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Xu XR, Zhang D, Oswald BE, Carrim N, Wang X, Hou Y, Zhang Q, Lavalle C, McKeown T, Marshall AH, Ni H. Platelets are versatile cells: New discoveries in hemostasis, thrombosis, immune responses, tumor metastasis and beyond. Crit Rev Clin Lab Sci 2016; 53:409-30. [PMID: 27282765 DOI: 10.1080/10408363.2016.1200008] [Citation(s) in RCA: 178] [Impact Index Per Article: 22.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Platelets are small anucleate blood cells generated from megakaryocytes in the bone marrow and cleared in the reticuloendothelial system. At the site of vascular injury, platelet adhesion, activation and aggregation constitute the first wave of hemostasis. Blood coagulation, which is initiated by the intrinsic or extrinsic coagulation cascades, is the second wave of hemostasis. Activated platelets can also provide negatively-charged surfaces that harbor coagulation factors and markedly potentiate cell-based thrombin generation. Recently, deposition of plasma fibronectin, and likely other plasma proteins, onto the injured vessel wall has been identified as a new "protein wave of hemostasis" that may occur even earlier than the first wave of hemostasis, platelet accumulation. Although no experimental evidence currently exists, it is conceivable that platelets may also contribute to this protein wave of hemostasis by releasing their granule fibronectin and other proteins that may facilitate fibronectin self- and non-self-assembly on the vessel wall. Thus, platelets may contribute to all three waves of hemostasis and are central players in this critical physiological process to prevent bleeding. Low platelet counts in blood caused by enhanced platelet clearance and/or impaired platelet production are usually associated with hemorrhage. Auto- and allo-immune thrombocytopenias such as idiopathic thrombocytopenic purpura and fetal and neonatal alloimmune thrombocytopenia may cause life-threatening bleeding such as intracranial hemorrhage. When triggered under pathological conditions such as rupture of an atherosclerotic plaque, excessive platelet activation and aggregation may result in thrombosis and vessel occlusion. This may lead to myocardial infarction or ischemic stroke, the major causes of mortality and morbidity worldwide. Platelets are also involved in deep vein thrombosis and thromboembolism, another leading cause of mortality. Although fibrinogen has been documented for more than half a century as essential for platelet aggregation, recent studies demonstrated that fibrinogen-independent platelet aggregation occurs in both gene deficient animals and human patients under physiological and pathological conditions (non-anti-coagulated blood). This indicates that other unidentified platelet ligands may play important roles in thrombosis and might be novel antithrombotic targets. In addition to their critical roles in hemostasis and thrombosis, emerging evidence indicates that platelets are versatile cells involved in many other pathophysiological processes such as innate and adaptive immune responses, atherosclerosis, angiogenesis, lymphatic vessel development, liver regeneration and tumor metastasis. This review summarizes the current knowledge of platelet biology, highlights recent advances in the understanding of platelet production and clearance, molecular and cellular events of thrombosis and hemostasis, and introduces the emerging roles of platelets in the immune system, vascular biology and tumorigenesis. The clinical implications of these basic science and translational research findings will also be discussed.
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Affiliation(s)
- Xiaohong Ruby Xu
- a Department of Laboratory Medicine and Pathobiology , University of Toronto , Toronto , ON , Canada .,b Department of Laboratory Medicine , Keenan Research Centre for Biomedical Science, St. Michael's Hospital, and Toronto Platelet Immunobiology Group, Li Ka Shing Knowledge Institute , Toronto , ON , Canada .,c Department of Medicine , Guangzhou University of Chinese Medicine , Guangzhou , Guangdong , P.R. China
| | - Dan Zhang
- b Department of Laboratory Medicine , Keenan Research Centre for Biomedical Science, St. Michael's Hospital, and Toronto Platelet Immunobiology Group, Li Ka Shing Knowledge Institute , Toronto , ON , Canada .,c Department of Medicine , Guangzhou University of Chinese Medicine , Guangzhou , Guangdong , P.R. China
| | - Brigitta Elaine Oswald
- b Department of Laboratory Medicine , Keenan Research Centre for Biomedical Science, St. Michael's Hospital, and Toronto Platelet Immunobiology Group, Li Ka Shing Knowledge Institute , Toronto , ON , Canada .,d Canadian Blood Services , Toronto , ON , Canada .,e Department of Physiology , University of Toronto , Toronto , ON , Canada
| | - Naadiya Carrim
- a Department of Laboratory Medicine and Pathobiology , University of Toronto , Toronto , ON , Canada .,b Department of Laboratory Medicine , Keenan Research Centre for Biomedical Science, St. Michael's Hospital, and Toronto Platelet Immunobiology Group, Li Ka Shing Knowledge Institute , Toronto , ON , Canada .,d Canadian Blood Services , Toronto , ON , Canada
| | - Xiaozhong Wang
- b Department of Laboratory Medicine , Keenan Research Centre for Biomedical Science, St. Michael's Hospital, and Toronto Platelet Immunobiology Group, Li Ka Shing Knowledge Institute , Toronto , ON , Canada .,f The Second Affiliated Hospital of Nanchang University , Nanchang , Jiangxi , P.R. China
| | - Yan Hou
