ABO blood group in Kuwaitis: detailed allele frequency distribution and identification of novel alleles

Identification of a novel A2 allele through nt543 substitution

BACKGROUND

ABO blood system has many subgroups. In A group, A₁ phenotype and A₂ phenotype are more common, and A₂ is caused by deletion or substitution in A¹ allele (ABO*A1.01).

METHODS

Based on standard ABO serological test, the subject was identified as A₂ phenotype. Direct sequencing and ABO gene cloning were performed to analyze the allele.

RESULTS

The subject had one A^1v allele (ABO*A1.02) and one O allele. The haplotype sequencing analysis of each allelic clone demonstrated that allele 1 was A^1v (ABO*A1.02) allele with nt543 variation (543 G > C) and allele 2 was O^1v allele (ABO*O.01.02) with nt261 deletion and nt220 variation.

CONCLUSION

The 543 G > C nucleotide substitution of the present A^1v allele (ABO*A1.02) shares the same sequence variation site with A^x allele (ABO*AW.33) (543 G > T), and both 543 G > C and 543 G > T nucleotide substitutions encode the same amino acid change of tryptophan to cysteine. Mechanism, such as allelic enhancement, has been proposed to explain this controversial phenotype-genotype relationship. But in present case, there has been no B allele to enhance the expression of A_x to that expected of A₂, so there could be another novel underlying mechanism to be investigated.

Determination of complete sequence information of the human ABO blood group orthologous gene in pigs and breed difference in blood type frequencies

The sequence information of the genomic form of the human ABO blood group orthologous gene (erythrocyte antigen A, EAA) is not complete in pigs. Therefore, we cloned and characterized the nucleotide sequence of EAA intron 7, which is critical to understand genetic difference between A and 0 blood groups in pigs, covering complete genomic sequence information of EAA excluding a ~560bp unsequencible gap. We also analyzed genetic polymorphisms within EAA intron 7 and exon 8. We found difference in A0 blood group frequencies among pig breeds. In addition, we designed a new genomic DNA-based A0 blood group typing method and improved the accuracy and simplicity of the typing.

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 polymorphism of the ABO blood group: a study in Poland, Spain, and Andorra

OBJECTIVES

The main goal of this study is to increase knowledge on the molecular level of the ABO blood group system in Europe by providing data for Poland, Spain, and Andorra populations.

METHODS

A total of 172 oral scrapings samples from individuals of Polish origin, 108 peripheral blood samples of autochthonous individuals from the province of Zamora (Spain), and 81 peripheral blood samples from individuals with Andorran origin, were analyzed. Molecular characterization of the allelic variants was performed by the analysis of exons 6 and 7 of the ABO gene.

RESULTS

Seven common alleles were identified, namely: A101, A102, A201, B101, O01, O02, and O03. Less common variants (O05, O09, O21, O26, O06, O11, and O12), were also detected.

CONCLUSIONS

The results obtained contribute to the knowledge of the molecular European ABO map, and are discussed in regard to the allelic frequency reported by other Caucasian and Asian populations.

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.

Brief communication: Evolution of a specific O allele (O1vG542A) supports unique ancestry of Native Americans

In this study, we explore the geographic and temporal distribution of a unique variant of the O blood group allele called O1v(G542A) , which has been shown to be shared among Native Americans but is rare in other populations. O1v(G542A) was previously reported in Native American populations in Mesoamerica and South America, and has been proposed as an ancestry informative marker. We investigated whether this allele is also found in the Tlingit and Haida, two contemporary indigenous populations from Alaska, and a pre-Columbian population from California. If O1v(G542A) is present in Na-Dene speakers (i.e., Tlingits), it would indicate that Na-Dene speaking groups share close ancestry with other Native American groups and support a Beringian origin of the allele, consistent with the Beringian Incubation Model. If O1v(G542A) is found in pre-Columbian populations, it would further support a Beringian origin of the allele, rather than a more recent introduction of the allele into the Americas via gene flow from one or more populations which have admixed with Native Americans over the past five centuries. We identified this allele in one Na-Dene population at a frequency of 0.11, and one ancient California population at a frequency of 0.20. Our results support a Beringian origin of O1v(G542A) , which is distributed today among all Native American groups that have been genotyped in appreciable numbers at this locus. This result is consistent with the hypothesis that Na-Dene and other Native American populations primarily derive their ancestry from a single source population.

