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Objectives: The aim of this study was to evaluate the applicability of genotyping of the ABCG2 gene using MALDI‐TOF MS and to estimate the allele frequency in the Japanese population. Background: Jr (a−) phenotype has a prevalence of approximately 0·05% among Japanese blood donors; DNA‐based genotyping was conducted to investigate the molecular basis of the Jr (a−) phenotype along with serological typing. To detect all SNPs of the ABCG2 gene, a high‐throughput SNP genotyping platform is needed. Methods: Overall, 1004 Jr (a−) blood samples were collected from blood donors in Japan and pre‐genotyped. To detect the SNPs of the ABCG2 gene using MALDI‐TOF MS, polymerase chain reaction and unextend primer were designed. In total, 205 Jr (a−) samples were genotyped using MALDI‐TOF MS analysis. Results: The SNPs of 1004 Jr (a−) samples were identified using the HRM analysis and DNA sequencing, and 799 of 1004 (80%) Jr (a−) samples had the homozygous for c.376 T. The designed primers for MALDI‐TOF MS perfectly detected the SNPs of the ABCG2 gene. A total of 205 Jr (a−) samples were genotyped using MALDI‐TOF MS. Calling failures occurred in only two samples with the mutations c.736CT to c.376C and c.421C to c.421CA. The concordance rate between the pre‐genotyped and MALDI‐TOF MS‐based genotyping results was very high (99·02%) for all ABCG2 alleles. Conclusions: Jr (a‐) Japanese donors had almost the homozygous for c.376 T. However, detections of more than 20 SNPs of the ABCG2 gene for the JR blood group genotyping are needed. MALDI‐TOF MS‐based genotyping was highly concordant with the pre‐genotyped results for all ABCG2 alleles. [ABSTRACT FROM AUTHOR]

SUMMARY Background Blood-group genotyping arrays have been widely used in Caucasian and African American populations, but have not been thoroughly tested in Japanese subjects. Aim To evaluate, using the BLOODchip® Reference genotyping system, the concordance of previously typed samples with expected phenotypes and the coverage of the Japanese variants. Methods Blood samples from 100 Japanese donors were obtained. DNA was extracted with QIAsymphony (Qiagen, Hilden, Germany). Samples were typed by serological methods and processed with the BLOODchip®. When a non-concordant result was identified, further sequencing by polymerase chain reaction-single specific primer ( PCR-SSP) was performed. Results Concordance between systems was 98% (736/751), and 98.8% (742/751) if only non-software-related non-concordances were considered. In the ABO group, 6 'No Call' ( NC, inability of the BLOODchip® to assign a result) were ascribed to a variant of blood subtype A1 ( A102; 467C>T), a common subtype in Asian populations, whereas three NC presented additional polymorphisms not contained in the BLOODchip® ( A102/ A205, A102/ O06 and A204/ O02). In the RhD group, one discrepancy was correctly genotyped as RHD* 1227A (Del phenotype) by the BLOODchip® (phenotyped as partial D, RHD* DIVb). Another was phenotyped as D+ by the BLOODchip® (phenotyped weak D by serology) and confirmed as RHD*D- CE(2)-D heterozygous by sequencing. The 3 RhD NC can be solved by further software update. For RhCE, one discrepancy was correctly genotyped for both systems; however, only the BLOODchip® was able to detect RHCE* CX allele. Conclusions By programming the A102 ABO variant into the system software with the new allele combinations, the BLOODchip® Reference is a suitable genotyping tool to be applied to Asian samples. [ABSTRACT FROM AUTHOR]