Collagenase3 MMP13 1, 1, 1, 1, 2, 2 ,

1
Molecular genetic analysis of Ael variant
phenotype of ABO blood group system  
Hyoun-Chan Cho1, Young Chul Kim1, Sung Ha Kang1,
Mina Hur1, Dong Hun Shin1, Kyu Man Lee1,
Dong-hee Seo2, Young Chul Oh21Department of
Laboratory Medicine, Hallym University College of
Medicine, Seoul, Korea,2Blood Transfusion
Research Institute, The Republic of Korea Red
Cross, Seoul, Korea.
Table 2. Comparison of nucleotide and deduced
aminoacid sequences of the alleles of the human
ABO blood group in relation to this study
Background
Since the genes encoding glycosyltransferases
synthesizing ABO antigens were cloned and
sequenced in 1990, genetic polymorphisms and
phenotype-genotype correlations have been
reported by several investigators, but the
genetic basis remains unclear for many subgroups.
The Ael phenotype is one of the important A
subgroups having very weak A antigen, and recent
studies suggested that different alleles can
result in this phenotype.
Method
Three unrelated Ael blood donors from Korea were
studied. Exons 6 and 7 of the ABO gene, 91 of
the catalytic active part of the
glycosyltransferase, were amplifed and subjected
to direct sequencing.
Table 1. Nucleotide sequence of primers used in
this study and polymerase chain reaction (PCR)
conditions for each primer pair
Only the differences from the nucleotide and
amino acid sequences of A1 concensus gene are
indicated. Dashes indicate deletion. A101, A102,
B101, O101 and O102, responsible for common ABO
phenotypes. Ael allele reported by Olsson et
al.(10) and Oagasawara et al.(13). ? indicates A
allele found in this paper. Abbreviations nt,
nucleotide position aa, amino acid ?, start of
frame shift due to single-base insertion.
Donor allele(O201)
261
297
646
681
771
829
?
Sense primers ABO-1 5'-CATGTGACCGCACGCCT-3' ABO-3
5'-CCGTTCGCCTGCCTTGCAG-3' ABO-5
5'-CAGCTGTCAGTGCTGGAGGTG-3' ABO-7
5'-AAGAGGTGCAGCGGCTTACCA-3' GS-AB
5'-AGGAAGGATGTCCTCGTGGTGG-3' GS-O
5'-AGGAAGGATGTCCTCGTGGTA-3' GS-AO
5'-CCATTGTCTGGGAGGGCATA-3' Antisense
primers ABO-2 5'-TCGGCCACCTCACTGACTTA-3' ABO-4
5'-AAGTCACTGATCATCCCAAT-3' ABO-6
5'-CCGTTGGCCTGGTCGACCATCATGGCCTG-3' ABO-8
5'-AGCCCTCCCAGAGCCCCTGGCA-3' ABO-10
5'-TGCTAAAACCAAGGGCGGGA-3'
Aceeptor allele(A102)
?
Products of gene conversion(Ae102)
646
681
Fig. 1. The proposed schem of generation of Ael02
allele through gene conversion. The vertical
lines represent the single nucleotide
polymorphism sites.
Result
Conclusion
Only C467T substitution in comparison with the
consensus sequence of A gene was found in one Ael
sample, but this mutation was commonly observed
in normal A1 phenotype of Orientals. The other
two samples had T646A (Phe216Ile) and G681A
(silent) substitutions beside C467T sustitution,
reported first from Japanese Ael individual.
T646A substitution is well known as a main cause
diminishing the transferse activity.
Interestingly the latter cases may be produced by
gene conversion between A1 and variant O alleles.
These results indicate that molecular genetic
heterogeneity within the Ael subgroup was also
seen and it is useful to analyze T646A
substitution by molecular genetic methods for
easy discoveries of A variant phenotypes with
very weak or undetectable A antigen. It seems to
be necessary to examine the promoter region and
exons 1-5 that are not believed to be involved
enzyme activity to define mutations in variant
ABO alleles clearly.