- b Department of Laboratory Medicine , Keenan Research Centre for Biomedical Science, St. Michael's Hospital, and Toronto Platelet Immunobiology Group, Li Ka Shing Knowledge Institute , Toronto , ON , Canada .,g Jilin Provincial Center for Disease Prevention and Control , Changchun , Jilin , P.R. China
| | - Qing Zhang
- b Department of Laboratory Medicine , Keenan Research Centre for Biomedical Science, St. Michael's Hospital, and Toronto Platelet Immunobiology Group, Li Ka Shing Knowledge Institute , Toronto , ON , Canada .,h State Key Laboratory of Biocontrol, School of Life Sciences, Sun Yat-Sen University , Guangzhou , Guangdong , P.R. China , and
| | - Christopher Lavalle
- b Department of Laboratory Medicine , Keenan Research Centre for Biomedical Science, St. Michael's Hospital, and Toronto Platelet Immunobiology Group, Li Ka Shing Knowledge Institute , Toronto , ON , Canada .,e Department of Physiology , University of Toronto , Toronto , ON , Canada
| | - Thomas McKeown
- b Department of Laboratory Medicine , Keenan Research Centre for Biomedical Science, St. Michael's Hospital, and Toronto Platelet Immunobiology Group, Li Ka Shing Knowledge Institute , Toronto , ON , Canada
| | - Alexandra H Marshall
- b Department of Laboratory Medicine , Keenan Research Centre for Biomedical Science, St. Michael's Hospital, and Toronto Platelet Immunobiology Group, Li Ka Shing Knowledge Institute , Toronto , ON , Canada
| | - Heyu Ni
- a Department of Laboratory Medicine and Pathobiology , University of Toronto , Toronto , ON , Canada .,b Department of Laboratory Medicine , Keenan Research Centre for Biomedical Science, St. Michael's Hospital, and Toronto Platelet Immunobiology Group, Li Ka Shing Knowledge Institute , Toronto , ON , Canada .,d Canadian Blood Services , Toronto , ON , Canada .,e Department of Physiology , University of Toronto , Toronto , ON , Canada .,i Department of Medicine , University of Toronto , Toronto , ON , Canada
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Buitrago L, Rendon A, Liang Y, Simeoni I, Negri A, Filizola M, Ouwehand WH, Coller BS. αIIbβ3 variants defined by next-generation sequencing: predicting variants likely to cause Glanzmann thrombasthenia. Proc Natl Acad Sci U S A 2015; 112:E1898-907. [PMID: 25827233 PMCID: PMC4403182 DOI: 10.1073/pnas.1422238112] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Next-generation sequencing is transforming our understanding of human genetic variation but assessing the functional impact of novel variants presents challenges. We analyzed missense variants in the integrin αIIbβ3 receptor subunit genes ITGA2B and ITGB3 identified by whole-exome or -genome sequencing in the ThromboGenomics project, comprising ∼32,000 alleles from 16,108 individuals. We analyzed the results in comparison with 111 missense variants in these genes previously reported as being associated with Glanzmann thrombasthenia (GT), 20 associated with alloimmune thrombocytopenia, and 5 associated with aniso/macrothrombocytopenia. We identified 114 novel missense variants in ITGA2B (affecting ∼11% of the amino acids) and 68 novel missense variants in ITGB3 (affecting ∼9% of the amino acids). Of the variants, 96% had minor allele frequencies (MAF) < 0.1%, indicating their rarity. Based on sequence conservation, MAF, and location on a complete model of αIIbβ3, we selected three novel variants that affect amino acids previously associated with GT for expression in HEK293 cells. αIIb P176H and β3 C547G severely reduced αIIbβ3 expression, whereas αIIb P943A partially reduced αIIbβ3 expression and had no effect on fibrinogen binding. We used receiver operating characteristic curves of combined annotation-dependent depletion, Polyphen 2-HDIV, and sorting intolerant from tolerant to estimate the percentage of novel variants likely to be deleterious. At optimal cut-off values, which had 69-98% sensitivity in detecting GT mutations, between 27% and 71% of the novel αIIb or β3 missense variants were predicted to be deleterious. Our data have implications for understanding the evolutionary pressure on αIIbβ3 and highlight the challenges in predicting the clinical significance of novel missense variants.
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Affiliation(s)
- Lorena Buitrago
- Allen and Frances Adler Laboratory of Blood and Vascular Biology and
| | - Augusto Rendon
- Department of Haematology, University of Cambridge, Cambridge CB2 0PT, United Kingdom; Medical Research Council Biostatistics Unit, Cambridge Biomedical Campus, Cambridge Institute of Public Health, Cambridge, United Kingdom; National Health Service Blood & Transplant, Cambridge, United Kingdom
| | - Yupu Liang
- Research Bioinformatics, The Rockefeller University, New York, NY 10065
| | - Ilenia Simeoni
- Department of Haematology, University of Cambridge, Cambridge CB2 0PT, United Kingdom; National Health Service Blood & Transplant, Cambridge, United Kingdom
| | - Ana Negri
- Department of Structural and Chemical Biology, Icahn School of Medicine at Mount Sinai, New York, NY 10029; and
| | - Marta Filizola
- Department of Structural and Chemical Biology, Icahn School of Medicine at Mount Sinai, New York, NY 10029; and
| | - Willem H Ouwehand
- Department of Haematology, University of Cambridge, Cambridge CB2 0PT, United Kingdom; National Health Service Blood & Transplant, Cambridge, United Kingdom; Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Hinxton, Cambridge, United Kingdom
| | - Barry S Coller
- Allen and Frances Adler Laboratory of Blood and Vascular Biology and
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