From www.bloodjournal.org by on October 15, 2008. For personal use only.

1996 88: 2732-2737

Molecular genetic analysis of variant phenotypes of the ABO bloodgroup system
K Ogasawara, R Yabe, M Uchikawa, N Saitou, M Bannai, K Nakata, M Takenaka, K Fujisawa, Y
Ishikawa, T Juji and K Tokunaga

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Copyright 2007 by The American Society of Hematology; all rights
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From www.bloodjournal.org by on October 15, 2008. For personal use only.

Molecular Genetic Analysis of Variant Phenotypes of theA B 0 Blood Group System
By Kenichi Ogasawara, Ryuichi Yabe, Makoto Uchikawa, Naruya Saitou, Makoto Bannai, Kenichi Nakata,
Michiko Takenaka, Kiyoshi Fujisawa, Yoshihide Ishikawa, Takeo Juji, and Katsushi Tokunaga
A 6 0 is clinically the most important blood group system intransfusion medicine and includes many variant phenotypes. To understand the molecular genetic basis of thispolymorphic system, we have analyzed genomic DNAs obtained from Japanese individuals possessing variant AB0
phenotypes including A,, Ax, A,,, cis-AB, B., and B-,. By polymerase chain reaction-single-strand conformation polymorphism (SSCP) and nucleotide sequence analyses, we identified 11 different alleles. These alleles had nucleotide
sequences different from those of the previously described
13 different alleles responsible for the common AB0 phenotypes. Analysis of the nucleotide sequences of the alleles
responsible for those variant phenotypes showed that theamino acid residues at positions 266 and 268 may be crucial

for transferase specificity, whereas those at positions 214,
216, 223, 291, and 352 may be critical for the activity level.
Nine of the 11 alleles, responsible for the A,, A,, Ael, cis-AB,
B,, and Bel phenotypes, were presumed to be generated
from common A B 0 alleles by single nucleotide mutations
such as nonsynonymoussubstitution, deletion, or insertion.
Two other alleles, responsible for the A2 and A., phenotypes,
may have originated by recombination, gene conversionlike
events or accumulation of nucleotide substitutions. Our data
indicate that different alleles could cause the same AB0 variant phenotypes, and that these alleles do not necessarily
belong to a single evolutionary lineage.
0 1996 b y The American Society of Hematology.

Tcritical for the specificity and activity level of transferases
in the catalytic domain. The evolutionary lineages of thesealleles and other A B 0 alleles are also discussed.

HREE MAJOR ALLELES (A’, B , and 0 ) encoding
transferases of the A B 0 blood group system were firstcloned and sequenced by Yamamoto et a1.1,2The A’ andB alleles encode 354-amino acid-long proteins, which are
predicted to be type I1 transmembrane glycosyltransferases
comprised of a short N-terminal domain, a hydrophobictransmembrane domain, and a long C-terminal catalytic domain. The 0 allele has a single nucleotide deletion at position
261 compared with the A’ allele, which results in a frame
shift to create a different amino acid sequence and a stopcodon at amino acid position 118, and thus the 0 allele
encodes a catalytically inactive protein.
In a previous study,3 we determined the sequences of 13
different alleles detected in 262 healthy Japanese individuals
possessing common A B 0 phenotypes and clarified the existence of several alleles responsible for single phenotypes.
These alleles were classified into three major lineages interms of their evolutionary relationships. In addition, weestablished a polymerase chain reaction (PCR)- singlestrand conformation polymorphism (SSCP) method whichallowed us to identify the common A B 0 alleles as well as
to detect unknown A B 0 alleles.
In the present work, we have extended our study to variant
A B 0 phenotypes. We report here eight newly sequenced
alleles. The results enabled us to predict amino acid residues

From the Japanese Red Cross Tokyo Metropolitan Blood Center;
Japanese Red Cross Central Blood Center; Laboratory of Evolutionary Genetics, National Institute of Genetics; and the Department of
Human Genetics, Graduate School of International Health, University of Tokyo, Tokyo,Japan.
Submitted January 16, 1996; accepted May 20, 1996.
Address reprint requests to Kenichi Ogasawara, PhD, Japanese
Red Cross Tokyo Metropolitan Blood Center, 1-26-1 Kyonan-cho,Musashino-shi, Tokyo 180, Japan.
The publication costs of this article were defrayed in part by page
charge payment. This article must therefore be hereby marked“advertisement” in accordance with 18 U.S.C. section 1734 solely toindicate this fact.
0 I996 by The American Society of Hematology.
0006-4971/96/8807-0023$3.00/0

