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Abstract HGVS meeting Toronto, October 26, 2004
Phenotypes vs Genotypes in the World of Blood Group Antigens
Olga O. Blumenfeld1 and Santosh K. Patnaik2
Deparments of Biochemi stry1 and Cell Biology2. Albert Einstein Coll ege of Medicine. New
York, NY 10461
Blood group antigens are proteins, gly cans or glycoli pids, of a variety of functions, whose
comm on feature is that all are expressed on the surface of red cell s and are polym orphic in the
population. The hallm ark of each antigen is an epitope or a li near or spatially arranged sequence
of ami no acids, or a carbohydrate sequence which, due to its variant nature, can be recognized as
non-self by the imm une system. The science (art) of serology is based on this recognition, and its
goal is to decipher and assign blood group phenotypes using antibodies to the polym orphic
epitopes as too ls. A blood group system is a set of variant antigens encoded by all eles of a single
locus, each expressing a related form of a comm on blood group phenotype.
The Blood Group Antigen Gene Mutation Database* documents 39 gene loci encoding 29 blood
group systems and comprising a tot al of 688 all eles that result in surface expression of at least
400 diff erent blood group phenotypes. Here we exami ne the correlation between the genotype,
the structure of the all ele and the blood group phenotype. This is a rare example in which a direct
correlation between a DNA alteration and a single physiologic function (antibody response) can
be establi shed, with modifi er genes or environmental factors playing a mi nim al role.
In the database, DNA alterations were documented in donors who were selected for study on the
basis of a variant blood group phenotype. Thus an alteration of the epitopic and/or coding
regions was expected. As generally observed for many documented human sequence variations,
among tot al DNA alterations, single nucleotide mutations predomi nated (sense ~8%; missense ~
50%, nonsense ~6%). Nonsense mutations and small deletions, insertions, or spli ce site
alterations, often accompanied by additional upstream or downstream mutations, gave rise to a
number of related all eles whose products were trunca ted or defective and resulted, directly or
indirectly (inactive glycosyltransferases), in the absence of epitopes from the cell surface. Thus,
for several blood group systems such diff erent all eles resulted in the null phenotype (for
example, the O phenotype of the ABO system). Gene rearrangements based on different
mechanisms (gene conversions, unequal recombinations) could also give rise to the same
epitopic sequence and the same phenotype that specifi ed diff erent hybrid all eles (the MN
system). In contrast, in most instances, mi ssense mutations li nked to the epitope, gave rise to
variant phenotypes each characteristic of a specifi c mutation and the ami no acid change (Rh,
Diego, Kell , others). This was observed whether the protein exhibited a single or multiple
epitopes and the effect of the mutation could be direct or indirect (affecting level of cell surface
expression). The majority of DNA alterations had no apparent effect on the function of the
erythrocyte. The subtle relationships among a single ami no acid replacement affecting the
epitopic region, the immune response and the abil ity to detect it, become apparent from a survey
of different blood group systems documented in the database.
*http://www. bioc.aecom.yu.edu/bgmut/index.htm
Phenotypes in the World of Blood Group Antigens
documented in the
Database of DNA Variation in Genes Encoding Blood Group Antigens
Olga O. Blumenfeld & Santosh K. Patnaik
Departments of Biochemistry (OOB) & Cell Biology (SKP)
Albert Einstein College of Medicine, New York
www.bioc.aecom.yu.edu/bgmut/index.htm
Blood Group Antigens
proteins, glycans or
glycolipids
variety of functions
expressed at the
surface of red cells
polymorphic in the
population
Blood Group System
A set of variant antigens
resulting from alleles of a single locus,
each defining a common serological phenotype.
