双碱基缺失型等位基因复合杂合导致的类孟买型个体1例

Para-Bombay Phenotype Caused by Combined Heterozygote of Two Bases Deletion on fut1 Alleles

本研究探索1例类孟买型血型的分子机制,为稀有血型的筛选和鉴定提供理论基础。以血型血清学方法鉴定该个体红细胞的ABO和H表型,利用聚合酶链反应扩增类孟买表型个体的abo基因第6、7外显子和α1,2岩藻糖基转移酶基因(fut1)编码区,并对PCR产物直接测序分析。对纯化的fut1扩增产物进行TOPO克隆和测序,对2处变异位点进行单倍体序列分析。结果表明:血清学分析确认该个体为罕见的类孟买表型;直接测序发现先证者fut1基因第547位和880位附近存在碱基缺失或插入变异;TOPO克隆测序法证实,fut1基因1条单倍体存在第547-552位两碱基AG缺失,另1条单倍体存在880-882位两碱基TT缺失。这2种变异均导致移码突变,并提前形成终止密码。结论:在献血人群中发现1例罕见的类孟买表型,其分子机制为双碱基缺失型fut1等位基因复合杂合所致的α1,2岩藻糖基转移酶活性减弱。

This study was purposed to investigate the molecular basis of a para-Bombay phenotype for screening and identification of rare blood group.ABO and H phenotypes of the proband were identified by serological techniques.The exon 6 to exon 7 of ABO gene and full coding region of α-1,2-fucosyltransferase（fut1） gene of the proband were analyzed by polymerase chain reaction and direct sequencing of the amplified fragments.The haplotype of compound heterozygote of fut1 was also identified by cloning sequencing.The results indicated that a rare para-Bombay phenotype was confirmed by serological techniques.Two deletion or insertion variant sites near nucleotide 547 and 880 were detected in fut1 gene.The results of cloning sequence showed that one haplotype of fut1 gene was two bases deletion at 547-552（AGAGAG→AGAG）,and another one was two bases deletion at position 880-882（TTT→T）.Both two variants caused a reading frame shift and a premature stop codon.It is concluded that a rare para-Bombay phenotype is found and confirmed in blood donor population.The molecular basis of this individual is compound heterozygote of two bases deletion on fut1 gene which weaken the activity of α-1,2-fucosyltransferase.