A haplotype framework for cystic fibrosis mutations in Iran

Genetic attributes of Iranian cystic fibrosis patients: the diagnostic efficiency of CFTR mutations in over a decade

Objectives: Cystic fibrosis (CF) is the most prevalent autosomal recessive disorder among Caucasians. Mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene cause this pathology. We, therefore, aimed to describe the CFTR mutations and their geographical distribution in Iran. Method: The mutation spectrum for 87 families from all Iranian ethnicities was collected using ARMS PCR, Sanger sequencing, and MLPA. Results: Mutations were identified in 95.8% of cases. This dataset revealed that the most frequent mutations in the Iranian population were F508del, c.1000C>T, c.1397C>G, c.1911delG, and c.1393-1G>A. In addition, we found weak evidence for Turkey being the possible geographical pathway for introducing CFTR mutations into Iran by mapping the frequency of CFTR mutations. Conclusion: Our descriptive results will facilitate the genetic detection and prenatal diagnosis of cystic fibrosis within the Iranian population.

Reporting Two Novel Mutations in Two Iranian Families with Cystic Fibrosis, Molecular and Bioinformatic Analysis

Background

Cystic fibrosis (CF) is the most common heredity disease among the Caucasian population. More than 350 known pathogenic variations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene (NM_000492.4) cause CF. Herein, we report the outcome of our investigation in two unrelated Iranian families with CF patients.

Methods

We conducted phenotypic examination, segregation, linkage analysis, and CFTR gene sequencing to define causative mutations.

Results

We found two novel mutations in the present study. The first one was a deletion causing frameshift, c.299delT p.(Leu100Profs*7), and the second one was a missense mutation, c.1857G>T, at nucleotide binding domain 1 of the CFTR protein. Haplotype segregation data supported our new mutation findings.

Conclusion

Findings of this study expand the spectrum of CFTR pathogenic variations and can improve prenatal diagnosis and genetic counseling for CF.

CFTR gene mutation spectrum among 735 Iranian patients with cystic fibrosis: A comprehensive systematic review

In this study, the spectrum and frequency of cystic fibrosis transmembrane conductance regulator (CFTR) gene mutations previously reported among Iranian cystic fibrosis (CF) patients have been reviewed and discussed. Using the keywords of Cystic Fibrosis, CF, CFTR, and Iran, along with their Persian equivalents, a comprehensive search was performed on the online databases. After applying the inclusion and exclusion criteria, 16 articles with an overall sample of 735 Iranian patients with CF, were included in this systematic review. A total of 101 different CFTR gene variants had been reported. The mutation of p.Phe508del (c.1521_1523delCTT) (21.22%) was the most frequent one among Iranian patients with CF. In conclusion, due to the fact that in many provinces of Iran no specific study has been done so far, it seems that the CFTR gene mutation spectrum in patients with CF from Iran is much wider.

Following the Trace of HVS II Mitochondrial Region Within the Nine Iranian Ethnic Groups Based on Genetic Population Analysis

The Iranian gene pool is seen as an important human genetic resource for investigating the region connecting Mesopotamia and the Iranian plateau. The main objective of this study was to explore gene flow in nine Iranian ethnic/subpopulation groups (402 samples) by examining mtDNA HVS2 sequence variations. This then allowed us to detect mtDNA HVS2 sequence mutations in two independent thalassemia and cystic fibrosis patient sample groups. The patient groups did not explicitly belong to any of the aforementioned nine subpopulations. Across all subpopulations, the haplogroups B4a1c3a, H2a2a1, N10b, H2a2a2, and J1 were seen to be predominant. High haplogroup diversities along with admixture of the exotic groups were observed in this study. The Arab subpopulation was shown to be independent from the others. It was revealed that there is a far distant relationship between Arab and Azeri groups. The thalassemia patient group, represented an almost random sample of most Iranian ethnic groups, and revealed few significant differences (P < 0.05) in their HVS2 sequence. It turned out that the IVS II-I (G → A) mutation in the thalassemia β-globin gene was highly significant. Since the thalassemia patients in the present study represent many unique haplotypes, we can begin to comprehend the importance of mtDNA with this disease and the necessity for more studies in this context.

