Three missense mutations, including a novel 860C>T transition, and allelic enhancement phenomenon associated with ABO blood subgroups A in Taiwan.
BACKGROUND
It was estimated that approximately 25 percent of Taiwanese residents were ABO blood group A. Many subgroups of A, however, revealed ambiguous serologic typing results. This study aimed to delineate the molecular basis of the A3, Ax, and weak A phenotypes.


METHODS
Serologic analyses including adsorption and elution assay, serum transferases activity assay, and saliva test were performed to determine the unique phenotypes of these samples. DNA sequencing and polymerase chain reaction-restriction fragment length polymorphism were performed to further investigate the relationships between the genetic characteristics and phenotypic features of these samples.


RESULTS
Three single-nucleotide transitions (745C>T, 820G>A, and a novel 860C>T) were found in nine A3/A3B cases. In addition, the Ax and A3B subjects shared the same 860C>T mutation. This A(x) allele with 860C>T transition expressed A3B phenotype in A(x)/B101 heterozygote but Ax phenotype in A(x)/O01 heterozygote. This allelic enhancement was also observed in the weak A family with Aw05 allele, which was previously not found in Taiwan.


CONCLUSIONS
This allelic enhancement phenomenon was prone to cause serologic discrepancy between parents and children. Genotyping could help us to resolve this problem. Thus, a novel mutation is reported among Taiwanese blood donors.
Li
Lei
L
Taipei Blood Center, Taiwan Blood Services Foundation, and the Institute of Biochemistry and Molecular Biology, National Yang Ming University, Taipei, Taiwan.
Yang
Meng-Hua
MH
Chak
Kin-Fu
KF
Lin
Pi-Hsiang
PH
Lai
Chao-Hung
CH
Lin
Kuan-Tsou
KT
Tsai
Su-Jen Lin
SJ
Lin
Kuo-Sin
KS
Chu
Da-Chang
DC
D000017:ABO Blood-Group System / Q000235:genetics*; D000483:Alleles; D044466:Asian People / Q000235:genetics; D001782:Blood Donors; D001788:Blood Grouping and Crossmatching; D004252:DNA Mutational Analysis; D005190:Family; D005260:Female; D005838:Genotype; D006801:Humans; D008297:Male; D020125:Mutation, Missense; D010375:Pedigree; D013624:Taiwan
D000017:ABO Blood-Group System