Objective To investigate the serological characteristics and molecular mechanism of an individual with Am phenotype.Methods The sample with ABO blood group discrepancy was confirmed by serological techniques.The full cod-ing and flanking regions of the ABO gene including intron 1 transcription factor binding site were identified through direct se-quencing of PCR-amplified products.PCR products of exon 6-7 were validated to isolate the ABO gene haplotypes by clo-ning and sequencing individual colonies.Bioinformatics software was used to analyze the structure of the mutant protein.Re-sults The serologic characteristics of ABO blood typing showed the rare Am phenotype.The c.467C/T and c.912C/A heter-ozygous sites in exon 7 were identified by direct sequencing analysis.Further TA cloning and sequencing revealed that the patient carried an ABO*O.01.01 allele and a novel ABO*A allele.The new allele sequence had one nucleotide alteration(C＞A)at position 912 on the background of the ABO*A1.02 allele.The new allele sequence has been included in the Gen-Bank database with the entry number JX489776.The c.912C＞A mutation was predicted to be"probably damaging"and"deleterious"by PolyPhen2 and PROVEAN algorithms,respectively.The free energy change(ΔΔG)value predicted it to have a destabilizing effect on the GTA protein.Meanwhile,modeling of the 3D structure predicted that the p.S304R amino acid substitution may alter the hydrogen bond of the GTA protein.Conclusion The p.S304R substitution of α-1,3-N-acetylgalactosaminyltransferase gene may reduce the antigen expression owing to a greatly destabilizing effect on the structure and function of the GTA protein.

【Objective】 To study the molecular basis of D variant and explore the molecular genetic mechanism of novel weak D alleles. 【Methods】 Blood samples were screened for D variants by serological method. The nucleotide sequences of coding region were amplified by PCR and sequenced directly, and RHD gene heterozygosity was detected. 【Results】 Weak D phenotype was confirmed by serological test, and two novel alleles were detected by DNA sequencing. The first was novel weak D 1102A allele, 1102G>A mutation in exon 8, resulting in a 368Glu>Arg substitution in two samples. The second was novel weak D 399C allele, carried a 399G>C mutation in exon 3, which led to a 133Lys>Asn substitution. 【Conclusion】 In this study, D variants were detected by sequence-based typing, and two new alleles were identified.