The occurrence of beta-thalassemia mutation and its interaction with hemoglobin E in the eastern India

Perspectives on Translational Genomics and Public Health in India

It is now recognized worldwide that anticipation and prevention of diseases have significant advantages for the health and healthy ageing of the population. Early recognition of the disease in a vulnerable population such as in children aged <5 years and adults aged >60 years enhances our preparedness for any eventualities and future burden of the diseases to society. It is also recognized that current public health practices alone cannot bring about the desired outcome. When tackling public health-related issues, such problems must be recognized and state-of-the-art principles and innovations from genomic sciences, information technologies, and medical specialties must be encompassed and embraced. These will enhance strategies for preparedness and provide us with a better understanding of how to identify, manage, and control disease burdens. The ever expanding landscape of genomics research also includes experimental and computational approaches for effectively utilizing DNA sequence information. From these perspectives, the intricacies of Mendelian single gene disorders are the least challenging compared to intricacies of multi-dimensional host factors for infectious diseases or complex disorders such as cancer. The concepts of public health in India are on firm footing; however, integration of contemporary advances to implement public health principles into practice has neither been attempted nor impacted on disease burden or our preparedness to prevent eventualities. At the same time, translational genomics is gradually paving the way for personalized medicine. Principles of personalized medicine remain to be fully understood and practiced despite the pharmacogenomics-based future of drug development, and treatment has not been as exciting as the advances in genomics we are witnessing today. The relevance, importance, and translational impediments of these advances will be discussed.

Anemia and hemoglobinopathies in tribal population of Eastern and North-eastern India

It is estimated that out of approximately 31.4 million people living in North-eastern India, about 8.1 million are tribal people of the hills and plains. Among four of the seven north-eastern states, tribal people are in majority. Arunachal Pradesh is made of approximately 24 major tribal groups, which constitute about 70% of the total population, Tripura 29% and in Assam constitutes 11%. A total of 1726 cases were randomly selected in this study, out of which 1263 cases were from North-east India, namely from Arunachal Pradesh, Assam, Tripura and the rest were from West Bengal. Hematological parameters were estimated and agarose gel electrophoresis for identification of the Hb variants was performed. DNA was isolated, amplified and analysed by PCR-ARMS technology. The incidence of anemia among the tribal people of Assam was 59.82%, in Arunachal Pradesh 53.77% and Tripura 57.45%. The presence of hemoglobinopathies and thalassemia account for anemia in a sizeable population of the north-eastern states in certain tribes and urgent health resources are needed to deal with this. HbE appears to be the commonest hemoglobin among the different tribes of north-east.

HbE/β-thalassemia: basis of marked clinical diversity

Hemoglobin E thalassemia accounts for about one-half of all cases of severe beta thalassemia. There is marked variability in its clinical severity ranging from an asymptomatic to a transfusion-dependent phenotype. The phenotypic variability and inadequate longitudinal data present challenges in determining the optimal management of patients. This article summarizes findings on the natural history of Hemoglobin E thalassemia and some factors responsible for its clinical heterogeneity. Major genetic factors include the type of beta thalassemia mutation, the co-inheritance of alpha thalassemia, and polymorphisms associated with increased synthesis of fetal hemoglobin. Other factors, including response to anemia, and the influence of infection with malaria and other environmental influences, may be important. The remarkable variation and instability of clinical phenotypes in Hemoglobin E thalassemia require individual management plans for each patient, which should be reassessed over time.

Interaction of Hb South Florida (codon 1; GTG-->ATG) and HbE, with beta-thalassemia (IVS1-1; G-->A): expression of different clinical phenotypes

INTRODUCTION

Interactions of different hemoglobin variants with thalassemia alleles can result in various clinical phenotypes. HbE-beta-thalassemia generally manifests with severe anemia where individuals exhibit beta-thalassemia major with regular blood transfusions or beta-thalassemia intermedia with periodic blood transfusions. This study presents a unique Malay family with three beta-globin gene defects-HbE, Hb South Florida, and IVS1-1 (G-->A).

MATERIALS AND METHODS

HbE activates a cryptic splice site that produces non-functional mRNAs. Hb South Florida is a rare beta-hemoglobin variant, and its interactions with other beta-thalassemia alleles have not been reported. IVS1-1 is a Mediterranean mutation that affects mRNA processing giving rise to beta(o)-thalassemia.

RESULTS AND DISCUSSION

Fifteen mutations along the beta-globin gene complex were analyzed using the amplification refractory mutation system. Hb South Florida was identified by direct sequencing using genomic DNA.

CONCLUSION

The affected child with HbE/IVS1-1 produced a beta-thalassemia major phenotype. Compound heterozygosity for Hb South Florida/IVS1-1 produced a beta-thalassemia carrier phenotype in the mother.

α-Thalassemia Among Tribal Populations of Eastern India

Five hundred and thirteen unrelated subjects belonging to various tribes of West Bengal, Arunachal Pradesh and Assam in Eastern India, were screened for the presence of alpha-thalassemia (thal) gene deletion(s) as a possible cause of unexplained anemia (Hb < 11 g/dL and/or MCH <28 pg, MCV < 78 fL). As reported earlier, beta-globin gene mutant alleles were found with a frequency of up to 20% in some tribes. In the present study, alpha-globin gene deletion alleles were found in 18% of subjects from West Bengal, 3.9% from Arunachal Pradesh and 3.84% from Assam tribesmen. Coexistence of alpha- and beta-globin gene abnormalities was observed in up to 18% of some tribal groups. The high inbreeding rate and lack of appropriate medical care make these populations particularly vulnerable.

