双重复合糖基转移酶的ABO基因启动子CpG岛甲基化

Methylation of CpG island in ABO gene promoter coding glycosyltransferase with dual donor specificity

背景:在ABO血型抗原的研究中,绝大多数样本是相同的ABO基因表达出正常的相同的ABH抗原。但有一定数量的样本表现出具有相同分子遗传背景但表达出来的抗原强度却随着家系\个体不同而有所差异,说明了ABO血型中复杂的表达调控机制。分析一类罕见的双重复合型标本的ABO血型血清学与基因背景情况,深入表观遗传学的研究,有利于部分揭示ABO基因表达机制。目的:探讨双重复合型ABO糖基转移酶表达相关的ABO基因启动子CpG岛甲基化水平与ABH抗原表达的关系。方法:6例经血型血清学定为CisAB或B(A)型的标本,进行ABO基因编码区全长序列和启动子序列的测定,采用重亚硫酸盐处理法检测ABO基因启动子CpG岛甲基化程度。结果与结论:6例双重复合AB型的标本中,在B101等位基因基础上存在nt803C>G突变的2个CisAB05/B(A)06等位基因,在ABO启动子CpG岛区域两者在nt-33(30%)、nt+27(50%)、nt+49(50%)具有甲基化差异;在A101等位基因序列的基础上存在nt803C>G突变的2个CisAB01等位基因,在ABO启动子CpG岛区域两者在nt-26(10%)位置有甲基化差异;在B101等位基因基础上存在nt640A>G突变的2个B(A)04等位基因ABO启动子CpG岛,在nt-33(10%)、nt+16(50%)、nt+57(60%)、nt+59(60%)、nt+68(60%)和nt+74(60%)位有甲基化差异。全部的6例标本ABO基因启动子区域DNA序列无任何突变异常。结果提示在相同的ABO遗传基因背景下,ABO基因启动子CpG岛区域某些位点甲基化可能影响ABH抗原在红细胞膜表面的表达。

BACKGROUND： During the research of ABO blood type antigen, the overwhelming majority samples of same ABO gene express a normal and same ABH antigen. But a certain amount samples with the same ABO genetic background show different antigen intensity expression as for different family or individuals. The ABO blood type has complex expression regulation mechanism. Analysis of ABO blood group serology and genetic background of these rare bi-specific AB phenotype specimens, and further studying on epigenetics may partly revealed ABO gene expression mechanism. OBJECTIVE： To study methylation of CpG island and explore the relationship between ABO gene promoter coding glycosyltransferase with dual donor specificity and ABH antigen expression. METHODS： Six samples detected as CisAB or B（A） phenotype were studied in this paper. The whole code sequences and promoter sequence of ABO gene were amplified respectively. The level of CpG methylation in promoter of ABO gene was further detected with bisulfite treatment method. RESULTS AND CONCLUSION： Among the six bi-specific AB phenotype samples, two previously-identified CisAB05/B（A）06 alleles with nt803C G on the basis of B101 allele sequence could be seen, and three additional methylated sites nt-33（30%）, nt＋27（50%） and nt＋49（50%） were found between the two regions of CpG island in promoter of ABO gene. Two CisAB01 alleles with nt803C G mutation on the basis of A101 sequence were found at nt-26C（10%）. Other two B（A）04 alleles contained nt640A G mutation on the basis of B101 sequence were found in the whole code sequences regions, and six additional methylated sites nt-33（10%）, nt＋16（50%）, nt＋57（60%）, nt＋59（60%）, nt＋68（60%） and nt＋74（60%） were found between the two samples. No abnormity was identified in the promoter region of ABO gene. Our results indicated that the differential methylation levels in the CpG island of ABO gene promoter region may affect ABH antigens expression on the red cell membrane even if the samples had the same ABO genetic background.