B亚型中Bx新等位基因的鉴定

Identification of a novel Bx allele in a Chinese Han individual with B subgroup

目的对ABO血型中B亚型分子遗传背景的研究,发现并鉴定ABO新等位基因。方法对5份血型血清学鉴定为B亚型的样本,采用PCR-SSP、ABO基因第6及第7外显子直接测序方法进行基因定型;并对目的B亚型样本进行RT-PCR、巢式PCR扩增、测序,分析其cDNA结构的差异。结果5份血清学为B亚型的样本中,血清学鉴定为Bx的个体发现了一个新的B等位基因。该等位基因与B101等位基因相比,差异仅在于第7外显子的B基因序列中nt721位C>T突变。其余4份B亚型样本的ABO基因第6、7外显子都未发现新的点突变。结论首次在中国汉族人中发现一个721C>T新变异的B等位基因,该等位基因nt721位由C转变为T,241位氨基酸由精氨酸转变为色氨酸,可导致糖基转移酶活性的降低,表明ABO基因的第241位氨基酸对决定糖基转移酶活性是至关重要的。

Objective To study the molecular genetic background of B subtypes and identify novel allele at the ABO locus, Methods Five samples from individuals diagnosed as B subgroup by serological tests, were genotyped by PCR-SSP and direct DNA sequencing at exons 6 and 7 ofABO gene. The Bx subgroup gene was amplified by reverse transcription PCR（RT-PCR） and nested PCR. Then the ABO eDNA was sequenced. Results A novel B variant allele was identified in an individual who was diagnosed as Bx subgroup. The novel B allele differs from allele B101 by single 721C〉T missense mutation in exon 7. No novel point mutation at exons 6 and 7 ofABO gene was detected in the other four samples with B subgroup. Conclusion We define this allele as a novel B allele in Chinese Han individuals. The mutation of this novel allele in which the nucleotide changes from C to T at position 721 in exon 7, resulting in an amino acid change from Arg to Trp, results in the decrease of the enzyme activity. It indicates that the alteration of amino acid at position of 241 is critical to the activity of glycosyltransferases.