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Attar LJ, Alelaimat A, Alshorman A, Aladily TN. MPIG6B Gene-Related Myelofibrosis: A Rare Inherited Disease That Is Frequently Described in Arab Population. Avicenna J Med 2024; 14:69-72. [PMID: 38694137 PMCID: PMC11057892 DOI: 10.1055/s-0044-1779697] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/04/2024] Open
Abstract
The megakaryocyte and platelet inhibitory receptor gene G6P (MPIG6B) is located on chromosome 6p21.33. It encodes G6b-B; an inhibitory receptor expressed on the surface of platelets. It regulates platelets production, aggregation, and activation. We describe a case of a 31-year-old man who presented with a long history of thrombocytopenia, anemia, and hepatosplenomegaly. The patient received multiple blood transfusions and his clinical course was stable. A bone marrow biopsy showed morphologic features similar to primary myelofibrosis. Whole exome sequencing study was performed and revealed homozygous pathogenic mutation in exon 2 of MPIG6B gene (c.324C > A, p.Cys108Ter) that is the second reported case in literature. In this report, we describe the main clinical and pathologic features of this disease and review the literature of previously documented cases.
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Affiliation(s)
- Leen Jihad Attar
- Department of Hematopathology, The University of Jordan, Amman, Jordan
| | | | - Alaa Alshorman
- Department of Hematology, Ministry of Health, Amman, Jordan
| | - Tariq N. Aladily
- Department of Hematopathology, The University of Jordan, Amman, Jordan
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2
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Mazharian A, Maître B, Bornert A, Hennequin D, Lourenco-Rodrigues M, Geer MJ, Smith CW, Heising S, Walter M, Montel F, Walker LSK, de la Salle H, Watson SP, Gachet C, Senis YA. Treatment of congenital thrombocytopenia and decreased collagen reactivity in G6b-B-deficient mice. Blood Adv 2023; 7:46-59. [PMID: 36269841 PMCID: PMC9813534 DOI: 10.1182/bloodadvances.2022008873] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2022] [Revised: 09/15/2022] [Accepted: 09/22/2022] [Indexed: 01/18/2023] Open
Abstract
Mice lacking the immunoreceptor tyrosine-based inhibition motif-containing co-inhibitory receptor G6b-B (Mpig6b, G6b knockout, KO) are born with a complex megakaryocyte (MK) per platelet phenotype, characterized by severe macrothrombocytopenia, expansion of the MK population, and focal myelofibrosis in the bone marrow and spleen. Platelets are almost completely devoid of the glycoprotein VI (GPVI)-FcRγ-chain collagen receptor complex, have reduced collagen integrin α2β1, elevated Syk tyrosine kinase activity, and a subset has increased surface immunoglobulins. A similar phenotype was recently reported in patients with null and loss-of-function mutations in MPIG6B. To better understand the cause and treatment of this pathology, we used pharmacological- and genetic-based approaches to rescue platelet counts and function in G6b KO mice. Intravenous immunoglobulin resulted in a transient partial recovery of platelet counts, whereas immune deficiency did not affect platelet counts or receptor expression in G6b KO mice. Syk loss-of-function (R41A) rescued macrothrombocytopenia, GPVI and α2β1 expression in G6b KO mice, whereas treatment with the Syk kinase inhibitor BI1002494 partially rescued platelet count but had no effect on GPVI and α2β1 expression or bleeding. The Src family kinase inhibitor dasatinib was not beneficial in G6b KO mice. In contrast, treatment with the thrombopoietin mimetic romiplostim rescued thrombocytopenia, GPVI expression, and platelet reactivity to collagen, suggesting that it may be a promising therapeutic option for patients lacking functional G6b-B. Intriguingly, GPVI and α2β1 expression were significantly downregulated in romiplostim-treated wild-type mice, whereas GPVI was upregulated in romiplostim-treated G6b KO mice, suggesting a cell intrinsic feedback mechanism that autoregulates platelet reactivity depending on physiological needs.
