The Molecular Analysis of β-Thalassemia Mutations in Lorestan Province, Iran

The Spectrum of HBB Mutations among 2315 Beta Thalassemia Patients of a Reference Clinic in Tehran-Iran

Beta Thalassemia is the most prevalent and well-studied single gene disorder in Iran. Here, we investigated the spectrum of HBB gene mutations, identified among 2315 patients, referred to a reference thalassemia clinic in Tehran, on the basis of suspicion to thalassemia major or intermedia. The patients were homozygous or compound heterozygous for HBB mutations, and were referred from various Iranian provinces, during 15 years (2001- 2016). The HBB mutations were classified based on their frequency, and the result was compared to a meta-analysis of 14,293 beta thalassemia cases in the Iranian population, within the same time period. The mutation spectrum in this study contained 43 HBB mutations, compared to the 90, presented by the meta-analysis. Similar to the meta-analysis, IVSII-1 (G > A) and IVSI-5 (G > C) were the most common mutations in this study. These two comprised 62.40% of the total HBB mutant alleles in the studied population, comparable to 51.92% of that in the meta-analysis. IVSII-1 (G > A) and IVSI-5 (G > C), followed by 17 other mutations that had frequencies ranging from 0.15% to 5.44%, were among the 20 common HBB mutations in Iran and neighboring countries, according to the meta-analysis. This study provided further evidence to support the spectrum of the most common HBB mutations in the Iranian population.

The Effect of HBB: c.-121C>T Variant [-71 (C>T)] on the β-Globin Promoter: Case Series Study

One of the effective strategies in controlling thalassemia is recognition of carriers, followed by prenatal diagnosis (PND) to prevent the occurrence of new cases. There are some rare mutations and variants, for which there are not enough evidences of their effects, and can lead to misdiagnosis and even cause confusion in decision about termination of pregnancy. That is why it is very critical to know the effect of each mutation on the β chain gene. The variant of HBB: c.-121C>T [-71 (C>T)] located in the CAAT box of the promoter region, is a rare mutation. We report seven patients in Hormozagn Province, Iran, who were referred to the PND Center of Hormozgan University of Medical Science (HUMS), Bandar Abbas, Iran during 10 years (2010-2020). Briefly, this mutation causes minor changes in blood indices [mean corpuscular volume (MCV): 75.0 ± 4.0 fL; mean corpuscular hemoglobin (MCH): 25.8 ± 2.5 pg; Hb A₂: 3.4 ± 0.5%] showed anemia with a trait milder than minor β-thalassemia (β-thal). Though the existence of α mutations (deletions/point mutations) along with HBB: c.-121C>T can change blood indices due to the changes in α/β ratio. The phenotype of β-thal intermedia (β-TI) was observed in one case, who was a compound heterozygosity for codon 15 (G>A)/-71(C>T) (HBB: c.48G>A/HBB: c.-121C>T. The analysis of transcription level by real-time polymerase chain reaction (real-time PCR) confirmed that this allele induces a mild β⁺ phenotype due to a decrease in the transcription level.

The worldwide molecular spectrum and distribution of thalassaemia: a systematic review

CONTEXT

Thalassaemia is one of the most common inherited autosomal recessive disorders around the world. A considerable amount of literature has been published about the type of mutations and the prevalence of thalassaemia, but findings are often contradictory.

OBJECTIVE

This systematic review aimed to provide a comprehensive view of the prevalence of thalassaemia-associated mutations in different countries, their effect on haemoglobin (Hb) levels, as well as reporting thalassaemia-associated rare mutations.

METHODS

A systematic search of the literature was carried out through major indexing databases (MEDLINE/PubMed, Scopus, EMBASE, Cochrane central, and ISI web of science) using keywords: "Co-inheritance, αα, β, thalassaemia" and "α-β thalassaemia, Mediterranean anemia, mutations" from 1998-September 2019. Hand-searching was also performed. There was no language restriction.

