The Genetic Analysis of Cystic Fibrosis Patients with Seven Novel Mutations in the CFTR Gene in the Central Anatolian Region of Turkey

Background: Cystic fibrosis, a pulmonary disease which is an autosomal recessive, inherited, multisystemic genetic disease commonly seen in the Caucasian race, is the most frequent cause of mortality and morbidity. So far, more than 2000 disease-causing gene variants have been found and this number has been increasing with the studies conducted. Although there is not yet enough data that include the Turkish population, the recent increase of studies is noteworthy. Aims: To discover the genetic variation in patients diagnosed with cystic fibrosis in the Central Anatolian region. Study Design: Cross-sectional study. Methods: The study was carried out in the Central Anatolian region in 3 pediatric pulmonology departments (Kayseri, Konya, and Ankara) in Turkey between July 2014 and December 2017. The Sanger and Next Generation Sequence analyses were used for exon and exon–intron boundaries in the cystic fibrosis transmembrane conductance regulatory (CFTR) gene, and in selected patients, mutation analysis was performed using the Multiplex Ligation-dependent Probe Amplification technique for large deletions and duplications. Results: CFTR gene analysis was performed for 316 patients and 215 of them were genetically diagnosed with cystic fibrosis. Sixtythree different variants were defined in these patients and 7 of these were large deletions/duplications detected with the MLPA method. The most frequent variants were F508del (29.6%), G85E (8.2%), N1303K (8.2%), Y515* (7.5%), and G542* (3.4%). Conclusion: Using sequencing and Multiplex Ligation-dependent Probe Amplification methods, the identification of seven new mutations that were not previously reported in the literature contributes to a better understanding of the heterogeneous nature of CFTR mutations in the Turkish population. When no mutations are detected (pathogenic/probably pathogenic) in clinically compatible cases, Multiplex Ligationdependent Probe Amplification analysis contributes significantly to the diagnosis.

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1. Salvatore D, Buzzetti R, Baldo E, et al. An overview of international literature from cystic fibrosis registries. Part 3. Disease incidence, genotype/phenotype correlation, microbiology, pregnancy, clinical complications, lung transplantation, and miscellanea. J Cyst Fibros. 2011;10(2):71-85. [CrossRef]
2. Southern KW, Munck A, Pollitt R, et al. A survey of newborn screening for cystic fibrosis in Europe. J Cyst Fibros. 2007;6(1):57-65. [CrossRef]
3. Mall MA, Hartl D. CFTR: cystic fibrosis and beyond. Eur Respir J. 2014;44(4):1042- 1054. [CrossRef]
4. Hangül M, Pekcan S, Kose M, et al. The incidence of cysticfibrosis in Central Anatolia region of Turkey in 2015 and 2016. Balkan Med J. 2019;36:179-183.
5. Grody WW, Cutting GR, Klinger KW, et al. Subcommittee on Cystic Fibrosis Screening, Accreditation of Genetic Services Committee, ACMG. Laboratory standards and guidelines for population-based cystic fibrosis carrier screening. Genet Med. 2001;3(2):149-154. [CrossRef]
6. Watson MS, Cutting GR, Desnick RJ, et al. Cystic fibrosis population carrier screening: 2004 revision of American College of Medical Genetics mutation panel. Genet Med. 2004;6(5):387-391. [CrossRef]
7. Schrijver I, Oitmaa E, Metspalu A, Gardner P. Genotyping microarray for the detection of more than 200 CFTR mutations in ethnically diverse populations. J Mol Diagn. 2005;7(3):375-387. [CrossRef]
8. Shrimpton AE. Molecular diagnosis of cystic fibrosis. Expert Rev Mol Diagn. 2002;2(3):240-256. [CrossRef]
9. De Boeck K, Amaral MD. Progress in therapies for cystic fibrosis. Lancet Respir Med. 2016;4(8):662-674. [CrossRef]
10. Marson FAL, Bertuzzo CS, Ribeiro JD. Classification of CFTR mutation classes. Lancet Respir Med. 2016;4(8):e37-e38. [CrossRef]
11. Kose M, Pekcan S, Kiper N, et al. Doll-like face: is it an under estimated clinical presentation of cystic fibrosis? Pediatr Pulmonol. 2008;43(7):634-637. [CrossRef]
