Mutational spectrum of thalassemias in India

Mutation Analysis of Exon 1 in the Hemoglobin Subunit Beta (HBB) Gene in Beta-Thalassemia

Introduction Thalassemia is a widely prevalent monogenic hematological disorder found worldwide. It exists in two forms: alpha- and beta-thalassemia. Alterations in the hemoglobin subunit beta (HBB) gene cause beta-thalassemia, with missense and point mutations affecting beta-globin synthesis. Consequently, genetic screening for beta-thalassemia is essential for genetic counseling, carrier screening, and prenatal diagnosis. Aim and objective This study aims to examine and identify mutations in the exon 1 region of the HBB gene in beta-thalassemia patients from the Vijayapura region. Methods This study involved 47 clinically diagnosed children with beta-thalassemia from a hospital in Vijayapura, India. Detailed clinical histories of all patients were recorded. Genomic DNA was extracted from the blood samples of these patients and subjected to polymerase chain reaction (PCR) using exon-specific primers for the HBB gene. The PCR products were then sequenced using the capillary-based Sanger sequencing method to identify mutations in the HBB gene. Results A total of 47 clinically diagnosed beta-thalassemia patients were included in the study, comprising 30 males and 17 females, aged between one and 20 years. Sequencing analysis of exon 1 in the beta-globin gene identified 17 beta-thalassemia variants. The most common mutation observed was T>G, G>C, C>A, and C>T in the exon 1 region of the HBB gene.  Conclusion This study identifies the pattern of beta-thalassemia mutations, aiding in the prevention of the disorder through prenatal diagnosis and genetic counseling. Mutations can alter codon sequences, affecting protein production. Research highlights the importance of a primary prevention program to analyze mutations and sequence variations at the molecular level, thereby helping to address numerous genetic disorders.

Spectrum of Rare and Novel Indel Mutations Responsible for β Thalassemia in Eastern India

There is limited data available regarding the clinical utility of routine molecular diagnosis of β Thalassaemia in addition to HPLC-based screening in low resource settings. The current study highlights the caveats of an HPLC-based screening compared to the inclusion of genetic confirmation as a second-tier test and its implications in terms of genotype-phenotype correlation. A prospective, institution-based, observational study was conducted at the Department of Paediatric Medicine, including 103 children aged up to 12 years. Five common mutations for β Thalassemia and the HbE mutation in the HBB gene were tested by a two-tiered approach using multiplex ARMS PCR and PCR RFLP methods respectively. Sanger sequencing of all three exons of the HBB gene was performed in all negative cases. Sequencing revealed many rare pathogenic mutations like c.316-106 C > G (dbSNP: 34,690,599); Hb Kairouan (c.92G > C); c.33 C > A (dbSNP rs35799536); c.47G > A (dbSNP rs63750783); c.51delC (HbVar ID 799); c.[93-2 A > C] and c.118 C > T (HbVar ID 845). We detected a novel Pathogenic M_000518.5(HBB):c.164_168delinsGGCATCA (p.Val55fs) mutation in a heterozygous state which was reported in the ClinVar database with accession ID VCV000590977.2. We also encountered several cases of silent carrier on HPLC and de novo occurrence of mutation. We conclude that the multiplex touchdown ARMS PCR methodology employed in the present study provides a low-cost solution for molecular diagnostics of Β Thalassaemia. The problem of silent carriers in HPLC is significant enough to rethink if we need supplemental genetic testing in the couple when one of the partners is a carrier.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12291-022-01098-w.

Global distribution of β-thalassemia mutations: An update

One excellent illustration of how a single gene abnormality may result in a spectrum of disease incidence is the incredible phenotypic variety of β-thalassemia, which spans from severe anemia and transfusion needs to an utterly asymptomatic sickness. However, genetic causes of β-thalassemia and how the anemia's severity might be altered at various stages in its pathophysiology have been well investigated. There are currently known to be more than 350 mutations that cause genetic disease. However only 20 β thalassemia mutations account for more than 80% of the β thalassemia mutation across the globe due to phenomenon of geographical clustering where each population has a few common mutations together with a varying number of rare ones. Due to migration of the population, the spectrum of thalassemia mutation in changing from time to time. In this review, efforts are made to collate β globin gene mutations in different countries and populations.