RESULTS

The initial searches yielded 1059 studies, of which 92 articles were included following inclusion and exclusion criteria. Of these, 3.3% (3) of articles were cohort studies, and 96.7% (89) of the remaining articles were cross-sectional studies. Our findings showed that 45.6% (42) of researchers investigated β-thalassaemia, 22.9% (21) αα-β thalassaemia, and 31.5% (29) α thalassaemia.

CONCLUSION

The present study provides valuable information about the spectrum of thalassaemia-associated mutations, which can be useful for preventing thalassaemia, reducing costs of care, reducing the treatment-related side effects, and showing the most defective mutations.HighlightEvaluating the increase or decrease in the birth prevalence of thalassaemiaIdentifying the most common and rare mutations in various parts of the worldComparing researchers' findings from various parts of the world.

Distribution of HBB Gene Mutations in the Kurdish Population of Ilam Province, West Iran

β-Thalassemia (β-thal) is one of the most common diseases in Iran. Here, we report the spectrum of HBB gene mutations in 176 Kurdish β-thal carriers from the northern part of Ilam Province, Iran. The amplification refractory mutation system-polymerase chain reaction (ARMS-PCR) technique was used to identify common β-globin gene mutations observed in Iran. Samples negative on ARMS-PCR were analyzed by direct sequencing of the β-globin gene. In total, 12 different mutations were identified on the β-globin gene. The mutations of IVS-II-1 (G>A) (HBB: c.315+1G>A), codons 8/9 (+G) (HBB: c.27_28insG), codons 36/37 (-T) (HBB: c.112delT) and IVS-I-110 (G>A) (HBB: c.93-21G>A), were the most prevalent mutations in our samples, with frequencies of 59.09, 10.80, 7.95 and 7.39%, respectively. In general, the mutation spectrum of the β-globin gene in the northern part of Ilam Province is most similar to that in other western provinces of Iran. On the other hand, due to the high prevalence of carriers and β-thal major (β-TM) patients in this province, our results can be helpful in identifying carriers as well as at-risk fetuses through the prenatal diagnosis program.

Clinical Laboratory Manifestation and Molecular Diagnosis of β-Thalassemia Patients in Iraq

Many studies determined the demographic and ethnic border of patients with beta (β)-thalassemia mutations and their migration. The effective way to health care policy of β-thalassemia is to prevent homozygote births and reduce the severity of the disease. The objectives of this study contributed to investigating the molecular and serologic characteristics of β-thalassemia patients in Iraq. Peripheral blood samples were collected from 97 β-thalassemia patients and 32 healthy control subjects. Quantitative sandwich enzyme-linked immunosorbent assay was performed to measure serum ferritin, 25-hydroxy vitamin D, and 8-hydroxydeoxyguanosine (8-OHdG) levels. Further, the β-globin mutation detection assay involving an extensive screening of β-globin mutations by direct Sanger DNA sequencing and gap-PCR was performed to detect the Δ619 deletion mutation. The results revealed that compared with the control subjects, the β-thalassemia patients showed significantly decreased vitamin D levels and significantly increased serum ferritin and 8-OHdG levels (all, P<0.001). Molecular analysis detected 9 types of mutations in the β-thalassemia patients, only 2 of which, namely IVS II-1 G>A and IVS 1-5 G>C, have been previously reported in Iraqi studies, whereas the remaining 7, namely IVS-II-666 C>T, CD2 CAT>CAC, IVS-II-850 G>A, IVS-II-16 G<C, Hb King's Mill, Hb Saveh, and IVS-II-81 C>T, have never been reported in the Iraqi population. This study showed that the serum ferritin and 8-OHdG levels were significantly higher, and the serum 25-hydroxy vitamin D levels were significantly lower in the β-thalassemia patients than in the control subjects. Moreover, the results revealed seven newly identified mutations among Iraqi β-thalassemia patients and 2 previously reported mutations.

