A_x04亚型的血清学特征及基因序列分析

The serological characteristic and sequencing analysis on an A_x04 phenotype of ABO blood typing

目的分析A_x04亚型的血清学特性及分子机制。方法对1例Ax亚型在标准血型血清学方法鉴定的基础上,采用聚合酶链反应-序列特异性引物（PCR-SSP）和ABO基因第6、7外显子PCR产物直接测序等方法进行ABO亚型基因分型。结果先证者红细胞含有A抗原,同时血清中含有抗-A。PCR-SSP结果显示样本基因型为A/O1。直接测序分析发现261G/del G和646T/A和681G/A杂合位点。单倍型序列分析得到2个等位基因A_x04和O01。A_x04基因序列与A101基因序列比对在646 T〉A的突变和681G〉A突变,导致多肽链F216I替换。结论α-1,3-N-乙酰半乳糖胺转移酶基因646T〉A突变导致A抗原表达减弱。

Objective To investigate the serological characteristics and molecular characteristics of the A_x04 phenotype.Methods The individual was confirmed by standard serological techniques. The genotyping and sequencing were performed using polymerase chain reaction-sequence specific primer（ PCR-SSP）. Direct sequencing of Exon6 and exon7 of the ABO locus were performed. Results A antigen was detected on red blood cells（ RBCs） of the proband and there was anti-A antibody in the serum. The result of PCR-SSP showed an A/O01 phenotype. DNA sequencing showed 261 G/del G,646 T/A and681 G/A heterozygote through exon6 to exon7. By haplotype sequence analysis,two alleles A_x04 and O01 were obtained. The sequence of Ax04 allele had two nucleotide acid alterations（ 646 T〉 A and 681 G〉A） at the exon 7,resulting in amino acid substitutions（ F216 I） when compared with A101 allele. Conclusion T〉A at nt646 causing α-1,3-N-acetylgalactosaminyltransferase gene mutations can result in the great reduction of A antigen activity.