2732

MATERIALS AND METHODSA B 0 grouping. AB0 phenotypes including A2,A,, 4,, B, , Be,,and cis-AB were determined by agglutination and adsorption-elution
tests using murine monoclonal anti-A and anti-B IgM antibodies(Ortho, Raritan, NJ), human polyclonal anti-A, anti-B (Dade, Miami,
E),and anti-A,B antibodies (Ortho), and plant lectins (Dolichos
bijorus for anti-A,, Ulex europaeus for anti-H; Sanko Junyaku Co,
Tokyo, Japan). The phenotypes A, and AZ were discriminated byanti-A,: strong agglutination (4+) for A, and no agglutination (0)for A2. The weak phenotypes A, and A,, were determined using
monoclonal anti-A and polyclonal anti-A,B antibodies, weak agglutination (1-2+) for A, and 0 for A,,, and the presence of the A
determinants on the A,, red blood cells (RBCs) was shown using anadsorption-elution technique with polyclonal anti-A antibodies. The
phenotypes B, and Be, were determined in the same manner using
anti-B and anti-A,B antibodies. The cis-AB positive individuals wereselected from two families. In total, we selected 19 A*, 3 A,, 4 A,,,
2 cis-AB, 1 B,, and 2 Be,positive individuals from among healthy
Japanese people.
The serum transferase activity levels were assayed by estimating
the degree (agglutination score4)of the conversion of group 0 RBCs
into A or B cells5 using the monoclonal anti-A and anti-B antibodies.
Discrimination of AB0 alleles. Genomic DNAs were preparedfrom peripheral blood samples of the above individuals by standard
phenol-chloroform extraction.6 The PCR-SSCP analysis, group-specific PCRs, and direct sequencing were performed as described prev i o ~ s l yExons.~
6 and 7 of the AB0 gene,’,’ which encode most of
the catalytic domain of the transferase, were amplified using four
primer pairs under appropriate conditions and the four fragments
obtained (I-IV) were subjected to SSCP analysis for detecting sequence differences.
SSCP analysis was performed using a 12S% to 15% polyacrylamide gel (acry1amide:bisacrylamide = 49:l) with or without 5%(vollvol) glycerol. Briefly, 1 pL of amplified DNA solution was
mixed with 7 pL of denaturing solution (95% formamide, 20 mmoll
L EDTA, O.OS% bromphenol blue, and 0.05% xylene cyano1 FF),
heated at 95°C for S minutes, and immediately chilled on ice, and1 WLof the mixture was subjected to polyacrylamide gel electrophoresis at 12°C to 30°C. The separated single-strand DNA fragments

Blood, Vol 88,No 7 (October I), 1996:pp 2732-2737

From www.bloodjournal.org by on October 15, 2008. For personal use only.
A B 0 VARIANT ALLELES

