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

Monogenic diseases in India

Studies on monogenic diseases are considered valuable because they give insights and expand our knowledge on gene function and regulation. Despite all the current advancement in science and technology, a deep understanding and knowledge as to why only those particular genes are affected in a disease is still vague. We also lack profound illumination as to why only certain mutations are seen in a disease. Though useful from a research perspective, a majority of these diseases are lethal resulting in death of the affected individual. Unfortunately, in the fast - growing land of India, the incidence of monogenic diseases is very high with few counter-measures in place. This article encompasses a list of all monogenic diseases ever to be reported in India with special focus on five diseases which has been stated to have the highest incidence in India. Here, we discuss about the limited research carried out in India on these high incidence monogenic diseases, the other diseases related to those genes, the range of treatments available for these diseases in India in contrast to its availability around the world and the need to develop treatment strategies to reduce the mortality and morbidity due to these rare but daunting diseases.

Hemoglobin E in Northeast India: A review on its origin, distribution, migration and health implication

A systematic review of the studies on hemoglobin E in Northeast India has been carried out to understand the magnitude of research undertaken on this aspect during the last seven decades. Owing to the high prevalence of hemoglobin E in this part of India different authors have studied this hemoglobin from different perspectives and found conflicting results. However a systematic review of such studies is lacking from a holistic point of view. Most of the epidemiological, in vitro as well as in vivo studies show signatures of selection with this hemoglobin locus. However, how this polymorphism is maintained at different rates at different geographical region is still a matter of contention. This review will fill the gap from all perspectives starting from the frequency distribution of hemoglobin E and its spread in different parts of Northeast India, its relationship with malaria hypothesis, the population migration, population affinity and most importantly the health implication arising out of it. A probable origin of hemoglobin E among an Austroasiatic population of Northeast India has been postulated with the help of advance molecular anthropological knowledge like the deep rooted markers of mt DNA and Y-chromosome haplotypes.

CD36 expression and lipid metabolism following an oral glucose challenge in South Asians

AIM: To investigate lipid metabolism and the relationship with monocyte expression of the fatty acid translocase CD36 in South Asians.

METHODS: An observational study of South Asians whom as an ethnic group have - a higher risk of developing diabetes. The susceptibility to diabetes is coupled with an earlier and more rapid progression of micro-, and macro-vascular complications. Twenty-nine healthy South Asian participants [mean age 34.6 (8.9) years, 76.2% male, mean body-mass index 25.0 (5.2) kg/m²] were recruited from an urban residential area of central Birmingham (United Kingdom). The main outcomes measured were post prandial (30 min) and post absorptive (120 min) changes from fasting (0 min) in circulating lipoproteins, lipds and hormones, and monocyte expression of CD36 post injection of a 75 g oral glucose challenge. The inducements of variations of monocyte CD36 expression were analysed.

RESULTS: Our results showed evident changes in monocyte CD36 expression following the glucose challenge (P < 0.001). Non-esterified fatty acids (NEFA) levels decreased progressively during the challenge (P < 0.001), in contrast to increased cholesterol (but not triglyceride) concentrations within very low density lipoprotein (VLDL) and low density lipoprotein subfractions (P < 0.01). Levels of, glucose, serum triglycerides and high density lipoprotein cholesterol remained largely unchanged. Variations of monocyte CD36 were negatively (r = -0.47, P = 0.04) associated to fat from the diet and positively to carbohydrate from the diet (r = 0.65, P < 0.001).

CONCLUSION: These data suggest that the initiation of VLDL genesis follows the consumption of glucose within this population, inferring that the sequestration of NEFA from these particles happens due to the increased availability of CD36 receptors. While these are preliminary results, it would appear that lifestyle exposures have a role in moderating the expression of CD36.

HbD Punjab/HbQ India Compound Heterozygosity: An Unusual Association

Background

Haemoglobinopathies are the commonest hereditary disorders in India and pose a major health problem. Both beta thalassaemia and structural haemoglobin variants are relatively common in northwestern India. Here we report a 29-year-old Sindhi female who was referred to us for a haemoglobinopathy work up and genetic counseling since her spouse was a classical beta thalassaemia carrier.

Method

A complete blood count was done on an automated cell counter. Haemoglobin analysis was carried out using HPLC Variant Haemoglobin Testing System. The cellulose acetate electrophoresis was carried out [pH 8.9]. Confirmation of mutations was done by automated DNA sequencing.

Results

HPLC analysis showed four major peaks, HbA₀, a peak in the HbD window, an unknown peak [retention time 4.74 minutes] and a peak in the HbC window. The HbA₂ level was 2.2%, and the HbF level was 0.7%. Cellulose acetate electrophoresis at alkaline pH, a slow moving band was seen at the HbS/D position along with a prominent band at the HbA₂ position. DNA sequencing of the β and α genes showed presence of the two hemoglobin variants: Hb D [β 121GAA → CAA] and Hb Q [α 64 AAG → GAG]. The δ globin gene was normal. The additional peak in the HbC window was due to the formation of a heterodimer hybrid.

