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Novel point mutations in the αIIb subunit (Phe 289 → Ser, Glu 324 → Lys and Gln 747 → Pro) causing thrombasthenic phenotypes in four Japanese patients
Author(s) -
Ambo Hironobu,
Kamata Tetsuji,
Handa Makoto,
Kawai Yohko,
Oda Atsushi,
Murata Mitsuru,
Takada Yoshikazu,
Ikeda Yasuo
Publication year - 1998
Publication title -
british journal of haematology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.907
H-Index - 186
eISSN - 1365-2141
pISSN - 0007-1048
DOI - 10.1046/j.1365-2141.1998.00824.x
Subject(s) - microbiology and biotechnology , point mutation , exon , complementary dna , chinese hamster ovary cell , biology , wild type , mutation , compound heterozygosity , genomic dna , mutant , gene , chemistry , genetics , cell culture
We analysed the molecular basis of Glanzmann thrombasthenia (GT) in four Japanese patients with type I or type II disease. Polymerase chain reaction (PCR) and subsequent direct sequencing of platelet RNA and genomic DNA revealed three single nucleotide substitutions of the αIIb gene, which were confirmed by allele‐specific PCR or restriction analysis. One patient with type I GT had a T to C base substitution in exon 11 resulting in a Phe (TTT)‐289 to Ser (TCT) mutation (F289S) of the subunit. Another type I patient had a G to A base substitution in exon 12 resulting in a Glu (GAA)‐324 to Lys (AAA) mutation (E324K). Interestingly, two unrelated patients with type II GT shared an A to C base substitution in exon 23, a region previously not associated with GT, resulting in a Gln (CAA)‐747 to Pro (CCA) mutation (Q747P). To analyse the effects of these mutations on αIIbβ3 surface expression, the wild‐type αIIb cDNA or mutant αIIb cDNAs were transfected into Chinese hamster ovary (CHO) cells together with a wild‐type β3 cDNA. Flow cytometric analysis using an anti‐αIIbβ3 complex antibody revealed that 50.6% of CHO cells with wild‐type αIIbβ3 expressed complexes, whereas only 1.6%, 7.7% and 31.3% of cells, with αIIb(F289S)β3, αIIb(E324K)β3 and αIIb(Q747P)β3 expressed complexes, respectively. Our data indicate that these three novel point mutations in the αIIb subunit may hamper surface expression of the αIIbβ3 complex, thus resulting in the quantitative GT phenotypes of platelets from these patients.