Comprehensive Cystic Fibrosis Mutation Epidemiology and Haplotype Characterization in a Southern Italian Population

Abstract

Summary We screened the whole coding region of the cystic fibrosis transmembrane regulator (CFTR) gene in 371 unrelated cystic fibrosis (CF) patients from three regions of southern Italy. Forty‐three mutations detected 91.5% of CF mutated chromosomes by denaturing gradient gel electrophoresis analysis, and three intragenic CFTR polymorphisms predicted a myriad of rare mutations in uncharacterized CF chromosomes. Twelve mutations are peculiar to CF chromosomes from southern Italy: R1158X, 4016insT, L1065P and 711+1G>T are present in 6.3% of CF chromosomes in Campania; G1244E and 852del22 are present in 9.6% of CF chromosomes in Basilicata and 4382delA, 1259insA, I502T, 852del22, 4016insT, D579G, R1158X, L1077P and G1349D are frequent in Puglia (19.6% of CF alleles). Several mutations frequently found in northern Italy (e.g., R1162X, 711+5G>T) and northern Europe (e.g., G551D, I507del and 621+1G>T) are absent from the studied population. The I148T‐3195del6 complex allele was present in two CF chromosomes, whereas I148T was present in both alleles (as a single mutation) in another CF patient and in five CF carriers; this could result from crossover events. The haplotype analysis of three intragenic polymorphisms (IVS8CA, IVS17bTA and IVS17bCA) compared with data from other studies revealed that several mutations (3849+10kbC>T, 1717‐1G>A, E585X, 3272‐26G>A, L558S, 2184insA and R347P) originated from multiple events, whereas others (R1158X and S549R) could be associated with one or more intragenic recombinant events. Given the large population migration from southern Italy, knowledge of the CF molecular epidemiology in this area is an important contribution to diagnosis, counselling and interlaboratory quality control for molecular laboratories worldwide.

A Clinical and Molecular Survey of 62 Cystic Fibrosis Patients from Umbria (Central Italy) Disclosing a High Frequency (2.4%) of the 2184insA Allele: Implications for Screening

“…Molecular analyses were performed by reverse dot blot as described by Castaldo et al [5] or by a commercial procedure: INNO-LiPA CFTR 12 and CFTR 17 + Tn assay or INNO-LiPA CFTR 17 and CFTR 19 + Tn and INNO-LiPA CFTR Italian Regional (Innogenetics, Ghent, Belgium). The CF alleles carrying unknown mutations were analyzed by denaturing gradient gel electrophoresis of all exons of the CFTR gene, following the protocol suggested by Fanen et al [11] and Costes et al [12].…”

“…Few mutations are frequent worldwide, the majority being ‘private' mutations, while a number of mutations are particularly frequent in certain ethnic groups. For instance, in Sardinians the c.1013C>T (T338I) mutation is common, whereas it seems absent in other European populations [4,5]. In Italy, the most common mutation is c.1521_1523delCTT (ΔF508) with a frequency of 51% (about 80% in Northern Europeans and 50% in Southern Europeans) followed by c.3909C>G (N1303K) and c.1624G>T (G542X), both with average frequencies of about 5%.…”

“…In fact, the incidence of the most frequent CFTR mutations differs between Italian regions. An analysis of the frequency and distribution of CF alleles in Italy has been carried out for several regions, but knowledge on mutation distribution is lacking for Umbria, a small and quite geographically isolated region with approximately 900,000 inhabitants situated in central Italy, which was not included in any of the previous surveys because the number of chromosomes tested was <50 [3,4,5,6,7,8,9]. In this study, we performed a comprehensive retrospective clinical and molecular survey of 62 CF patients (124 chromosomes) coming from this region.…”

Three Novel CFTR Polymorphic Repeats Improve Segregation Analysis for Cystic Fibrosis

“…In southern Italy, for example, this first-level approach detects 70%-80% of CF alleles (5 ). Second-level approaches, which are based on the analysis of all the CFTR-coding regions, detect approximately 90% of mutant CF alleles (6 ). A few CF alleles bear large gene rearrangements (7 ).…”

Heterozygous variant at nucleotide position 875+11A>T in exon 6A cystic fibrosis transmembrane conductance regulator gene induces 852del22 mutation false-positivity by line probe assay

“…The mutation has a frequency of 5.8% in CF chromosomes from the Basilicata region and 3.2% in CF chromosomes from the Puglia region (8).…”