2733

Fragment JIIi

IUf IUk me IUI IUh m i IUj IUd ma IUc IUm IUb IIIg

Fragment IV

As shown in Table 1. we identified I I different alleles
from the SSCP patterns which were different from the previously identified A BO alleles.' Assay of serum transferase
showed that all the samples possessing these alleles had nodetectable activity, except for the sample possessing
ABO*RIOI. The alleles responsible for specific phenotypes
were often heterogeneous: 4 alleles (ARO*AIOS. *A106*A107. and *RIOI) for A?. 2 alleles (ABO*A109 and *AIIO)
for A,,, and 2 alleles (ABO*BIOS and *BlO6) for Bel. In A2
phenotype samples, the relative frequencies of ABO*AIOS.
*AlO6, *A107. and *RIOI were 5% 53%, 37%. and 5%
respectively. In addition, 2 of 3 alleles obtained from the A,
phenotype samples were ABO*A108, but the other allele
showed SSCP patterns identical to those of the previously
described ABO*A102 (forfor fragments I-IV (data notshown). Similarly, 2 of 4 alleles obtained from the A,, phenotype samples were different from the alleles responsible forcommon AB0 phenotypes and thus named ABO*AIOY and*AIIO. whereas the other 2 alleles could not be discriminatedfrom ABO*A102 in the present SSCP analysis. In contrast,
we found the same allele, ABO*CIOI, in the two unrelatedfamilies with the cis-AB phenotype (Fig 2). Although we
examined only one B, phenotype sample, the identified allele, ABO*BI04, showed a specific SSCP pattern (IVf) as
shown in Fig I .
Nucleotide sequences of variant AB0 alleles. The nucleotide sequences of the 1 1 different alleles* responsible forthe variant AB0 phenotypes are summarized in Table 2.
One of the four alleles responsible for the A2 phenotype.
ABO*AIOS, had a nonsynonymous substitution. CCG (Pro)to CTG (Leu), at codon 156, and a nucleotide deletion (oneof the cytosines at nucleotide positions 1059-1061) compared with ABO*AIOI. and thus had a sequence identical tothat of the previously described allele responsible for the A2
phenotype." The other three alleles responsible for the A?
phenotype, ABO*A 106, *A107, and *RIOI. had sequences
different from those of the previously described AB0 alleles.
BothABO*A106 and *A107 had a single nucleotide substitution (C to T and C to G, respectively) at position 1054
compared withABO*A101 resulting in an amino acid substitution at position 352 (Arg to Trp and Arg to Gly, respectively). ABO*RIOI had six nucleotide differences, at positions 297, 526, 657, 703, 771, and 829, compared with
ABO*A 101 resulting in three amino acid substitutions, at
positions 176, 235. and 277.
ABO*CIOI responsible for the cis-AB phenotype had two
nonsynonymous substitutions, at codons I56 (CCG codingfor Pro to CTG for Leu) and 268 (GGG coding for Gly
to GCG for Ala), as compared with ARO*AIOI, and thenucleotide sequence was identical to that of the previously
described allele responsible for the cis-AB phenotype."
ABO*AIO8 responsible for the A, phenotype also had a sequence identical to that of the previously described allele'2

r]

Ivc

IVa

Ne

IVd

IVb

IVf

Fig 1. PCR-SSCP analysis of fragments 111 and IV of AB0 bloodgroup gene. Only the patterns of single alleles obtained either bygroup-specific PCR or from homozygous samples are shown.

in the gel were visualized by silver staining (Daiichi Pure Chemicals,Tokyo, Japan).
Group-specific PCRs were then performed to prepare the DNA
templates for sequence analysis. The prepared DNAs were directly
sequenced at least twice for each direction by a cycle-sequencing
method with the same primers as those used for PCR-SSCP using
an automated DNA sequencer (373A: Applied Biosystems. Foster
City, CA).
The observed alleles were provisionally named according to theguidelines for human gene nomenclature.'' When an identified allele
was presumed to be generated by recombination. R was used as thefirst letter of the allele name. In the case of an allele responsible forthe cis-AB phenotype, the letter C was used.
RESULTS

AB0 alleles identified by PCR-SSCP. Typical SSCP patterns of the alleles obtained from healthy Japanese with variant AB0 phenotypes are shown in Fig 1. The newly observed
SSCP patterns were Illg, Illh, IIli, IIIj, IIIk, 1111, and lllm
for fragment 111, and IVc, IVd, We, and IVf for fragment
IV. As for fragments I and 11, all the alleles identified inthis study showed SSCP patterns identical to some of thosereported previously for common AB0 phenotypes3(data notshown).

* The nucleotide sequences in this report have been suhmitted
to the DDBJEMBUGenBank data bases (accession nos. D82835D82845).

From www.bloodjournal.org by on October 15, 2008. For personal use only.
2734

OGASAWARA ET AL
Table 1. SSCP Patterns and Serum Transferase Activity Levels for Alleles Obtained From Blood Samples of Each Phenotype~~

Serum Transferaset
Allele*ABO*Al01*A 102*A 105*A 106*A 107*RlOl*ClOl*A 108*A109*A I10ABO*BIOI
*E104
'8105

*E106

Phenotype of Blood
Sample

Ai
Ai
A2
A2
A2
A2
cis-AB
AX
A.1
&I

B
8.
61
.
61
.