The Spectrum of β-Thalassemia Mutations in Hamadan Province, West Iran

β-Thalassemia (β-thal) is one of the most common hemoglobinopathies worldwide and is caused by mutations on the β-globin (HBB) gene. The aim of the present study was to determine the mutation spectrum of the β-globin gene in β-thal carriers who were originally from Hamadan Province, Western Iran. Two hundred and eighty-two β-thal carriers participated in the study. Amplification refractory mutation system-polymerase chain reaction (ARMS-PCR) and direct sequencing were used for detection of different mutations. A total of 25 different mutations, including 21 β-thal mutations and four other hemoglobin (Hb) variants, in 280 β-thal carriers (99.3%) were detected in the present study. Three types of mutations including IVS-II-1 (G>A) (HBB: c.315+1G>A) (26.24%), codons 8/9 (+G) (HBB: c.27_28insG) (14.54%) and codons 36/37 (-T) (HBB: c.112delT) (12.76%) accounted for more than 50.0% of the identified mutations. Moreover, IVS-I-110 (G>A) (HBB: c.93-21G>A), codon 44 (-C) (HBB: c.135delC) and IVS-I (25 bp deletion) (HBB: c.93-21_del), had frequencies of 7.09, 7.09 and 5.67%, respectively. Allele frequencies of the remaining 19 mutations were less than 5.0%. This study is the first comprehensive study on a large sample size in Hamadan Province, Iran. In conclusion, the present study significantly increased the spectrum of HBB gene mutations in Hamadan Province compared with previous studies. Therefore, these results can be helpful in identifying β-thal carriers and at-risk fetuses through prenatal diagnosis (PND).

Novel Multiplex Fluorescent PCR-Based Method for HLA Typing and Preimplantational Genetic Diagnosis of β-Thalassemia

BACKGROUND AND AIMS

Thalassemia is curable by bone marrow transplantation; however, finding suitable donors with defined HLA combination remains a major challenge. Cord blood stem cells with preselected HLA system through preimplantation genetic diagnosis (PGD) proved very useful for resolving scarce HLA-matched bone marrow donors.

METHODS

A thalassemia trait couple with an affected child was included in this study. We used informative STR markers at the HLA and beta globin loci to develop a single cell multiplex fluorescent PCR protocol. The protocol was extensively optimized on single lymphocytes isolated from the couple's peripheral blood. The optimized protocol was applied on single blastomeres biopsied from day 3 cleavage stage IVF embryos of the couple.

RESULTS

Four IVF embryos biopsied on day 3 and a single blastomere of each were provided for genetic diagnosis of combined β-thalassemia mutations and HLA typing. Of these, one embryo was diagnosed as homozygous normal for the thalassemia mutation and HLA matched with the existing affected sibling.

CONCLUSION

The optimized protocol worked well in PGD clinical cycle for selection of thalassemia-unaffected embryos with the desired HLA system.

The Frequency of HBB Mutations Among β-Thalassemia Patients in Hamadan Province, Iran

β-Thalassemia (β-thal) caused by mutations on the HBB gene is the most common single-gene disorder in the world. In this study, the HBB gene mutation was investigated in Hamadan province, Iran. Forty-one patients referred to a referral hospital were admitted to the study. DNA samples were extracted from peripheral blood. The HBB gene was sequenced in all recruited patients. Eleven mutations and eight polymorphisms were found in the studied patients. IVS-II-1 (G>A) (HBB: c.315+1 G>A) was the most common mutation, accounting for 25.61% of mutant alleles. Other mutations included codon 8 (-AA) (HBB: c.25-26delAA); IVS-I-110 (G>A) (HBB: c.93-21 G>A); codons 8/9 (+G) (HBB: c.27-28insG); IVS-I-1 (G>A) (HBB: c.92 G>A); codon 44 (-C) (HBB: c.135delC); codons 25/26 (+T) (HBB: c.78-79insT); IVS-I-130 (G>C) (HBB: c.93-1 G>C); -28 (A>C) (HBB: c.-78 A>C); codons 36/37 (-T) (HBB: c.112delT) and IVS-I-6 (T>C) (HBB: c.92+6 T>C). According to our findings, the IVS-II-1 mutation has the highest prevalence in Hamadan Province. It was found that the total frequency of the IVS-II-1, codons 25/26 (+T), codons 8/9 (+G), IVS-I-110 and IVS-I-1 mutations was 82.92%. Therefore, given these findings, it is recommended that these five mutations are screened for as a first step in laboratories without sequencing instruments, and that the rest of the gene is subsequently examined.

