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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.

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 (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.

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.

We used signs and letters to offer free cystic fibrosis (CF) carrier screening to nonpregnant adults in stable relationships who visited numerous clinical and nonclinical sites in Nashville. A total of 179 individuals (<<1% of those eligible) elected to be tested. To understand this observation, we used questionnaires to assess individuals' attitudes about genetic testing in general and about CF carrier screening in particular (n=873). Participants expressed conflicting views about carrier screening. More than 90% of people thought that genetic testing should at least be available. Most respondents said that the views of their partners and physicians were important in their decision making, and most believed that these others favored genetic testing. Yet, more than two-thirds indicated that such factors as insurability, being "at risk," what they would need to learn, abortion, and religious beliefs were important in their decision making, opinions that mitigated against genetic testing. In particular, one-third feared that carriers would lose their health insurance, one-quarter said that they would have been more interested had they been able to provide DNA by buccal swab rather than by finger stick, and less than one-sixth believed that genetic testing was meddling in God's plan. In the face of both the low level of use of free CF carrier screening by nonpregnant couples when it was not offered in person by health-care professionals and the wide variety of concerns demonstrated, we believe that clinicians should not routinely offer carrier screening to nonpregnant individuals who do not have a family history of CF.

We performed two studies using only written and video materials to educate people about cystic fibrosis (CF) and carrier screening. Participants were randomized to receive written or video materials. All received a brief questionnaire. Subjects in group I (n = 238) were (1) individuals in steady relationships and their partners, (2) > or = 18 years old, and (3) not pregnant. Those who accepted free screening and were not demonstrable carriers were sent a letter explaining their results and another questionnaire. Subjects in group II (n = 108) were parents seeking well child care in a university clinic. The main outcome measures were ability to answer questions correctly about (1) health status of CF carriers and people with CF, (2) the possibility of false-negative results, and (3) for those who had screening, the implications of their own results. Written and video materials were equally effective in conveying information. Prior to screening, subjects answered an average of 86% of questions correctly. Subjects with less formal education answered fewer questions correctly; 60% of those with less than a high school education had adequate knowledge of the health consequences of having CF or being a carrier, compared with > or = 94% of college graduates. Performance improved after screening. Where neither partner was a demonstrable carrier, 88% knew their own and their partner's test results, and 90% indicated that their risk of having a child with CF was not zero. Written and video educational materials can be used without face-to-face counseling to inform most people about carrier screening and their test results. These materials may be less effective for those with lower educational backgrounds.

A 3 bp deletion of codon 508 (phenylalanine) of the cystic fibrosis (CF) gene constitutes the mutation of most CF chromosomes. The frequency of this mutation (referred to as delta F508), varies considerably between populations, ranging from 26% of the CF mutations in Turkey to 88% in Denmark. To determine the frequency of the delta F508 mutation in Brazilian Caucasoid CF patients, we used direct polymerase chain reaction (PCR) amplification of DNA obtained from dried blood spots on Guthrie cards, followed by ethidium bromide staining of gels. Although the overall frequency of the delta F508 mutation was 47% of 380 CF chromosomes from Brazilian Caucasoids born in five different states, significant interstate differences were observed, ranging from a delta F508 frequency of 27% to 53%. While our method could be used to screen patients and their relatives for carrier testing and prenatal diagnosis, the efficacy of screening only for the delta F508 mutation would be low, and would vary from state to state. Screening for a panel of local mutations will be needed to increase the mutation detection rate and optimize genetic counseling.

In the United States the most common cystic fibrosis (CF) alleles known are F508, G551D, G542X, R553X, and N1303K. These mutations comprise approximately 85% of U.S. CF alleles, and their detection along with analysis of XV-2C and KM-19 restriction fragment length polymorphisms (RFLPs) can enable the determination of CF status. To facilitate studies for determining CF carrier status, we developed methods to detect each of these mutations and RFLPs by direct PCR amplification of dried blood spots collected on newborn screening (Guthrie) cards. Following collection, samples were protected from contamination by individual plastic bags. One-mm2 segments of filter paper were added directly to 100-microliters PCR reactions containing 1/16 mM spermidine. Three initial cycles at 96 degrees C, then 55 degrees C, for 3 min were performed to free DNA and minimize inhibition by other related materials. Next, 1 unit of Taq polymerase was added and a 2-min extension was carried out at 72 degrees C, followed by 33 amplification cycles using denaturing, annealing, and extension temperatures and times optimal for each primer set. Then, 35 microliters of each reaction was run on 8% acrylamide gels directly or 1% agarose gels following digestion; genotypes were inferred by ethidium bromide staining of gels. Guthrie blood spots of 250 CF probands and their parents were screened and the frequencies of all five mutations as well as the XV-2C KM-19 RFLP haplotypes were determined.(ABSTRACT TRUNCATED AT 250 WORDS)

Cystic fibrosis (CF) is a disease characterized by significant variability in both presentation and clinical course. The genetic and environmental factors responsible for the phenotypic expression of CF are most likely legion, and their relationship to the disease complex. Therefore, it was not until the isolation and characterization of the CF gene and the ability to genotype individual patients that further elucidation of the genotype-phenotype relationship in CF was possible. Currently, the pancreatic status of CF patients appears to be primarily determined by genetic factors and patients homozygous for the most common mutation, delta F508 are, as a rule, pancreatic insufficient. Other specific alleles that confer pancreatic sufficiency have been identified. Patients having these alternative alleles remain pancreatic sufficient, are diagnosed later, have lower sweat chloride values, milder respiratory disease, and a better prognosis than patients with alleles associated with pancreatic insufficiency. Other clinical manifestations, including meconium ileus and the presence of liver disease, appear to be associated with pancreatic insufficiency. The variability in the pulmonary course for homozygous delta F508 patients suggests that genetic heterogeneity at other loci or environmental factors are important. Therefore, the CF genotype does not precisely predict pulmonary status.

DNA diagnostic tests often utilize restriction endonuclease digestion of PCR-amplified portions of genes under analysis. When partial digestion occurs, the resulting patterns may lead to error in diagnosis. To overcome such potential errors in cystic fibrosis testing, we have developed internal markers that can increase the precision and reliability of genotype assignments.

We examined the association between clinical status and exposure to tobacco smoke in 44 patients homozygous for the F508 cystic fibrosis mutation. Heavy exposure to tobacco smoke was significantly associated with lower Shwachman scores, poorer results of pulmonary function tests, and a fivefold increase in the number of pulmonary-related hospitalizations during the previous year.