Haplotype analysis of the CFTR gene on normal and mutant CFTR genes

BACKGROUND

Mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene are responsible for Cystic Fibrosis (CF) disease. Since the distribution of polymorphisms varies among populations, a comparison between the frequency of CFTR polymorphisms in patients and healthy population may further identify their role in CF disease. The results obtained from this research may facilitate the prediction of disease phenotype in prenatal diagnosis or newborn screening program as well as determine the possible associations between haplotypes and specific mutations.

METHODS

Blood samples collected from 27 unrelated West Iranian families contain at least one CF patient and 55 control families with no history of CF. Samples were analyzed for c.1210-12 T [5-9], c.1242-35-1242-12GT [8-10], c.744-33GATT [6-8] and c.869 + 11C > T polymorphisms by automated direct DNA sequencing following DNA extraction.

RESULTS

Our results showed that the T7 allele is the most common allele in normal and non-ΔF508 CF chromosomes with the frequencies of 93.6% and 100%, respectively. Conversely, T9 was the only allele detected in ΔF508 chromosomes. Moreover, the c.1242-35-1242-12GT analysis showed that (TG)11 repeat was the most common dinucleotide repeat in both, non-ΔF508 and normal chromosomes with the frequencies of 91% and 71%, respectively. The c.744-33GATT and c.869 + 11C > T polymorphism analyses indicated that (GATT)6 and T allele are only found in ΔF508 CF chromosomes. Besides, the [T7-TG11-GATT7-C] haplotype was the most common haplotype in both, normal and non-ΔF508 CF subjects while the [T9-TG10- GATT6-T] haplotype was only detected in CF patients carrying ΔF508 mutation.

CONCLUSIONS

Our findings identified an informative haplotype that could be used in genetic counseling, prenatal diagnosis and future screening of CF in Iran.

Genotype patterns for mutations of the cystic fibrosis transmembrane conductance regulator gene: a retrospective descriptive study from Saudi Arabia

BACKGROUND

Cystic fibrosis (CF) occurs in populations in Saudi Arabia and the Gulf area. Approximately 2000 known variants have been identified for the CF transmembrane conductance regulator (CTFR) gene. Screening for ten of the most common variants can detect 80% of alleles.

OBJECTIVE

Determine the pattern of CFTR variants in the CF population of Saudi Arabia.

DESIGN

A retrospective, descriptive.

SETTING

Tertiary care center.

PATIENTS AND METHODS

We examined the medical records of 396 confirmed CF patients of all age groups that were positive for a CFTR variant from the period of 1 January 1998 to 1 December 2017.

MAIN OUTCOME MEASURES

Zygosity, morbidity and mortality patterns of different types of CFTR variants.

SAMPLE SIZE

312 families that included 396 patients.

RESULTS

Of 48 variants identified, 6 were novel, having not been described in the medical literature. A homozygous state was found in 283 families (90.7%) and compound heterozygosity in 23 (7.4%). Six families were heterozygous (1.9%). Median age (interquartile range) was 10.2 months (4.4 months to 5.7 years) at diagnosis and 9.7 (5.4-16.5) years at follow up. Of 396 patients, 378 patients (95.5%) survived and 18 (4.5%) died. The ten most common variants identified in descending frequency were: p.Gly473GlufsX54 in 98 alleles (16%), p.Ile1234Val in 66 alleles (11%), F508del in 64 alleles (11%), 711+1G>T in 62 alleles (10%), 3120+1G>A in 62 alleles (11%), p.His139Leuin 38 alleles (6.4%), p.Gln637Hisfs in 30 alleles (5.2%), p.Ser549Arg in 27 alleles (4.5%), p.Asn1303Lys in 14 alleles (2.3%), delExon19-21in 10 alleles (1.6%). This analysis identified 79.2% of our CFTR variants.

CONCLUSION

CFTR mutational patterns in our CF population are characterized by a high allelic heterogeneity. The high prevalence of homozygous variants reflects the high level of consanguinity between parents.

