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+1G!A mutation in Brazil, where it appears to be a frequent diseaseassociated molecular alteration in the CFTR gene

Rastreamento da fibrose cística usando-se a análise combinada do teste de IRT neonatal e o estudo molecular da mutação deltaF508

Um total de 117 cartões de rastreamento neonatal foi selecionado anonimamente para a avaliação de fibrose cística (FC) pela análise da mutação deltaF508 usando-se a técnica da reação em cadeia da polimerase (PCR), seguida de eletroforese em gel de poliacrilamida (Page) e pela quantificação da imunotripsina reativa (IRT, Delfia). Uma concentração de IRT menor que 140ng/ml foi encontrada em 116 recém-nascidos. Entre estes foi detectado um heterozigoto deltaF508 com uma concentração de IRT de 4,44ng/ml. Um dos 117 recém-nascidos era homozigoto não-deltaF508 e apresentava uma IRT anormal de 410,7ng/ml. A média da concentração da IRT diferia significativamente conforme este recém-nascido com IRT alterada era incluído ou excluído da amostragem populacional (n = 117, média = 8,207 ± 38,101; n = 116, média = 4,737 ± 6,597, respectivamente). Outra amostra de oito recém-nascidos, previamente rastreados pelo teste de IRT e com níveis elevados do analito, foi testada para a mutação deltaF508. Em cinco deles a mutação deltaF508 foi encontrada em um ou em ambos os cromossomos, correspondendo a 62,25% dos recém-nascidos. De acordo com os resultados obtidos com triagem neonatal pela análise combinada IRT/DNA, pode-se concluir que o método só será eficiente se: a) forem excluídos os fatores que determinam os falso-positivos ou falso-negativos; e b) a detecção de outras mutações forem incluídas na análise dos resultados duvidosos.<br>A total of 117 newborn screening cards were anonymously selected for cystic fibrosis (CF) screening, searching for the deltaF508 mutation using polymerase chain reaction (PCR) followed by polyacrylamide gel electrophoresis (Page) and by quantification of Immunoreactive trypsin (IRT, Delfia). In 116 newborns an IRT concentration lower than 140ng/ml was evidenced. One of these was a deltaF508 heterozygote with an IRT concentration of 4,44ng/ml. One newborn was a non-deltaF508 homozygote with an IRT concentration of 410,7ng/ml. The IRT concentration average was significantly different if the newborn with the abnormal IRT was included or excluded from the population sample (n = 117, means = 8.207 ± 38.101; n = 116, means = 4.737 ± 6.597, respectively). Another sample of 8 newborns previously screened by IRT test and with elevated IRT levels was analyzed for deltaF508 mutation. The deltaF508 mutation was found in one or both chromosomes in five newborns, corresponding to 62.25% of the sample. Results obtained with two-tier IRT/DNA analysis showed that the approach only will be effective if: a) factors leading to false positives and false negatives are excluded; and b) molecular analysis of other mutations are included among those children with undefined results

Cystic Fibrosis: Low Frequency of DF508 Mutation in 2 Population Samples from Rio de Janeiro, Brazil

Blood samples from 44 unrelated cystic fibrosis (CF) patients from Rio de Janeiro, Brazil, were analyzed for the 8 European CF mutations. Six homozygous and 15 heterozygous carriers of the DF508 mutation were found, corresponding to 47.7% of CF patients (allele frequency 0.3068). The G542X and G551D mutations were also observed with allele frequencies of 0.0227 and 0.0114, respectively. An analysis of the DF508 mutation in 291 randomly chosen, healthy individuals was performed, and only 3 heterozygous carriers were identified. These results show that the frequency of the DF508 allele in Rio de Janeiro is much lower than the world average; this may be due to the extremely heterogeneous ethnic admixture of the study population. By combining the results of these 2 different samples (CF patients and random population) and admixture data from Rio de Janeiro, we can estimate the CF incidence in this population to be 1:3542 individuals. However, taking into account the Rio de Janeiro ethnic admixture, we can find an estimate of 1:6902 individuals