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Current Opinion in Hematology Sep 2021Megakaryocytes are rare hematopoietic cells that play an instrumental role in hemostasis, and other important biological processes such as immunity and wound healing.... (Review)
Review
PURPOSE OF REVIEW
Megakaryocytes are rare hematopoietic cells that play an instrumental role in hemostasis, and other important biological processes such as immunity and wound healing. With the advent of cell reprogramming technologies and advances in differentiation protocols, it is now possible to obtain megakaryocytes from any pluripotent stem cell (PSC) via hematopoietic induction. Here, we review recent advances in PSC-derived megakaryocyte (iMK) technology, focusing on platform validation, disease modeling and current limitations.
RECENT FINDINGS
A comprehensive study confirmed that iMK can recapitulate many transcriptional and functional aspects of megakaryocyte and platelet biology, including variables associated with complex genetic traits such as sex and race. These findings were corroborated by several pathological models in which iMKs revealed molecular mechanisms behind inherited platelet disorders and assessed the efficacy of novel pharmacological interventions. However, current differentiation protocols generate primarily embryonic iMK, limiting the clinical and translational potential of this system.
SUMMARY
iMK are strong candidates to model pathologic mutations involved in platelet defects and develop innovative therapeutic strategies. Future efforts on generating definitive hematopoietic progenitors would improve current platelet generation protocols and expand our capacity to model neonatal and adult megakaryocyte disorders.
Topics: Animals; Blood Platelet Disorders; Blood Platelets; Cell Differentiation; Genetic Diseases, Inborn; Hematopoiesis; Humans; Megakaryocytes; Models, Genetic; Pluripotent Stem Cells
PubMed: 34397590
DOI: 10.1097/MOH.0000000000000671 -
British Journal of Haematology Jan 1999The recent discovery of the specific molecular defects in many patients with hereditary spherocytosis and hereditary elliptocytosis/pyropoikilocytosis partially... (Review)
Review
The recent discovery of the specific molecular defects in many patients with hereditary spherocytosis and hereditary elliptocytosis/pyropoikilocytosis partially clarifies the molecular pathology of these diseases. HE and HPP are caused by defects in the horizontal interactions that hold the membrane skeleton together, particularly the critical spectrin self-association reaction. Single gene defects cause red cells to elongate as they circulate, by a unknown mechanism, and are clinically harmless. The combination of two defective genes or one severe alpha spectrin defect and a thalassaemia-like defect in the opposite allele (alphaLELY) results in fragile cells that fragment into bizarre shapes in the circulation, with haemolysis and sometimes life-threatening anaemia. A few of the alpha spectrin defects are common, suggesting they provide an advantage against malaria or some other threat. HS, in contrast, is nearly always caused by family-specific private mutations. These involve the five proteins that link the membrane skeleton to the overlying lipid bilayer: alpha and beta spectrin, ankyrin, band 3 and protein 4.2. Somehow, perhaps through loss of the anchorage band 3 provides its lipid neighbours (Peters et al, 1996), microvesiculation of the membrane surface ensues, leading to spherocytosis, splenic sequestration and haemolysis. Future research will need to focus on how each type of defect causes its associated disease, how the spleen aggravates membrane skeleton defects (a process termed 'conditioning'), how defective red, cells are recognized and removed in the spleen, and why patients with similar or even identical defects can have different clinical severity. Emphasis also needs to be given to improving diagnostic tests, particularly for HS, and exploring new options for therapy, like partial splenectomy, which can ameliorate symptoms while better protecting patients from bacterial sepsis and red cell parasites, and perhaps from atherosclerosis (Robinette & Franmeni, 1977) and venous thrombosis (Stewart et al, 1996).
Topics: Blood Platelet Disorders; Cell Membrane; Humans; Membrane Proteins; Mutation
PubMed: 10027705
DOI: 10.1111/j.1365-2141.1999.01130.x -
International Journal of Molecular... Feb 2020RasGRP2 is calcium and diacylglycerol-regulated guanine nucleotide exchange factor I that activates Rap1, which is an essential signaling-knot in "inside-out" αIIbβ3... (Review)
Review
RasGRP2 is calcium and diacylglycerol-regulated guanine nucleotide exchange factor I that activates Rap1, which is an essential signaling-knot in "inside-out" αIIbβ3 integrin activation in platelets. Inherited platelet function disorder caused by variants of RASGRP2 represents a new congenital bleeding disorder referred to as platelet-type bleeding disorder-18 (BDPLT18). We review here the structure of RasGRP2 and its functions in the pathophysiology of platelets and of the other cellular types that express it. We will also examine the different pathogenic variants reported so far as well as strategies for the diagnosis and management of patients with BDPLT18.