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Affiliation(s)
- Alexandra Mazharian
- Université de Strasbourg, INSERM, Etablissement Français du Sang Grand-Est, Unité Mixte de Recherche-S 1255, Fédération de Médecine Translationnelle de Strasbourg, Strasbourg, France
- Institute of Cardiovascular Sciences, College of Medical and Dental Sciences, University of Birmingham, Edgbaston, Birmingham, United Kingdom
| | - Blandine Maître
- Université de Strasbourg, INSERM, Etablissement Français du Sang Grand-Est, Unité Mixte de Recherche-S 1255, Fédération de Médecine Translationnelle de Strasbourg, Strasbourg, France
| | - Alicia Bornert
- Université de Strasbourg, INSERM, Etablissement Français du Sang Grand-Est, Unité Mixte de Recherche-S 1255, Fédération de Médecine Translationnelle de Strasbourg, Strasbourg, France
| | - Desline Hennequin
- Université de Strasbourg, INSERM, Etablissement Français du Sang Grand-Est, Unité Mixte de Recherche-S 1255, Fédération de Médecine Translationnelle de Strasbourg, Strasbourg, France
| | - Marc Lourenco-Rodrigues
- Université de Strasbourg, INSERM, Etablissement Français du Sang Grand-Est, Unité Mixte de Recherche-S 1255, Fédération de Médecine Translationnelle de Strasbourg, Strasbourg, France
| | - Mitchell J. Geer
- Institute of Cardiovascular Sciences, College of Medical and Dental Sciences, University of Birmingham, Edgbaston, Birmingham, United Kingdom
- Laura and Isaac Perlmutter Cancer Center, New York University School of Medicine, NYU Langone Health, New York, NY
| | - Christopher W. Smith
- Institute of Cardiovascular Sciences, College of Medical and Dental Sciences, University of Birmingham, Edgbaston, Birmingham, United Kingdom
| | - Silke Heising
- Institute of Cardiovascular Sciences, College of Medical and Dental Sciences, University of Birmingham, Edgbaston, Birmingham, United Kingdom
| | - Michaela Walter
- Boehringer Ingelheim Pharma GmbH and Company KG, Ingelheim, Germany
| | - Florian Montel
- Boehringer Ingelheim Pharma GmbH and Company KG, Ingelheim, Germany
| | - Lucy S. K. Walker
- Division of Infection and Immunity, Institute of Immunity and Transplantation, University College London, Royal Free Campus, London, United Kingdom
| | - Henri de la Salle
- Université de Strasbourg, INSERM, Etablissement Français du Sang Grand-Est, Unité Mixte de Recherche-S 1255, Fédération de Médecine Translationnelle de Strasbourg, Strasbourg, France
| | - Steve P. Watson
- Institute of Cardiovascular Sciences, College of Medical and Dental Sciences, University of Birmingham, Edgbaston, Birmingham, United Kingdom
| | - Christian Gachet
- Université de Strasbourg, INSERM, Etablissement Français du Sang Grand-Est, Unité Mixte de Recherche-S 1255, Fédération de Médecine Translationnelle de Strasbourg, Strasbourg, France
| | - Yotis A. Senis
- Université de Strasbourg, INSERM, Etablissement Français du Sang Grand-Est, Unité Mixte de Recherche-S 1255, Fédération de Médecine Translationnelle de Strasbourg, Strasbourg, France
- Institute of Cardiovascular Sciences, College of Medical and Dental Sciences, University of Birmingham, Edgbaston, Birmingham, United Kingdom
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G6b-B regulates an essential step in megakaryocyte maturation. Blood Adv 2022; 6:3155-3161. [PMID: 35134123 PMCID: PMC9131916 DOI: 10.1182/bloodadvances.2021006151] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2021] [Accepted: 01/20/2022] [Indexed: 12/05/2022] Open
Abstract
Loss of G6b-B leads to an unexpected megakaryocyte development defect resulting in severe macrothrombocytopenia. G6b-B–deficient mice display reduced levels of MK-specific transcripts, surface receptors, GATA-1, and thrombopoietin signaling.
G6b-B is a megakaryocyte lineage-specific immunoreceptor tyrosine-based inhibition motif–containing receptor, essential for platelet homeostasis. Mice with a genomic deletion of the entire Mpig6b locus develop severe macrothrombocytopenia and myelofibrosis, which is reflected in humans with null mutations in MPIG6B. The current model proposes that megakaryocytes lacking G6b-B develop normally, whereas proplatelet release is hampered, but the underlying molecular mechanism remains unclear. We report on a spontaneous recessive single nucleotide mutation in C57BL/6 mice, localized within the intronic region of the Mpig6b locus that abolishes G6b-B expression and reproduces macrothrombocytopenia, myelofibrosis, and osteosclerosis. As the mutation is based on a single-nucleotide exchange, Mpig6bmut mice represent an ideal model to study the role of G6b-B. Megakaryocytes from these mice were smaller, displayed a less-developed demarcation membrane system, and had a reduced expression of receptors. RNA sequencing revealed a striking global reduction in the level of megakaryocyte-specific transcripts, in conjunction with decreased protein levels of the transcription factor GATA-1 and impaired thrombopoietin signaling. The reduced number of mature MKs in the bone marrow was corroborated on a newly developed Mpig6b-null mouse strain. Our findings highlight an unexpected essential role of G6b-B in the early differentiation within the megakaryocytic lineage.