A review on the origin and spread of deleterious mutants of the beta-globin gene in Indian populations

Deleterious mutations of the human beta-globin gene are responsible for beta-thalassaemia and other haemoglobinopathies, which are the most common genetic diseases in Indian populations. A highly heterogeneous distribution of those mutations is observed in India and certain mutations are restricted to some extent to particular groups only. The reasons behind the geographical clustering and origin of the mutations in India is a highly debated issue and the evidence is conflicting. Our present article aims at tracing the origin of the deleterious beta-globin mutation and evaluates the role of different evolutionary forces responsible for the spread and present distribution of those mutations in Indian populations, using data from molecular biology and statistical methods. Mutations are generated essentially randomly, but "hot-spot" sites for mutation are reported for the beta-globin gene cluster, indicating sequence dependency of mutation. A single origin of a deleterious beta-globin mutation, followed by recombination (in a hot spot region) and/or interallelic gene conversion (within beta-globin gene) through time is the most plausible hypothesis to explain the association of those mutations with multiple haplotype backgrounds and frameworks. It is suggested that India is the place of origin of HbE and HbD mutations and that they dispersed to other parts of the would by migration. HbS mutants present in Indian populations are not of Middle East origin but rather a fresh mutation is the probable explanation for the prevalence among tribal groups. beta-thalassaemia represents a heterogeneous group of mutant alleles in India. Five common and twelve rare mutations have been reported in variable frequencies among different Indian populations. Gene flow of those mutant alleles from different populations of the world by political, military and commercial interactions possibly accounts for the heterogenous nature of beta-thalassaemia among Indians. A multiple allelic polymorphic system of the beta-globin gene exists in different populations. Dynamic interaction of the mutant alleles in the presence of different selective forces including falciparum malaria and biosocial patterns of Indian populations is discussed in order to explain the variable distribution and maintenance of those mutant alleles.

Few reports of hemoglobin E/beta-thalassemia in Northeast India: underdiagnosis or complete exclusion of beta-thalassemia by hemoglobin E

PURPOSE

India bears a major burden of homozygous beta-thalassemia. Hemoglobin (Hb) E/beta-thalassemia has been described mainly among Bengalis in Eastern India. Ethnic groups in northeastern India have among the highest known gene frequency for Hb E. However, there are few reports of Hb E/beta-thalassemia from these ethnic groups. This study aims to determine whether the paucity of reports of Hb E/beta-thalassemia from this region are because of underdiagnosis or complete elimination of beta-thalassemia by Hb E.

POPULATIONS AND METHODS

The published literature concerning Hb E, beta-thalassemia, and the syndrome of Hb E/beta-thalassemia in Indid, Tibeto-Burman, and Austro-Asiatic ethnic groups in northeast India was analyzed to determine the gene frequency of Hb E and beta-thalassemia for different ethnic groups. The expected cases of Hb E/beta-thalassemia were calculated using the Hardy-Weinberg law.

RESULTS

The Bodo-Kachari have a gene frequency of 0.50 for Hb E, the highest anywhere in the world. There are, however, no reports of beta-thalassemia in this group. Among ethnic groups in which prevalence of Hb E and beta-thalassemia are known, there is a vast discrepancy between the reported number of cases of Hb E/beta-thalassemia and the number predicted by Hardy-Weinberg law. Thus, there are only seven cases of Hb E/beta-thalassemia from northeast India reported in the literature as opposed to 67,332 predicted cases.

CONCLUSION

A potentially large pool of unsuspected Hb E/beta-thalassemia cases exist in northeast India. The significance of this finding and possible contributory factors are discussed.

Interaction of different hemoglobinopathies in Eastern India with a view to establish genotype-phenotype correlation

Analysis of the molecular basis of hemoglobinopathies provides an opportunity to define genotype-phenotype variations as well as establish the origin of mutation. The present study deals with a large cohort of 1,661 cases referred to the counseling unit and 889 individuals from random screening of the population of Tripura. Characterization of mutation in 291 cases (582 alleles) was performed by the PCR-ARMS method using genomic DNA. The haplotype of 56 beta(E) mutation-bearing chromosomes were identified by the RFLP-PCR method. Genotypes were constructed and correlated with hematological and clinical phenotypes. IVS-1nt 5 (G-->C) mutation was observed as the most frequent mutation, followed by codon 30 (G-->C). Production of HbE was significantly (P < 0.001) higher in nontransfusion-dependent Ebeta-thalassemia patients. beta(E) mutation was observed only on four haplotypes linked to framework 2. Type 2 haplotype was observed mainly from chromosomes of Tripura origin, but none from South Bengal. Homozygous E individuals with 1//1 genotype were significantly (P < 0.01) more anemic compared to individuals with 2//2 genotype. This work creates a database of hemoglobinopathy mutations for the population of Eastern India which will facilitate prenatal diagnosis and counseling. Am. J. Hum. Biol. 12:454-459, 2000. Copyright 2000 Wiley-Liss, Inc.

A study of spectrin and lipid peroxidation of red blood cell membrane in thalassaemia carrier

The aim of the present work is to understand the lipid peroxidation of RBC membrane and the spectrin protein content of RBC membrane cytoskeleton of thalassaemic carrier state (trait) of β and hemoglobin E variant (HbE). We have measured the hemoglobin (Hb), malondialdehyde (MDA) and spectrin content of RBC membrane of thalassaemic carrier. The spectrin content (α and β band) of both β and HbE carrier was not changed than normal individuals. However, lipid peroxidation of RBC membrane was significantly increased in both β and HbE trait, and Hb level was also decreased in thalassaemic carrier. It may be assumed that oxidative damage by excess lipid peroxidation may have no role on irreversible membrane damage in β thalassaemia and HbE thalassaemia carrier.