Topics: Blood Platelet Disorders; Blood Platelets; Child, Preschool; Female; Guanine Nucleotide Exchange Factors; Hemorrhage; Humans; Infant; Male; Platelet Glycoprotein GPIIb-IIIa Complex; Shelterin Complex; Signal Transduction; Telomere-Binding Proteins
PubMed: 32041177
DOI: 10.3390/ijms21031075 -
Seminars in Thrombosis and Hemostasis Apr 2016Flow cytometry enables studies of several different aspects of platelet function in response to a variety of platelet agonists. This can be done using only a small... (Review)
Review
Flow cytometry enables studies of several different aspects of platelet function in response to a variety of platelet agonists. This can be done using only a small volume of whole blood, and also in blood with low platelet counts. These properties, together with the increasing number of flow cytometers available in hospitals worldwide, make flow cytometry an interesting option for laboratories interested in studies of platelet function in different clinical settings. This review focuses on practical issues regarding the use of flow cytometry for platelet function testing. It provides an overview of available activation markers, platelet agonists, and experimental setup issues. The review summarizes previous experience and factors important to consider to perform high-quality platelet function testing by flow cytometry. It also discusses its current use and possibilities and challenges for future use of flow cytometry in clinical settings.
Topics: Blood Platelet Disorders; Blood Platelets; Flow Cytometry; Humans; Platelet Activation; Platelet Aggregation; Platelet Function Tests; Reproducibility of Results; Sensitivity and Specificity; Thrombosis
PubMed: 26886398
DOI: 10.1055/s-0035-1570082 -
Journal of Thrombosis and Haemostasis :... Aug 2020Inherited bleeding and platelet disorders (BPD) are highly heterogeneous and their diagnosis involves a combination of clinical investigations, laboratory tests, and... (Review)
Review
Inherited bleeding and platelet disorders (BPD) are highly heterogeneous and their diagnosis involves a combination of clinical investigations, laboratory tests, and genetic screening. This review will outline some of the challenges that geneticists and experts in clinical hemostasis face when implementing high-throughput sequencing (HTS) for patient care. We will provide an overview of the strengths and limitations of the different HTS techniques that can be used to diagnose BPD. An HTS test is cost-efficient and expected to increase the diagnostic rate with a possibility to detect unexpected diagnoses and decrease the turnaround time to diagnose patients. On the other hand, technical shortcomings, variant interpretation difficulties, and ethical issues related to HTS for BPD will also be documented. Delivering a genetic diagnosis to patients is highly desirable to improve clinical management and allow family counseling, but making incorrect assumptions about variants and providing insufficient information to patients before initiating the test could be harmful. Data-sharing and improved HTS guidelines are essential to limit these major drawbacks of HTS.
Topics: Blood Coagulation Disorders, Inherited; Blood Platelet Disorders; Blood Platelets; Genetic Testing; High-Throughput Nucleotide Sequencing; Humans
PubMed: 32521110
DOI: 10.1111/jth.14945 -
Journal of Thrombosis and Haemostasis :... Jun 2013The diagnosis of inherited thrombocytopenias is difficult, for many reasons. First, as they are all rare diseases, they are little known by clinicians, who therefore... (Review)
Review
The diagnosis of inherited thrombocytopenias is difficult, for many reasons. First, as they are all rare diseases, they are little known by clinicians, who therefore tend to suspect the most common forms. Second, making a definite diagnosis often requires complex laboratory techniques that are available in only a few centers. Finally, half of the patients have forms that have not yet been described. As a consequence, many patients with inherited thrombocytopenias are misdiagnosed with immune thrombocytopenia, and are at risk of receiving futile treatments. Misdiagnosis is particularly frequent in patients whose low platelet count is discovered in adult life, because, in these cases, even the inherited origin of thrombocytopenia may be missed. Making the correct diagnosis promptly is important, as we recently learned that some forms of inherited thrombocytopenia predispose to other illnesses, such as leukemia or kidney failure, and affected subjects therefore require close surveillance and, if necessary, prompt treatments. Moreover, medical treatment can increase platelet counts in specific disorders, and affected subjects can therefore receive drugs instead of platelet transfusions when selective surgery is required. In this review, we will discuss how to suspect, diagnose and manage inherited thrombocytopenias, with particular attention to the forms that frequently present in adults. Moreover, we describe four recently identified disorders that belong to this group of disorders that are often diagnosed in adults: MYH9-related disease, monoallelic Bernard-Soulier syndrome, ANKRD26-related thrombocytopenia, and familial platelet disorder with predisposition to acute leukemia.
