Research paperMutation and new polymorphisms insight in introns 11 to 14a of CFTR gene of northern Iranian cystic fibrosis patients
Introduction
Cystic fibrosis (CF) is one of the most common deadly genetic diseases in Caucasians with clinical manifestations due to exocrine pancreatic insufficiency and increase in sweat NaCl concentration resulting in male infertility in some patients and airway disease. This disease is caused by mutation in the cystic fibrosis transmembrane conductance regulator (CFTR) gene. CFTR encodes a protein which constitutes the most predominant chloride channel in exocrine epithelia where it regulates transepithelial fluid and electrolyte transport (Cai et al., 2004, Guggino and Bruce, 2006, Lubamba et al., 2012, Tabaripour et al., 2012).
The 230 kb CFTR gene with 27 exons located at chromosome region 7q31.2 encodes a protein with 1480 amino acids that forms a cAMP-regulated chloride channel in lipid bilayers of the apical membrane of epithelial cells (Guillot et al., 2014).
The basic defects in CF cells are the imperfect chloride transport and the inhibition of the epithelial sodium channel (ENaC) which cause dehydration of secretions with hyperviscous mucus and lead to chronic airway obstruction, pancreatic insufficiency and intestinal malabsorption. While many organs are affected in CF, pulmonary disease is the major cause of morbidity and mortality (Boucher, 2007, Weiler and Drumm, 2013).
Although nearly 2000 different mutations have been reported in the CFTR gene (CF Genetic Analysis Consortium), the most common CFTR mutation is a 3-bp deletion located in exon 10 named F508del. which results in a phenylalanine deletion at position 508 of the protein (Perone et al., 2010). This mutation occurs in about 70–90% of CF patients in Northern Europe and North America (Villella et al., 2013). The distribution of these mutations varies among different populations according to the geographical and ethnic origin of patients (Alibakhshi et al., 2008). In countries like Iran that show a high heterogeneity of CFTR mutations, direct mutation analysis is not easy because firstly none of the mutation scanning methods is 100% sensitive, and second CFTR gene is a large multi-exon gene with many non-pathologic mutations (Kholghi Oskooei et al., 2013). Few previous reports of CFTR mutations in Iran demonstrated that the pattern and distribution of CFTR mutations in this population are distinct from Caucasians (Alibakhshi et al., 2008, Esmaeili Dooki et al., 2011). The aim of this study was to investigate introns 11 to 14a which correspond to the regulatory domain (R domain) of the CFTR protein, regulating the movement of chloride ions across the membrane, in patients who were previously screened for common Caucasian mutations by sequencing and reverse dot blot (RDB) screening (Esmaeili Dooki et al., 2011).
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Patients
The parents of patients all consented to participate in this study after being informed of the nature of the research. The forty patients were diagnosed with CF based on clinical evaluation (pulmonary complications) and elevated sweat chloride values (> 60 mEq/L). The study has been approved by the ethics committee of Babol University of Medical Sciences. Patients were collected from the pediatric hospital of Babol University of Medical Sciences. All subjects were from the north of Iran and had
Results
Forty CF patients were analyzed for the presence of mutations within introns 11 to 14a by sequencing and reverse dot blot reactions. Screening of the first ten DNA samples for mutation detection in exon 13 by sequencing revealed the presence of c.2043delG both in homozygous and heterozygous state. This mutation was subsequently screened for the remaining thirty patients by RDB hybridization assay which led to the identification of 10 (12.5%) c.2043delG alleles. Three patients had homozygous
Discussion
There are only a few reports that describe the distribution and frequency of CFTR gene mutations in Iran (Elahi et al., 2006, Alibakhshi et al., 2008, Esmaeili Dooki et al., 2011). The overall distribution of CFTR mutations in the Iranian population significantly differs from those reported in the neighboring countries like Pakistan, India, Turkey and Arabian countries (Bobadilla et al., 2002). In the present study, we analyzed introns 11 to 14a region of the CFTR gene. We have detected one
Conflict of interest
Authors declare no conflict of interest.
Acknowledgments
Authors would like to express their gratitude to all patients and their parents who consented to participate in this study.
References (23)
A comprehensive molecular characterization of beta thalassemia in a highly heterogeneous population
Blood Cells Mol. Dis.
(2011)- et al.
Analysis of the CFTR gene in Iranian cystic fibrosis patients: identification of eight novel mutations
J. Cyst. Fibros.
(2008) Cystic fibrosis: a disease of vulnerability to airway surface dehydration
Trends Mol. Med.
(2007)A haplotype framework for cystic fibrosis mutations in Iran
J. Mol. Diagn.
(2006)Mutational spectrum of cystic fibrosis in the Lebanese population
J. Cyst. Fibros.
(2010)- et al.
Lung disease modifier genes in cystic fibrosis
Int. J. Biochem. Cell Biol.
(2014) - et al.
CFTR haplotypes in northern Iranian population
Gene
(2013) - et al.
Robot printing of reverse dot blot arrays for human mutation detection
Mol. Diagn.
(2001) - et al.
Cystic fibrosis: insight into CFTR pathophysiology and pharmacotherapy
Clin. Biochem.
(2012) - et al.
Cystic fibrosis: worldwide analysis of CFTR mutations—correlation with incidence data and application to screening
Hum. Mutat.
(2002)
Strategies to investigate the mechanism of action of CFTR modulators
J. Cyst. Fibros.
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