A nonsynonymous SNP in the ITGB3 gene disrupts the conserved membrane-proximal cytoplasmic salt bridge in the αIIbβ3 integrin and cosegregates dominantly with abnormal proplatelet formation and macrothrombocytopenia
Ghevaert, Cedric; Salsmann, Alexandre; Watkins, Nicholas A.et al.
[en] We report a 3-generation pedigree with 5 individuals affected with a dominantly inherited macrothrombocytopenia. All 5 carry 2 nonsynonymous mutations resulting in a D723H mutation in the beta3 integrin and a P53L mutation in glycoprotein (GP) Ibalpha. We show that GPIbalpha-L53 is phenotypically silent, being also present in 3 unaffected pedigree members and in 7 of 1639 healthy controls. The beta3-H723 causes constitutive, albeit partial, activation of the alphaIIbbeta3 complex by disruption of the highly conserved cytoplasmic salt bridge with arginine 995 in the alphaIIb integrin as evidenced by increased PAC-1 but not fibrinogen binding to the patients' resting platelets. This was confirmed in CHO alphaIIbbeta3-H723 transfectants, which also exhibited increased PAC-1 binding, increased adhesion to von Willebrand factor (VWF) in static conditions and to fibrinogen under shear stress. Crucially, we show that in the presence of fibrinogen, alphaIIbbeta3-H723, but not wild-type alphaIIbbeta3, generates a signal that leads to the formation of proplatelet-like protrusions in transfected CHO cells. Abnormal proplatelet formation was confirmed in the propositus's CD34+ stem cell-derived megakaryocytes. We conclude that the constitutive activation of the alphaIIbbeta3-H723 receptor causes abnormal proplatelet formation, leading to incorrect sizing of platelets and the thrombocytopenia observed in the pedigree.
Disciplines :
Hematology
Identifiers :
UNILU:UL-ARTICLE-2013-032
Author, co-author :
Ghevaert, Cedric; University of Cambridge, United Kingdom
Salsmann, Alexandre ; University of Luxembourg > Faculty of Science, Technology and Communication (FSTC) > Life Science Research Unit
Watkins, Nicholas A.; University of Cambridge, United Kingdom
Schaffner-Reckinger, Elisabeth ; University of Luxembourg > Faculty of Science, Technology and Communication (FSTC) > Life Science Research Unit
Rankin, Angela; University of Cambridge, United Kingdom
Garner, Stephen F.; University of Cambridge, United Kingdom
Stephens, Jonathan; University of Cambridge, United Kingdom
Smith, Graham A.; National Health Service Blood and Transplant, Cambridge, United Kingdom
Debili, Najet; Inserm U790, Institut Gustave Roussy, Villejuif, France
Vainchenker, William; Inserm U790, Institut Gustave Roussy, Villejuif, France
de Groot, Philip G.; Utrecht Medical Centre, The Netherlands
Huntington, James A.; University of Cambridge, United Kingdom
Laffan, Mike; Department of Haematology, Imperial College London, United Kingdom
Kieffer, Nelly ; University of Luxembourg > Faculty of Science, Technology and Communication (FSTC) > Life Science Research Unit
Ouwehand, Willem H.; University of Cambridge, United Kingdom
A nonsynonymous SNP in the ITGB3 gene disrupts the conserved membrane-proximal cytoplasmic salt bridge in the αIIbβ3 integrin and cosegregates dominantly with abnormal proplatelet formation and macrothrombocytopenia
Publication date :
2008
Journal title :
Blood
ISSN :
1528-0020
Publisher :
American Society of Hematology, Washington, United States - District of Columbia