Search

Made available in DSpace on 2015-12-30T10:19:30Z (GMT). No. of bitstreams: 0 Previous issue date: 2001

We report a large genomic deletion of the cystic fibrosis transmembrane conductance regulator (CFTR) gene, viz.. a deletion that is frequently observed in Central and Eastern Europe. The mutation, termed CFTRdele2.3(21 kb), deletes 21,080 bp spanning introns 1-3 of the CFTR gene. Transcript analyses have revealed that this deletion results in the loss of exons 2 and 3 in epithelial CFTR mRNA, thereby producing a premature termination signal within exon 4. In order to develop a simple polymerase chain reaction assay for this allele, we defined the end-points of the deletion at the DNA sequence level. We next screened for this mutation in a representative set of European and European-derived populations. Some 197 CF patients, including seven homozygotes, bearing this mutation have been identified during the course of our study. Clinical evaluation of CFTRdele2.3(21 kb) homozygotes and a comparison of compound heterozygotes for Delta F508/CFTRdele2,3(21 kb) with pairwise-matched Delta F508 homozygotes indicate that this deletion represents a severe mutation associated with pancreatic insufficiency and early age at diagnosis. Current data show that the mutation is particularly common in Czech (6.4% of all CF chromosomes), Russian (5.2%), Belorussian (3.3%). Austrian (2.6%), German (1.5%), Polish (1.5%), Slovenian (1.5%), Ukrainian (1.2%), and Slovak patients (1.1%). It has also been found in Lithuania, Latvia, Macedonia and Greece and has sporadically been observed in Canada, USA, France, Spain, Turkey, and UK, but not in CF patients from Bulgaria, Croatia, Romania or Serbia. Haplotype analysis has identified the same extragenic CF-haplotype: XV-2c/KM. 19 “A” and the same infrequent intragenic microsatellite haplotype 16-33-13 (IVS8CA-IVS17bTA-IVSI7bCA) in all examined CFTRdele2,3(21 kb) chromosomes, suggesting a common origin for this deletion. We conclude that the 21-kb deletion is a frequent and severe CF mutation in populations of Eastern- and Western-Slavic descent.

We showed elsewhere that the pancreatic function status of cystic fibrosis (CF) patients could be correlated to mutations in the CF transmembrane conductance regulator (CFTR) gene. Although the majority of CF mutations- including the most common, ΔF508-strongly correlated with pancreatic insufficiency (PI), approximately 10% of the mutant alleles may confer pancreatic sufficiency (PS). To extend this observation, genomic DNA of 538 CF patients with well-documented pancreatic function status were analyzed for a series of known mutations in their CFTR genes. Only 20 of the 25 mutations tested were found in this population. They accounted for 84% of the CF chromosomes, with ΔF508 being the most frequent (71%), and the other mutations accounted for less than 5% each. A total of 30 different, complete genotypes could be determined in 394 (73%) of the patients. The data showed that each genotype was associated only with PI or only with PS, but not with both. This result is thus consistent with the hypothesis that PI and PS in CF are predisposed by the genotype at the CFTR locus; the PS phenotype occurs in patients who have one or two mild CFTR mutations, such as R117H, R334W, R347P, A455E, and P574H, whereas the PI phenotype occurs in patients with two severe alleles, such as ΔF508, ΔI507, Q493X, G542X, R553X, W1282X, 621 + 1G→T, 1717-1G→A, 556delA, 3659delC, I148T, G480C, V520F, G551D, and R560T., published_or_final_version

Additional mutations in the cystic fibrosis (CF) gene were identified in the regions corresponding to the two putative nucleotide (ATP)-binding folds (NBFs) of the predicted polypeptide. The patient cohort included 46 Canadian CF families with well-characterized DNA marker haplotypes spanning the disease locus and several other families from Israel. Eleven mutations were found in the first NBF, 2 were found in the second NBF, but none was found in the R-domain. Seven of the mutations were of the missense type affecting some of the highly conserved amino acid residues in the first NBF; 3 were nonsense mutations; 2 would probably affect mRNA splicing; 2 corresponded to small deletions, including another 3-base-pair deletion different from the major mutation (ΔF508), which could account for 70% of the CF chromosomes in the population. Nine of these mutations accounted for 12 of the 31 non-ΔF508 CF chromosomes in the Canadian families. The highly heterogeneous nature of the remaining CF mutations provides important insights into the structure and function of the protein, but is also suggests that DNA-based genetic screening for CF carrier status will not be straightforward., published_or_final_version