Résumé
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 al eles with nt803C>G on the basis of B101 al ele 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 al eles with nt803C>G mutation on the basis of A101 sequence were found at nt-26C(10%). Other two B(A)04 al eles 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 cel membrane even if the samples had the same ABO genetic background.