Effectiveness of β-thalassemia prenatal diagnosis in Southern Iran: a cohort study

AIM

The aim of this study was to evaluate the effectiveness of prenatal diagnosis (PND) for the prevention of thalassemia in Southern Iran.

METHODS

From 2004 to 2012 1346 couples with β-thalassemia minor were referred to our center. Mutation analyses utilized different methods including polymerase chain reaction-based technique of amplification refractory mutation system (ARMS), Restriction Fragment Length Polymorphism Analysis of PCR-Amplified Fragments (PCR-RFLP) and Gel Electrophoresis and direct sequencing. Haplotype analysis of the β-globin gene cluster was done routinely using the PCR-RFLP technique.

RESULTS

Of the 1346 couples, 884 (66%) requested PND. They had a total of 985 pregnancies (954 singleton and 31 twin pregnancies): the 1016 fetuses underwent chorionic villus sampling (CVS). Thalassemia major was diagnosed in 266 cases (26.2%), and termination of pregnancy was requested by the parents in 264 of them (99%). Thalassemia trait was detected in 499 (49.1%) and 251 cases (24.7%) showed no β-thalassemia mutations. There were three misdiagnoses (0.4%) (affected children diagnosed as carriers at PND). A unique pattern of thalassemia mutations was present in the study population, with IVS II-I (G→A), C36-37(-T), IVS I-5(G>C), -25bpdel (252-276), IVS I-110(G>A) and C44 (-C) being present in 62% of cases.

CONCLUSION

The pattern of distribution of thalassemia mutations differs among ethnic groups within the same country.

Genetic epidemiology, hematological and clinical features of hemoglobinopathies in Iran

There is large variation in the molecular genetics and clinical features of hemoglobinopathies in Iran. Studying structural variants of hemoglobin demonstrated that the β-chain variants of hemoglobin S and D-Punjab are more prevalent in the Fars (southwestern Iran) and Kermanshah (western Iran) provinces, respectively. Also, α-chain variants of Hb Q-Iran and Hb Setif are prevalent in western Iran. The molecular basis and clinical severity of thalassemias are extremely heterogenous among Iranians due to the presence of multiethnic groups in the country. β-Thalassemia is more prevalent in northern and southern Iran. Among 52 different β-thalassemia mutations that have been identified among Iranian populations, IVSII-1 G:A is the most frequent mutation in most parts of the country. The presence of IVS I-5 G:C mutation with high frequency in southeastern Iran might reflect gene flow from neighboring countries. A wide spectrum of α-thalassemia alleles has been detected among Iranians with -α(3.7 kb) as the most prevalent α-thalassemia mutation. The prevention program of thalassemia birth in Iran has reduced the birth rate of homozygous β-thalassemia since the implementation of the program in 1997. In this review genetic epidemiology, clinical and hematological aspects of hemoglobinopathies, and the prevention programs of β-thalassemia in Iran will be discussed.

Profile of β-thalassemia and its prenatal diagnosis in Khorasan-e-Jonobi Province, Iran

This study was performed to determine the molecular spectrum of β-thalassemia (β-thal) mutations in at-risk couples from Khorasan-e-Jonobi Province in East Iran. During the past 9 years, 106 couples were referred to our Center for detection of their β-thal carrier status. Samples were initially tested for the most common Iranian α- and β-thal mutations by gap-polymerase chain reaction (gap-PCR) and amplification refractory mutation system (ARMS)-PCR, respectively. In cases with negative results, direct DNA sequencing was used to identify additional β-globin mutations. Fetal DNA was obtained from chorionic villus sampling (CVS) (n = 55), 47.2% were referred during pregnancy and 23.0% of couples underwent more than one prenatal diagnosis (PND). Of the 14 mutations that were detected in Khorasan-e-Jonobi Province, Iran, the IVS-I-5 (G>C) and codon 44 (-C) mutations were the most frequently identified variants, representing 45.9 and 24.8% of the total; these were followed by three mutations in the following order: -88 (C >T) (5.3%); codons 8/9 (+G), a rare mutation, and codons 37/38/39 [-7 nucleotides (nts)], each with a frequency of 4.5%. These findings provide complementary information on the region specific profile of β-thal in eastern Iran.