LIMITATIONS

Our CFTR screening reflected only about 80% of CF patients in Saudi Arabia.

CONFLICT OF INTEREST

None.

CFTR Mutation Analysis in Western Iran: Identification of Two Novel Mutations

BACKGROUND

Cystic fibrosis (CF) is one of the most common autosomal recessive disorders in Caucasian population. The incidence of disorder varies among different religious, ethnic and geographical isolates. The aim of this study was to identify the spectrum and the frequency of known and unknown disease-causing mutations in Iranian CF patients.

METHODS

Genomic DNA was extracted from peripheral whole blood with a QIAamp DNA Mini-Kit. Mutation analysis was done in the CFTR gene including complete coding region and intron/exon boundaries using a direct sequencing method.

RESULTS

In general, ten mutations were identified in 27 CF cases. Two out of 10 mutations, 754delT and GGTGGCdel/TTGins, were reported as novel mutations. The most common observed mutations in patients were R334W (40.74%), ΔF508 (18.5%), K710X (12.96%) and D110H (5.5%), 1897C>G (1.85%), R1162X (1.85%), S466X (1.85%) and T1036I (1.85%).

CONCLUSION

The finding indicated a unique mutation panel which can be used in genetic counseling, prenatal diagnosis and future screening of CF in Iran. Although ΔF508 is the most common mutation in other populations including Caucasian, this mutation seem not to have an important role in Iranian CF patients. Findings suggest that a different approach in molecular genetics diagnostic strategies in Middle Eastern countries including Iran should be considered.

A fuzzy rule-based expert system for diagnosing cystic fibrosis

Background

Finding a valid diagnosis is mostly a prolonged process. Current advances in the sector of artificial intelligence have led to the appearance of expert systems that enrich the experiences and capabilities of doctors for making decisions for their patients.

Objective

The objective of this research was developing a fuzzy expert system for diagnosing Cystic Fibrosis (CF).

Methods

Defining the risk factors and then, designing the fuzzy expert system for diagnosis of CF were carried out in this cross-sectional study. To evaluate the performance of the proposed system, a dataset that corresponded to 70 patients with respiratory disease who were serially admitted to the CF Clinic in the Pediatric Respiratory Diseases Center, Masih Daneshvari Hospital in Tehran, Iran during August 2016 to January 2017 was considered. Whole procedures of system construction were implemented in a MATLAB environment.

Results

Results showed that the suggested system can be used as a strong diagnostic tool with 93.02% precision, 89.29% specificity, 95.24% sensitivity and 92.86% accuracy for diagnosing CF. There was also a good relationship between the user and the system through the appealing user interface.

Conclusion

The system is equipped with information, knowledge, and expertise from certified specialists; hence, as a training tool it can be useful for new physicians. It is worth mentioning that the accomplishment of this project depends on advocacy of decision making in CF diagnosis. Nevertheless, it is expected that the system will reduce the number of false positives and false negatives in unusual cases.

Deep resequencing of CFTR in 762 F508del homozygotes reveals clusters of non-coding variants associated with cystic fibrosis disease traits

Extensive phenotypic variability is commonly observed in individuals with Mendelian disorders, even among those with identical genotypes in the disease-causing gene. To determine whether variants within and surrounding CFTR contribute to phenotypic variability in cystic fibrosis (CF), we performed deep sequencing of CFTR in 762 patients homozygous for the common CF-causing variant, F508del. In phase 1, ~200 kb encompassing CFTR and extending 10 kb 5' and 5 kb 3' of the gene was sequenced in 486 F508del homozygotes selected from the extremes of sweat chloride concentration. In phase 2, a 510 kb region, which included the entire topologically associated domain of CFTR, was sequenced in 276 F508del homozygotes drawn from extremes of lung function. An additional 163 individuals who carried F508del and a different CF-causing variant were sequenced to inform haplotype construction. Region-based burden testing of both common and rare variants revealed seven regions of significance (α=0.01), five of which overlapped known regulatory elements or chromatin interactions. Notably, the -80 kb locus known to interact with the CFTR promoter was associated with variation in both CF traits. Haplotype analysis revealed a single rare recombination event (1.9% frequency) in intron 15 of CFTR bearing the F508del variant. Otherwise, the majority of F508del chromosomes were markedly similar, consistent with a single origin of the F508del allele. Together, these high-resolution variant analyses of the CFTR locus suggest a role for non-coding regulatory motifs in trait variation among individuals carrying the common CF allele.

