Background: Mutation epidemiology in each ethnic group is a crucial step of strategies for cystic fibrosis (CF) diagnosis and counselling. To date, the scanning of the whole coding region of the cystic fibrosis transmembrane conductance regulator (CFTR) gene permits to identify about 90% of alleles from patients bearing CF and a lower percentage in patients bearing atypical CF. CFTR rearrangements in heterozygosis elude current techniques for molecular analysis, and some of them have been reported with a frequency up to 6% in various ethnic groups.
Methods: Using quantitative PCR analysis of all coding regions, we assessed the occurrence of CFTR rearrangements in 130 alleles from classic CF patients and in 198 alleles from atypical CF patients (all unrelated and from Italian descent) bearing unidentified mutations after the scanning of CFTR.
Results: Seven rearrangements (i.e., dele1, dele2, dele2_3, dele 14b_17b, dele17a_18, dele22_23, and dele22_24) were identified in 34/131 (26.0%) CF alleles bearing undetected mutations (which means about 2.5% of all CF alleles) and in none of the 198 alleles from atypical CF. The CFTR haplotype and the sequence analysis of the breakpoints confirmed the common origin of all the rearrangements. Thus, we set up a novel duplex PCR assay for the large-scale analysis of the seven rearrangements. The procedure was rapid (all PCR amplifications were obtained under the same conditions), costless and repeatable.
Conclusions: It is useful to select the CFTR rearrangements more frequent in specific ethnic groups and to set up procedures for large-scale analysis. Their study can be performed in cases in which a high detection rate is required (i.e., partners of CF carriers/patients). On the contrary, the analysis of rearrangement is useless in atypical CF patients.