the normal chromosomes and on only 37.5% of pancreatic sufficient CF chromosomes. All patients with meconium ileus were homozygous for the deletion.     

Frequency of the F508 deletion in cystic fibrosis patients from the European part of the USSR

Summary The frequency of the F508 deletion (F508) has been analyzed in 189 cystic fibrosis (CF) patients from the European part of the USSR, viz. 127 nothern Slavonians (Leningrad region), 30 southern Slavonians (the Ukraine), 10 central Slavonians (Moscow region), 14 Moldavians (Kishenev region) and 8 Lithuanians (Vilnius region). The distribution of CF⁺ chromosomes with and without F508 varied significantly in the different ethnic groups studied and correlated with the clinical manifestation of CF. The overall frequency of F508 in Slavonian patients is equal to 62.5%, approximately 90% of them being heterozygous or homozygous for this mutation. The frequency of the deletion among 99 Slavonian patients with severe disease manifestation (pancreatic insufficiency, PI) is equal to 67.5%, only 12 patients having pancreatic sufficiency (PS, 17.5%). The highest value of F508 (77.4%) is registered in PI/CF patients of the southern Slavonian group; it is much less frequent (about 57%) in relevant groups of Slavonians from the northern and central parts of the country. Unusually low frequencies (24% and 26%) of F508 are detected in a few samples of Lithuanian and Moldavian CF patients, respectively. All F508⁺CF-chromosomes of Slavonian origin are associated with haplotypes 2.2.2. defined by the restriction fragment length polymorphism sites KM19/PstI, CS.7/Hin6I and MP6d-9/MspI, although a high proportion (about 25%) of unknown mutations is associated with the same haplotype. Haplotype B (allele 1XV2c/TaqI; allele 2 KM19/PstI) accounts for 91% of F508⁺CF chromosomes. Our data are consistent with the hypothesis of a single origin and subsequent diffusion of this major CF mutation; however, its interpopulational dissemination in Eastern Europe does not follow the suggested south-east to north-west gradient in Western Europe. The significance of these data for prenatal diagnosis and carrier screening of CF mutations is briefly discussed.     

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.     

ΔF508 deletion in cystic fibrosis in Italian families

Summary In 20 Italian families with cystic fibrosis (CF), restriction fragment length polymorphisms were detected by five linked markers; a strong linkage disequilibrium is observed between the haplotype B (alleles 2/1 with respect to KM19/XV2c) and CF. The frequency of the ΔF508 deletion in CF chromosomes of this sample is 50%. A significant correlation is found between the absence of the ΔF508 mutation and pancreatic sufficiency.     

Haplotypes in cystic fibrosis patients with or without pancreatic insufficiency from four European populations

We examined the allele and haplotype frequencies of five polymorphic DNA markers in 355 European cystic fibrosis (CF) patients (from Belgium, the German Democratic Republic, Greece, and Italy) who were divided into two groups according to whether they were or not taking supplementary pancreatic enzymes. The level of linkage disequilibrium between each polymorphism and the CF mutation varied among the different populations; there was no significant association between KM.19 and CF in the Greek population. The distributions of alleles and haplotypes derived from the polymorphisms revealed by probes KM.19 and XV.2c were always different in patients with or without pancreatic insufficiency (PI) in all the populations studied. In particular, among 32 patients without PI, only 9 (or 28%) were homozygous for the KM.19-XV.2c = 2-1 haplotype (which was present in 73% of all the CF chromosomes in our sample) compared to 162 of 252 patients (or 64%) with PI. These findings are consistent with the hypothesis that pancreatic insufficiency or sufficiency may be determined by different mutations at the CF locus.     

Molecular analysis of cystic fibrosis in the Hungarian population

Summary Hungarian cystic fibrosis (CF) families (n = 33) including 114 family members have been analysed for the presence of the F508 mutation within the cystic fibrosis transmembrane conductance regulator (CFTR) gene, and have been haplotyped with probes for restriction fragment length polymorphisms (RFLPs) known to be linked to the CFTR gene. The F508 deletion was present in 64% of CF chromosomes. As in many other populations, linkage disequilibrium was found between the CF locus and the haplotype B (XV-2c: allele 1, KM1-9: allele 2), which accounts for 95% of F508 CF chromosomes in our families.     

Molecular data on cystic fibrosis in Bulgaria

Summary A group of 42 cystic fibrosis (CF) patients and 80 heterozygote carriers was analysed for determining the prevalent CF haplotypes and the frequency of ΔF508. The “high-risk” haplotype B (XV2c-KM19/1 2) was found in 66% of CF chromosomes. The prevalent normal haplotypes were A (1 1) and B (2 1). The deletion was detected in 54 CF chromosomes (56%), homozygotes constituting 35% of all CF patients. In 88% of cases the mutation was linked to haplotype B, and in 12% to haplotype D (2 2). Chromosomes that did not have ΔF508 were found to be evenly distributed among all four XV2c-KM19 haplotypes. The use of restriction fragment length polymorphisms and direct detection of the mutation makes 94% of CF families fully informative for prenatal analysis.     

The incidence of ΔF508 CF mutation,and associated haplotypes,in a sample of English CF families

Summary Data are presented for ΔF508 screening and KM19/XV2c haplotype analysis of 195 cystic fibrosis (CF) chromosomes from the British Caucasian population. We report the frequency of ΔF508 in this group to be 80% and find pronounced disequilibrium between the deletion and the KM 2, XV 1 haplotype. Haplotype analysis of 71 normal chromosomes is also presented. We report one individual who had meconium ileus and who does not have the ΔF508 mutation on either chromosome.     

