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1.
Rinsho Ketsueki ; 60(9): 1046-1055, 2019.
Artigo em Japonês | MEDLINE | ID: mdl-31597826

RESUMO

Human iPS cells are somatic cells reprogrammed to the pluripotent state. Because of their pluripotent nature, iPS cells are now commonly used to model several developmental processes including hematopoiesis in vitro. The in vitro models can be used to study the mechanisms regulating not only normal hematopoiesis but also hematological diseases ranging from monogenic congenital disorders to genetically multifactorial malignancies. Those disease models can also be used to investigate novel treatments through procedures including high throughput drug screening. The possible clinical applications of iPS cell-derived hematopoietic cells include immunotherapy with T lymphocytes, NK cells and macrophages, and transfusion therapy with platelets and red blood cells. Platelets have now been produced from iPS cells in quantities sufficient for clinical use. By developing expandable immortalized megakaryocyte cell lines (imMKCLs), several novel drugs and turbulence-incorporated bioreactors, efficient and scalable generation of platelets was achieved. This review summarizes the current status of iPS cell research in hematopoiesis with details on iPS cell-derived platelets.


Assuntos
Plaquetas/citologia , Terapia Baseada em Transplante de Células e Tecidos , Células-Tronco Pluripotentes Induzidas/citologia , Diferenciação Celular , Eritrócitos , Hematopoese , Humanos , Imunoterapia , Células Matadoras Naturais , Macrófagos , Megacariócitos , Linfócitos T
3.
Blood ; 133(16): 1700-1701, 2019 Apr 18.
Artigo em Inglês | MEDLINE | ID: mdl-31000515
4.
Proc Natl Acad Sci U S A ; 116(11): 4983-4988, 2019 03 12.
Artigo em Inglês | MEDLINE | ID: mdl-30804189

RESUMO

Platelets mediate primary hemostasis, and recent work has emphasized platelet participation in immunity and inflammation. The function of the platelet-specific integrin αIIbß3 as a fibrinogen receptor in hemostasis is well defined, but the roles of αIIbß3 or integrin-associated proteins in nonhemostatic platelet functions are poorly understood. Here we show that human platelets express the integrin-associated protein SHARPIN with functional consequences. In leukocytes, SHARPIN interacts with integrin α cytoplasmic tails, and it is also an obligate member of the linear ubiquitin chain assembly complex (LUBAC), which mediates Met1 linear ubiquitination of proteins leading to canonical NF-κB activation. SHARPIN interacted with αIIb in pull-down and coimmunoprecipitation assays. SHARPIN was partially localized, as was αIIbß3, at platelet edges, and thrombin stimulation induced more central SHARPIN localization. SHARPIN also coimmunoprecipitated from platelets with the two other proteins comprising LUBAC, the E3 ligase HOIP and HOIL-1. Platelet stimulation with thrombin or inflammatory agonists, including lipopolysaccharide or soluble CD40 ligand (sCD40L), induced Met1 linear ubiquitination of the NF-κB pathway protein NEMO and serine-536 phosphorylation of the p65 RelA subunit of NF-κB. In human megakaryocytes and/or platelets derived from induced pluripotent stem (iPS) cells, SHARPIN knockdown caused increased basal and agonist-induced fibrinogen binding to αIIbß3 as well as reduced Met1 ubiquitination and RelA phosphorylation. Moreover, these SHARPIN knockdown cells exhibited increased surface expression of MHC class I molecules and increased release of sCD40L. These results establish that SHARPIN functions in the human megakaryocyte/platelet lineage through protein interactions at the nexus of integrin and immune/inflammatory signaling.


