Fukumori Y, Ohnoki S, Yoshimura K, Nagao N, Shibata H, Tomita T, Okubo Y, Yamaguchi H
Osaka Red Cross Blood Centre, Japan.
Transfus Med. 1996 Dec;6(4):337-44. doi: 10.1111/j.1365-3148.1996.tb00093.x.
DNA samples were analysed from Japanese individuals with the very rare ABO variant phenotype, cisAB (A2B3), which is characterized by the apparent inheritance of both A and B genes on one chromosome. The nature of the bases present at nucleotide positions (nps) 261, 526, 703, 796 and 803 is important for the specificity of the alleles at the ABO locus and the DNA from the cis AB donors was analysed by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) to determine which nucleotides are present at these positions. The results indicated that the cisAB allele had the AAAB-structure, which was a chimera of normal A and B alleles, when the expression 'AAAA' and 'BBBB' indicated the nucleotides of normal A (C, G, C and G) and B (G, A, A and C) genes at nps 526, 703, 796 and 803, respectively. The AAAB allele was found in all 27 individuals (17 families) with the cisAB including three phenotypes A2B3, A1B3 and A2B and no other chimeric gene was found. The causative gene of cisAB was the AAAB allele, and the A and B alleles were not on one chromosome. The cisAB allele appeared to be a product of the normal A allele due to a point mutation at nucleotide position 803, from G to C. The AAAB allele is thought to be normally transcribed and translated to produce an unusual transferase polypeptide, which has weak A- and weaker B-specific activity. PCR-RFLP is a rapid and useful means of detecting the cisAB allele (the AAAB allele) without a family study, even when they have A1B3 and A2B phenotypes, because trans-type A1B3 and A2B samples have obviously different PCR-RFLP profiles.
对具有极为罕见的ABO变异表型即顺式AB（A2B3）的日本个体的DNA样本进行了分析，该表型的特征是一条染色体上同时存在A和B基因的明显遗传现象。ABO基因座上等位基因的特异性对于核苷酸位置（nps）261、526、703、796和803处的碱基性质很重要，通过聚合酶链反应-限制性片段长度多态性（PCR-RFLP）分析了顺式AB供体的DNA，以确定这些位置上存在哪些核苷酸。结果表明，当用“AAAA”和“BBBB”分别表示正常A基因（C、G、C和G）和B基因（G、A、A和C）在nps 526、703、796和803处的核苷酸时，顺式AB等位基因具有AAAB结构，它是正常A和B等位基因的嵌合体。在所有27例（17个家系）具有顺式AB的个体中均发现了AAAB等位基因，包括三种表型A2B3、A1B3和A2B，未发现其他嵌合基因。顺式AB的致病基因是AAAB等位基因，A和B等位基因并不在一条染色体上。顺式AB等位基因似乎是正常A等位基因由于核苷酸位置803处发生从G到C的点突变而产生的产物。AAAB等位基因被认为通常会被转录和翻译以产生一种异常的转移酶多肽，其具有较弱的A特异性活性和更弱的B特异性活性。即使对于具有A1B3和A2B表型的个体，PCR-RFLP也是一种无需家系研究就能快速且有用地检测顺式AB等位基因（AAAB等位基因）的方法，因为反式A1B3和A2B样本具有明显不同的PCR-RFLP图谱。
