一种新的B3变异型相关的B糖基转移酶基因M142T突变研究

目的 研究中国人个体ABO血型系统中具有混合外观凝集特征的B3变异型的分子遗传背景.方法 血型血清学方法鉴定2例ABO血型疑难样本的红细胞表型,应用连续凝集方法和13个短串联重复序列(short tandem repeat,STR)位点检测法,排除外源性或内源性DNA嵌合的可能.对ABO基因第6、7外显子和部分内含子进行聚合酶链反应和DNA序列分析,并进一步通过克隆测序法鉴定2个样本的ABO基因单倍型.结果 2个无关个体红细胞与抗-B和抗-AB发生混合外观凝集,连续凝集法和STR检测排除了样本的外源性DNA污染和内源性遗传嵌合子,根据血清学特征确定这2个个体红细胞均为A183血型.单倍型序列分析发现2个样本为A1B杂合子,其中B等位基因与B101相比,差异仅在第7外显子的425T>C错义突变,导致B糖基转移酶多肽链M142T替换.结论 在中国人群中发现一种新的可能导致B3变异型的ABO等位基因.

A novel M142T mutation in the B glycosyltransferase gene associated with B3 variant in Chinese

Objective To investigate the molecular genetic basis of the B3 variant of ABO blood group system with mixed-field hemagglutination in Chinese. Methods Serological techniques were performed to characterize the erythrocyte phenotype of two discrepant samples. A sequential agglutination method and 13 short tandem repeat (STR) loci were tested to exclude the possibility of exogenous or endogenous DNA chimera. Mutations in exons 6 and 7, including partial intron of the ABO gene, were screened by polymerase chain reaction and DNA sequencing. Haplotypes of the two individuals were also analyzed by sequencing. Results A mixed-field hemagglutination of RBCs with anti-B and anti-AB antibodies was detected in the two unrelated individuals. Exogenous ABO-incompatible RBC transfusion and endogenous genetic chimera were excluded by sequential agglutination method and STR. The ABO phenotypes of the two individuals were classified as A1B3 according to the ABO subgroup definition. The sequence region from intron 5 to 3'-UTR of the B allele was identical to that of ABO * B101 allele, except for a T to C substitution at nucleotide position 425 in exon 7. This substitution resulted in an amino acid change of M142T in the B glycosyltransferase. Conclusion A novel B allele with 425T>C substitution resulting in B3 subgroup was identified in two Chinese individuals.