Topics: Adult; Bernard-Soulier Syndrome; Blood Platelet Disorders; Blood Platelets; Diagnosis, Differential; Genetic Predisposition to Disease; Hematologic Diseases; Humans; Intercellular Signaling Peptides and Proteins; Leukemia; Leukemia, Myeloid, Acute; Middle Aged; Molecular Motor Proteins; Myosin Heavy Chains; Nuclear Proteins; Platelet Count; Thrombocytopenia
PubMed: 23510089
DOI: 10.1111/jth.12196 -
Journal of Thrombosis and Haemostasis :... Feb 2023Inherited platelet disorders (IPDs) are a heterogeneous group of rare diseases that are caused by the defects in early megakaryopoiesis, proplatelet formation, and/or...
BACKGROUND
Inherited platelet disorders (IPDs) are a heterogeneous group of rare diseases that are caused by the defects in early megakaryopoiesis, proplatelet formation, and/or mature platelet function. Although genomic sequencing is increasingly used to identify genetic variants underlying IPD, this technique does not disclose resulting molecular changes that impact platelet function. Proteins are the functional units that shape platelet function; however, insights into how variants that cause IPDs impact platelet proteomes are limited.
OBJECTIVES
The objective of this study was to profile the platelet proteomics signatures of IPDs.
METHODS
We performed unbiased label-free quantitative mass spectrometry (MS)-based proteome profiling on platelets of 34 patients with IPDs with variants in 13 ISTH TIER1 genes that affect different stages of platelet development.
RESULTS
In line with the phenotypical heterogeneity between IPDs, proteomes were diverse between IPDs. We observed extensive proteomic alterations in patients with a GFI1B variant and for genetic variants in genes encoding proteins that impact cytoskeletal processes (MYH9, TUBB1, and WAS). Using the diversity between IPDs, we clustered protein dynamics, revealing disrupted protein-protein complexes. This analysis furthermore grouped proteins with similar cellular function and location, classifying mitochondrial protein constituents and identifying both known and putative novel alpha granule associated proteins.
CONCLUSIONS
With this study, we demonstrate a MS-based proteomics perspective to IPDs. By integrating the effects of IPDs that impact different aspects of platelet function, we dissected the biological contexts of protein alterations to gain further insights into the biology of platelet (dys)function.
Topics: Humans; Proteomics; Proteome; Blood Platelet Disorders; Blood Platelets; Thrombopoiesis
PubMed: 36700500
DOI: 10.1016/j.jtha.2022.11.021 -
Small GTPases 2021Platelets are master regulators and effectors of haemostasis with increasingly recognized functions as mediators of inflammation and immune responses. The Rho family of... (Review)
Review
Platelets are master regulators and effectors of haemostasis with increasingly recognized functions as mediators of inflammation and immune responses. The Rho family of GTPase members Rac1, Cdc42 and RhoA are known to be major components of the intracellular signalling network critical to platelet shape change and morphological dynamics, thus playing a major role in platelet spreading, secretion and thrombus formation. Initially linked to the regulation of actomyosin contraction and lamellipodia formation, recent reports have uncovered non-canonical functions of platelet RhoGTPases in the regulation of reactive oxygen species (ROS), where intrinsically generated ROS modulate platelet function and contribute to thrombus formation. Platelet RhoGTPases orchestrate oxidative processes and cytoskeletal rearrangement in an interconnected manner to regulate intracellular signalling networks underlying platelet activity and thrombus formation. Herein we review our current knowledge of the regulation of platelet ROS generation by RhoGTPases and their relationship with platelet cytoskeletal reorganization, activation and function.