Blood group O alleles in Native Americans: implications in the peopling of the Americas

All major ABO blood alleles are found in most populations worldwide, whereas the majority of Native Americans are nearly exclusively in the O group. O allele molecular characterization could aid in elucidating the possible causes of group O predominance in Native American populations. In this work, we studied exon 6 and 7 sequence diversity in 180 O blood group individuals from four different Mesoamerican populations. Additionally, a comparative analysis of genetic diversity and population structure including South American populations was performed. Results revealed no significant differences among Mesoamerican and South American groups, but showed significant differences within population groups attributable to previously detected differences in genetic drift and founder effects throughout the American continent. Interestingly, in all American populations, the same set of haplotypes O(1), O(1v), and O(1v(G542A)) was present, suggesting the following: (1) that they constitute the main genetic pool of the founding population of the Americas and (2) that they derive from the same ancestral source, partially supporting the single founding population hypothesis. In addition, the consistent and restricted presence of the G542A mutation in Native Americans compared to worldwide populations allows it to be employed as an Ancestry informative marker (AIM). Present knowledge of the peopling of the Americas allows the prediction of the way in which the G542A mutation could have emerged in Beringia, probably during the differentiation process of Asian lineages that gave rise to the founding population of the continent.

Development of a laboratory project to determine human ABO genotypes-Limitations lead to further student explorations

A multiplex allele-specific PCR analysis was developed to identify six "common" genotypes: AA, AO, BB, BO, OO, and AB. This project included a pre-laboratory exercise that provided active learning experiences and developed critical thinking skills. This laboratory resulted in many successful analyses, which were verified by student knowledge of their phenotypes. However, the design was found to be deficient for the analysis of variants. The limitations in the original allied-health multiplex design were verified through a student designed problem-based laboratory project in an advanced level biochemistry class. Variants were further analyzed in an undergraduate research project using SSCP analyses. The topic of ABO genotyping provides several opportunities for student-centered explorations.

Molecular basis of the A2B in Taiwan

Molecular genotyping of the ABO alleles has been widely used in ABO subgroups analysis and has been able to solve the rare ABO blood grouping discrepancies. The genotypes of sixty-one A2B phenotype donors recruited from the middle and south of Taiwan were analyzed by means of molecular methods. The A2B phenotype was initially identified by serological test. The polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method was used to screen the ABO alleles at nucleotides (nt) 261 and 703 based on the nt differences found in the ABO alleles. The subgroups of the A2 allele were determined by the PCR-RFLP and direct sequencing methods. The discrepancies between the phenotype and genotype of the A2B were then studied by subcloning and nucleotide sequence analysis. Our results show that 55 of the 61 A2B donors (90%) are A205/B allele and two are A201/B allele. Four cases were heterozygotes of the cis-AB/O or B alleles. Two were cis-AB04/O allele, one was cis-AB01/O allele and the other was cis-AB02/B allele. In conclusion, most A2B genotypes belong to the A205/B allele in Taiwan. In this study, we report for the first time the presence of the A205, A201, and cis-AB02 alleles in Taiwan.

Systematic sequence analysis of the human fucosyltransferase 2 (FUT2) gene identifies novel sequence variations and alleles

BACKGROUND

The FUT2 gene regulates the expression of ABH antigens in body secretions and hence controls the secretor status. It is highly polymorphic.

STUDY DESIGN AND METHODS

Healthy Chinese (n = 79) and Caucasian (n = 20) subjects were recruited for this study. Lewis blood group and secretor status were determined. The entire FUT2 coding region was amplified and screened for sequence variations by single-strand conformation polymorphism analysis under four different conditions to ensure comprehensive detection, and representative samples with distinct banding patterns were characterized by DNA sequencing. The haplotypes of novel alleles were determined by sequencing of cloned inserts.

RESULTS

Seventeen single-nucleotide polymorphisms and one 3-base duplicating insertion were identified. Six novel FUT2 alleles each found in a heterozygous individual were defined by six novel sequence variations: 210A>G (T70T), 380G>A (R127H), 572G>A (R191Q), 748_750dupGTG (V250dup), 853G>A (A285T), and 855A>C (A285A). The three most common alleles were Se, Se(357), and Se(357,385) in Chinese persons (total frequency, 94%) and se(428), Se(357), and Se in Caucasian persons (total frequency, 85%). The FUT2 genotypes correlated with Lewis phenotypes and secretor status.

CONCLUSION

This study identified 18 sequence variations in the FUT2 gene, and 6 were novel. The frequencies of alleles and genotypes were also determined in Chinese and Caucasian persons.