A

SSCP Pattern of Each Fragment
B

90 (89-91)
82 (76-89)
0
0
0
75
0
0
0
0

n

FI

FII

Flll

FIV

4

la
la
la
la
la
Ib
la
la
la
la
Ib
lb
Ib
Ib

Ila
Ilb
Ilb
Ila
Ha
Ild
Ilb
Ila
Ila
Ilb
Ild
Ild
Ild
Ild

llla
llla
llla
llla
llla
lllg
lllh
llli
lllj
lllk
lllb
lllb
1111
lllm

IVa
IVa
IVC
IVd
IVe
IVa
IVa
IVa
IVa
IVa
IVb
IVf
IVb
IVb

4
1

0

79 (75-89)
0
0
0

10
7
1
2
2
1
1
4
1
1
1

* Because all the samples, except for one of the cis-AB phenotype samples, examined possessed an 0 allele ( * 0 1 0 1 , *0201, or *02023),only
the SSCP patterns of the alleles presumed to be responsible for each variant phenotype are shown. ABO*Al01 and *AI02 responsible for Ai
phenotype and *BIOI responsible for B phenotype are also shown.
t A and B transferase activity levels are indicated by agglutination score, mean, and (range). Sera of one of the cis-AB and two of the A2(*AlO6) samples were not available.

with a nonsynonymous substitution at codon 216 (TTC coding for Phe to ATC for Ile) compared with ABO*AlOl.
One of the alleles responsible for the &, phenotype,
ABO*Al09, had a single nucleotide insertion (G) in the guanine repeat at positions 798-804 resulting in a frame shift
as compared with ABO*AIOI. In addition, ABO*AIIO, responsible for the 4,
phenotype, had three nucleotide differences, at positions 467 (C to T), 646 (T to A) and 681 (Gto A), resulting in two amino acid substitutions, at positions
156 (Phe to Leu) and 216 (Phe to Ile), compared with
ABO*AIOI. The nonsynonymous substitution at nucleotide
position 461 was also detected in ABO*AIOS, *CIOI andthe previously described ABO*A102,3 and the other two nucleotides, at positions 646 and 681, were the same as thosein ABO*0201.
All three B variant alleles (ABO*B104, *B105, and *B106)
and ABO*BIOl shared seven nucleotide differences, at positions 297,526,657,703,796,803, and 930, compared with
ABO*AIOI. In addition, ABO*B104 responsible for the B,
phenotype had a single nonsynonymous substitution at codon

291 (GAC coding for Asp to AAC for Asn) compared withABO*BIOI. ABO*BlOS and *B106 responsible for the B,,
phenotype also had single nonsynonymous substitutions, atcodons 214 (ATG coding for Met to AGG for Arg) and223 (GAG coding for Glu to GAT for Asp), respectively,
compared with ABO*BIOI.
In total, 8 of the above 11 alleles (ABO*AI06, *A107,*R101, *A109, *AIIO, *B104, *BIOS, and *B106) were
newly sequenced A B 0 variant alleles.
DISCUSSION

The amino acid differences of the transferase for eachvariant phenotype deduced in the present nucleotide sequence analysis and the previous reportI3are summarized inTable 3. Because the amounts of A or B determinants onerythrocytes are, in order of quantity, A,>A2>A3>A,>&,or B>B,>B,>B,,, it is predictable that the most criticalamino acids for the enzymatic activity level are found at
positions 214 (Met or Arg), 216 (Phe or Ile) and 223 (Gluor Asp). The amino acid substitutions at positions 291 (AspFrom www.bloodjournal.org by on October 15, 2008. For personal use only.
AB0 VARIANT ALLELES

2735

Table 2. Comparison of Nucleotide and Deduced Amino Acid Sequences of the AB0 Allales Identified by PCR-SSCP
Nucleotideand Amino Acid Position
526
(176)

nt 261
(aa)

297

467
(156)

703
(235)

771

796
(266)

'A107

G

A

C

- -

C
G
(Leu) (Gly)*A 105

C
C
T
T
C
G
G
G
(Pro) (Arg) (Met) (Phe)
(Glu)
(Gly)
T
- - - - (Leu)

*A106

-

'A107

- -

'ClOl

- -

- -

"A709
*A710

- -

657

681

803
(268)

798-804

GGGGGGG

829
(2771

871
(291)

930

1054
(352)

1059-61GG(Val) (Asp)

G

C
(Arg)