Topics: Animals; Blood Platelet Disorders; Blood Platelets; Humans; Reactive Oxygen Species; rho GTP-Binding Proteins
PubMed: 33459160
DOI: 10.1080/21541248.2021.1878001 -
International Journal of Molecular... Jul 2022Platelets are generated and released into the bloodstream from their precursor cells, megakaryocytes that reside in the bone marrow. Though platelets have no nucleus or... (Review)
Review
Platelets are generated and released into the bloodstream from their precursor cells, megakaryocytes that reside in the bone marrow. Though platelets have no nucleus or DNA, they contain a full transcriptome that, during platelet formation, is transported from the megakaryocyte to the platelet. It has been described that transcripts in platelets can be translated into proteins that influence platelet response. The platelet transcriptome is highly dynamic and has been extensively studied using microarrays and, more recently, RNA sequencing (RNA-seq) in relation to diverse conditions (inflammation, obesity, cancer, pathogens and others). In this review, we focus on bulk and single-cell RNA-seq studies that have aimed to characterize the coding transcriptome of healthy megakaryocytes and platelets in humans. It has been noted that bulk RNA-seq has limitations when studying in vitro-generated megakaryocyte cultures that are highly heterogeneous, while single-cell RNA-seq has not yet been applied to platelets due to their very limited RNA content. Next, we illustrate how these methods can be applied in the field of inherited platelet disorders for gene discovery and for unraveling novel disease mechanisms using RNA from platelets and megakaryocytes and rare disease bioinformatics. Next, future perspectives are discussed on how this field of coding transcriptomics can be integrated with other next-generation technologies to decipher unexplained inherited platelet disorders in a multiomics approach.
Topics: Blood Platelet Disorders; Blood Platelets; Humans; Megakaryocytes; RNA; Thrombopoiesis; Transcriptome
PubMed: 35886993
DOI: 10.3390/ijms23147647 -
Journal of Thrombosis and Haemostasis :... Aug 2005Qualitative disorders of platelet function and production form a large group of rare diseases which cover a multitude of genetic defects that by and large have as a... (Review)
Review
Qualitative disorders of platelet function and production form a large group of rare diseases which cover a multitude of genetic defects that by and large have as a common symptom, excessive mucocutaneous bleeding. Glanzmann thrombasthenia, is enabling us to learn much about the pathophysiology of integrins and of how alphaIIb beta3 functions. Bernard-Soulier syndrome, an example of macrothrombocytopenia, combines the production of large platelets with a deficit or non-functioning of the major adhesion receptor of platelets, the GPIb-IX-V complex. Amino acid substitutions in GPIb alpha, may lead to up-regulation and spontaneous binding of von Willebrand factor as in Platelet-type von Willebrand disease. In disorders with defects in the MYH9 gene, macrothrombocytopenias are linked to modifications in kidney, eye or ear, whereas other inherited thrombocytopenias variously link a low platelet count with a propensity to leukemia, skeletal defects, learning impairment, and abnormal red cells. Defects of secretion from platelets include an abnormal alpha-granule formation as in the gray platelet syndrome (with marrow myelofibrosis), and of organelle biogenesis in the Hermansky-Pudlak and Chediak-Higashi syndromes where platelet dense body defects are linked to abnormalities of other lysosomal-like organelles including melanosomes. Finally, defects involving surface receptors (P2Y(12), TPalpha) for activating stimuli, of proteins essential for signaling pathways (including Wiskott-Aldrich syndrome), and of platelet-derived procoagulant activity (Scott syndrome) show how studies on platelet disorders are helping unravel the pathways of primary hemostasis.
Topics: Bernard-Soulier Syndrome; Blood Platelet Disorders; Blood Platelets; Coagulants; Genetic Therapy; Humans; Integrins; Megakaryocytes; Models, Biological; Platelet Aggregation; Protein Binding; Signal Transduction; Thrombasthenia; Thrombocytopenia; Up-Regulation; von Willebrand Factor
PubMed: 16102044
DOI: 10.1111/j.1538-7836.2005.01428.x