Hematological and genetic profiles of persons with co-inherited heterozygous β-thalassemia and supernumerary α-globin genes

INTRODUCTION

Thalassemias are common monogenic autosomal recessive hemoglobin disorders. The usually asymptomatic heterozygotes (β-thalassemia traits, βTT) may rarely develop non-transfusion-dependent-thalassemia (NTDT) due to co-inheritance of supernumerary α-globin genes. Literature on phenotypic/genotypic features of these rare combinations is limited.

MATERIALS AND METHODS

We studied the demographic, clinical, and laboratory data from 47 persons with co-inherited βTT + supernumerary α-globin genes. HBB mutations were tested for by ARMS-PCR and/or Sanger sequencing, ααα^(anti3.7) /ααα^(anti4.2) and deletional α-thalassemia testing by multiplex gap-PCRs, and Xmn1^G γ genotyping by PCR-RFLP.

RESULTS

The 47 cases comprised 0.08% of 61 010 hemoglobinopathy screenings during the study period. Mean age was 31.9 ± 14.7 years (range 5.5-83 years), with 57.4% males. Thirty (63.8%) had NTDT-phenotype, 16 (34%) were asymptomatic/minimally symptomatic, and 1 became transfusion-dependent at the age of 20 years. Anemia/pallor and jaundice were the commonest complaints (76% each); 40% had required blood transfusions. Twenty-one had splenomegaly, 14 had hepatomegaly. Mean hemoglobin was 9.0 ± 1.9 g/dl (range 4.0-13.0). HbA2 was 5.1 ± 0.7% (3.4%-6.3%) and HbF% 4.2 ± 3.2% (0.5%-18.4%). Forty-four (93.6%) had ααα^anti3.7 , while 3 (6.4%) had ααα^anti4.2 triplications. HBB:c.92+5G>C (47%), HBB:c.27_28insG (14.9%), and HBB:c.47G>A (8.5%) were the commonest β-globin mutations. One case showed HBB:c.-138C>T (β⁺⁺ ), while the rest had β⁰ or severe-β⁺ mutations. Symptomatic cases had significantly lower hemoglobins and higher HbF% than asymptomatic ones.

CONCLUSION

This largest Indian and globally second-largest study reports the βTT + ααα^4.2 state for the first time in such genotypically-complex Indian cases. Supernumerary α-genes should be suspected in all βTT with disproportionate clinical symptoms, mild-to-moderately elevated HbF, and unexplained anisopoikilocytosis.

Dutch-beta thalassemia: A rare mutation from India

Introduction

Aims

Materials and methods

Results

Conclusion

Identifying Gingival Pigmentation Patterns and Skin Color and Its Co-relation With Serum Ferritin Levels in Thalassemic Patients

Background: Patients with β-thalassemia major (β-TM), a genetic issue due to hemoglobin (Hb) synthesis disorder, require life-long erythrocyte transfusion. The purpose of this study is to evaluate and compare gingival pigmentation and skin color with serum ferritin levels of patients with β-TM, using the Dummett's oral pigmentation index (DOPI) and Fitzpatrick skin scale, respectively.

Methods: A total of 100 patients were monitored at a thalassemia care center. Each patient's gingival pigmentation and skin color were matched with DOPI and the skin scale under natural light. Serum ferritin levels, the interval of blood transfusions, and iron chelation medications were studied. A gingival pigmentation score and skin color type were compared with the serum ferritin.

Results: A significant correlation was found between age, serum ferritin, pigmentation score, and skin color, which means as serum ferritin level increases, gingival pigmentation score increases, and skin color darkens.

Conclusion: This study evaluated the correlation between gingival pigmentation and skin color with serum ferritin levels and established gingival pigmentation as a sign of iron deposition in β-TM patients. This is the simplest and least invasive method for evaluating serum ferritin level parameters in β-TM patients.

