Caractérisation de l’ADNc et de l’ADN génomique codant l’intégrine plaquettaire αIIb‐β3 chez un cheval atteint de Thrombasthénie de Glanzmann
Glanzmann thrombasthenia (GT) is  characterized by a defect of platelet aggregation. This autosomal recessive genetic disorder is caused by an abnormality of the platelet receptor for fibrinogen. This receptor is an integrin located on the plasma membrane formed by a complex of αIIb‐β3 subunits. Recently, we identified a horse with clinical and pathological features of GT. Flow cytometry studies revealed a deficiency of the αIIb subunit suggesting the presence of one or several mutations in the gene encoding for the αIIb subunit. The aim of this study was to describe this case of GT at the molecular level by characterizing the cDNAs encoding for the β3 (ITGB3) and αIIb (ITGA2B) subunits. Total RNA was extracted from platelets and converted into cDNA by reverse transcription using a poly‐dT primer. Genomic DNA was extracted from white blood cells. Specific primers for αIIb and β3 sequences were used to amplify by PCR the corresponding cDNA or genomic regions that were further characterized by sequencing and compared by BLAST analysis (GenBank). A point mutation from G to C in exon 2 of ITGA2B was identified, causing a substitution of the expected amino acid arginine 72 (Arg72) by a proline (Pro72). This amino acid change may result in abnormal structural conformations that yield an inactive αIIb subunit. The analysis of genomic DNA showed that this horse was homozygous for the missense mutation. The genomic DNA sequences encoding exon 2 of the dam, grand dam and the sire were heterozygous for this nucleic acid change and were clinically normal. The analysis of ITGB3 was unremarkable.
Glanzmann thrombasthenia hémostase hemostasis horse mutation exon 2 exon 2 mutation