High allelic heterogeneity between Afro-Brazilians and Euro-Brazilians impacts cystic fibrosis genetic testing.

Cystic fibrosis (CF) is an autosomal recessive disease caused by at least 1,000 different mutations in the cystic fibrosis transmembrane conductance regulator gene (CFTR). To determine the frequency of 70 common worldwide CFTR mutations in 155 Euro-Brazilian CF patients and in 38 Afro-Brazilian CF patients, we used direct PCR amplification of DNA from a total of 386 chromosomes from CF patients born in three different states of Brazil. The results show that screening for seventy mutations accounts for 81% of the CF alleles in Euro-Brazilians, but only 21% in the Afro-Brazilian group. We found 21 different mutations in Euro-Brazilians and only 7 mutations in Afro-Brazilians. The frequency of mutations and the number of different mutations detected in Euro-Brazilians are different from Northern European and North American populations, but similar to Southern European populations; in Afro-Brazilians, the mix of CF-mutations is different from those reported in Afro-American CF patients. We also found significant differences in detection rates between Euro-Brazilian (75%) and Afro-Brazilian CF patients (21%) living in the same state, Minas Gerais. These results, therefore, have implications for the use of DNA-based tests for risk assessment in heterogeneous populations like the Brazilians. Further studies are needed to identify the remaining CF mutations in the different populations and regions of Brazil.

Analysis of cystic fibrosis transmembrane conductance regulator gene mutations in patients with congenital absence of the uterus and vagina.

The relationship between cystic fibrosis transmembrane conductance regulator gene (CFTR) mutations and congenital absence of the uterus and vagina (CAUV) was examined. CFTR mutations have previously been associated with congenital bilateral absence of the vas deferens (CBAVD). CBAVD is caused by a disruption in the vas deferens, a Wolffian duct derivative. Because the embryologic development of the Müllerian ducts directly depends on the prior normal development of the Wolffian ducts, the same gene products may be necessary for normal embryologic development of both ductal systems. This study evaluated the role of CFTR mutations in the development of CAUV. DNA samples from 25 patients with CAUV were tested for the presence of 33 of the most common CFTR mutations. Protein-coding DNA fragments from the CFTR gene were amplified in vitro by the polymerase chain reaction (PCR) and analyzed for mutations using allele-specific oligonucleotide (ASO) probes. Two patients were heterozygous for CFTR mutations. One was heterozygous for the W1282X mutation and the other was heterozygous for the DeltaF508 mutation. The incidence of the 33 CFTR mutations found in the patients with CAUV (8%) was twice that found in the general population (4%), but much less than the incidence of CFTR mutations in men with CBAVD (80%). This data suggests that it is unlikely for CFTR mutations to cause CAUV in females as they cause CBAVD in some males. Furthermore, the data suggest that CAUV in females may be the same disorder as CBAVD in males who do not have CFTR mutations.