Molecular heterogeneity of β-thalassemia variants in the Eastern region of Morocco

Background

β‐thalassemia syndromes are the most common hereditary blood disorders in the world and are recognized as a major health problem in Morocco. They are characterized by the reduction or the absence of β‐globin chain synthesis. The severity of the disease depends on the nature of the variants affecting the β‐globin gene (HBB), and each ethnic group has its own mutation spectrum. Hereby, we present, for the first time, the molecular profile of β‐thalassemia in the Eastern region of Morocco.

Methods

This study concerns 39 cases from 33 families who were enrolled in the BRO Biobank. Nineteen were diagnosed with β‐thalassemia major and 20 with β‐thalassemia minor. To detect mutations of the β‐globin gene, we have used RFLP‐PCR and Sanger sequencing.

Results

Nine known β‐thalassemia variants have been identified. Among these, we reported, for the first time in the Moroccan population, the Czechoslovakian variant C38/39(‐C) at homozygous state. The C39(C > T) was the most frequent variant (72.54%), followed by FSC5(‐CT) (5.88%), FSC6(−A), IVS‐1‐110(G > A), −29(A > G), C38/39(‐C) (3.92% each), and finally by IVS‐I‐1(G > A), IVS‐II‐1(G > A), and −56(G > C) (1.96%). Of particular interest this mutational spectrum of β‐thalassemia is very different from that found in previous studies in Morocco or in other North African countries.

Conclusion

This study is the first contribution to the description of the molecular profile of β‐thalassemia in the Eastern region of Morocco. It shows the high molecular heterogeneity of β‐thalassemia in our country. Therefore, these results can be valuable for the implementation of carrier screening, genetic counseling, and prenatal diagnosis programs.

Molecular genetics of β-thalassemia: A narrative review

ABSTRACT

β-thalassemia is a hereditary hematological disease caused by over 350 mutations in the β-globin gene (HBB). Identifying the genetic variants affecting fetal hemoglobin (HbF) production combined with the α-globin genotype provides some prediction of disease severity for β-thalassemia. However, the generation of an additive composite genetic risk score predicts prognosis, and guide management requires a larger panel of genetic modifiers yet to be discovered.Presently, using data from prior clinical trials guides the design of further research and academic studies based on gene augmentation, while fundamental insights into globin switching and new technology developments have inspired the investigation of novel gene therapy approaches.Genetic studies have successfully characterized the causal variants and pathways involved in HbF regulation, providing novel therapeutic targets for HbF reactivation. In addition to these HBB mutation-independent strategies involving HbF synthesis de-repression, the expanding genome editing toolkit provides increased accuracy to HBB mutation-specific strategies encompassing adult hemoglobin restoration for personalized treatment of hemoglobinopathies. Allogeneic hematopoietic stem cell transplantation was, until very recently, the curative option available for patients with transfusion-dependent β-thalassemia. Gene therapy currently represents a novel therapeutic promise after many years of extensive preclinical research to optimize gene transfer protocols.We summarize the current state of developments in the molecular genetics of β-thalassemia over the last decade, including the mechanisms associated with ineffective erythropoiesis, which have also provided valid therapeutic targets, some of which have been shown as a proof-of-concept.

Novel genetic therapeutic approaches for modulating the severity of β-thalassemia (Review)

