Bel亚型新等位基因c.620T>C 1例的分子研究

Molecular study of an individual with Bel subtype due to a novel c.620T>C variant

目的对1例ABO血型Bel亚型新等位基因(c.620T>C)先证者进行分子生物学研究,以揭示该突变对α-1,3-半乳糖苷转移酶(GTB)结构的影响。方法选取2023年2月11日于郑州大学第一附属医院输血科就诊的1例先证者为研究对象。首先采用血清学方法进行ABO表型的鉴定,接着对ABO基因的7个外显子进行直接测序,进一步采用单倍体特异性引物进行单链测序,最后用Modeller软件对突变的GTB进行同源建模,并用PyMOL软件分析突变对GTB空间结构的影响。结果先证者血清学表型为Bel亚型,直接测序发现了1个新的突变位点c.620T>C,导致多肽链发生p.Leu207Pro氨基酸替换。结合单链测序,最终确定基因型为ABO*BELnew/ABO*O.01.02。蛋白质三维结构建模显示,与野生型相比,脯氨酸与p.Gly272之间的1条氢键距离变大,另1条氢键消失。结论上述研究鉴定出1例新的B等位基因突变c.620T>C(p.Leu207Pro),该突变影响了GTB空间结构的稳定性,酶的活性减弱导致了B抗原表达减弱,血清学表现Bel亚型。

Objective To explore the molecular basis for an individual with Bel subtype of the ABO blood type due to a novel c.620T>C variant gene,and assess its impact on the structure of GTB transferase.Methods An individual who had visited the First Affiliated Hospital of Zhengzhou University on February 11,2023 was selected as the study subject.ABO phenotyping was initially conducted with serological methods,which was followed by direct sequencing of 7 exons of the ABO gene.Subsequently,single-strand sequencing was carried out by using allele-specific primers,and the variant in the B transferase was homology-modeled using the Modeller software.The impact of the variant on the transferase′s spatial structure was analyzed with the PyMOL software.Results The serological phenotype of the patient was identified as the Bel subtype.Direct sequencing revealed that she has harbored a novel c.620T>C variant,resulting in a p.Leu207Pro substitution in the polypeptide chain.Combined with single-strand sequencing,her genotype was ultimately determined as ABO*BELnew/ABO*O.01.02.Three-dimensional protein structure modeling showed that,compared with the wild type,the distance of one hydrogen bond between Proline and Glycine at position 272 has increased,along with disappearance of another hydrogen bond.Conclusion The novel c.620T>C(p.Leu207Pro)variant of B allele may affect the structural stability of the glycosyltransferase.The weakened enzyme activity in turn may lead to reduced B antigen expression,manifesting as the Bel subtype by serological analysis.