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ASXL2 mutated myelodysplastic syndrome in a novel germline G6b variant. Leuk Res Rep 2022; 17:100303. [PMID: 35330689 PMCID: PMC8938321 DOI: 10.1016/j.lrr.2022.100303] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2022] [Revised: 03/07/2022] [Accepted: 03/16/2022] [Indexed: 11/22/2022] Open
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5
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Glembotsky AC, De Luca G, Heller PG. A Deep Dive into the Pathology of Gray Platelet Syndrome: New Insights on Immune Dysregulation. J Blood Med 2021; 12:719-732. [PMID: 34408521 PMCID: PMC8364843 DOI: 10.2147/jbm.s270018] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2021] [Accepted: 06/16/2021] [Indexed: 12/22/2022] Open
Abstract
The gray platelet syndrome (GPS) is a rare platelet disorder, characterized by impaired alpha-granule biogenesis in megakaryocytes and platelets due to NBEAL2 mutations. Typical clinical features include macrothrombocytopenia, bleeding and elevated vitamin B12 levels, while bone marrow fibrosis and splenomegaly may develop during disease progression. Recently, the involvement of other blood lineages has been highlighted, revealing the role of NBEAL2 outside the megakaryocyte-platelet axis. Low leukocyte counts, decreased neutrophil granulation and impaired neutrophil extracellular trap formation represent prominent findings in GPS patients, reflecting deranged innate immunity and associated with an increased susceptibility to infection. In addition, low numbers and impaired degranulation of NK cells have been demonstrated in animal models. Autoimmune diseases involving different organs and a spectrum of autoantibodies are present in a substantial proportion of GPS patients, expanding the syndromic spectrum of this disorder and pointing to dysregulation of the adaptive immune response. Low-grade inflammation, as evidenced by elevation of liver-derived acute-phase reactants, is another previously unrecognized feature of GPS which may contribute to disease manifestations. This review will focus on the mechanisms underlying the pathogenesis of blood cell abnormalities in human GPS patients and NBEAL2-null animal models, providing insight into the effects of NBEAL2 in hemostasis, inflammation and immunity.
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Affiliation(s)
- Ana C Glembotsky
- Departamento Hematología Investigación, Instituto de Investigaciones Médicas "Dr. A. Lanari", Facultad de Medicina, Universidad de Buenos Aires, Buenos Aires, Argentina.,Departamento Hematología Investigación, Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Universidad de Buenos Aires, Instituto de Investigaciones Médicas (IDIM), Buenos Aires, Argentina
| | - Geraldine De Luca
- Departamento Hematología Investigación, Instituto de Investigaciones Médicas "Dr. A. Lanari", Facultad de Medicina, Universidad de Buenos Aires, Buenos Aires, Argentina.,Departamento Hematología Investigación, Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Universidad de Buenos Aires, Instituto de Investigaciones Médicas (IDIM), Buenos Aires, Argentina
| | - Paula G Heller
- Departamento Hematología Investigación, Instituto de Investigaciones Médicas "Dr. A. Lanari", Facultad de Medicina, Universidad de Buenos Aires, Buenos Aires, Argentina.,Departamento Hematología Investigación, Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Universidad de Buenos Aires, Instituto de Investigaciones Médicas (IDIM), Buenos Aires, Argentina
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6
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Batis H, Almugairi A, Almugren O, Aljabry M, Alqahtani F, Elbashir E, Elfaki M, Alsultan A. Detrimental variants in MPIG6B in two children with myelofibrosis: Does immune dysregulation contribute to myelofibrosis? Pediatr Blood Cancer 2021; 68:e29062. [PMID: 33871931 DOI: 10.1002/pbc.29062] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/22/2021] [Revised: 03/29/2021] [Accepted: 03/30/2021] [Indexed: 12/26/2022]
Affiliation(s)
- Hasan Batis
- Department of Pediatrics, College of Medicine, King Saud University, Riyadh, Saudi Arabia.,Oncology Center, King Saud University Medical City, Riyadh, Saudi Arabia
| | - Areej Almugairi
- Department of Pathology and Laboratory Medicine, King Abdulaziz Medical City and National Guard Health Affairs, Riyadh, Saudi Arabia
| | - Omar Almugren
- Department of Pathology and Laboratory Medicine, College of Medicine, King Saud University, Riyadh, Saudi Arabia
| | - Mansour Aljabry