12. Richards S, Aziz N, Bale S, et al. Standards and guidelines for the interpretation of sequence variants: a joint consensus recommendation of the American College of Medical Genetics and Genomics and the Association for Molecular Pathology. Genet Med. 2015;17(5):405-424. [CrossRef]
13. Onay T, Zielenski J, Topaloglu O, et al. Cystic fibrosis mutations and associated haplotypes in Turkish cystic fibrosis patients. Hum Biol. 2001;73(2):191-203. [CrossRef]
14. Kilinç MO, Ninis VN, Dağli E, et al. Highest heterogeneity for cystic fibrosis: 36 mutations account for 75% of all CF chromosomes in Turkish patients. Am J Med Genet. 2002;113(3):250-257. [CrossRef]
15. Onay T, Topaloglu O, Zielenski J, et al. Analysis of the CFTR gene in Turkish cystic fibrosis patients: identification of three novel mutations (3172delAC, P1013L and M1028I). Hum Genet. 1998;102(2):224-230. [CrossRef]
16. Dogru D, Cakır E, Şişmanlar T, et al. Cystic fibrosis in Turkey: first data from the national registry. Pediatr Pulmonol. 2020;55(2):541-548. [CrossRef]
17. Dörk T, Mekus F, Schmidt K, et al. Detection of more than 50 different CFTR mutations in a large group of German cystic fibrosis patients. Hum Genet. 1994;94(5):533- 542. [CrossRef]
18. Kanavakis E, Efthymiadou A, Strofalis S, et al. Cystic fibrosis in Greece: molecular diagnosis, haplotypes, prenatal diagnosis and carrier identification amongst high-risk individuals. Clin Genet. 2003;63(5):400-409. [CrossRef]
19. Angelicheva D, Calafell F, Savov A, et al. Cystic fibrosis mutations and associated haplotypes in Bulgaria-comparative population genetic study. Hum Genet. 1997 ;99(4):513-520. [CrossRef]
20. Alibakhshi R, Kianishirazi R, Cassiman JJ, Zamani M, Cuppens H. Analysis of the CFTR gene in Iranian cystic fibrosis patients: identification of eight novel mutations. J Cyst Fibros. 2008;7(2):102-109. [CrossRef]
21. Alonso MJ, Heine-Suñer D, Calvo M, et al. Spectrum of mutations in the CFTR gene in cystic fibrosis patients of Spanish ancestry. Ann Hum Genet. 2007;71(2):194-201. [CrossRef]
22. Chevalier-Porst F, Bonardot AM, Gilly R, et al. Mutation analysis in 600 French cystic fibrosis patients. J Med Genet. 1994;31(7):541-544. [CrossRef]
23. Gasparini P, Marigo C, Bisceglia G, et al. Screening of 62 mutations in a cohort of cystic fibrosis patients from North Eastern Italy: their incidence and clinical features of defined genotypes. Hum Mutat. 1993;2(5):389-394. [CrossRef]
24. Quint A, Lerer I, Sagi M, Abeliovich D. Mutation spectrum in Jewish cystic fibrosis patients in Israel: implication to carrier screening. Am J Med Genet A. 2005;136(3):246- 248. [CrossRef]
25. Schwartz M. Cystic fibrosis transmembrane conductance regulator (CFTR) gene: mutations and clinical phenotypes. Ugeskr Laeger. 2003;165(9):912-916.
26. Ziętkiewicz E, Rutkiewicz E, Pogorzelski A, et al. CFTR mutations spectrum and efficiency of molecular diagnostic in Polish cystic fibrosis patients. PLoS One. 2014;9(2):e89094. [CrossRef]
27. Jarjour RA, Al-Berrawi S, Ammar S, Majdalawi R. Spectrum of cystic fibrosis mutations in Syrian patients. Minerva Pediatr. 2018;70(2):159-164. [CrossRef]
28. Rawashdeh M, Manal H. Cystic fibrosis in Arabs: a prototype from Jordan. Ann Trop Paediatr. 2000;20(4):283-286. [CrossRef]
29. Banjar H. Geographic distribution of cystic fibrosis transmembrane regulator gene mutations in Saudi Arabia. East Mediterr Health J. 1999;5(6):1230-1235. [CrossRef]
30. El-Harith EA, Dörk T, Stuhrmann M, et al. Novel and characteristic CFTR mutations in Saudi Arab children with severe cystic fibrosis. J Med Genet. 1997;34(12):996-999. [CrossRef]
31. Eskandarani HA. Cystic fibrosis transmembrane regulator gene mutation in Bahrain. J Trop Pediatr. 2001;47:110-112.
32. Zielenski J, Bozon D, Kerem B, et al. Identification of mutations in exons 1 through 8 of the cystic fibrosis transmembrane conductance regulator (CFTR) gene. Genomics. 1991;10(1):229-235. [CrossRef]
33. Giordani B, Amato A, Majo F, et al. Gruppo di lavoro RIFC. Italian Cystic Fibrosis Registry Report. 2011-2014. Epidemiol Prev. 2018;42(1S1):1-32. [CrossRef]
34. Yalçıntepe S, Gürkan H, Atlı E, Sayın NC, Başaran ÜN. Two cases of cystic fibrosis with compound heterozygous variants reported for the first time. Balk Med J. 2020;37(5):297-298. [CrossRef]