A novel nonsense mutation found in the CD177 gene of Thai individuals with the HNA-2 null phenotype.

OBJECTIVES:The aim of this study is to explore the molecular basis and to develop a simple sequence-specific primer polymerase chain reaction (PCR-SSP) technique for screening genotypes associated with the human neutrophil antigen-2 (HNA-2) null phenotype among Thai blood donors. BACKGROUND:Single-nucleotide polymorphisms (SNPs) c.787A>T of the CD177 gene is well known to be primarily demonstrated as a genetic determinant for HNA-2 deficiency. METHODS:The SNPs in the CD177 gene (exons 7 and 9) of 49 Thai blood donors with the known percentage of CD177 expression by flow cytometry including 48 HNA-2 positive and 1 HNA-2 null individuals were identified by long-range PCR amplification and sequencing. Moreover, screening for the c.1254G>A mutation was developed using an in-house PCR-SSP technique and tested among 771 unrelated donor samples. RESULTS:A HNA-2 null sample from the first cohort was heterozygous for c.787A/T and homozygous for c.1291G/G, namely, a 787A-1291G/787T-1291G (AG/TG) genotype. Interestingly, we could identify SNP c.1254G>A (rs188387562, p. Trp418Ter) that caused a nonsense mutation of the CD177 gene in exon 9. This individual might have the 787A-1254A-1291G/787T-1254G-1291G genotype. From the second cohort (771 unrelated donors), the 1254GG homozygote was the most common (96.37%), followed by the 1254GA heterozygote (3.50%) and 1254AA homozygote (0.13%). Blood samples of two individuals with 787AT-1254GA-1291GG and 787AA-1254AA-1291GG genotypes were tested and the HNA-2 antigen expressions were 0.03% and 0.16% in rank. CONCLUSIONS:The c.787A>T is a primary genetic hallmark to determine the HNA-2 null phenotype. Additional screening of the novel c.1254G>A in combination with c.787A>T is a suitable, convenient and effective diagnosis among Thais.

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