一例ABO亚型CisAB个体的分子遗传学分析

目的研究1例ABO亚型的分子机制。方法先证者红细胞ABO表型鉴定采用常规血清学技术,ABO基因第6~7外显子序列采用PCR技术扩增并应用Sanger法双向进行测序分析。先证者ABO基因第6~7外显子单体型检测采用单链扩增测序技术。结果先证者红细胞与抗-A凝集强度4+、抗-A1不凝集,抗-B凝集强度3+,抗-H凝集强度4+;其血清与标准A细胞、O细胞和自身细胞不凝集,与标准B细胞在4℃呈现弱凝集,先证者血清学特性符合ABO亚型。ABO基因第6~7外显子双链测序分析显示先证者261 G/del、297AG、526CG、657CT、703GA、803GC、930GA杂合,796CC纯合。单体型测序显示先证者一个等位基因为ABO*O.01.01,另一个等位基因与ABO*B.01相比仅c.796A>C变异,导致266位蛋氨酸变成亮氨酸;比较国际输血协会ABO等位基因已命名的数据,发现该变异属于新等位基因。结论ABO*B.01等位基因c.796 A>C变异,导致266位蛋氨酸变成亮氨酸,可引起CisAB亚型。准确鉴定ABO亚型应结合血清学技术和分子生物学技术。

Molecular analysis of an individual with CisAB phenotype

Objective To explore the molecular basis for an individual with ABO subtype.Methods The ABO phenotype of the proband was determined by convention serological testing.Exons 6 and 7 of the ABO gene were subjected to PCR amplification and bi-directional Sanger sequencing.Haplotypes for exons 6 and 7 of the proband was determined using an ABO haplotype-specific amplification and sequencing technique.Results Red blood cells of the proband showed a 4+agglutination strength with anti-A or anti-H,no agglutination reaction with anti-A1,and a 3+agglutination strength with anti-B.His serum had no reaction with standard A cells,O cells or self cells,but was weakly reactive with B cells at 4℃.The proband was assigned as an ABO subtype based on his serological features.Bi-directional sequencing of the ABO gene revealed heterozygosity of 261 G/del,297AG,526CG,657CT,703GA,803GC and 930GA,and homozygosity of 796CC in the proband.Haplotype-specific amplification and sequencing showed that one of his alleles was ABO*O.01.01,and another contained a c.796A>C variation compared with the ABO*B.01 allele,which led to replacement of methionine by leucine at position 266.Searching the ABO allele database of International Society of Blood Transfusion suggested the variation to be a novel one.Conclusion The c.796A>C variation in the ABO*B.01 allele probably underlies the CisAB subtype.Accurate identification of the ABO subtype requires combined use of serological method and genetic testing.