Fluorescent multiplex microsatellites used to define haplotypes associated with 75 CFTR mutations from the UK on 437 CF chromosomes

The cystic fibrosis (CF) transmembrane conductance regulator (CFTR) gene contains three highly informative microsatellites: IVS8CA, IVSI7bTA, and IVSI7bCA. Their analysis improves prenatal / carrier diagnosis and generates haplotypes from CF chromosomes that are strongly associated with specific mutations. Microsatellite haplotypes were defined for 75 CFTR mutations carried on 437 CF chromosomes (220 for ΔF508, 217 for other mutations) from Northern Ireland and three English regions: the North-West, East Anglia, and the South. Fluorescently labelled microsatellites were amplified in a triplex PCR reaction and typed using an ABI373A fluorescent fragment analyser. These mutations cover all the common and most of the rare CF defects found in the UK, and their corresponding haplotypes and geographic region are tabulated here. Ancient mutations, ΔF508, G542X, N1303K, were associated with several related haplotypes due to slippage during replication, whereas other common mutations were associated with the one respective haplotype (e.g., G55ID and R560T with 16-7-17, R117H with 16-30-13, 621 + 1G>T with 21-31-13, 3659delC with 16-35-13). This simple, fast, and automated method for fluorescent typing of these haplotypes will help to direct mutation screening for uncharacterised CF chromosomes.