Genotype-phenotype correlation and functional studies in patients with cystic fibrosis bearing CFTR complex alleles

Vito Terlizzi, Giuseppe Castaldo, Donatello Salvatore, Marco Lucarelli, Valeria Raia, Adriano Angioni, Vincenzo Carnovale, Natalia Cirilli, Rosaria Casciaro, Carla Colombo, Antonella Miriam Di Lullo, Ausilia Elce, Paola Iacotucci, Marika Comegna, Manuela Scorza, Vincenzina Lucidi, Anna Perfetti, Roberta Cimino, Serena Quattrucci, Manuela SeiaValentina Maria Sofia, Federica Zarrilli, Felice Amato

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Abstract

Background The effect of complex alleles in cystic fibrosis (CF) is poorly defined for the lack of functional studies. Objectives To describe the genotype-phenotype correlation and the results of either in vitro and ex vivo studies performed on nasal epithelial cells (NEC) in a cohort of patients with CF carrying cystic fibrosis transmembrane conductance regulator (CFTR) complex alleles. Methods We studied 70 homozygous, compound heterozygous or heterozygous for CFTR mutations: p. [Arg74Trp;Val201Met;Asp1270Asn], n=8; p.[Ile148Thr; Ile1023_Val1024del], n=5; p.[Arg117Leu;Leu997Phe], n=6; c.[1210-34TG[12];1210-12T[5];2930C>T], n=3; p. [Arg74Trp;Asp1270Asn], n=4; p.Asp1270Asn, n=2; p. Ile148Thr, n=6; p.Leu997Phe, n=36. In 39 patients, we analysed the CFTR gating activity on NEC in comparison with patients with CF (n=8) and carriers (n=4). Finally, we analysed in vitro the p.[Arg74Trp;Val201Met;Asp1270Asn] complex allele. Results The p.[Ile148Thr;Ile1023_Val1024del] caused severe CF in five compound heterozygous with a class I-II mutation. Their CFTR activity on NEC was comparable with patients with two class I-II mutations (mean 7.3% vs 6.9%). The p.[Arg74Trp;Asp1270Asn] and the p. Asp1270Asn have scarce functional effects, while p. [Arg74Trp;Val201Met;Asp1270Asn] caused mild CF in four of five subjects carrying a class I-II mutation in trans, or CFTR-related disorders (CFTR-RD) in three having in trans a class IV-V mutation. The p.[Arg74Trp;Val201Met; Asp1270Asn] causes significantly (p<0.001) higher CFTR activity compared with compound heterozygous for class I-II mutations. Furthermore, five of six compounds heterozygous with the p.[Arg117Leu;Leu997Phe] had mild CF, whereas the p.Leu997Phe, in trans with a class I-II CFTR mutation, caused CFTR-RD or a healthy status (CFTR activity: 21.3-36.9%). Finally, compounds heterozygous for the c.[1210-34TG[12];1210-12T[5];2930C>T] and a class I-II mutation had mild CF or CFTR-RD (gating activity: 18.5-19.0%). Conclusions The effect of complex alleles partially depends on the mutation in trans. Although larger studies are necessary, the CFTR activity on NEC is a rapid contributory tool to classify patients with CFTR dysfunction.

Original languageEnglish
JournalJournal of Medical Genetics
DOIs
Publication statusAccepted/In press - Oct 13 2016

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ASJC Scopus subject areas

  • Genetics
  • Genetics(clinical)

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Terlizzi, V., Castaldo, G., Salvatore, D., Lucarelli, M., Raia, V., Angioni, A., Carnovale, V., Cirilli, N., Casciaro, R., Colombo, C., Di Lullo, A. M., Elce, A., Iacotucci, P., Comegna, M., Scorza, M., Lucidi, V., Perfetti, A., Cimino, R., Quattrucci, S., ... Amato, F. (Accepted/In press). Genotype-phenotype correlation and functional studies in patients with cystic fibrosis bearing CFTR complex alleles. Journal of Medical Genetics. https://doi.org/10.1136/jmedgenet-2016-103985