A tyrosine703serine polymorphism of CD109 defines the Gov platelet alloantigens.
The biallelic platelet-specific Gov antigen system-implicated in refractoriness to platelet transfusion, neonatal alloimmune thrombocytopenia, and posttransfusion purpura-is carried by the glycosylphosphatidylinositol (GPI)-linked protein CD109. The recent identification of the human CD109 complementary DNA (cDNA) has allowed the molecular nature of the Gov alleles to be elucidated. By using reverse transcriptase-polymerase chain reaction (RT-PCR) to amplify CD109 cDNAs from 6 phenotypically homozygous Gov(aa) and Gov(bb) individuals, we have determined that the Gov alleles differ by an A to C single nucleotide polymorphism (SNP) at position 2108 of the coding region, resulting in a Tyr/Ser substitution at CD109 amino acid 703. Allele-specific PCR sequence-specific primers (SSP), PCR-restriction fragment length polymorphism, and real-time PCR studies of 15 additional donors (5 Gov(aa), 5 Gov(bb), and 5 Gov(ab)) confirmed that this SNP correlates with the Gov phenotype. In addition, Chinese hamster ovary cells transiently expressing nucleotide 2108 A>C CD109 cDNA variants were recognized specifically by allele-specific Gov antisera, indicating that this polymorphism defines the Gov alloantigenic determinants. Real-time PCR was then used to genotype 85 additional Gov phenotyped donors. In all but 3 cases, genomic testing concurred with the Gov phenotype. Repeat testing corrected 2 of these discrepancies in favor of the genotyping result. The third discrepancy could not be resolved, likely reflecting low-level CD109 expression below the sensitivity of the phenotyping assay. We conclude that the Gov alleles are defined by a 2108 A>C SNP that results in a Tyr703Ser substitution of CD109 and that genotyping studies are more accurate for Gov alloantigen determination than are conventional serologic methods.
Schuh
Andre C
AC
Institute of Medical Science and the Department of Medicine, University of Toronto, ON, Canada. andre.schuh@utoronto.ca
Watkins
Nick A
NA
Nguyen
Quang
Q
Harmer
Nicholas J
NJ
Lin
Martin
M
Prosper
Joseph Y A
JY
Campbell
Kate
K
Sutherland
D Robert
DR
Metcalfe
Paul
P
Horsfall
Wendy
W
Ouwehand
Willem H
WH
D019943:Amino Acid Substitution; D015703:Antigens, CD / Q000235:genetics*; D016824:Antigens, Human Platelet / Q000235:genetics*; D001483:Base Sequence; D004252:DNA Mutational Analysis; D058851:GPI-Linked Proteins; D005838:Genotype; D006801:Humans; D016130:Immunophenotyping; D007519:Isoantigens / Q000235:genetics; D008969:Molecular Sequence Data; D009363:Neoplasm Proteins; D016133:Polymerase Chain Reaction; D020641:Polymorphism, Single Nucleotide / Q000235:genetics*
D015703:Antigens, CD; D016824:Antigens, Human Platelet; C120523:CD109 protein, human; D058851:GPI-Linked Proteins; D007519:Isoantigens; D009363:Neoplasm Proteins