CCC

cc

- -

-

-

-

-

-

T
(Trp)
G
(Gly)

-

-

-

(+)

-

- -

-

-

- -

-

-

-

-

-

-

-

-

- - - -

-

-

-

-

-

-

-

-

T

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

A

-

-

-

-

-

-

C
(Ala)

-

-

-

-

-

-

-

-

-

-

-

-

-

-

GGGGGGGG

-

-

-

-

-

(-4
-

-

-

-

-

-

- - - -

646
(216)

-

(Leu)

*A 108

641
(214)

€69
(223)

Allele

-

T

-

-

(He)

-

-

-

A

-

-

A

-

A

-

T

A
(Sed
A
(Sed
A
(Sed
A
(Sed
A
(Ser)

T

_

-

T

-

-

T

-

-

T

-

-

T

-

-

T

T
(Asp)

-

-

-

-

A
(Met)
A
(Met)
A
(Met)
A
(Met)

-

C
(Ala)
C
(Ala)
C
(Ala)
C
(Ala)

Only the difference from the nucleotide and amino acid sequences of *A101 are indicated. '0201 and '8101, responsible for common AB0

phenotype^.?^ are also indicated.
Abbreviations: nt, nucleotide; aa, amino acid; -+,start of frame shift due to single-base deletion or insertion.

to Asn) and 352 (Arg to Glynrp) may also lead to a decreasein the activity level, but amino acid changed at positions
156 (Pro to Leu) and 277 (Val to Met) may have little affect.
The serum transferase activity levels of these variant samples(Table 1) support the above prediction.

Table 3. Relationship Betwwn Amino Acid Sequences ofTianderasea and Produced AB0 Characters Deduced
From Nucleotide Sequences
AB0 Character

Ai or BAi
A2
AZ or B,*A2
As* or B.
B.,
AX
%I

Bel

Amino Acid Position and Residue
156
Pro
Leu

214
Met

216
Phe

277
Val

-

-

-

223
Glu

-

-

-

-

-

-

-

Met

-

ASP

-

-

Ile
Ile

-

Arg

-

Leu

-

* Described by Yamamoto et al."

-

-

-

-

-

Interestingly, we found a single nucleotide insertion (G)in the guanine repeat at positions 798-804 in one of thealleles obtained from thephenotype sample, ABO*A109,
which resulted in a frame shift to create a different aminoacid sequence and a stop codon at a different position. This
frame shift resulted in a greater decrease in the level of the
enzymatic activity than that of ABO*AlOS (for A2) possessing a single nucleotide deletion between positions 1059
and 1061. According to the sequence of a genomic clone
described by Yamamoto et al,8 the new stop codon (TGA)
is postulated to be at nucleotide positions 1170-1172. Veryrecently, Olsson et all4 detected the same allele in &*phenotype samples.
Concerning the alleles obtained from A2 individuals, it isinteresting to note the difference in the allele frequencies
described by us and others." Yamamoto et al" reported that
all of the eight alleles from A2 phenotype blood samples
obtained from the American Red Cross (Portland, OR) had asingle nucleotide deletion between positions 1059 and 1061,
which was identical to that of the ABO*AlOS in the present
study. In contrast, we found three other alleles from 19 Japanese possessing the A2 phenotype. Among them, ABO*A106
and *AI07 were predominant at relative frequencies of 53%

From www.bloodjournal.org by on October 15, 2008. For personal use only.
OGASAWARA ET AL

2736

467

467

467

Fig 3. A phylogenetic network for 12 alleles described inTable 2. Open circles designate
intermediate states, and numbers on each branch are nucleotide positions where mutations
occurred. The five numbers inparentheses between the * A and*E lineages, 297, 526, 657, 703,
and 796, could not be assigned
to specific branches.

