Abstract
Cystic fibrosis (CF) is the most common severe autosomal recessive genetic disorder in Caucasian populations, with an incidence of about 1 in 2000 live births, implying a carrier frequency of about 1 in 22. In 1989, the CF gene was isolated and characterized and the major mutation (ΔF508), a 3-bp deletion that results in the loss of a phenylalanine residue at position 508, was detected. To determine the frequency of the ΔF508 mutation and the predicted number of additional mutations in our population, we have undertaken a collaborative study of 215 CF patients and 175 CF parents in Switzerland. The ΔF508 mutation in exon 10 has been found in 70% of the CF chromosomes, and the exon-11 mutation R553X seems to be the second most common CF mutation in our population, with a frequency of 5.3%, whereas the G551D mutation (also in exon 11) has not been detected at all. Haplotype determination of 430 CF and 175 normal chromosomes using XV-2c, KM19, MP6d-9, and J3.ll has been proven to be very helpful in providing additional carrier risk calculations: Haplotypes 1 (1221), 2 (1222), 6 (2111), and 7 (2221) increase the risk of being a carrier from 1 in 55 (haplotype 6) to 1 in 17 (haplotype 1), whereas haplotypes 3 (1122), 4 (1112), 8 (2222) and 10 (1111) lower the risk from 1 in 144 (haplotype 3) to 1 in 1678 (haplotype 10). Moreover, the mutation R553X shows strong correlation with haplotype 3, leading to the suggestion that haplotypes 1, 2, 5, and 6 may account for four additional mutations in Switzerland. It is concluded that haplotype analyses should be offered to partners of individuals with a family history of CF, giving a more informative carrier risk estimation than the global 1 in 80. For couples at increased risks, where no completely reliable prenatal tests exist, microvillar enzyme testing in combination with DNA analysis is recommended.
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Liechti-Gallati, S., Malik, N., Alkan, M. et al. Association between Haplotypes and Specific Mutations in Swiss Cystic Fibrosis Families. Pediatr Res 30, 304–308 (1991). https://doi.org/10.1203/00006450-199110000-00003
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DOI: https://doi.org/10.1203/00006450-199110000-00003