Prevalence of CYP1A1 and GST polymorphisms in the population of northeastern India and susceptibility of oral cancer.

Individual cancer susceptibility is the result of several host factors, including differences in lifestyle habits and genetic susceptibility. There is a correlation between CYP1A1 polymorphism (MspI) and oral cancer susceptibility. Individuals carrying the deletions of GSTM1 and GSTT1 are at high risk of developing oral cancers. In the present study on healthy tribal and nontribal individuals of Assam, we found that the genetic variation of GSST polymorphisms is evident (p = 0.20) with differential dose of toxic exposure. Prevalence of different polymorphic alleles of CYP1A1 also proves the same result. A mini-case-control study with very small sample size showed no marked increase in the risk of developing oral cancer as the frequencies of the studied GST genotypes did not show any statistical significance. But GSTT1-null genotypes were found to have higher risk of developing leukoplakia (OR 1.94, 95% CI 2.61-18.54). CYP1A1 genotype m2 allele was also not found to be associated with the risk of developing leukoplakias in the population.

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.

Induction of micronuclei by zinc in human leukocytes: a study using cytokinesis-block micronucleus assay.

In the present study, we report the results of the capability of zinc chloride for the induction of micronuclei in cultured human leukocytes using cytokinesis-block micronucleus assay. Two concentrations of zinc chloride (1.5 x 10(-4) M and 3.0 x 10(-4) M) were used to evaluate the potential of this zinc salt to induce micronucleus formation. This effect was compared with positive (mitomycin C treated) and negative controls (no salt added). Our results show a significant (p < or = 0.001) increase of micronucleated cytokinesis-blocked cells (MNCBs) in zinc-chloride-treated cells compared to the negative control. Induction of MNCBs was not in a dose-dependent manner for zinc chloride concentrations tested. This report is the first to describe the efficiency of cytokinesis-block micronucleus assay to evaluate the genotoxic effects of zinc salt.

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.

Alpha-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.

Spectrum of beta-thalassemia mutations and their association with allelic sequence polymorphisms at the beta-globin gene cluster in an Eastern Indian population.

In this report, the spectrum of beta-thalassemia mutations and genotype-to-phenotype correlations were defined in large number of patients (beta-thalassemia carriers and major) with varying disease severity in an Eastern Indian population mainly from the state of West Bengal. The five most common beta-thalassemia mutations were detected, which included IVS1-5 (G-->C), codon 15 (G-->A), codon 26 (G-->A), codon 30 (G-->C), and codon 41/42 (-TCTT). These accounted for 85% in 80 beta-thalassemic alleles deciphered from 56 patients, including beta-thalassemia major and carriers, and 15% of alleles remained uncharacterized in these patients. Expression of the human beta-globin gene is regulated by an array of cis-acting DNA elements, including five DNase I hypersensitive sites (HSs) in the locus control region (LCR), promoters that incorporate certain silencer elements, and enhancers at 3' of the beta-globin gene. For detailed studies and to understand the molecular basis of beta-thalassemia, we studied two groups of subjects: a group of 12 patients from four families having beta-thalassemia major and carrier phenotype and a control group of 26 healthy individuals. In these two groups, we examined portions of the beta-globin gene locus control region HSs 1, 2, 3, and 4, which included the (CA)(x)(TA)(y) repeat motif, the (AT)(x)N(y)(AT)(z) repeat motif, the inverted repeat sequence TGGGGACCCCA, the promoter region of the (G)gamma-globin gene, an (AT)(x)(T)(y) repeat 5' of the silencer region, and the beta-globin gene and its 3' flanking region. We investigated the allelic sequence polymorphisms in these regions and their association with the beta-thalassemia mutations to know the possible genotype-phenotype relationship in beta-thalassemia patients. An analysis of cis-acting regulatory regions showed varied sequence haplotypes associated with some frequent beta-thalassemia mutations in this Eastern Indian population.

Study of the single nucleotide polymorphism (SNP) at the palindromic sequence of hypersensitive site (HS)4 of the human beta-globin locus control region (LCR) in Indian population.

LCR, a genetic regulatory element, was examined in beta-thalassemia patients who do not show any mutation in the beta-globin genes. We sequenced LCR-HS2, HS3, and HS4 in samples from 16 such patients from the Indian population and found only one SNP A-G in the inverted repeat in HS4. A significant association was observed between the G allele and occurrence of beta-thalassemia by Fisher's exact test. The AG and GG genotypes showed higher relative risk as compared to the AA genotype. We also observed linkage disequilibrium between the A/G polymorphism and the AT-rich motif of the LCR HS2 region, suggesting that the G allele could be an evolutionarily new mutation in the study population.