Frequency of Genotype With ΔF508 Mutation in CFTR Gene Among Iranian Cystic Fibrosis Patients With Pancreatic Insufficiency

Background:

Cystic fibrosis (CF) is the most prevalent lethal autosomal recessive disease with a broad spectrum of phenotypes. Mutation of ΔF508 in the CFTR gene is the most important and lethal mutation in CF, which contains 70% of all predisposing mutations for CF worldwide.

Objectives:

Determining frequency of genotypes with ΔF508 mutation in CFTR gene, and evaluation of correlation between genotype and phenotype of Iranian patients with CF.

Patients and Methods:

Thirty six patients were included in this cross sectional study. ΔF508 mutations in both alleles of the CFTR gene were checked.

Results:

Among 36 pediatric patients, ΔF508 mutation was detected in 9 (25%) patients; 2 patients were heterozygous, and 7 patients homozygous for this mutation. From overall 72 tracked alleles, 11 (15.2%) were found to have ΔF508 mutations. Differences in prevalence of dyspnea and bronchiectasis were significant in homozygote group, compared with non-mutated group for ΔF508.

Conclusions:

It seems that more ΔF508 mutated alleles lead to more severe symptoms of CF.

Epidemiology and genetics of cystic fibrosis in Asia: In preparation for the next-generation treatments

Cystic fibrosis (CF) in the Asian population is less frequently reported due to under-diagnosis and lack of centralized CF patient registries. Clinical studies on CF cases from Asia have documented a severe course of the disease. The spectrum of the cystic fibrosis transmembrane conductance regulator (CFTR) variants in this population is quite heterogeneous. In total, 166 variants have been reported on approximately 3700 Asian CF chromosomes. The frequency of F508del among Asians is low compared with Caucasians. Recent in vitro studies have shown promise of small molecule correction and potentiation of 45 different CFTR variants. Of these variants, 16 (including G551D and F508del) have also been observed among Asian CF individuals. We suggest undertaking molecular studies extensively to annotate CFTR variants that will help Asian CF individuals to benefit from the precision medicine gaining momentum in the Western countries.

Mutation and new polymorphisms insight in introns 11 to 14a of CFTR gene of northern Iranian cystic fibrosis patients

BACKGROUND

Cystic fibrosis (CF) is the most common autosomal recessive disease in Caucasians, caused by mutation in cystic fibrosis transmembrane conductance regulator (CFTR). The type and distribution of mutations vary widely between different countries and ethnic groups. We therefore aimed to perform a comprehensive analysis of the CFTR gene in northern Iranian CF patients.

METHODS

Forty northern Iranian CF patients were analyzed for mutations in introns 11 to 14a of their CFTR genes, using sequencing and reverse dot blot methods. Five normal subjects were also analyzed as normal control.

RESULTS

One mutation and seven polymorphisms were identified. Of the eighty alleles studied, c.2043delG in exon 13 represented 12.5% of mutant alleles and was associated with two distinct haplotypes. rs1042077T>G, rs4148712delAT, rs4148711T>A and rs3808183 T>C with frequencies varying between 29.2% and 6.9% for the least common allele, as well as three new polymorphisms c.1680-224C>A (11.1%), c.2491-275T>G (14.1%) and c.2491-274C>G (35.9%) were detected.

CONCLUSION

These findings suggest a founder effect for c.2043delG in the Middle East and will assist in genetic counseling, prenatal diagnosis and future screening of CF in Iran.

