Heterogeneity of O blood group in India: Peeping through the window of molecular biology.

BACKGROUND: Molecular genotyping of ABO blood group system has identified more than 60 "O" group alleles based on the single-nucleotide polymorphisms present in the ABO gene. Heterogeneity of O group alleles has been observed in various countries from South America, Europe, Middle East, and Asia. India is a vast country with more than 1300 million population which is divided into various ethnic and tribal groups. However, very little is known about the heterogeneity of O alleles in Indians. MATERIALS AND METHODS: A total of 116 O group individuals from the mixed population of Mumbai, India, were enrolled in the present study. DNA was extracted using the standard phenol-chloroform method. The exons 6 and 7 of the ABO gene were genotyped by polymerase chain reaction-single-strand conformation polymorphism and/or DNA sequencing. The genotyping results were compared with our earlier findings. RESULTS AND DISCUSSION: Overall, ten different genotypes were identified. Three rare alleles, namely, O05, O11, and O26 were seen in the mixed group category. These results suggest that there is an internal heterogeneity in the mixed group while Dhodias and Parsis, the groups which were screened earlier, seem to be more homogenous groups. An important piece of information emerges out from this study, that is, O01O02 genotype is expressing some selective force in population groups screened in India as well as many other groups worldwide. CONCLUSION: In the future, molecular genotyping of the ABO blood group system among different ethnic and tribal Indian groups would help in generating data to fill up the gaps in the molecular ABO map of the world.

Molecular genotyping of ABO blood groups in some population groups from India.

BACKGROUND & OBJECTIVES: Indian population is characterized by the presence of various castes and tribal groups. Various genetic polymorphisms have been used to differentiate among these groups. Amongst these, the ABO blood group system has been extensively studied. There is no information on molecular genotyping of ABO blood groups from India. Therefore, the main objective of this study was to characterize the common A, B and O alleles by molecular analysis in some Indian population groups. METHODS: One hundred samples from the mixed population from Mumbai, 101 samples from the Dhodia tribe and 100 samples from the Parsi community were included in this study. Initially, the samples were phenotyped by standard serologic techniques. PCR followed by single strand conformational polymorphsim (SSCP) was used for molecular ABO genotyping. Samples showing atypical SSCP patterns were further analysed by DNA sequencing to characterize rare alleles. RESULTS: Seven common ABO alleles with 19 different genotypes were found in the mixed population. The Dhodias showed 12 different ABO genotypes and the Parsis revealed 15 different ABO genotypes with six common ABO alleles identified in each of them. Two rare alleles were also identified. INTERPRETATION & CONCLUSIONS: This study reports the distribution of molecular genotypes of ABO alleles among some population groups from India. Considering the extremely heterogeneous nature of the Indian population, in terms of various genotype markers like blood groups, red cell enzymes, etc., many more ABO alleles are likely to be encountered.

Molecular characterization of weaker variants of A and B in Indian population--the first report.

BACKGROUND AND OBJECTIVES: The ABO blood group system is extremely important blood group system in transfusion medicine and weaker variants of A and B are subgroups of the system. From a Country like India with 1.2 billion population sporadic reports detecting weaker variants of A and B serologically are published. Therefore the main objective of the present study is to identify weaker variants of A and B serologically and characterize them at molecular level. MATERIALS AND METHODS: Eight samples which were referred to us for resolving discrepancies in forward and reverse grouping were first phenotype in our laboratory by standard serologic techniques for ABO blood groups. Molecular genotyping for the ABO locus was done by PCR-SSCP. Altered SSCP patterns were analysed by DNA sequencing. Sequencing of intron 6 and exons 1-5 was done in one sample each. RESULTS AND CONCLUSION: Nine rare alleles affecting the normal expression of A and B antigens have been identified among Indians. They were two Aw06, one A209, one Ax20, two O05, one O49, one O56 and one O19 alleles. This is the first report demonstrating molecular studies on weaker variants of A and B from India.