- Department of Pathology and Laboratory Medicine, College of Medicine, King Saud University, Riyadh, Saudi Arabia
| | - Fatima Alqahtani
- Department of Pathology and Laboratory Medicine, College of Medicine, King Saud University, Riyadh, Saudi Arabia
| | - Enas Elbashir
- Department of Pediatric Hematology/Oncology, King Abdullah Specialist Children's Hospital, Riyadh, Saudi Arabia
| | - Mohammed Elfaki
- Department of Pediatrics, College of Medicine, King Saud University, Riyadh, Saudi Arabia.,Oncology Center, King Saud University Medical City, Riyadh, Saudi Arabia
| | - Abdulrahman Alsultan
- Department of Pediatrics, College of Medicine, King Saud University, Riyadh, Saudi Arabia.,Oncology Center, King Saud University Medical City, Riyadh, Saudi Arabia
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Stavnichuk M, Tauer JT, Nagy Z, Mazharian A, Welman M, Lordkipanidzé M, Senis YA, Komarova SV. Severity of Megakaryocyte-Driven Osteosclerosis in Mpig6b-Deficient Mice Is Sex-Linked. J Bone Miner Res 2021; 36:803-813. [PMID: 33434328 DOI: 10.1002/jbmr.4245] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/01/2020] [Revised: 12/16/2020] [Accepted: 12/29/2020] [Indexed: 01/15/2023]
Abstract
Patients with chronic myelofibrosis often suffer from osteosclerosis, which is associated with bone pain and may lead to bone marrow failure. The pathogenesis of myelofibrosis is linked to aberrant megakaryocyte development and function. Null and loss-of-function mutations in MPIG6B, which codes for the inhibitory heparan sulfate receptor G6b-B, result in severe macrothrombocytopenia, large megakaryocyte clusters, and focal primary myelofibrosis in mice and humans. We investigated the development of osteosclerosis in Mpig6b null (Mpig6b-/- ) mice. Although male and female Mpig6b-/- mice presented with elevated bone marrow megakaryocyte number and macrothrombocytopenia, female Mpig6b-/- mice developed progressive splenomegaly starting at 8 weeks of age. Micro-computed tomography (μCT) of femurs showed that female Mpig6b-/- mice had increased cortical thickness and reduced bone marrow area starting at 8 weeks of age and developed occlusion of the medullary cavity by trabeculae by 16 weeks of age. In contrast, male Mpig6b-/- mice developed only a small number of trabeculae in the medullary cavity at the proximal diaphysis and demonstrated a temporary decrease in bone volume fraction and trabecular thickness at 16 weeks. Ovariectomy of 10-week-old female Mpig6b-/- mice prevented the development of medullary cavity osteosclerosis, whereas orchiectomy of male Mpig6b-/- mice did not exacerbate their disease. Importantly, ovariectomized female Mpig6b-/- mice also demonstrated improvement in spleen weight compared to sham-operated Mpig6b-/- mice, establishing estrogen as a contributing factor to the severity of the megakaryocyte-driven osteosclerosis. © 2021 American Society for Bone and Mineral Research (ASBMR).
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Affiliation(s)
- Mariya Stavnichuk
- Department of Biological and Biomedical Engineering, McGill University, Montreal, QC, Canada.,Shriners Hospital for Children-Canada, Montreal, QC, Canada
| | - Josephine T Tauer
- Shriners Hospital for Children-Canada, Montreal, QC, Canada.,Faculty of Dentistry, McGill University, Montreal, QC, Canada
| | - Zoltan Nagy
- Institute of Experimental Biomedicine, University Hospital and Rudolf Virchow Center, University of Würzburg, Würzburg, Germany
| | - Alexandra Mazharian
- Université de Strasbourg, Institut National de la Santé et de la Recherche Médicale (INSERM), Etablissement Français du Sang Grand Est, Unité Mixte de Recherche (UMR)-S 1255, Fédération de Médecine Translationnelle de Strasbourg, Strasbourg, France
| | - Mélanie Welman
- Research Center, Montreal Heart Institute, Montreal, QC, Canada
| | - Marie Lordkipanidzé
- Research Center, Montreal Heart Institute, Montreal, QC, Canada.,Faculty of Pharmacy, University of Montreal, Montreal, QC, Canada
| | - Yotis A Senis
- Université de Strasbourg, Institut National de la Santé et de la Recherche Médicale (INSERM), Etablissement Français du Sang Grand Est, Unité Mixte de Recherche (UMR)-S 1255, Fédération de Médecine Translationnelle de Strasbourg, Strasbourg, France
| | - Svetlana V Komarova
- Department of Biological and Biomedical Engineering, McGill University, Montreal, QC, Canada.,Shriners Hospital for Children-Canada, Montreal, QC, Canada.,Faculty of Dentistry, McGill University, Montreal, QC, Canada
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