RESUMEN
Cystic fibrosis (CF; OMIM #219700) is a common autosomal recessive disease. The spectrum and frequency of CFTR mutations vary significantly in different populations and ethnic groups. A genetic epidemiological study was conducted in the indigenous ethnic group of people known as the Karachais. They live in the Republic of Karachay-Cherkessia, which lies in the northwest of Russia's North Caucasus region. Karachai's are Turkic-speaking and consist of 194 thousand people (approximately 40% of the population of the Republic). Molecular genetic analysis was performed in 10 unrelated Karachai families with CF patients from three districts in the Republic. A high frequency of W1282X mutation was found (18 of 20 mutant alleles): eight patients were homozygous for the W1282X mutation, and two were compound heterozygous (the second alleles were R1066C and R709X). Analysis for 13 common CF mutations in the sample of 142 healthy Karachais identified two 1677delTA and two W1282X mutation carriers. Thus, the most common CFTR mutation, F508del, was not detected among the CF patients or in healthy Karachais. The most frequent mutation among Karachai patients is W1282X (90%). Its frequency in healthy Karachais is approximately 0.007. Haplotype analysis using the CFTR intragene DNA markers IVS1CA, IVS6aGATT, IVS8CA and IVS17bCA showed that the origins of the W1282X mutation in Karachay-Cherkessia and the Eastern European part of Russia are different.