Assuntos
Plaquetas/metabolismo , Transdução de Sinais , Ubiquitinas/metabolismo , Linhagem da Célula , Técnicas de Silenciamento de Genes , Homeostase , Humanos , Quinase I-kappa B/metabolismo , Células-Tronco Pluripotentes Induzidas/metabolismo , Inflamação/patologia , Megacariócitos/metabolismo , Modelos Biológicos , NF-kappa B/metabolismo , Glicoproteína IIb da Membrana de Plaquetas/metabolismo , Ligação Proteica , Ubiquitina/metabolismo , Ubiquitina-Proteína Ligases/metabolismo , Ubiquitinação
5.
Rinsho Ketsueki ; 59(10): 1905-1913, 2018.
Artigo em Japonês | MEDLINE | ID: mdl-30305491

RESUMO

Platelet transfusion products derived from induced pluripotent stem cells (iPSCs) have been pursued as a blood donor-independent and genetically manipulative measure to complement or as an alternative to current platelet products. Platelets are enucleate blood cells indispensable for hemostasis. Thus, platelet transfusions have been clinically established to treat patients with severe thrombocytopenia. However, current blood products face issues in the balance of supply and demand, alloimmune responses, and infections and are expected to meet the shortage of donors in aging societies. iPSc-derived platelet products are qualitatively and quantitatively approaching a clinically applicable level, owing to advances and novel findings in expandable megakaryocyte cell lines, turbulence-incorporating bioreactors, and reagents that enable feeder cell-free production and improve platelet quality. Currently, the establishment of guidelines to assure the quality of iPSC-derived blood products for clinical application is in process. Considering the low risk of tumorigenicity and the large demand, ex vivo production of iPSC-derived platelets could lead to iPSC-based regenerative medicine becoming a common clinical practice and the development of a future system in which anyone can safely receive a platelet transfusion in their time of need.

6.
Blood Adv ; 2(17): 2262-2272, 2018 Sep 11.
Artigo em Inglês | MEDLINE | ID: mdl-30206099

RESUMO

During maturation, megakaryocytes (MKs) express ß1-tubulin (TUBB1) and rearrange their microtubule components to enlarge, form proplatelets, and eventually release platelets. The development of a platform to identify in vitro conditions that would efficiently promote MK development could potentially enable large-scale platelet production. Here, we show that an immortalized MK cell line (imMKCL) genetically modified to express the ß1-tubulin-Venus reporter provides a practical system to efficiently monitor the in vitro production of platelet-like particles (PLPs). The Venus transgene was inserted downstream of the TUBB1 locus in imMKCLs using CRISPR/Cas9, and the expression was visualized by Venus fluorescence intensity. This imMKCL reporter line was then used for high-throughput drug screening. We identified several compounds that significantly improved the efficiency of PLP production in vitro under feeder-free conditions and showed a significant tendency to recover platelets in vivo in a mouse thrombocytopenia model induced by anti-GPIbα antibody administration. Interestingly, most of these compounds, including a WNT signaling pathway inhibitor, Wnt-C59, antagonized the aryl hydrocarbon receptor (AhR) to increase PLP production, confirming the crucial role of AhR inhibition in MK maturation. Consistently, small interfering RNA treatment against AhR increased the Venus intensity and PLP production. TCS 359, an FLT3 inhibitor, significantly increased PLP production independently of FLT3 or AhR. This study highlights the usefulness of the ß1-tubulin reporter MK line as a useful tool to study the mechanisms underlying thrombopoiesis and to identify novel inducers of ex vivo platelet production.

