THE HUMAN PLATELET ALLOANTIGENS, HPA-5(A-) AND HPA-5(A-,B+), ARE ASSOCIATED WITH A GLU(505)(,B)LYS(505) POLYMORPHISM OF GLYCOPROTEIN IA (THE ALPHA(2) SUBUNIT OF VLA-2)/
S. Simsek et al., THE HUMAN PLATELET ALLOANTIGENS, HPA-5(A-) AND HPA-5(A-,B+), ARE ASSOCIATED WITH A GLU(505)(,B)LYS(505) POLYMORPHISM OF GLYCOPROTEIN IA (THE ALPHA(2) SUBUNIT OF VLA-2)/, British Journal of Haematology, 86(3), 1994, pp. 671-674
GP Ia/IIa (also called VLA-2 or alpha 2 beta 1) is the primary recepto
r for collagen on platelets. The human platelet alloantigens HPA-5a(Br
-b) and HPA-5b(Br-a) have been found to reside on the platelet GP Ia/I
Ia complex. In order to establish the molecular basis of the HPA-5 sys
tem, platelet RNA was isolated from HPA-5 (a+,b-) and HPA-5(a-,b+) ind
ividuals. After reverse transcription, cDNA coding for glycoprotein Ia
(GP Ia) was amplified by the polymerase chain reaction (PCR). Nucleot
ide sequence analysis of the PCR products revealed an A --> G polymorp
hism at base pair 1648 of the coding region of the mature protein, res
ulting in a substitution of lysine (AAG) in HPA-5b (Br-a) by glutamic
acid (GAG) in HPA-5a(Br-b) at amino acid 505. Subsequent PCR-ASRA (all
ele-specific restriction enzyme analysis) with Mnl I using cDNA derive
d from three HPA-5 (a+,b-), one HPA-5 (a+,b+) individuals demonstrated
that HPA-5a and -5b alleles are distinguishable by DNA typing. In add
ition to the A --> G substitution at base pair 1648, three silent muta
tions were identified, G --> C(195 bp), C --> T (837 bp), G --> A (104
1 bp).