Conclusion

Both HbD Punjab and HbQ India are relatively common in India, but their co-inheritance has not been described in the country. This case is the third report of compound heterozygosity for HbQ India/HbD Punjab haemoglobinopathy globally and the second one from India.

Molecular epidemiological characterization and health burden of thalassemia in Jiangxi Province, P. R. China

BACKGROUND

Thalassemia is the most common inherited disease in southern China. However, this disorder is usually ignored by Jiangxi provincial health system and government due to lack of epidemiological data.

MATERIALS AND METHODS

A total of 9489 samples from Hakka Han and Gan-speaking Han in three geographical areas of Jiangxi Province were analyzed for both complete blood cell (CBC) count and reverse dot blot (RDB) gene chip for thalassemia.

RESULTS

1182 cases of suspected thalassemia carriers with microcytosis (MCV<82 fL) were found by CBC count, and were tested by RDB gene chip to reveal a total of 594 mutant chromosomes, including 433 α-thalassemia mutant chromosomes and 172 β-thalassemia mutant chromosomes. Our results indicated a higher prevalence of thalassemia with the heterozygote frequency of 9.49% in southern Jiangxi province, whereas the low frequency was found in middle (3.90%) and northern Jiangxi (2.63%).

CONCLUSIONS

Based on the epidemiological data, the estimated numbers of pregnancies in Jiangxi province in which the fetus is at risk for β-thalassemia major or intermedia, Bart's hydrops fetalis and Hb H disease are 34 (95% CI, 16 to 58), 79 (95% CI, 50 to 114) and 39 (95% CI, 27 to 58) per year, respectively. We suggested that prevention network of thalassemia should be established, especially in high prevalent southern Jiangxi (Hakka Han), including establishment of thalassemia database collection, hematological analysis laboratories, genetic counselling clinics, prenatal diagnosis centers and neonatal screening centers.

The host genetic diversity in malaria infection

Populations exposed to Plasmodium infection develop genetic mechanisms of protection against severe disease. The clinical manifestation of malaria results primarily from the lysis of infected erythrocytes and subsequent immune and inflammatory responses. Herein, we review the genetic alterations associated with erythrocytes or mediators of the immune system, which might influence malaria outcome. Moreover, polymorphisms in genes related to molecules involved in mechanisms of cytoadherence and their influence on malaria pathology are also discussed. The results of some studies have suggested that the combinatorial effects of a set of genetic factors in the erythrocyte-immunology pathway might be relevant to host resistance or susceptibility against Plasmodium infection. However, these results must be interpreted with caution because of the differences observed in the functionality and frequency of polymorphisms within different populations. With the recent advances in molecular biology techniques, more robust studies with reliable data have been reported, and the results of these studies have identified individual genetic factors for consideration in preventing severe disease and the individual response to treatment.

Vitamin D deficiency amongst minority ethnic groups in the UK: a cross sectional study

BACKGROUND

Vitamin D deficiency is common amongst minority groups in Britain but its magnitude amongst South Asian (SA) and Black African-Caribbean (AC) groups is not well defined. The steroidal, endocrine nature of vitamin D provides it with a putative link with cardiovascular disease (CVD), and we hypothesised that aberrant levels of this hormone would reflect a heightened risk of CVD in these ethnic groups.

METHODS

SA (n=1105, 57% male) and AC (n=748, 51% male) were recruited as part of a community heart failure study from 20 primary care practices, Birmingham, UK. Vitamin D2/D3 levels were measured to determine rates of total vitamin D status, which were age/sex adjusted.

RESULTS

The majority of SAs had severe vitamin D deficiency (42.2%, 95% CI: 39.2-45.1), which was more frequent than in AC (12.5%, 10.2-14.9, p<0.001. Vitamin status in SA and AC was unrelated to the presence of osteoporosis, and on multivariate analysis of SA, vitamin D levels were independently associated with age (β=0.18, p<0.001), haemoglobin (β=0.12, p=0.002), and negatively with alkaline phosphatase (a marker of bone mineralisation, β=-0.11, p=0.022). Amongst AC, vitamin D was independently associated with having ever smoked (β=-0.13, p=0.006) and systolic blood pressure (β=0.10, p=0.038).

CONCLUSIONS

Vitamin D deficiency is a frequent biochemical observation amongst minority groups in Britain but the clinical significance is unclear, and ethnically specific. A proportionate susceptibility to bone disease is not apparent in either minority group.