Thalassemia is a genetic haematological disorder that arises due to defects in the α and β-globin genes. Worldwide, 0.3-0.4 million children are born with haemoglobinopathies per year. Thalassemic patients, as well as their families, face various serious clinical, socio-economic, and psychosocial challenges throughout their life. Different therapies are available in clinical practice to minimize the suffering of thalassemic patients to some extent and potentially cure the disease. Predominantly, patients undergo transfusion therapy to maintain their haemoglobin levels. Due to multiple transfusions, the iron levels in their bodies are elevated. Iron overload results in damage to body organs, resulting in heart failure, liver function failure or endocrine failure, all of which are commonly observed. Certain drugs have been developed to enhance the expression of the γ-gene, which ultimately results in augmentation of fetal haemoglobin (HbF) levels and total haemoglobin levels in the body. However, its effectiveness is dependent on the genetic makeup of the individual patient. At present, allogeneic haematopoietic Stem Cell Transplantation (HSCT) is the only practically available option with a high curative rate. However, the outcome of HSCT is strongly influenced by factors such as age at transplantation, irregular iron chelation history before transplantation, histocompatibility, and source of stem cells. Gene therapy using the lentiglobin vector is the most recent method for cure without any mortality, graft rejection and clonal dominance issues. However, delayed platelet engraftment is being reported in some patients. Genome editing is a novel approach which may be used to treat patients with thalassemia; it makes use of targeted nucleases to correct the mutations in specific DNA sequences and modify the sequence to the normal wild-type sequence. To edit the genome at the required sites, CRISPR/Cas9 is an efficient and accurate tool that is used in various genetic engineering programs. Genome editing mediated by CRISPR/Cas9 has the ability to restore the normal β-globin function with minimal side effects. Using CRISPR/Cas9, expression of BCL11A can be downregulated along with increased production of HbF. However, these genome editing tools are still under in-vitro trials. CRISPR/Cas9 has can be used for precise transcriptional regulation, genome modification and epigenetic editing. Additional research is required in this regard, as CRISPR/Cas9 may potentially exhibit off-target activity and there are legal and ethical considerations regarding its use.

Molecular spectrum of α-thalassemia mutations in Erbil province of Iraqi Kurdistan

α-Thalassemia is a globally prevalent genetic disorder of hemoglobin (Hb) structure where the rate of α-globin chain synthesis is reduced or absent based on the underlying α-globin mutation(s). This study aimed to define the spectrum of α-globin gene mutations and assess their relative frequency within a group of α-thalassemia carriers. A total of 96 young subjects with unexplained hypochromia and microcytosis were recruited. They were referred from the premarital hemoglobinopathy screening and genetic counseling center in Erbil. All subjects were genetically tested for 21 common α-globin gene mutations using multiplex PCR and reverse hybridization. Six different α-globin gene mutations and nine different genotypes were detected in 84 carrier subjects. Their mean Hb was 12.9 (± 1.29) g/dL, of whom 49 subjects (58.3%) had a normal Hb level. The two most frequently encountered mutations were -α^3.7 deletion (62.86%) and α2^-5nt mutation (20%). Deletions were encountered in 71.43% of the mutated alleles. The most commonly observed genotype was -α^3.7/αα (46.43%), followed by -α^3.7/-α^3.7 and α^-5ntα/αα genotypes (10.72% each). Carriers of α^poly-A1α/αα and -α^3.7/-α^-5ntα genotypes showed significantly lower Hb, mean cell volume, and mean cell Hb values comparing to carriers of most other genotypes. In our population, the spectrum of α-globin mutations was confined to a limited number of mutations with deletions being mostly observed.

Prenatal diagnosis of α- and β-thalassemias in southern Thailand

We report our work on prenatal diagnosis of α-thalassemia, β-thalassemia and other hemoglobinopathies in southern Thailand. DNA-based diagnosis was offered to 1906 pregnancies at risk for thalassemia using a combination method of multiplex-PCR and reverse dot blot analysis to detect seven α-globin and 47 β-globin mutations. The most commonly detected mutation of α⁰-thalassemia was a South-East Asian deletion (98%), followed by a Thai deletion (2%). Twenty-eight β-globin mutations were identified. Fourteen common mutations, including cod 19 A-G (18.6%), cod 41/42 -TCTT (14.4%), IVS1#5 G-C (13.2%), 3.5 kb deletion (9.2%), cod 17 A-T (7.7%), -28 A-G (7.3%), IVSI#1 G-T (7.1%), 12.5 kb deletion (δβ)⁰ (5.7%), HPFH6 (4.2%), IVS2#654 C-T (2.7%), 45 kb deletion (1.9%), Asian Indian-inversion-deletion Gγ(Aγδβ)⁰ (1.6%), cod 41 -C (1.5%) and cod 71/72 +A (1.3%) were detected, accounting for 96.5% of all mutations detected. The most common hemoglobin variant was Hb E, accounting for 97.86%. Prenatal diagnosis of 1906 couples at risk showed 22.0% normal, 51.2% carrier and 26.8% affected. The present study provides important information for diagnosis and control of severe thalassemia diseases.

