New antigen in the Dombrock blood group system, DOYA, ablates expression of Doa and weakens expression of Hy, Joa, and Gya antigens

DO/ART4 gene sequencing in sub-Saharan cohorts and African migrants: useful data describing the diversity and spreading of rare variants

BACKGROUND

Due to the unavailability of immunological reagents, the Dombrock blood group is insufficiently explored in African populations and can be a source of alloimmunization. A large study including pygmoid and nonpygmoid ethnic groups from East, Central, and West continental Africa, together with African migrants like Comorians, Afro-Caribbean from Martinique, and Maroons from French Guiana would be helpful to increase transfusion safety.

STUDY DESIGN AND METHODS

Using genomic DNA extracted from blood samples collected from 336 nonpygmoid and 51 pygmoid Africans as well as 268 samples of African descent, DO coding regions were PCR-amplified and sequenced.

RESULTS

DO*A and DO*B alleles were detected in almost all groups, with a clear predominance of DO*B in every cohort tested. DO*JO and DO*HY allele frequencies reached 10% or more in several ethnic groups. DO*B-SH-Gln149Lys, DO*B-Ile5Thr, and DO*DODE variants were identified both in African ethnic groups and outside Africa. Twelve novel variants were characterized on a DO*A or a DO*B background. Five of them were found in both African and migrant cohorts, the others were restricted to either within or outside Africa. No DO*DOYA, DO*DOLG, DO*DOLC, nor DO*DOMR variants were observed. A first phylogenetic tree was proposed including all variant alleles.

CONCLUSION

This study across continental Africa and countries with African migrants provides a useful overview of Dombrock allele diversity and distribution. The identification of 12 new alleles underlines the importance of genotyping for Dombrock alleles, particularly to improve transfusion safety in countries hosting migrant populations of African descent.

Extended blood group molecular typing and next-generation sequencing

Several high-throughput multiplex blood group molecular typing platforms have been developed to predict blood group antigen phenotypes. These molecular systems support extended donor/patient matching by detecting commonly encountered blood group polymorphisms as well as rare alleles that determine the expression of blood group antigens. Extended molecular typing of a large number of blood donors by high-throughput platforms can increase the likelihood of identifying donor red blood cells that match those of recipients. This is especially important in the management of multiply-transfused patients who may have developed several alloantibodies. Nevertheless, current molecular techniques have limitations. For example, they detect only predefined genetic variants. In contrast, target enrichment next-generation sequencing (NGS) is an emerging technology that provides comprehensive sequence information, focusing on specified genomic regions. Target enrichment NGS is able to assess genetic variations that cannot be achieved by traditional Sanger sequencing or other genotyping platforms. Target enrichment NGS has been used to detect both known and de novo genetic polymorphisms, including single-nucleotide polymorphisms, indels (insertions/deletions), and structural variations. This review discusses the methodology, advantages, and limitations of the current blood group genotyping techniques and describes various target enrichment NGS approaches that can be used to develop an extended blood group genotyping assay system.

Dombrock genotyping in Brazilian blood donors reveals different regional frequencies of the HY allele

Background

Dombrock blood group system genotyping has revealed various rearrangements of the Dombrock gene and identified new variant alleles in Brazil (i.e., DO*A-SH, DO*A-WL and DO*B-WL). Because of the high heterogeneity of the Brazilian population, interregional differences are expected during the investigation of Dombrock genotypes.

Objective

The present study aims to determine the frequencies of Dombrock genotypes in blood donors from Minas Gerais and compare the frequencies of the HY and JO alleles to those of another population in Brazil.

Methods

The frequencies of the DO alleles in Minas Gerais, a southeastern state of Brazil, were determined from the genotyping of 270 blood donors. Genotyping involved polymerase chain reaction and restriction fragment length polymorphism analysis to identify the 323G>T, 350C>T, 793A>G, and 898C>G mutations, which are related to the HY, JO, DO*A/DO*B, and DO*A-WL/DO*B-WL alleles, respectively. Moreover, the frequencies of rare HY and JO alleles were statistically compared using the chi-square test with data from another Brazilian region.

