TY - JOUR
T1 - Human CalDAG-GEFI gene (RASGRP2) mutation affects platelet function and causes severe bleeding
AU - Canault, Matthias
AU - Ghalloussi, Dorsaf
AU - Grosdidier, Charlotte
AU - Guinier, Marie
AU - Perret, Claire
AU - Chelghoum, Nadjim
AU - Germain, Marine
AU - Raslova, Hana
AU - Peiretti, Franck
AU - Morange, Pierre E
AU - Saut, Noemie
AU - Pillois, Xavier
AU - Nurden, Alan T
AU - Cambien, François
AU - Pierres, Anne
AU - van den Berg, Timo K
AU - Kuijpers, Taco W
AU - Alessi, Marie-Christine
AU - Tregouet, David-Alexandre
N1 - © 2014 Canault et al.
PY - 2014/6/30
Y1 - 2014/6/30
N2 - The nature of an inherited platelet disorder was investigated in three siblings affected by severe bleeding. Using whole-exome sequencing, we identified the culprit mutation (cG742T) in the RAS guanyl-releasing protein-2 (RASGRP2) gene coding for calcium- and DAG-regulated guanine exchange factor-1 (CalDAG-GEFI). Platelets from individuals carrying the mutation present a reduced ability to activate Rap1 and to perform proper αIIbβ3 integrin inside-out signaling. Expression of CalDAG-GEFI mutant in HEK293T cells abolished Rap1 activation upon stimulation. Nevertheless, the PKC- and ADP-dependent pathways allow residual platelet activation in the absence of functional CalDAG-GEFI. The mutation impairs the platelet's ability to form thrombi under flow and spread normally as a consequence of reduced Rac1 GTP-binding. Functional deficiencies were confined to platelets and megakaryocytes with no leukocyte alteration. This contrasts with the phenotype seen in type III leukocyte adhesion deficiency caused by the absence of kindlin-3. Heterozygous did not suffer from bleeding and have normal platelet aggregation; however, their platelets mimicked homozygous ones by failing to undergo normal adhesion under flow and spreading. Rescue experiments on cultured patient megakaryocytes corrected the functional deficiency after transfection with wild-type RASGRP2. Remarkably, the presence of a single normal allele is sufficient to prevent bleeding, making CalDAG-GEFI a novel and potentially safe therapeutic target to prevent thrombosis.
AB - The nature of an inherited platelet disorder was investigated in three siblings affected by severe bleeding. Using whole-exome sequencing, we identified the culprit mutation (cG742T) in the RAS guanyl-releasing protein-2 (RASGRP2) gene coding for calcium- and DAG-regulated guanine exchange factor-1 (CalDAG-GEFI). Platelets from individuals carrying the mutation present a reduced ability to activate Rap1 and to perform proper αIIbβ3 integrin inside-out signaling. Expression of CalDAG-GEFI mutant in HEK293T cells abolished Rap1 activation upon stimulation. Nevertheless, the PKC- and ADP-dependent pathways allow residual platelet activation in the absence of functional CalDAG-GEFI. The mutation impairs the platelet's ability to form thrombi under flow and spread normally as a consequence of reduced Rac1 GTP-binding. Functional deficiencies were confined to platelets and megakaryocytes with no leukocyte alteration. This contrasts with the phenotype seen in type III leukocyte adhesion deficiency caused by the absence of kindlin-3. Heterozygous did not suffer from bleeding and have normal platelet aggregation; however, their platelets mimicked homozygous ones by failing to undergo normal adhesion under flow and spreading. Rescue experiments on cultured patient megakaryocytes corrected the functional deficiency after transfection with wild-type RASGRP2. Remarkably, the presence of a single normal allele is sufficient to prevent bleeding, making CalDAG-GEFI a novel and potentially safe therapeutic target to prevent thrombosis.
KW - Adenosine Diphosphate/genetics
KW - Blood Coagulation Disorders, Inherited/genetics
KW - Blood Platelets/metabolism
KW - Cell Line
KW - Female
KW - Guanine Nucleotide Exchange Factors/genetics
KW - Guanosine Triphosphate/genetics
KW - Hemorrhage/genetics
KW - Heterozygote
KW - Homozygote
KW - Humans
KW - Male
KW - Megakaryocytes/metabolism
KW - Membrane Proteins/genetics
KW - Mutation
KW - Neoplasm Proteins/genetics
KW - Platelet Aggregation/genetics
KW - Platelet Glycoprotein GPIIb-IIIa Complex
KW - Protein Kinase C/genetics
KW - Telomere-Binding Proteins/genetics
U2 - 10.1084/jem.20130477
DO - 10.1084/jem.20130477
M3 - Article
C2 - 24958846
VL - 211
SP - 1349
EP - 1362
JO - Journal of Experimental Medicine
JF - Journal of Experimental Medicine
SN - 0022-1007
IS - 7
ER -