Molecular basis and prenatal diagnosis of β-thalassemia among Balouch population in Iran

OBJECTIVE

To determine the molecular spectrum of β-thalassemia mutations among at-risk Balouch couples in Iran.

METHODS

Mutations' detection in DNAs extracted from the blood of partners of at-risk couples was characterized, and chorion villus sampling by amplification refractory mutation system and DNA sequencing was performed. Fetal diagnosis was also confirmed by linkage analysis.

RESULTS

Out of a total of 1234 at-risk Balouch couples referred to the center for prenatal diagnosis (PND) from June 2002 to June 2010, a high percentage of '67.4%' were from consanguineous marriages and 37.4% had between one and four affected children. The trend in referring gradually increased from 34 cases in 2002 to 357 cases in 2010. The astonishing finding was that, unlike most previous studies, only IVS 1-5 with an unusual frequency of 87.20% along with codon 8/9 (+G) with 4% constitutes about 91% of mutations. Altogether, 729 PNDs were made in 583 couples, 25% of whom had over one PND, and surprisingly five PNDs were made in the same woman within just 8 years.

CONCLUSION

Regarding the limited types of frequent mutations among Balouch population, it is hopefully believed that the incidence of β-thalassemia could be controlled by a correct diagnosis in the due time.

Global burden, distribution and prevention of β-thalassemias and hemoglobin E disorders

The β-thalassemias, including the hemoglobin E disorders, are not only common in the Mediterranean region, South-East Asia, the Indian subcontinent and the Middle East but have now become a global problem, spreading to much of Europe, the Americas and Australia owing to migration of people from these regions. Approximately 1.5% of the global population are heterozygotes or carriers of the β-thalassemias. While the overall frequencies of carriers of these disorders are known in most countries, there have been few attempts at micromapping and wherever this has been done, significant variations are seen even within small geographic regions. Thus, the figures for the estimated numbers of births each year of homozygous β-thalassemia and the severe compound states involving other hemoglobin disorders may be an underestimate. Screening strategies have varied from premarital to antenatal in different countries depending on socio-cultural and religious customs in different populations. Prenatal diagnosis programs are ongoing in many countries and the knowledge of the distribution of mutations has facilitated the establishment of successful control programs. Many of these were through North-South partnerships and networking. Yet, there are many countries in Asia where they are lacking, and South-South partnerships are now being developed in South-East Asia and the Indian subcontinent to link centers with expertise to centers where expertise needs to be developed. Although the carrier frequencies will remain unaltered, this will eventually help to bring down the burden of the birth of affected children with β-thalassemias and hemoglobin E disorders in Asia.

Comprehensive spectrum of the β-Thalassemia mutations in Khuzestan, southwest Iran

β-Thalassemia (β-thal) is characterized by reduction or absence of β-globin gene expression. We describe the spectrum of mutations observed in a large cohort of β-thal carriers in Khuzestan, Southwest Iran. All together 1,241 blood samples from individuals with decreased mean corpuscular volume (MCV) and elevated Hb A(2) levels, were analyzed either by reverse dot-blot or by direct sequencing of the HBB gene. We found 42 different mutations associated with β-thal and identified eight common β-globin variants, namely, Hb S [β6(A3)Glu→Val], Hb C [β6(A3)Glu→Lys], Hb D-Punjab [β121(GH4)Glu→Gln] and Hb O-Arab [β121(GH4)Glu→Lys]. No mutations were found in two individuals. The distribution is characteristic of a heterogenous population with three preferential mutations being present [codons 36/37 (-T), IVS-II-1 (G>A) and IVS-I-110 (G>A)] at a frequency of 20.5, 20.0 and 14.2%, respectively, followed by 39 mutations in decreasing frequencies from 5.2 down to 0.1%. These data are of importance when planning prevention strategies in the country.