Mutation Analysis of Exons 10 and 17a of CFTR Gene in Patients with Cystic Fibrosis in Kermanshah Province, Western Iran

BACKGROUND

Cystic fibrosis (CF) is the most common genetic disorder with autosomal recessive inheritance among Caucasian populations. So far, more than 1950 different mutations were identified in cystic fibrosis transmembrane conductance regulator (CFTR) gene. CFTR gene has 27 exons. The type and distribution of mutations vary widely among different countries and/or ethnic groups. Therefore, a comprehensive analysis was performed on exon10 and exon17a of CFTR gene in CF patients in the Kermanshah province, western Iran.

METHODS

We tested 27 patients admitted to the medical genetics laboratory of Kermanshah University of Medical Sciences. The patients were from different cities of Kermanshah province. All the patients had the clinical signals and two positive sweat tests. After filling agreement forms and questionnaire, the peripheral blood sampling and DNA extraction were done. DNA samples were extracted. PCR and sequencing special PCR were done. Finally analysis of the results with DNA sequencing analysis version 5.2 software was performed.

RESULTS

CFTR mutations analysis identified 4 different mutations in our CF patients. The disease-causing mutations were p.F508del (ΔF508) (14.81%), p.S466X (1.85%), and p.T1036I (1.85%). M470V polymorphism with frequency of 74.1% was found in 23 patients (17 homozygous and 6 heterozygous).

CONCLUSION

Three disease-causing mutations in CF patients in the present study account for approximately 18.51% of mutations. The frequency of p.F508del, the most common mutation was 16-18.1% in Iranian population. The results of the present study can be applied for genetic counseling, population screening and prenatal diagnosis.

Analysis of CFTR Gene Mutations in Children with Cystic Fibrosis, First Report from North-East of Iran

OBJECTIVE(S)

More than 1500 registered mutations in cystic fibrosis transmembrane regulator (CFTR) gene are responsible for dysfunction of an ion channel protein and a wide spectrum of clinical manifestations in patients with cystic fibrosis (CF). This study was performed to investigate the frequency of a number of well-known CFTR mutations in North Eastern Iranian CF patients.

MATERIAL AND METHODS

A total number of 56 documented CF patients participated in this study. Peripheral blood was obtained and DNA extraction was done by the use of routin methods. Three steps were taken for determining the target mutations: ARMS-PCR was performed for common CFTR mutations based on previous reports in Iran and neighboring countries. PCR-RFLP was done for detection of R344W and R347P, and PCR-Sequencing was performed for exon 11 in patients with unidentified mutation throughout previous steps. Samples which remained still unknown for a CFTR mutation were sequenced for exon 12.

RESULTS

Among 112 alleles, 24 mutated alleles (21.42%) were detected: ΔF508 (10.71%), 1677delTA (3.57%), S466X (3.57%), N1303K (0.89%), G542X (0.89%), R344W (0.89%), L467F (0.89%). Eight out of 56 individuals analyzed, were confirmed as homozygous and eight samples showed heterozygous status. No mutations were detected in exon 12 of sequenced samples.

CONCLUSION

Current findings suggest a selected package of CFTR mutations for prenatal, neonatal and carrier screening along with diagnosis and genetic counseling programs in CF patients of Khorasan.

Clinical and genetic features in patients with cystic fibrosis in southwestern iran

OBJECTIVE

Cystic fibrosis (CF) is a common autosomal recessive genetic disease caused by a mutation in the CF transmembrane conductance regulatory (CFTR) gene. This study attempted to identify the most common CFTR mutations and any correlations between certain mutations and the clinical presentation of the disease in CF patients in southwestern Iran.

METHODS

Twenty nine common CFTR gene mutations were examined in 45 CF patients.

FINDINGS

Chronic cough, intestinal obstruction, dehydration, heat exhaustion and steatorrhea were the most common early clinical symptoms among our patients. The most common mutation was ΔF508, with an allele frequency of 21%. The homozygous ΔF508 mutation was observed in eight patients (18%), and three patients (7%) were ΔF508 carriers. The 2183AA > G mutation was observed in four patients, one of whom was also a ΔF508 carrier. The R1162X mutation was detected in two patients. The G542X, R334W and N1303K mutations were detected each in one patient, the first of whom was also a ΔF508 carrier.

