Prevalence of ΔF508 mutation in the cystic fibrosis transmembrane conductance regulator gene among cystic fibrosis patients from a Brazilian referral center

Abstract

Objective: To verify the presence of ΔF508 mutation in the cystic fibrosis transmembrane conductance regulator gene among patients with cystic fibrosis diagnosed by the sweat test for sodium and chlorine and followed at the Pediatric Pneumology Outpatient Clinic of Universidade Estadual de Campinas, Brazil, a referral center for the treatment of cystic fibrosis. Methods:The study analyzed 167 DNA samples from cystic fibrosis patients. Patients' genotype was determined by polymerase chain reaction, and allele and genotype frequencies of ΔF508 mutation were calculated. Results:The genotype frequencies found for -/-, ΔF508/-, and ΔF508/ΔF508 genotypes were respectively: 43.7% (73 patients), 32.9% (55 patients), and 23.4% (39 patients). Of the 334 alleles analyzed, we observed a frequency of 201 (60.18%) alleles for the absence of ΔF508 mutation and of 133 (39.82%) for the presence of ΔF508 mutation. Hardy-Weinberg equilibrium was calculated, obtaining a chi-square value = 16.34 (p ≤ 0.001). The study population was out of equilibrium.The expected values for -/-, ΔF508/-, and ΔF508/ΔF508 genotypes were respectively: 32.22% (60.48 patients), 47.93% (80.04 patients), and 15.86% (26.48 patients). Conclusions:In the analyzed population, ΔF508 mutation was less prevalent than the allele without this mutation. The frequency observed in this study was similar to that from other areas in Brazil and in the world, mainly due to the predominantly Caucasian origin of the population included in the study.J Pediatr (Rio J). 2012;88(6):531-4: Mucoviscidosis, ΔF508, genotype. ResumoObjetivo: Verificar a presença da mutação ΔF508 no gene cystic fibrosis transmembrane conductance regulator na população de pacientes com fibrose cística, diagnosticados pelo teste de sódio e cloro no suor, em acompanhamento no Ambulatório de Pneumologia Pediátrica da Universidade Estadual de Campinas, centro de referência no tratamento da fibrose cística. Métodos:Foram analisadas 167 amostras de DNA de pacientes com fibrose cística. O genótipo dos pacientes foi determinado pela técnica de reação da polimerase e realizado cálculo para a frequência dos alelos e genótipos da mutação ΔF508. Resultados:A frequência genotípica encontrada foi, respectivamente, para os genótipos -/-, ΔF508/-e ΔF508/ΔF508: 43,7% (73 pacientes), 32,9% (55 pacientes) e 23,4% (39 pacientes). Do total de 334 alelos analisados, foi observada a frequência de 201 (60,18%) alelos para a ausência da mutação ΔF508 e de 133 (39,82%) para a presença da mutação ΔF508. O cálculo do equilíbrio de Hardy-Weinberg foi realizado, e obtivemos o valor de qui-quadrado = 16,34 (p ≤ 0,001). A população analisada está fora do equilíbrio. Os valores esperados são, para os respectivos genótipos -/-, ΔF508/-e ΔF508/ΔF508: 32,22% (60,48 pacientes), 47,93% (80,04 pacientes) e 15,86% (26,48 pacientes).Conclusões: Na população analisada, a mutação ΔF508 se mostrou menos prevalente em relação ao alelo sem a mutação. A frequência encontrada neste estudo foi semelhante à de outras regiões do Brasil e do m...

Identification of a novel large deletion and other copy number variations in theCFTRgene in patients with Cystic Fibrosis from a multiethnic population

“…For example, among the Brazilian states, we can observe differences in the frequency of F508del. In São Paulo, the frequency is around 40% (Bieger et al, 2012), in Minas Gerais 48% (Perone, Medeiros, Castillo, Aguiar, & Januário, 2010;Raskin et al, 2008), Pará, 23% (De Araújo et al, 2005), and in Rio de Janeiro, ~30% (Cabello et al, 2005;da Silva Martins et al, 2014), different from the frequency observed in Caucasian Europeans that can be of up to 90% (Riordan, 2008). Despite all the efforts to identify new mutations circulating in the country, a large number of variants remain unknown.…”

“…In some Caucasian populations, the F508del is present in one or both alleles in ~90% of cases (Riordan, 2008). In Brazil, its frequency varies from 23% to 48% (Bieger, Marson, & Bertuzzo, 2012). This may be due to the migration of different peoples, as well as to the heterogeneous gene flow within the country, occurring among Europeans, Africans, and Amerindians and resulting in a complex Brazilian genetic pool (Cabello, Cabello, Llerena, & Fernandes, 2006).…”

Nasal Potential Difference in Cystic Fibrosis considering SevereCFTRMutations

“…Genomic DNA was obtained by direct extraction from peripheral blood lymphocytes according to standard procedures [ 31 ]. CFTR mutations were determined in the following order: F508del identification using the primers forward 5′-GGC ACC ATT AAA GAA AAT ATC-3′ and reverse 5′-TGG CAT GCT TTG ATG ACG C-3′ [ 25 , 26 ]; CFTR exon sequencing, including exon/intron boundaries, performed as previously described [ 24 , 32 , 33 ]; duplication, deletion, and LOH identification using the SALSA MLPA Kit P091-C1 CFTR-MRC-Holland (MRC-Holland, Willem Schoutenstraat, DL Amsterdam, Netherlands) performed according to the manufacturer instructions; and 1584–18672 pb A>G (intron 10) identification performed as previously described [ 34 ].…”

“…Therefore, other tools are being studied for CF diagnosis, including the following: (i) the concentrations of chloride and sodium in the saliva [ 21 ]; (ii) β -adrenergic sweat secretion [ 22 ]; (iii) measurements of CFTR-mediated chlorite (Cl) secretion in human rectal biopsies [ 20 ]; (iv) newborn screening (NBS) by assessing immunoreactive trypsinogen (IRT) (that is, following a positive IRT, the sweat test should be performed for CF diagnosis confirmation [ 23 ]); and (v) sequencing of the entire CFTR gene [ 24 ]. In developing countries, a CF diagnosis can be obtained by measuring chloride and sodium levels and usually by performing an F508del (cDNA: c.1521_1523delCTT) mutation screening [ 25 , 26 ].…”

Manifestações clínicas da mutação f508del: uma série de casos de pacientes com fibrose cística

“…Em países economicamente desenvolvidos e com etnias bem definidas é possível identificar mais facilmente todas as mutações presentes no gene CFTR dos pacientes, porém, em populações em desenvolvimento e/ou miscigenadas como a brasileira a caracterização genotípica é mais complexa. No Brasil, a frequência média da F508del é 50%, variando de 8,7% a 50% 10,11,12,13,14,15,16,17 , a depender da região avaliada.…”