467

d 0 5 9 - 1 0 6 1

and 37%, respectively. These results clearly indicate thatmultiple alleles could cause a certain A B 0 phenotype andthat their frequencies vary among various populations.
Yamamoto et a!' were the first to report that there wereseven nucleotide differences between A and B alleles. at
nucleotide positions 297, 526, 657, 703, 796, 803, and 930,
resulting in four amino acid differences, at positions 176,
235, 266, and 268. They showed that the last two aminoacid residues at positions 266 and 268 are critical for A/
B transferase sugar specificity in gene reconstruction andexpression studies." An allele encoding a bifunctional transferase for sugar specificity was subsequently identified in
cis-AB individuals." This allele encodes a transferase with
an amino acid sequence identical to that of A, transferase
except for a substitution at position 268 which is shared withAi

ABO*0201 t

X

ABO*B101t

ABO*R 101II

703 771

B
ABO*A 102
X

ABO*0201 t

ABO*AllO1t
646 681

Fig 4. Schemesfor generationof (A) ABO*R707and (B) ABO*A'A110
alleles.

the B transferase. As a result of this amino acid substitution.
the RBCs of cis-AB individuals may express both A and B
determinants. In the present study, we also identified anallele, provisionally called ABO*CIOI, in two unrelated cisAB families by PCR-SSCP analysis, and its nucleotide sequence was identical to that of the previously described allele
responsible for the cis-AB phenotype."
On the other hand, in an A? individual we detected a
new allele (ABO*RIOI) that had six nucleotide differences
resulting in three amino acid differences, at positions 176.
235, and 277, compared with the common AI transferase
encoded by ABO*AIOI. Although the transferase encodedby ABO*RIOI has amino acid residues at positions 176 and235 identical to those of the B transferase. those at positions
266 and 268 are identical to those of the AI transferase.
Thus, the amino acid residues at positions 176 and 235 do
not affect A/B transferase specificity. whereas those at positions 266 and 268 are concluded to be critical.
In a previous study,' we classified the alleles responsible
for common AB0 phenotypes into three major lineages. *A/*OI, *B, and *02, in terms of their evolutionary relationships. Six of the 1 I different alleles from the variant phenotypes determined in this study, ABO*AIOS, *AI06 *A107.
*CIOI, *AIOS. and *AI09, have only a single nucleotide
difference compared with ABO*AIOI or *AI02. Thus, thesesix variant alleles may belong to the ABO*A lineage. Similarly, three variant B alleles (ABO*BI04. *BIOS. and *B106)
have a single nucleotide difference compared withABO*BIOI, and thus may belong to the ABO*B lineage.
We constructed phylogenetic networks to delineate therelationships among the nucleotide sequences determined inthis study, as we did in our previous study.' A phylogenetic
network can contain many equally parsimonious trees." andcan be considered to be a generalization of the discordancy
diagram proposed by Fitch." Figure 3 shows a phylogenetic
network for all the alleles shown in Table 2 (except for
ABO*0201 and ABO*RIOI). It is clear that there are two
distinct *A and *B lineages.
In contrast, ABO*RIOI has six nucleotide differences. at
positions 297, 526. 657, 703, 771, and 829, compared with
ABO*AIOI. The nucleotide sequence of ABO*RIOI is identical to that of ABO*BIOI upstream of nucleotide position
703 and to that of *0201 downstream of nucleotide position
771. Based on these findings, ABO*RIOI may have originated by recombination between ABO*BIOI and *0201 at

From www.bloodjournal.org by on October 15, 2008. For personal use only.
2737

A B 0 VARIANT ALLELES

around positions 703-771, and may belong to a lineage intermediate between ABO*B and * 0 2 (Fig 4A). Similarly,
ABO*AIlO has a nucleotide sequence identical to that of
ABO*A102,’ except for the nucleotides at positions 646 and681 which are the same as in * 0 2 0 1 . Thus, ABO*AIIO islikely to have originated both by a double recombination ora gene conversion-like event (Fig 4B) and by accumulationof nucleotide substitutions.
These results indicate that there are different alleles responsible for the same A B 0 variant phenotypes, and that
their evolutionary lineages are not necessarily the same.
ACKNOWLEDGMENT
We thank Kazuo Nishida (Japanese Red Cross Tokyo Northern
Blood Center) for his valuable help on the serological analysis, andRyouichi Sumi (Japanese Red Cross Gifu Blood Center) for thefamily study of &-AB.
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major lineages of the alleles for the common AB0 phenotypes. Hum
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A Laboratory Manual (ed 2). Cold Spring Harbor, NY, Cold Spring
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AG: Genomic cloning of the human histo-blood group AB0 locus.
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for human gene nomenclature: An intemational system for humangene nomenclature (ISGN). Cytogenet Cell Genet 46:11, 1987
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