CONCLUSION

Out of 45 patients, 27 (60%) had none of the CFTR gene mutations we tested for. The most frequent mutations in southwestern Iranian patients with CF should be identified by sequencing the entire CFTR gene in order to optimize the design of a diagnostic kit for common regional mutations.

Analysis of c.3499+200TA(7_56) and D7S523 Microsatellites Linked to Cystic Fibrosis Transmembrane Regulator

Cystic fibrosis (CF) is a life-limiting autosomal recessive disorder affecting principally respiratory and digestive system. It is caused by cystic fibrosis transmembrane conductance regulator (CFTR) gene mutation. The aim of this study was to determine the extent of repeat numbers and the degree of heterozygosity for c.3499+200TA(7_56) and D7S523 located in intron 17b and 1 cM proximal to the CFTR gene respectively. Both microsatellites were analyzed by direct electrophoresis of PCR product on 20% polyacrylamide gel in 40 Normal subjects and 40 CF patients originating from North Iran. 9 different alleles were found for D7S523 ranging from 16 to 24 repeats alleles. (CA)20 was the most prevalent allele both in normal individuals and CF patients with 21.3% and 20% frequencies respectively. Heterozygosity frequency of D7S523 in normal individuals and CF patients was 97.5% and 90% respectively. Eighteen different alleles were found for c.3499+200TA(7_56) ranging from 8 to 38 repeats alleles. (TA)9 was the most prevalent allele both in normal individuals and CF patients with 30% and 23.5% frequencies respectively. All normal subjects and 97.5% of CF patients showed heterozyous genotype. The high heterozygosity of the two studied microsatellites witnesses the dynamism of such markers. High degree of heterozygosity of c.3499+200TA(7_56) and D7S523 make these markers, a very useful tool for prenatal diagnosis especially in Iranian population.

Detecting Common CFTR Mutations by Reverse Dot Blot Hybridization Method in Cystic Fibrosis First Report from Northern Iran

OBJECTIVE

Cystic fibrosis and its distribution vary widely in different countries and/or ethnic groups. Common cystic fibrosis transmembrane conductance regulator (CFTR) mutations were reported from Iran, but the northern population was not or underrepresented in those studies. The aim of this study was to determine the frequency of common CFTR mutations in children from northern Iran.

METHODS

Thirty unrelated Iranian cystic fibrosis patients aged less than 11 years and living in Mazandaran province (in Iran) were screened for 5 common CFTR gene mutations. deltaF508, N1303K, G542X, R347H and W1282X using Reverse Dot Blot method.

FINDINGS

Only one mutation, DeltaF508, was found in 7 patients accounting for 21.7% (13/60) of alleles.

CONCLUSION

These findings can be used for planning future screening and appropriate genetic counseling programs in Iranian CF families.

Contributions of MYOC and CYP1B1 mutations to JOAG

PURPOSE

To investigate the role of MYOC and CYP1B1 in Iranian juvenile open angle glaucoma (JOAG) patients.

METHODS

Twenty-three JOAG probands, their available affected and unaffected family members, and 100 ethnically matched control individuals without history of ocular disease were recruited. Clinical examinations of the probands included slit lamp biomicroscopy, intraocular pressure (IOP) measurement, gonioscopic evaluation, fundus examination, and perimetry measurement. Familial cases were classified according to the mode of inheritance. Exons of MYOC and CYP1B1 were sequenced, and novel variations assessed in the control individuals. Potential disease-associated variations were tested for segregation with disease status in available family members.

RESULTS

The mode of inheritance of the disease in the families of four probands (17.4%) appeared to be autosomal dominant and in at least eight (34.8%) to be autosomal recessive. Four patients carried MYOC mutations, and an equal number carried CYP1B1 mutations. The MYOC mutations were heterozygous; two of them (p.C8X and p.L334P) are novel, and one codes for the shortest truncated protein so far reported. Autosomal recessive inheritance was consistent with inheritance observed in families of patients carrying CYP1B1 mutations. All these patients carried homozygous mutations.