Association of xmn I polymorphism and hemoglobin e haplotypes on postnatal gamma globin gene expression in homozygous hemoglobin e

Background and Objectives. To explore the role of cis-regulatory sequences within the β globin gene cluster at chromosome 11 on human γ globin gene expression related to Hb E allele, we analyze baseline hematological data and Hb F values together with β globin haplotypes in homozygous Hb E. Patients and Methods. 80 individuals with molecularly confirmed homozygous Hb E were analyzed for the β globin haplotypes and Xmn I polymorphism using PCR-RFLPs. 74 individuals with complete laboratory data were further studied for association analyses. Results. Eight different β globin haplotypes were found linked to Hb E alleles; three major haplotypes were (a) (III), (b) (V), and (c) (IV) accounting for 94% of Hb E chromosomes. A new haplotype (Th-1) was identified and most likely converted from the major ones. The majority of individuals had Hb F < 5%; only 10.8% of homozygous Hb E had high Hb F (average 10.5%, range 5.8–14.3%). No association was found on a specific haplotype or Xmn I in these individuals with high Hb F, measured by alkaline denaturation. Conclusion. The cis-regulation of γ globin gene expression might not be apparent under a milder condition with lesser globin imbalance such as homozygous Hb E.

Mapping hypoendemic, seasonal malaria in rural Bandarban, Bangladesh: a prospective surveillance

Background

Until recently the Chittagong Hill tracts have been hyperendemic for malaria. A past cross-sectional RDT based survey in 2007 recorded rates of approximately 15%. This study was designed to understand the present epidemiology of malaria in this region, to monitor and facilitate the uptake of malaria intervention activities of the national malaria programme and to serve as an area for developing new and innovative control strategies for malaria.

Methods

This research field area was established in two rural unions of Bandarban District of Bangladesh north of Bandarban city, which are known to be endemic for malaria due to Plasmodium falciparum. The project included the following elements: a) a demographic surveillance system including an initial census with updates every four months, b) periodic surveys of knowledge attitude and practice, c) a geographic information system, d) weekly active and continuous passive surveillance for malaria infections using smears, rapid tests and PCR, f) monthly mosquito surveillance, and e) daily weather measures. The programme included both traditional and molecular methods for detecting malaria as well as lab methods for speciating mosquitoes and detecting mosquitoes infected with sporozoites.

Results

The demographic surveillance enumerated and mapped 20,563 people, 75% of which were tribal non-Bengali. The monthly mosquito surveys identified 22 Anopheles species, eight of which were positive by circumsporozoite ELISA. The annual rate of malaria was close to 1% with 85% of cases in the rainy months of May-October. Definitive clustering identified in the low transmission season persisted during the high transmission season.

Conclusion

This demographically and geographically defined area, near to the Myanmar border, which is also hypoendemic for malaria, will be useful for future studies of the epidemiology of malaria and for evaluation of strategies for malaria control including new drugs and vaccines.

Bayesian estimates of the prevalence of β-thalassemia trait in voluntary blood donors of central India: a survey

Early detection of β-thalassemia (β-thal) trait is important. Voluntary blood donors represent an important group who are accessible and cooperative for this purpose. However, the usefulness of this population in β-thal trait detection programs has not been studied in India. We conducted a hematological survey of 5,045 blood donors who visited the Bhopal Memorial Hospital & Research Centre, Bhopal in central India. Using robust Bayesian methods, we estimated the prevalence of β-thal trait. The overall prevalence of β-thal trait in the study population was 9.59% [95% confidence interval (95% CI) 8.78-10.4%]. The prevalence of β-thal trait varied across the states of origin and within the state of Madhya Pradesh. We observed a cline effect for β-thal trait prevalence in relation to the latitude (p = 0.024). We conclude that blood donors offer an attractive adjunct to β-thal trait detection in national programs. Our study also offers insights into the β-thal trait gene flow and migration in India.

Mechanisms of genetically-based resistance to malaria

Malaria remains one of the most prevalent parasitoses worldwide. About 350 to 500 million febrile episodes are observed yearly in African children alone and more than 1 million people die because of malaria each year. Multiple factors have hampered the effective control of this disease, some of which include the complex biology of the Plasmodium parasites, their high polymorphism and their increasingly high resistance to antimalarial drugs, mainly in endemic regions. The ancient interaction between malarial parasites and humans has led to the fixation in the population of several inherited alterations conferring protection against malaria. Some of the mechanisms underlying protection against this disease are described in this review for hemoglobin-inherited disorders (thalassemia, sickle-cell trait, HbC and HbE), erythrocyte polymorphisms (ovalocytosis and Duffy blood group), enzymopathies (G6PD deficiency and PK deficiency) and immunogenetic variants (HLA alleles, complement receptor 1, NOS2, tumor necrosis factor-α promoter and chromosome 5q31-q33 polymorphisms).

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.