Summary: 29 blood group systems, 40 genes, 707 alleles
Also detailed: non-human counterparts for H/h, MN, Rh
System
Locus
ABO
Chido- Rodgers
ABO
enzyme 115
C4A,
factor
7+
C4B
AQP1
channel
7
DAF
receptor 13
SLC4A1 exchanger 78
DO
unknown 9
FY
receptor 7
GYPC
structure 9
AQP3
channel 2
FUT1,
enzymes 57
FUT2
GCN2
enzyme 8
(IGnT)
CD44
adhesion 2
SEMA7A signaling 0
KEL,
enzyme 67
XK
SLC14A1 transport 8
CR1
receptor 24+
Colton
Cromer
Diego
Dombrock
Duffy
Gerbich (Ge)
GIL
H/h
I
Indian (IN)
JMH
Kell (with Kx)
Kidd
Knops
Funcion Alleles System
LandsteinerWeiner
Lewis
Lutheran
MNS
OK
P-related
RAPH-MER2
Rh
Scianna
Xg
YT
Locus
Function Alleles
ICAM4 adhesion
(LW)
FUT3,
enzymes
FUT6,
FUT7
LU
adhesion
GYPA,
unknown
GYPB,
GYPE
BSG
adhesion
A4GALT, enzymes
B3GALT3
CD151
RHCE, transport
RHD, RHCG
RHAG, RHBG
ERMAP adhesion
XG,
adhesion
CD99 (MIC2)
ACHE
enzyme
3
36
16
43
5
27
3
126
4
0
4
Summary of DNA alterations
Locus
Sens e Mis sense
Nonsense
Spli cing
Inse rtion Deletion
Rerrange ments Gross
Recur rent
identical
alt erations
at same sit es
ABO
A4GALT
CR1
KEL
XK
FUT1
FUT2
FUT3
17
3
1
2
1
3
-
29
4
16
26
2
16
6
11
2
1
6
6
4
3
-
3
5
-
1
3
1
1
1
-
2
4
6
3
2
-
22
-
8
-
FUT6
GYPA
GYPB
RHCE
RHD
RHAG
SLC4A1
BGMUT
db total
HGMD
total
7
2
2
2
-
9
14
7
13
45
5
48
1
1
3
4
1
1
6
3
19
1
1
3
7
19
2
2
12
33
243
243
183
24
92
2
2
12
3207
2093
5498
340
1827
312
19368
1. For comparison, nu mber of corresponding en tries in H GMD is shown in pa renthes es;
n/a: no t ava il able in HG MD. Not includ ed: regu latory mutations , small inde ls , repeat
variations , gross insertions & duplic ations. Total docu mented for 1338 gen es
2. Minimal number; approximate nu mbers as breakpoints for the p roposed intragen ic
rearrange ments and g ene conv ersions are unknown
3. Rough e stimate of all numb ers because o f a variety o f nu merous gene rearrang ements
Total
DNA
chang es1
19
4
5
6
Recur rent
dif ferent
alt erations
at same
sit es
3
2
-
13
-
-
18 (5)
41 (1)
35 (n/a)
37 (12)
77 (8)
14 (11)
74 (78)
497
53 (20)
15 (n/a)
17 (n/a)
38 (14)
28 (n/a)
25 (25)
14 (15)
11 (10)
32333
Phenotype vs genotype
A number of alleles give rise to the same blood group phenotype
Silencing mutations
nonsense, deletions, insertions, splicing, regulatory regions
rearrangements, gross deletions (null phenotype in nearly all
systems) Kell, Rh, Diego, ABO, others
Gene rearrangements
GYPA, Rh ex. Sta - 7 genotypes; RH neg - 17 genotypes
A single allele gives rise to a unique blood group phenotype
Missense mutations
Kell, Diego, RH, Duffy, ABO and others
Gene rearrangements
GYPA, Miltenberger series; Rh, weak D(Du), DAU & others
Same Blood Group Phenotype,
Multiple Genotypes
Kell null
1 phenotype
11 genotypes
7 nonsense
3 splicing
1 deletion
Same Blood Group Phenotype, Multiple Genotypes
O gene-null
Same deletion in many alleles (261delG in 38 of 43 O null alleles)
Band 3 Glycoprotein
anion exchanger
19 blood group phenotypes
54 other phenotypes (spherocytosis, etc.)
del
19 variants
Binds to
rbc cytoskeleton
del
anion ex.
Popov et al. JBC.1997,272,18325
Multiple Blood
Group
Phenotypes,
Multiple
Genotypes
Diego
19 of 19 alleles
Sites and distribution of alterations vs location of epitopes:
Kell (KEL)
Each polymorphic site can be assigned to a different Kell antigen
24 missense mutations at positions in extracellular domains
7 nonsense; 3 splicing ;1 del
Sets of polymorphic residues
Each expressed in different individuals at different frequencies.
Common phenotype
K-1, 2*; -3, -21, 4*; -6, 7*; 11*, -17; 14*, -24; 10, 5, 12, 13, 16, 18, 20,
22, -23
Known antithetical partners
K2/K1; K4/K3/K21; K7/K6; K11/K17
The Kell Glycoprotein
Single Blood Group Phenotype, Single Genotype
Kell
22 of 24 alleles
note
note
note
Same Blood Group Phenotype, Multiple Genotypes:
Examples in the KEL blood group system
Single Blood Group Phenotype, Single Genotype
Rh
Examples of genotypes vs phenotypes due to DNA
rearrangements in GYPA family
Gene
Sequence
Phenotype
GYPA
GYPB
GYPB
ex3 EET ex4 GERVQL
ex2 QTN ex4 GETGQL
ex2 QTN ex4 GEMGQL
wild type
wild type s
wild type S
hyb.A-Bs Recombination
hyb.A-BS Recombination
hyb.BAB Gene conversion
hyb.B-A Recombination
ex3 EET ex4 GETGQL
ex3 EET ex4 GEMGQL
ex3 EET ex4 GETGQL
ex2 QTN ex4 GERVQL
HIL
SJL
HIL
Sta
Johe,Vengelen-Tyler,Leger,Blumenfeld Blood 1991,78:2456
Examples were provided showing that, on the red cell
surface, single amino acid or carbohydrate alterations,
resulting from missense mutations or other DNA changes
are recognized, as one might expect, as foreign by the
immune system and, remarkably, can be detected by
serological approaches .
Acknowledgements
Contributors to the database
Departments of Biochemistry and Cell Biology,
Albert Einstein College of Medicine
Thank you!