Results

The HY allele frequency in Minas Gerais (2.4%) was almost twice that of the JO allele (1.5%). The frequency of the HY allele was significantly higher (p-value = 0.001) than that in another Brazilian population and includes a rare homozygous donor with the Hy- phenotype. In addition, the DO*A-WL and DO*B-WL alleles, which were first identified in Brazil, were found in the state of Minas Gerais.

Conclusions

The data confirm that the frequencies of DO alleles differ between regions in Brazil. The population of Minas Gerais could be targeted in a screening strategy to identify the Hy- phenotype in order to develop a rare blood bank.

Synonymous nucleotide polymorphisms influence Dombrock blood group protein expression in K562 cells

To gain further insight into ART4 (DO) gene alleles (DO*A, DO*JO1, DO*A-WL, DO*DOYA, DO*B, DO*B-WL, DO*B-SH-Q149K, DO*B-(WL)-I175N, DO*HY1, DO*HY2, DO*DOMR) and evaluate the impact of synonymous nucleotide polymorphisms on protein expression and mRNA accumulation of DO*A-HA, DO*A-SH and DO*B-SH alleles, human erythroleukaemic K562 cells were transducted with variant DO-lentiviral particles and analysed by flow cytometry and quantitative reverse transcription polymerase chain reaction. Monoclonal antibody (MoAb) detection of DO*A-HA and DO*JO1 transductants was lower than DO*A transductants, while detection of DO*A-SH, DO*A-WL and DO*DOYA transductants was higher. Variant DO*B alleles, i.e. DO*B-SH, DO*B-WL, DO*HY1, DO*HY2 and DO*DOMR, showed reduced MoAb binding. The unexpected modifications of protein expression of the DO*A-HA, DO*A-SH and DO*B-SH alleles that differ from the DO*A or DO*B alleles by a single synonymous polymorphism were abolished by reversion, thus implying involvement of these polymorphisms. Depending on the Leu208 codon used, detection level ranged from 1 to 4·14. In the variant alleles resulting from single synonymous polymorphism, mRNA accumulation correlated roughly with MoAbs detection levels, suggesting post-transcriptional regulation. Other than a few reports involving aberrant splicing, the experiments described herein provide the first evidence that synonymous nucleotide polymorphisms can influence Dombrock blood group expression. Such polymorphisms should be taken into account for molecular screening and potential impact on transfusion.

Heterogeneity of alleles encoding high- and low-prevalence red blood cell antigens across Africa: useful data to facilitate transfusion in African patients

Ethnic variations in red blood cell (RBC) antigens can be a source of alloimmunization, especially in migrant populations. To improve transfusion safety in continental Africa and countries with African migrants, we performed RBC genotyping to determine allele frequencies coding for high- and low-prevalence antigens. A total of 481 blood samples were collected in ethnic groups from West, Central and East Africa. Molecular typing was performed using a polymerase chain reaction - reverse sequence specific oligonucleotide method. Results demonstrated no DI*1, DI*3, YT*2, SC*2, LW*7, KN*2 alleles in any sample and the CO*2 allele was rare. The frequency of LU*1 was comparable to that of European-Caucasians (2%) except in Biaka pygmies (8%). The frequency of CROM*-1 was high in Mbuti pygmies (13%). High frequency of KN*7 and KN*6 may reflect selection pressure in the countries investigated. Analysis of Dombrock allele patterns confirmed uneven distribution of the DO*1 and DO*2 alleles with high frequencies of DO*-4 and DO*-5 in all groups. Altogether, findings demonstrated extensive allele-frequency heterogeneity across Africa and suggested that knowledge of patient ethnicity gives information about the high-prevalence antigens that may be lacking. These data are medically useful to support transfusion care of African migrants living in countries where the majority of the population is from a different ethnical background.

Emily Cooley lecture 2012: Emily Cooley and techniques that have been applied to characterize DO and JR blood groups

Emily Cooley was a well-respected medical technologist and morphologist with a remarkable skill set. She was highly regarded both professionally and personally. The "Emily Cooley Lectureship and Award" was established to honor her in particular and medical technologists in general. This article first reviews the history of the Emily Cooley award and provides some of the reasons why it carries her name. Then, using two blood group systems, DO and JR, it illustrates how many discoveries regarding blood groups were dependent on access to techniques.