c.224G>A, p.Arg75Gln (R75Q) presumably leads to an amino-acid change from arginine to glutamine in the membrane-spanning domain of the CFTR protein. Initially reported as a benign sequence variation, p.Arg75Gln was shown to be associated with a high risk of pancreatitis, a risk that was strikingly higher when p.Arg75Gln was combined with a SPINK1 variant. In addition, it was shown that p.Arg75Gln alters bicarbonate but not chloride conductance and that the mutation also induces exon 3 skipping. To investigate the role of p.Arg75Gln in idiopathic chronic pancreatitis (ICP), we performed genotyping of the CFTR gene in 880 patients with ICP, 198 patients with idiopathic bronchiectasis (IB), 74 patients with classical cystic fibrosis (CF), 48 patients with congenital bilateral absence of the vas deferens (CBAVD) and 148 healthy controls. p.Arg75Gln variant was identified in 3.3% (29/880) of patients with ICP, 3.3% (9/272) patients with a pulmonary disease, 2.1% (1/48) of patients with CBAVD and 4.7% (7/148) of healthy controls. It was frequently associated with the c.[1210-12T[7];1408A>G] (T7-p.Val470) allele and this CFTR genetic background could not explain the putative pathogenicity of this variant. To assess whether CFTR and SPINK1 mutations are co-inherited in pancreatitis, we sequenced SPINK1 gene exon 3 in the 46 patients who were previously identified to be heterozygous for p.Arg75Gln. Two SPINK1 pancreatitis-associated variants, p.Asn34Ser and p.Pro55Ser, were found in 6 patients: 4 of 29 (13.8%) patients with ICP (3 p.Asn34Ser and 1 p.Pro55Ser), 1 of 7 (14.3%) healthy controls (p.Asn34Ser) and 1 of 9 (11.1%) patients with IB (p.Pro55Ser). Our study does not confirm that the CFTR p.Arg75Gln mutation confers a significant risk of pancreatitis both when considered individually and with a concurrent SPINK1 mutation, suggesting the role of other genetic and environmental factors.

Examination of genotype-phenotype correlations along with functional evaluation of CFTR mutations may not be straightforward. The c.1865G>A, p.Gly622Asp (G622D), located at the NBD1 C terminus of the CFTR protein, was initially reported in patients with male infertility. However, the substitution of Gly622 by an aspartic acid in vitro would perturb the local structure or even affect the CFTR folding itself. In order to determine whether p.Gly622Asp affects the risk of developing a CFTR-Related disorder (CFTR-RD) or cystic fibrosis (CF), we analyzed the phenotype of subjects bearing the p.Gly622Asp mutation. We report molecular and clinical analyses in eleven unrelated patients with CF or CFTR-RD with compound heterozygosity for the p.Gly622Asp mutation. On the basis of the clinical features presented by the eleven patients, we postulate that the p.Gly622Asp might be associated with a wide spectrum of phenotypes including classical cystic fibrosis.

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