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Genotype–phenotype correlation and functional studies in patients with cystic fibrosis bearing CFTR complex alleles
  1. Vito Terlizzi1,
  2. Giuseppe Castaldo2,3,
  3. Donatello Salvatore4,
  4. Marco Lucarelli5,
  5. Valeria Raia6,
  6. Adriano Angioni7,
  7. Vincenzo Carnovale8,
  8. Natalia Cirilli9,
  9. Rosaria Casciaro10,
  10. Carla Colombo11,
  11. Antonella Miriam Di Lullo2,3,12,
  12. Ausilia Elce13,
  13. Paola Iacotucci8,
  14. Marika Comegna2,3,
  15. Manuela Scorza2,14,
  16. Vincenzina Lucidi15,
  17. Anna Perfetti2,
  18. Roberta Cimino16,
  19. Serena Quattrucci17,
  20. Manuela Seia18,
  21. Valentina Maria Sofia7,
  22. Federica Zarrilli19,
  23. Felice Amato2,3
  1. 1Dipartimento di Pediatria, Centro Regionale Toscano per la Fibrosi Cistica, Azienda Ospedaliero-Universitaria Meyer, Florence, Italy
  2. 2CEINGE-Biotecnologie Avanzate, Naples, Italy
  3. 3Dipartimento di Medicina Molecolare e Biotecnologie Mediche, Università di Napoli Federico II, Naples, Italy
  4. 4Centro Fibrosi Cistica, AOR San Carlo, Potenza, Italy
  5. 5Dipartimento di Biotecnologie Cellulari ed Ematologia, Istituto Pasteur Fondazione Cenci Bolognetti, Sapienza Università e Policlinico Umberto I, Rome, Italy
  6. 6Centro Regionale Fibrosi Cistica, Sezione Pediatrica, Dipartimento di Scienze Mediche Traslazionali, Università di Napoli Federico II, Naples, Italy
  7. 7Laboratorio di Genetica Medica, Ospedale Pediatrico Bambino Gesù, Rome, Italy
  8. 8Dipartimento di Scienze Mediche Traslazionali, Centro Regionale Fibrosi Cistica, Sezione Adulti, Università di Napoli Federico II, Naples, Italy
  9. 9Dipartimento Materno-Infantile, Ospedali Riuniti Ancona, Centro Regionale Fibrosi Cistica, Ancona, Italy
  10. 10Dipartimento di Pediatria, Centro Regionale Fibrosi Cistica, IRCCS G. Gaslini, Genova, Italy
  11. 11Centro Regionale Fibrosi Cistica, Fondazione IRCCS Ca’ Granda, Ospedale Maggiore Policlinico, Università degli Studi di Milano, Milan, Italy
  12. 12Dipartimento di Neuroscienze, Sezione di ORL, Università di Napoli Federico II, Naples, Italy
  13. 13Università Telematica Pegaso, Napoli, Italy
  14. 14Dipartimento di Biotecnologie e Bioscienze, Università di Milano Bicocca, Milan, Italy
  15. 15Unità di Fibrosi Cistica, IRCCS Ospedale Pediatrico Bambin Gesù, Rome, Italy
  16. 16Dipartimento di Scienze Neurologiche, Riproduttive ed Odontostomatologiche, Università di Napoli Federico II, Naples, Italy
  17. 17Centro Fibrosi Cistica, Sapienza Università e Policlinico Umberto I, Rome, Italy
  18. 18Laboratorio Genetica Medica, Ospedale Maggiore Policlinico, Milano, Italy
  19. 19Dipartimento di Bioscienze e Territorio, Università del Molise, Isernia, Italy
  1. Correspondence to Dr Vito Terlizzi, Centro Regionale Toscano per la Fibrosi Cistica, Dipartimento di Pediatria, Azienda Ospedaliero-Universitaria Meyer, Viale Gaetano Pieraccini 24, Florence 50139, Italy; terlizzivito{at}libero.it

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.

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Footnotes

  • Contributors VT, GC and FA conceived and designed the study, interpreted data and wrote the paper; DS and ML recruited patients and contributed to manuscript preparation; VR, AA, VC, NC, RC, CC, PI, VL, SQ, MS and VMS recruited patients; AMDL, AE, MC, MC, AP, RC and FZ analysed the CFTR gating activity on nasal epithelial cells and described the results of either in vitro and ex vivo studies. All authors approved the final manuscript.

  • Competing interests None declared.

  • Patient consent Obtained.

  • Ethics approval Ethical committee of the University of Naples Federico II.

  • Provenance and peer review Not commissioned; externally peer reviewed.

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