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.     

Association between XV2c/CS7/KM19/D9 haplotypes and the ΔF508 mutation A study of 57 Belgian families

Summary Using Southern blotting and the polymerase chain reaction, the prevalence of the haplotypes for XV2c, CS7, KM19 and D9 on CF and on normal chromosomes could be determined in 35 Belgian families. A set of primers complementary to the DNA sequence of the CF gene around the ΔF508 deletion was used to amplify this particular segment of the gene. In a total of 57 families, deletion screening showed that 69 out of 116 CF chromosomes (59.5%) carried the ΔF508 deletion. Both the ΔF508 deletion and another mutation(s) showed strong association with the haplotype 1-2-2-2.     

Cystic fibrosis typing with DNA probes and screening for ΔF508 deletion in families from Southern France

Summary A sample of 235 individuals from 49 French cystic fibrosis (CF) families with at least one living affected child was typed with probes for restriction fragment length polymorphisms (RFLPs) known to be linked to the CF gene, and was screened for the ΔF508 mutation. Using a combination of six probes, 44 out of the 49 families were sufficiently informative to enable prenatal diagnosis or carrier determination. As in many other populations, linkage disequilibrium was found between the CF locus and the haplotype B (XV2c: allele 1; KM19: allele 2), which accounts for about 78% of CF chromosomes in our families. The ΔF508 deletion was present in 64.3% of CF chromosomes.     

The cystic fibrosis ΔF508 mutation in the French population

Summary French families (n = 129) with at least one cystic fibrosis (CF) affected child and 44 unrelated subjects from the general population were tested for the presence of the ΔF508 mutation by the polymerase chain reaction. The ΔF508/CF mutation ratio (CF: uncharacterised CF mutations) was tested in the CF families with and without meconium ileus. The association between ΔF508 and CF mutations and restriction fragment length polymorphism haplotypes (XV2c and KM19) has been estimated; these data suggest that the CF chromosomes include a panel of independent and probably different mutations.     

Different haplotypes for cystic fibrosis-linked DNA polymorphisms in Polish and Dutch populations

Summary We analyzed DNA from 34 Polish and 63 Dutch cystic fibrosis (CF) patients and their families using the polymorphic markers XV2c and KM19, which are in linkage disequilibrium with the CF mutation. Strong linkage disequilibrium was found in the Dutch population sample, but the haplotypes of the Polish chromosomes showed a significantly less extreme disequilibrium. Our data and previous studies indicate that the highest degree of homogeneity of the CF defect and hence the best possible use of the XV2c/KM19/CF linkage disequilibrium for CF carrier detection/exclusion is in populations of northern European origin.     

Genetic differences in cystic fibrosis patients with and without pancreatic insufficiency

Summary To determine the number and frequency of mutations that occur at the cystic fibrosis locus (CF), we have examined the allele and haplotype frequencies of eight polymorphic DNA markers linked to CF in 163 Italian patients who were sub-divided according to their clinical presentations. The distribution of haplotypes for the tightly linked polymorphisms KM.19 and XV-2c differ significantly between patients with and those without pancreatic insufficiency. The haplotype found most commonly in CF chromosomes occurs much more frequently in pancreatic insufficient than in pancreatic sufficient patients. Among the 19 pancreatic sufficient patients, 6 (31.6%) show at least one copy of the rare KM.19 = 1, XV-2c = 2 haplotype, as against 16 of 138 patients (11.6%) with pancreatic insufficiency. In addition, only 5 pancreatic sufficient patients (26.3%) are homozygous for the common 2,1 haplotype, as compared with 88 patients (63.8%) with pancreatic insufficiency. These findings support the hypothesis of allelic heterogeneity at a single locus in CF and suggest that different mutations underlie the presence or absence of pancreatic insufficiency in this disorders.     

Marker haplotype association with growth in German cystic fibrosis patients

Summary In 84 families with 101 children with cystic fibrosis (CF) and 103 unaffected siblings, the haplotype of CF chromosomes was determined with six restriction fragment length polymorphism (RFLP) markers that span the CF gene locus. Patient groups with different genotypes in the more distant flanking marker loci MET D, MET H, and D7S8 differed significantly from each other with respect to percentile height and weight, and percentage of weight for height. Patients homozygous 1-1 in met D (TaqI) and met H (TaqI) were thin and tall when homozygous 1-1 in J3.11 (MspI), and small when homozygous 2-2 in J3.11. Heterozygosity in 3.11 and met H and homozygosity 1-1 in met D segregated with the most severe growth retardation. In contrast, growth was normal in patients who were heterozygous in met D and/or had an uncommon KM.19/XV-2c haplotype. Most patients with pancreatic sufficiency and/or borderline sweat test values were carrying rare haplotypes on their CF chromosomes. Adult patients clustered in genotype groups with normal height percentile distributions. This association between haplotype and clinical severity of CF in the German population provides evidence for genetic microheterogeneity of the CF locus, either because of the existence of multiple alleles of the CF gene itself and/or because of the existence of closely linked polymorphic genes that control growth and development and hence modulate the clinical course and prognosis of CF.