Informativity of intragenic microsatellites for carrier detection and prenatal diagnosis of cystic fibrosis in the Italian population

Search for mutations in pancreatic sufficient cystic fibrosis Italian patients: detection of 90% of molecular defects and identification of three novel mutations

A cohort of 31 cystic fibrosis patients showing pancreatic sufficiency and bearing an unidentified mutation on at least one chromosome was analyzed through denaturing gradient gel electrophoresis of the whole coding region of the cystic fibrosis transmembrane conductance regulator gene, including intron-exon boundaries. Three new and 19 previously described mutations were detected. The combination of these with known mutations detected by other methods, allowed the characterization of mutations on 56/62 (90.3%) chromosomes. Among those identified, 17 can be considered responsible for pancreatic sufficiency, since they were found in patients carrying a severe mutation on the other chromosome. Among these presumed mild mutations, eight were detected more than once, R352Q being the most frequent in this sample (4.83%). Intragenic microsatellite analysis revealed that the six chromosomes still bearing unidentified mutations are associated with five different haplotypes. This may indicate that these chromosomes bear different mutations, rarely occurring among cystic fibrosis patients, further underlying the molecular heterogeneity of the genetic defects present in patients having pancreatic sufficiency.

Analysis of linkage disequilibrium between different cystic fibrosis mutations and three intragenic microsatellites in the Italian population

Three intragenic microsatellites of the CFTR gene, a TA and a CA repeats, namely IVS17bTA and IVS17bCA, located in intron 17b and a CA repeat (IVS8CA) located in intron 8 of the CFTR gene, were analyzed in a large sample of Italian cystic fibrosis (CF) and normal chromosomes. Linkage disequilibrium was evaluated between each marker and difference CF mutations on a total of 377 CF and 358 normal chromosomes. Our results are consistent with the hypothesis that all delta F508 chromosomes derive from a single mutational event. The same hypothesis is valid for mutations G542X, N1303K, 1717-1G-->A, which might have been originated more recently than delta F508.