Novel Dombrock Blood Group Genetic Variants in Different Ethnic Groups Identified by High Throughput Beadchip DNA Analysis.

Background : Modern bioarray chip technology enables rapid allele determination in a large number of donors by DNA typing when compared to classical serological methods. We analyzed five single nucleotide polymorphisms (SNPs) associated with Dombrock (DO) alleles in blood samples from donors of different ethnic groups, and found new genetic variants.

Method : The BeadChip^™ technology used primers for a single multiplex PCR reaction, and allele-specific oligonucleotides with variable 3′-terminal nucleotide for elongation-mediated multiplex analysis (eMAP^TM) of the DO polymorphisms. Color-encoded beads displaying the elongation probes were assembled into planar arrays of small footprint on semiconductor chips, permitting the instant imaging of fluorescent elongation products from the entire array. Five SNPs of DO blood group antigens DOA/DOB (nt 378 C>T, 624 T>C, 793 A>G), Hy+/Hy− (nt 323 G>T) and Jo(a+)/Jo(a−)(nt 350 C>T) were analyzed simultaneously. Blood samples from a total of 445 donors, comprising of 100 Thai, 69 Jewish, 58 Chinese and 218 random New York City donors were analyzed.

Results : As shown in the table below, the predominant diploid allelic combinations observed in all the groups were DOB/DOB followed by DOA/DOB and then DOA/DOA. In the random donor group, we also observed several less prevalent allele combinations: DOB/HY (14.2%), DOB/JO (1.4%), DOA/HY (0.5%), DOA/JO (2.3%), HY/HY (1.4%), JO/JO(1.8%), and HY/JO (0.9%). Interestingly, two novel alleles in trans with the known alleles: DOB/HA (11% in Thai, 2.9% in Jewish, 6.9% in Chinese and 2.8% in random donors), DOA/HA (1.8% in random donors, 1.7% in Chinese and 1.4% in Jewish), DOB/SH (0.5% in random donors) and HY/SH (1.4 % in random donors) were also detected. HA allele is 378T, 624T, 793A (like JO but with 350C). Hemagglutination studies showed that HA, as predicted from the nucleotide at position 793, encoded Do^a antigen. SH allele is 378C, 624C, 793C (like HY but with 323G) and is predicted to encode Do^b antigen.

Conclusion: The BeadChip^™ technology facilitated the identification of novel genetic variants, in addition to accelerating blood group typing.

Most prevalent DO allele combinations (in %)