Alpha-globin gene mutation spectrum in patients with microcytic hypochromic anemia from Mazandaran Province, Iran

Background

It is estimated about 7% of the world population is carriers of hemoglobin diseases. Alpha‐thalassemia is one of the most common hereditary hemoglobin disorders in the world. This study investigated alpha‐globin mutations in potential carriers with hypochromic and microcytic anemia from Mazandaran, in northern Iran.

Methods

A total of 859 subjects were selected; genomic DNA was extracted and examined for the presence of mutations in the alpha‐globin genes.

Results

Mutation analysis of alpha‐globin genes revealed 27 different mutations. Seven variants were seen in 91.45% of all alpha‐1 and alpha‐2 mutations among patients in this study. The 3.7 kb deletion is the most frequent mutation with a frequency of 49.53%, followed by PolyA2 (15.19%), −4.2 deletion (8.76%), ‐‐MED (5.84%), IVSI‐5nt deletion (5.49%), Hb constant spring (3.62%), and Cd 19 (−G; 3.04%), respectively. There are also seven new variants which were reported for the first time either in alpha‐1 or alpha‐2 genes, including codon 9 (C > A; α2), deletion of codon 60 (AAG deletion; α2), duplication of codon 94‐100 plus 3 base pairs of intron 2 (IVSII + 3; α1), codon 99 (C > A; α2), codon 108 (A > G; α2), codon 128 (A > T; α2), and codon 129 (T > G; α2), respectively. The MLPA method also revealed three rare and novel deletions in alpha‐cluster region with about 30 kilobases long.

Conclusion

This study showed an efficient identification of α‐thalassemia can be achieved using standard hematological indices in our population. The details of these variations will help local genetic services for diagnostic and prenatal diagnosis services.

High resolution melting curve analysis targeting the HBB gene mutational hot-spot offers a reliable screening approach for all common as well as most of the rare beta-globin gene mutations in Bangladesh

BACKGROUND

Bangladesh lies in the global thalassemia belt, which has a defined mutational hot-spot in the beta-globin gene. The high carrier frequencies of beta-thalassemia trait and hemoglobin E-trait in Bangladesh necessitate a reliable DNA-based carrier screening approach that could supplement the use of hematological and electrophoretic indices to overcome the barriers of carrier screening. With this view in mind, the study aimed to establish a high resolution melting (HRM) curve-based rapid and reliable mutation screening method targeting the mutational hot-spot of South Asian and Southeast Asian countries that encompasses exon-1 (c.1 - c.92), intron-1 (c.92 + 1 - c.92 + 130) and a portion of exon-2 (c.93 - c.217) of the HBB gene which harbors more than 95% of mutant alleles responsible for beta-thalassemia in Bangladesh.

RESULTS

Our HRM approach could successfully differentiate ten beta-globin gene mutations, namely c.79G > A, c.92 + 5G > C, c.126_129delCTTT, c.27_28insG, c.46delT, c.47G > A, c.92G > C, c.92 + 130G > C, c.126delC and c.135delC in heterozygous states from the wild type alleles, implying the significance of the approach for carrier screening as the first three of these mutations account for ~85% of total mutant alleles in Bangladesh. Moreover, different combinations of compound heterozygous mutations were found to generate melt curves that were distinct from the wild type alleles and from one another. Based on the findings, sixteen reference samples were run in parallel to 41 unknown specimens to perform direct genotyping of the beta-thalassemia specimens using HRM. The HRM-based genotyping of the unknown specimens showed 100% consistency with the sequencing result.

CONCLUSIONS

Targeting the mutational hot-spot, the HRM approach could be successfully applied for screening of beta-thalassemia carriers in Bangladesh as well as in other countries of South Asia and Southeast Asia. The approach could be a useful supplement of hematological and electrophortic indices in order to avoid false positive and false negative results.

Generic Direct Acting Antivirals in Treatment of Chronic Hepatitis C Infection in Patients of Thalassemia Major

BACKGROUND

There is no published data of treating hepatitis C in thalassemia major patients with any sofosbuvir based direct acting antivirals (DAAs). This study was performed to determine the efficacy and safety of these regimes using generic drugs in the thalassemia major population.