β-Thalassemia mutations in the Kurdish population of northeastern Iraq

A random 123 carriers of β-thalassemia (β-thal), identified by the Sulaimaniyah Provincial Premarital Screening Program in northeastern Iraq, were screened for β-thal mutations using multiplex polymerase chain reaction followed by reverse hybridization StripAssay and direct sequencing. A total of 11 different β-thal mutations was identified in the studied samples, of which eight represented 96% of the mutated β-globin genes. These were IVS-II-1 (G>A), IVS-I-110 (G>A), codon 8 (-AA), codons 8/9 (+G), IVS-I-5 (G>C), codon 5 (-CT), IVS-I-6 (T>C) and IVS-I-1 (G>A). Other mutations were less common or sporadic. There were some notable differences in frequencies of various mutations in comparison to other eastern Mediterranean populations, as well as with previous studies of Iraqi Kurds. The latter illustrate the relative heterogeneity of the mutations distributed in Iraq, and the need to screen other areas of the country, to ensure the establishment of an effective prenatal diagnosis program.

β-Thalassemia Mutations among Transfusion-Dependent Thalassemia Major Patients in Northern Iraq

Molecular defects responsible for β-thalassemias (thal) were investigated among 254 chromosomes from 127 transfusion-dependent unrelated thalassemic patients from two provinces in Northern Iraq. Among fourteen identified mutations, the seven most common found in 88.2% of the thal chromosomes were: IVS-II-1 (G → A), IVS-I-1 (G → A), codon 8 (−AA), codon 39 (G → T), codon 8/9 (+G), codon 44 (−C), and codon 5 (−CT). There were some notable differences in frequencies of various mutations in comparison to other Eastern Mediterranean populations, as well as between the two provinces studied. The latter illustrates the relative heterogeneity of the mutations distribution in Iraq, and the need to screen other areas of the country, to ensure establishing an effective prenatal program.

Identification of three novel mutations [-41 (A>C), codon 24 (-G), and IVS-I-109 (-T)], in a study of beta-thalassemia alleles in the Isfahan region of Iran

Beta-thalassemia (beta-thal) is one of the most common autosomal recessive disorders in Iran, with more than 15,000 registered cases of thalassemia major in the country. Iran has a multiethnic society and knowledge of the mutation spectrum and regional distribution is an essential requirement for health planning and a prenatal diagnosis program. We have determined the spectrum of mutations in patients from the Isfahan region of Iran. A study of 190 chromosomes revealed 24 different mutations, including three novel ones: -41 (A>C), IVS-I-109 (-T) and codon 24 (-G). The most common mutation was IVS-II-1 (G>A) (20.5%), followed by IVS-I-5 (G>C) (11%). The findings for the Isfahan region confirm the extremely heterogeneous nature of the molecular basis of beta-thal in Iran. The results show that a strategy of using the amplification refractory mutation system-polymerase chain reaction (ARMS-PCR) for 14 of the most common mutations and DNA sequencing for the rare mutations can be used for prenatal diagnosis of beta-thal in this region.

Is the frameshift codons 8/9 (+G) [FSC 8/9 (+G)] beta-thalassemia mutation, detected by the polymerase chain reaction-amplification refractory mutation system, really FSC 8/9 (+G)?

There are several polymerase chain reaction (PCR)-based approaches for the analysis of known mutations. The PCR-amplification refractory mutation system (PCR-ARMS) is one of the best known and frequently used for the detection of beta-thalassemia (beta-thal) mutations. However, there is an important point to be considered when searching for the frameshift codon (FSC) 8 (-AA) and FSC 8/9 (+G) mutations. Whereas the primer is specific for the FSC 8 mutation only, the primer for the FSC 8/9 mutation does not discriminate between the FSC 8/9 and FSC 8 mutations. Thus, the high number of FSC8/9 mutations reported in countries like India, Pakistan and some regions of Iran may be due to the use of the FSC 8/9 primer, without taking the FSC 8 mutation into account. It is thus advisable to test for FSC 8 before the FSC 8/9 mutation whenever PCR-ARMS is the method of investigation for these two mutations.