title: Human CalDAG-GEFI gene (RASGRP2) mutation affects platelet function and causes severe bleeding.
abstract: 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.
authors: Institut National de la Santé et de la Recherche Médicale (Inserm), UMR_S 1062, 13005 Marseille, France Inra, UMR_INRA 1260, 13005 Marseille, France Aix Marseille Université, 13005 Marseille, France.
authors: Matthias
authors: M
authors: Canault
authors: Institut National de la Santé et de la Recherche Médicale (Inserm), UMR_S 1062, 13005 Marseille, France Inra, UMR_INRA 1260, 13005 Marseille, France Aix Marseille Université, 13005 Marseille, France.
authors: Dorsaf
authors: D
authors: Ghalloussi
authors: Institut National de la Santé et de la Recherche Médicale (Inserm), UMR_S 1062, 13005 Marseille, France Inra, UMR_INRA 1260, 13005 Marseille, France Aix Marseille Université, 13005 Marseille, France.
authors: Charlotte
authors: C
authors: Grosdidier
authors: Post-Genomic Platform of Pitié-Salpêtrière (P3S), Pierre and Marie Curie University, F-75013 Paris, France.
authors: Marie
authors: M
authors: Guinier
authors: Sorbonne Universités, UPMC Univ Paris 06, UMR_S 1166, F-75013 Paris, France Inserm, UMR_S 1166, Team Genomics and Pathophysiology of Cardiovascular Diseases, F-75013 Paris, France ICAN Institute for Cardiometabolism and Nutrition, F-75013 Paris, France.
authors: Claire
authors: C
authors: Perret
authors: Post-Genomic Platform of Pitié-Salpêtrière (P3S), Pierre and Marie Curie University, F-75013 Paris, France.
authors: Nadjim
authors: N
authors: Chelghoum
authors: Sorbonne Universités, UPMC Univ Paris 06, UMR_S 1166, F-75013 Paris, France Inserm, UMR_S 1166, Team Genomics and Pathophysiology of Cardiovascular Diseases, F-75013 Paris, France ICAN Institute for Cardiometabolism and Nutrition, F-75013 Paris, France.
authors: Marine
authors: M
authors: Germain
authors: Hématopoïèse Normale et Pathologique, Inserm Médicale U1009, 94805 Villejuif, France.
authors: Hana
authors: H
authors: Raslova
authors: Institut National de la Santé et de la Recherche Médicale (Inserm), UMR_S 1062, 13005 Marseille, France Inra, UMR_INRA 1260, 13005 Marseille, France Aix Marseille Université, 13005 Marseille, France.
authors: Franck
authors: F
authors: Peiretti
authors: Institut National de la Santé et de la Recherche Médicale (Inserm), UMR_S 1062, 13005 Marseille, France Inra, UMR_INRA 1260, 13005 Marseille, France Aix Marseille Université, 13005 Marseille, France.
authors: Pierre E
authors: PE
authors: Morange
authors: Institut National de la Santé et de la Recherche Médicale (Inserm), UMR_S 1062, 13005 Marseille, France Inra, UMR_INRA 1260, 13005 Marseille, France Aix Marseille Université, 13005 Marseille, France.
authors: Noemie
authors: N
authors: Saut
authors: LIRYC, Plateforme Technologique et d'Innovation Biomédicale, Hôpital Xavier Arnozan, Pessac, France Inserm, UMR_1034, 33600 Pessac, France.
authors: Xavier
authors: X
authors: Pillois
authors: Inserm, UMR_1034, 33600 Pessac, France.
authors: Alan T
authors: AT
authors: Nurden
authors: Sorbonne Universités, UPMC Univ Paris 06, UMR_S 1166, F-75013 Paris, France Inserm, UMR_S 1166, Team Genomics and Pathophysiology of Cardiovascular Diseases, F-75013 Paris, France ICAN Institute for Cardiometabolism and Nutrition, F-75013 Paris, France.
authors: François
authors: F
authors: Cambien
authors: Aix Marseille Université, 13005 Marseille, France Inserm, UMR_1067, 13288 Marseille, France CNRS UMR_7333, 13288 Marseille, France.
authors: Anne
authors: A
authors: Pierres
authors: Department of Blood Cell Research, Sanquin Research and Landsteiner Laboratory, Academic Medical Center, University of Amsterdam, 1105 AZ Amsterdam, Netherlands.
authors: Timo K
authors: TK
authors: van den Berg
authors: Department of Blood Cell Research, Sanquin Research and Landsteiner Laboratory, Academic Medical Center, University of Amsterdam, 1105 AZ Amsterdam, Netherlands.
authors: Taco W
authors: TW
authors: Kuijpers
authors: Institut National de la Santé et de la Recherche Médicale (Inserm), UMR_S 1062, 13005 Marseille, France Inra, UMR_INRA 1260, 13005 Marseille, France Aix Marseille Université, 13005 Marseille, France marie-christine.alessi@univ-amu.fr.
authors: Marie-Christine
authors: MC
authors: Alessi
authors: Sorbonne Universités, UPMC Univ Paris 06, UMR_S 1166, F-75013 Paris, France Inserm, UMR_S 1166, Team Genomics and Pathophysiology of Cardiovascular Diseases, F-75013 Paris, France ICAN Institute for Cardiometabolism and Nutrition, F-75013 Paris, France.
authors: David-Alexandre
authors: DA
authors: Tregouet
mesh_terms: D000244:Adenosine Diphosphate / Q000235:genetics / Q000378:metabolism; D025861:Blood Coagulation Disorders, Inherited / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D001792:Blood Platelets / Q000378:metabolism / Q000473:pathology; D002460:Cell Line; D005260:Female; D020662:Guanine Nucleotide Exchange Factors / Q000235:genetics / Q000378:metabolism; D006160:Guanosine Triphosphate / Q000235:genetics / Q000378:metabolism; D006470:Hemorrhage / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D006579:Heterozygote; D006720:Homozygote; D006801:Humans; D008297:Male; D008533:Megakaryocytes / Q000378:metabolism / Q000473:pathology; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D009154:Mutation; D009363:Neoplasm Proteins / Q000235:genetics / Q000378:metabolism; D010974:Platelet Aggregation / Q000235:genetics*; D019039:Platelet Glycoprotein GPIIb-IIIa Complex; D011493:Protein Kinase C / Q000235:genetics / Q000378:metabolism; D000089804:Shelterin Complex; D034501:Telomere-Binding Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: C477322:FERMT3 protein, human; D020662:Guanine Nucleotide Exchange Factors; D008565:Membrane Proteins; D009363:Neoplasm Proteins; D019039:Platelet Glycoprotein GPIIb-IIIa Complex; C415483:RASGRP2 protein, human; D000089804:Shelterin Complex; C440809:TERF2IP protein, human; D034501:Telomere-Binding Proteins; D000244:Adenosine Diphosphate; D006160:Guanosine Triphosphate; D011493:Protein Kinase C