METHODS

In this observational study, 902 patients of thalassemia major from five transfusion centres in Mumbai were screened for HCV antibody. Of the 120 positive patients, HCV RNA was detected in 50%. The first 29 patients were enrolled for evaluating the efficacy and safety of generic sofosbuvir based DAAs.

RESULTS

The 29 patients' had a mean age of 24 years with genotype 1 in 17, genotype 3 in 11patients, while 1 patient's genotype could not be classified. Six patients had compensated cirrhosis and 8 patients were treatment experienced. SVR 12 was achieved in 100% of patients. There was significant increase in PRC (packed red cell) requirements (P = 0.0003) during treatment. At 12 weeks post-treatment, PRC requirements returned to baseline with a significant fall in serum ferritin (P = 0.03). Headache, fatigue and diarrhoea were the most common side effects. The difference in side effects including anaemia between patients who received ribavirin (19/29) and those who did not receive ribavirin (10/29) was not significant. Presence of diabetes, splenectomy, high ferritin or liver or heart iron overload on MRI T2* did not affect the efficacy of treatment.

CONCLUSION

Generic DAAs are safe in thalassemia major patients with hepatitis C with efficacy of 100%. Serum ferritin falls significantly after treatment despite an increase in transfusion requirements during treatment.

Is hemoglobin e gene widely spread in the state of madhya pradesh in central India? Evidence from five typical families

Background

Red cell inherited hemoglobin (Hb) anomalies are commonly encountered in the central region of India. These cause a public health concern due to high level of morbidity, mortality, and fetal loss in the backward, underprivileged, and vulnerable people.

Purpose

To report five typical families of Hb E disorders for the first time detected and identified from various districts of the state of Madhya Pradesh in central India.

Methods

Out of a total of 447 couples/families referred from a tertiary hospital in central India for investigations of anemia/hemoglobinopathies during the period from March 2010 to February 2014, we came across five typical rare couples/families of Hb E disorders (1.1%) worthy of detailed investigations that we have reported here. Laboratory investigations were carried out following the standard procedures after cross checking for quality control from time to time.

Results

For the first time, out of total 27 cases studied, we have encountered nine cases of heterozygous Hb E trait (33.3%), two members (7.4%) with Hb E-β-thalassemia (double heterozygosity), two cases (7.4%) of sickle cell-Hb E disease (double heterozygosity), two β-thalassemia traits (7.4%), three sickle cell traits (11.1%), 9 normal (33.3%), and none with homozygous Hb E disease. Cases of Hb E trait, Hb E-β-thalassemia, and sickle cell-E disease showed moderate to severe anemia, and target cells, and reduced values of red cell indices like red blood cell count, Hb level, hematocrit, mean cell volume, mean cell Hb and mean cell Hb cencentration, describing abnormal hematological profile and clinical manifestations before blood transfusion.

Conclusions

Double heterozygosity of β-thalassemia with Hb S and Hb E is a rare entity, but occurs with severe clinical manifestations, testifying either migrations and/or genetic admixture. Co-occurrence of Hb E/β-thalassemia in different districts indicates that these anomalies along with other hemoglobinopathies are wide spread in Madhya Pradesh and posing a major genetic burden on vulnerable people of central India.

Transfusion transmitted infections in thalassaemics: need for reappraisal of blood screening strategy in India

The aim of the study was to assess the blood safety in India through prevalence in thalassaemic population. Safety of the blood supply is a subject of great concern for all recipients. This review attempts to assess the relevance and format of tests for viruses in the context of transfusion transmitted infection (TTI) prevalence in India. Serological marker testing for human immunodeficiency virus-1/2 (HIV-1/2), hepatitis C virus (HCV) and hepatitis B virus (HBV) is mandatory in India. Numerous TTI incidents in the repeat recipients supported by results from nucleic acid technology (NAT) testing indicate the deficiencies in blood safety. The β-thalassaemic population (3-17%) in India has been used to reflect on blood safety. The prevalence of HIV-1/2, HCV and HBV in the Indian donor population, the limitations in accessing safe donors, quality of serological tests and the impact on repeat recipients is evaluated. The reports point to prevalence of ˜2% of viral diseases in the blood donor population, and the insufficiency of serology testing resulting in up to 45% TTIs in thalassaemics. The revelation by individual donation (ID) NAT testing, of 1 per 310 units being serology negative-NAT reactive is alarming. Extrapolating the serology negative NAT reactive yields, for an annual blood supply of 7.9 million units, 23,700 units or nearly 100,000 blood components are likely to be infectious. Though the cost for ID-NAT testing is considered unaffordable for a medium development country such as India, the enormity of TTIs will place an unmanageable cost burden on the society.

