Cystic fibrosis in Afro-Brazilians: XK haplotypes analysis supports the European origin of p.F508del mutation.

Cystic fibrosis (CF) is a common autosomal recessive disorder, being the p.F508del the most frequent mutation. Also, a nearby restriction fragment length polymorphism (RFLP) named XK (KM19 and XV2C) is non-randomly associated with specific CF alleles. Our aim was to analyze the occurrence of the p.F508del mutation and XK haplotypes in Afro-Brazilians CF patients and controls, since these data is available for the other two main ethnic groups found in Brazil (Euro-Brazilians and Brazilian Amerindians), contributing for the whole comprehension of these haplotypes in the Brazilian population. A total of 103 patients and 54 controls were studied. PCR and PCR-RFLP methodologies were used to identify the presence of the p.F508del and the XK haplotype in the subjects. The combined data show that 84.2% of p.F508del mutation is associated with haplotype B and only 15.8% with haplotype A; no other haplotypes were found to be associated with this mutation. Our data suggest that the occurrence of p.F508del mutation and haplotype B in Afro-Brazilian patients occurs probably due to admixture with Euro-descendants. Therefore this mutation and haplotype could be used as a admixture marker.

Cystic fibrosis gene variability in two southern Brazilian Amerindian populations: analysis of the deltaF508 mutation and the KM19 and XV2C haplotypes.

The frequencies of the deltaF508 deletion, the most common cystic fibrosis mutation in Europeans and European-derived populations, and the XV2C and KM19 restriction fragment length polymorphisms that are tightly linked to the CFTR locus vary among populations. To determine the distribution of these extragenic markers and of the deltaF508 mutation, we analyzed 326 chromosomes of individuals from two South American Indian populations, the Guarani and the Kaingang. The allele and haplotype frequencies differed greatly between the two populations as well as among Amerindians and normal European Brazilians and European Brazilian cystic fibrosis patients. The absence of the deltaF508 mutation and the B haplotype are in agreement with the hypothesis that the deltaF508 mutation occurred after the divergence of these two populations. This finding is useful for populations containing a large Amerindian component and helps us to understand the origins of the deltaF508 deletion, the most common cystic fibrosis mutation in Europeans and European-derived populations, as well as the different incidences of cystic fibrosis in continental groups.

Cystic fibrosis in a southern Brazilian population: characteristics of 90% of the alleles.

Cystic fibrosis (CF) is a genetic disease that frequently leads to death in infancy among Europeans and their descendants. The goals of the present study were to analyze the molecular aspects of CFTR gene characterizing mutations, their frequencies, and the haplotypes formed by four CFTR gene intragenic markers, IVS8-6(T)n, IVS8CA, IVS17bTA and IVS17bCA, in a southern Brazilian population of Caucasian origin. DNA samples from 56 non-related CF patients were analyzed using scanning techniques (single strand conformation polymorphism and denaturing gradient gel electrophoresis), restriction fragment length polymorphism and direct DNA sequencing to identify the mutations. Our results revealed a total of 25 different CF mutations representing nearly 90% of CF alleles, two being novel mutations. Microsatellite haplotypes were defined for CF and normal alleles. The mutational spectrum and the associated haplotypes described for the first time in this study should prove relevant for genetic counselling and CF population screening in Brazil. Moreover, our results suggest the presence of a major Mediterranean component in the contemporary Brazilian CF patient pool.

Geographic heterogeneity of 4 common worldwide cystic fibrosis non-DF508 mutations in Brazil.

Cystic fibrosis (CF) is an autosomal recessive disease caused by at least 750 different mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene. The frequency of the most common mutation (DF508) in Brazilian patients of European origin is 47%. To determine the frequency of 4 other common CF mutations (G542X, G551D, R553X, and N1303K) in Brazilian patients of European origin, we used direct polymerase chain reaction (PCR) amplification of DNA obtained from dried blood spots on Guthrie cards. The DNA came from 247 non-DF508 chromosomes from 172 Brazilian CF patients ascertained from 5 different states of Brazil. The results show that the 4 mutations account for 17% of the non-DF508 alleles and only 9% of the total number of Brazilian CF alleles. Overall, the frequency of each mutation is different from northern European and North American populations but similar to southern European populations, mainly the Italian and Spanish populations. When Brazilian patients of European origin are grouped according to state of birth, the frequencies of the mutations are significantly different between southern and southeastern states of Brazil. Therefore there are serious implication for risk assessment of DNA-based tests in heterogeneous populations such as Brazilians. Further studies are needed to identify the remaining 44% of CF mutations for the different populations and regions of Brazil.

Cystic fibrosis in the Brazilian population: DF508 mutation and KM-19/XV-2C haplotype distribution.

We have used PCR amplification of DNA obtained from Guthrie cards to identify the DF508 mutation and correlate it with the allele frequencies at two polymorphic loci (XV-2C and KM-19) closely linked to the cystic fibrosis gene. The DNA came from 193 white Brazilian families affected by cystic fibrosis and living in five different states of Brazil. The distribution of the haplotypes derived from the DF508 and non-DF508 XV-2C/KM-19 genotypes indicates that 88% of the DF508 alleles are linked to haplotype B and suggests that high heterogeneity exists among the non-DF508 cystic fibrosis alleles occurring in different states. Our data can be used to compare linkage disequilibrium between Brazilians and other heterogeneous populations where the DF508 mutation frequency is low and where many different rare mutations account for the remaining recessive cystic fibrosis alleles.

Regional distribution of cystic fibrosis-linked DNA haplotypes in Brazil: multicenter study.

The restriction fragment length polymorphism (RFLP) haplotypes of cystic fibrosis (CF) alleles vary between populations. To determine the distribution of two RFLPs (XV-2C and KM-19) that are tightly linked to the CF locus, we analyzed a white sample from five different states of Brazil. The haplotypes of 314 CF- and 237 non-CF-bearing chromosomes were uniformly distributed over the five states. The XV-2C allele and haplotype frequencies and the degree of linkage disequilibrium were determined. These were similar to values previously reported in southern European countries but different from results reported for northern and central Europe and North America. In contrast, although KM-19 allele frequencies differed between Brazilian states and European and North American countries, these frequencies were similar to values reported in black Americans. A significant proportion of Brazilian CF-bearing chromosomes had less common haplotypes, suggesting a heterogeneous distribution of CF gene mutations among Brazilians. Further studies are needed to identify the mutations affecting the Brazilian CF patients with various haplotypes.

Esterase D in a sample of caucasian and black individuals from the population of Curitiba State of Parana, Brazil.

Os fenotipos da esterase D (E.C.3.1.1.1) foram determinados em 100 brancos e 390 negroides da populacao de Curitiba empregando-se eletroforese em gel de amido.Nao se detectaram diferencas quanto a prevalencia do alelo ESD1 nos dois grupos etnicos. Entre os primeiros, a frequencia do referido alelo foi de 0,88 e, ente os ultimos, de 0,89. Estes resultados diferem de maneira estatisticamente significativa dos encontrados na comunidade de Parintins (AM), e, sao similares, aos calculados em dois outros estudos realizados com amostras brasileiras nao indigenas.As frequencias fenotipicas encontradas estao de acordo com as esperadas pelo equilibrio de Hardy-Weinberg. Discute-se a hipotese da existencia de um alelo silencioso neste sistema