CONCLUSIONS

MYOC and CYP1B1 contributed equally to the disease status of the Iranian JOAG patients studied. The contribution of the two genes appeared to be independent in that no patient carried mutations in both genes. The fraction of Iranian patients carrying MYOC mutations was comparable to previously reported populations.

CYP1B1 mutation profile of Iranian primary congenital glaucoma patients and associated haplotypes

The mutation spectrum of CYP1B1 among 104 primary congenital glaucoma patients of the genetically heterogeneous Iranian population was investigated by sequencing. We also determined intragenic single nucleotide polymorphism (SNP) haplotypes associated with the mutations and compared these with haplotypes of other populations. Finally, the frequency distribution of the haplotypes was compared among primary congenital glaucoma patients with and without CYP1B1 mutations and normal controls. Genotype classification of six high-frequency SNPs was performed using the PHASE 2.0 software. CYP1B1 mutations in the Iranian patients were very heterogeneous. Nineteen nonconservative mutations associated with disease, and 10 variations not associated with disease were identified. Ten mutations and three variations not associated with disease were novel. The 13 novel variations make a notable contribution to the approximately 70 known variations in the gene. CYP1B1 mutations were identified in 70% of the patients. The four most common mutations were G61E, R368H, R390H, and R469W, which together constituted 76.2% of the CYP1B1 mutated alleles found. Six unique core SNP haplotypes were identified, four of which were common to the patients with and without CYP1B1 mutations and controls studied. Three SNP blocks determined the haplotypes. Comparison of haplotypes with those of other populations suggests a common origin for many of the mutations.

Analysis of the CFTR gene in Iranian cystic fibrosis patients: identification of eight novel mutations

BACKGROUND

Cystic fibrosis (CF) is the most common inherited disorder in Caucasian populations, with over 1400 mutations identified in the Cystic Fibrosis Transmembrane conductance Regulator (CFTR) gene. Mutations in the CFTR gene may be also causative for CBAVD (Congenital Bilateral Absence of the Vas Deferens). The type and distribution of mutations varies widely between different countries and/or ethnic groups, and is relatively unknown in Iran. We therefore performed a comprehensive analysis of the CFTR gene in Iranian CF patients.

METHODS

69 Iranian CF patients, and 1 CBAVD patient, were analysed for mutations in the complete coding region, and its exon/intron junctions, of their CFTR genes, using different methods, such as ARMS (amplification refractory mutation system)-PCR, SSCP (single stranded conformation polymorphism) analysis, restriction enzyme digestion analysis, direct sequencing, and MLPA (Multiplex Ligation-mediated Probe Amplification).

RESULTS

CFTR mutation analysis revealed the identification of 37 mutations in 69 Iranian CF patients. Overall, 81.9% (113/138) CFTR genes derived from Iranian CF patients could be characterized for a disease-causing mutation. The CBAVD patient was found to be homozygous for the p.W1145R mutation. The most common mutations were p.F508del (DeltaF508) (18.1%), c.2183_2184delAAinsG (2183AA>G) (6.5%), p.S466X (5.8%), p.N1303K (4.3%), c.2789+5G>A (4.3%), p.G542X (3.6%), c.3120+1G>A (3.6%), p.R334W (2.9%) and c.3130delA (2.9%). These 9 types of mutant CFTR genes totaled for 52% of all CFTR genes derived from the 69 Iranian CF patients. Eight mutations, c.406-8T>C, p.A566D, c.2576delA, c.2752-1_2756delGGTGGCinsTTG, p.T1036I, p.W1145R, c.3850-24G>A, c.1342-?_1524+?del, were found for the first time in this study.

CONCLUSIONS

We identified 37 CFTR mutations in 69 well characterized Iranian CF patients, obtaining a CFTR mutation detection rate of 81.9%, the highest detection rate obtained in the Iranian population so far. These findings will assist in genetic counseling, prenatal diagnosis and future screening of CF in Iran.