The Prevalence Of β-Thalassemia Mutations in South Western Maharashtra

Thalassemia has been recognized by the World Health Organization as important inherited disorders principally impacting on the populations of low income countries. In this report, the prevalence of common β-thalassemia mutations in India was defined in 126 β-thalassemia carrier subjects in a western Indian population mainly from the south-western Maharashtra. The six most common β-thalassemia mutations were detected, which included IVS I-5 (G-C), IVS I-1 (G-T), codon 8-9 (+G), codon 41/42 (-TCTT), Codon 15 (G-A), and 619 bp deletion at 3' end of β-globin gene. These mutations accounted for 93.66 % in 126 β-thalassemia carrier subjects and 6.34 % remained uncharacterized. Out of 126, 82 (65.07 %) showed the most common (prevalent) type of mutation, IVS I-5 (G-C), followed by IVS I-1 (G-T) showed by 12 (9.52 %) subjects. Three (2.38 %) subjects showed 619 bp deletion, codon 8/9 (+G) and codon 15 (G-A) mutations were present in eight subjects each (6.34 %). Only five (3.96 %) subjects showed codon 41/42 (-TCTT). There were eight (6.34 %) subjects where mutation was not any of the six mutations studied. This study provides the pattern of β thalassemia mutations from south-western Maharashtra, which will help to prevent β-thalassemia using prenatal diagnosis and proper counseling.

Combination of two rare mutations causes β-thalassaemia in a Bangladeshi patient

Screening of mutations that cause β-thalassaemia in the Bangladeshi population led to the identification of a patient with a combination of two rare mutations, Hb Monroe and HBB: −92 C > G. The β-thalassaemia major male individual was transfusion-dependent and had an atypical β-globin gene cluster haplotype. Of the two mutations, Hb Monroe has been characterized in detail. Clinical effects of the other mutation, HBB: −92 C > G, are unknown so far. Bioinformatics analyses were carried out to predict the possible effect of this mutation. These analyses revealed the presence of a putative binding site for Egr1, a transcription factor, within the HBB: −92 region. Our literature survey suggests a close relationship between different phenotypic manifestations of β-thalassaemia and Egr1 expression.

Mutation analysis of the HBB gene in selected Bangladeshi beta-thalassemic individuals: presence of rare mutations

INTRODUCTION AND AIMS

Bangladesh has a large number of thalassemic patients. However, no extensive analysis of the mutations in the HBB gene of thalassemic patients has been previously carried out. We have conducted a systematic research to reveal thalassemia mutations in the Bangladeshi population. In this preliminary analysis of 587 bp of the HBB gene in selected thalassemic individuals, some rare mutations in world perspective have been found to be significantly high in the Bangladeshi population, together with the common mutations for thalassemia.

RESULTS

A 587-bp segment of the HBB gene from 32 chromosomes of 16 beta-thalassemic individuals was analyzed for molecular characterization of the disease. Splice junction mutation IVS-I-5 was found to be the most common. The analysis also revealed some rare mutations HBB: c.-80T>C, HBB: c. 92G>C, HBB: c-92C>G, which are not prevalent in geographically adjacent populations.

CONCLUSION

This is a first of this kind of study in the Bangladeshi population. Although the small sample size makes it difficult to make any population genetics inference, this study can be regarded as the seminal research for a large-scale study to determine the complete mutation profile underlying thalassemia in the Bangladeshi population. The complete mutation profile will provide invaluable strategies (e.g., prenatal diagnosis and genetic counseling) for better management of thalassemia in the Bangladeshi population.