Systematic analysis of the ABO gene diversity within exons 6 and 7 by PCR screening reveals new ABO alleles.
BACKGROUND
Mutations critical for ABO blood group phenotypes have predominantly been found in exons 6 and 7 of the ABO gene, both of which encode the catalytic domain of ABO glycosyltransferase. To design rapid and reliable ABO genotyping assays, a profound knowledge of the prevalent alleles is required and a reliable sequence database needs to be established.


METHODS
A PCR screening system was established consisting of 102 different PCRs, each specific for a single nucleotide (nt) variation. The primer mixes were developed to walk from the 5' to the 3' end of exons 6 and 7 of the ABO gene to screen for nt mutations at 50 known polymorphic sites. A total of 109 unrelated individuals with common and rare ABO characteristics were screened. All blood samples in which the PCR results were inconclusive or inconsistent with the ABO phenotypes were subjected to sequence analysis of exons 6 and 7.


RESULTS
The results of PCR screening were conclusive and consistent with the ABO phenotypes in 90 cases. In the remaining 19 cases, PCR screening revealed unusual allele combinations or amplification results that were incompatible with known ABO allele combinations or subgroups predicted by serologic analysis. In these 19 cases, sequencing revealed new ABO alleles (one ABO*Ael allele, one ABO*B(A) allele and two ABO*O alleles) in two individuals with common and seven individuals with variant ABO phenotypes.


CONCLUSIONS
This PCR screening strategy is an effective tool for obtaining deeper insight into the ABO gene diversity and diversification and may be useful to increase the quality of the ABO sequence database.
Seltsam
Axel
A
Department of Transfusion Medicine, Hannover Medical School, Carl-Neuberg-Strasse 1, D-30625 Hannover, Germany.
Hallensleben
Michael
M
Kollmann
Anke
A
Burkhart
Jürgen
J
Blasczyk
Rainer
R
D000017:ABO Blood-Group System / Q000235:genetics*; D000483:Alleles; D005091:Exons; D014644:Genetic Variation; D005838:Genotype; D006801:Humans; D016130:Immunophenotyping; D010641:Phenotype; D016133:Polymerase Chain Reaction; D011110:Polymorphism, Genetic; D017422:Sequence Analysis, DNA
D000017:ABO Blood-Group System