7.
Proc Natl Acad Sci U S A ; 115(35): E8228-E8235, 2018 08 28.
Artigo em Inglês | MEDLINE | ID: mdl-30104364

RESUMO

New mechanisms behind blood cell formation continue to be uncovered, with therapeutic approaches for hematological diseases being of great interest. Here we report an enzyme in protein synthesis, known for cell-based activities beyond translation, is a factor inducing megakaryocyte-biased hematopoiesis, most likely under stress conditions. We show an activated form of tyrosyl-tRNA synthetase (YRSACT), prepared either by rationally designed mutagenesis or alternative splicing, induces expansion of a previously unrecognized high-ploidy Sca-1+ megakaryocyte population capable of accelerating platelet replenishment after depletion. Moreover, YRSACT targets monocytic cells to induce secretion of transacting cytokines that enhance megakaryocyte expansion stimulating the Toll-like receptor/MyD88 pathway. Platelet replenishment by YRSACT is independent of thrombopoietin (TPO), as evidenced by expansion of the megakaryocytes from induced pluripotent stem cell-derived hematopoietic stem cells from a patient deficient in TPO signaling. We suggest megakaryocyte-biased hematopoiesis induced by YRSACT offers new approaches for treating thrombocytopenia, boosting yields from cell-culture production of platelet concentrates for transfusion, and bridging therapy for hematopoietic stem cell transplantation.


Assuntos
Plaquetas/metabolismo , Hematopoese , Megacariócitos/metabolismo , Poliploidia , Trombocitopenia/metabolismo , Tirosina-tRNA Ligase/metabolismo , Plaquetas/patologia , Técnicas de Cultura de Células , Células Cultivadas , Feminino , Células-Tronco Hematopoéticas/metabolismo , Células-Tronco Hematopoéticas/patologia , Humanos , Células-Tronco Pluripotentes Induzidas/metabolismo , Células-Tronco Pluripotentes Induzidas/patologia , Masculino , Megacariócitos/patologia , Transdução de Sinais , Trombocitopenia/patologia , Trombopoetina/metabolismo
8.
Am J Hum Genet ; 103(3): 440-447, 2018 Sep 06.
Artigo em Inglês | MEDLINE | ID: mdl-30146126

RESUMO

Inherited bone-marrow-failure syndromes (IBMFSs) include heterogeneous genetic disorders characterized by bone-marrow failure, congenital anomalies, and an increased risk of malignancy. Many lines of evidence have suggested that p53 activation might be central to the pathogenesis of IBMFSs, including Diamond-Blackfan anemia (DBA) and dyskeratosis congenita (DC). However, the exact role of p53 activation in each clinical feature remains unknown. Here, we report unique de novo TP53 germline variants found in two individuals with an IBMFS accompanied by hypogammaglobulinemia, growth retardation, and microcephaly mimicking DBA and DC. TP53 is a tumor-suppressor gene most frequently mutated in human cancers, and occasional germline variants occur in Li-Fraumeni cancer-predisposition syndrome. Most of these mutations affect the core DNA-binding domain, leading to compromised transcriptional activities. In contrast, the variants found in the two individuals studied here caused the same truncation of the protein, resulting in the loss of 32 residues from the C-terminal domain (CTD). Unexpectedly, the p53 mutant had augmented transcriptional activities, an observation not previously described in humans. When we expressed this mutant in zebrafish and human-induced pluripotent stem cells, we observed impaired erythrocyte production. These findings together with close similarities to published knock-in mouse models of TP53 lacking the CTD demonstrate that the CTD-truncation mutations of TP53 cause IBMFS, providing important insights into the previously postulated connection between p53 and IBMFSs.

9.
Cell ; 174(3): 636-648.e18, 2018 Jul 26.
Artigo em Inglês | MEDLINE | ID: mdl-30017246

RESUMO

The ex vivo generation of platelets from human-induced pluripotent cells (hiPSCs) is expected to compensate donor-dependent transfusion systems. However, manufacturing the clinically required number of platelets remains unachieved due to the low platelet release from hiPSC-derived megakaryocytes (hiPSC-MKs). Here, we report turbulence as a physical regulator in thrombopoiesis in vivo and its application to turbulence-controllable bioreactors. The identification of turbulent energy as a determinant parameter allowed scale-up to 8 L for the generation of 100 billion-order platelets from hiPSC-MKs, which satisfies clinical requirements. Turbulent flow promoted the release from megakaryocytes of IGFBP2, MIF, and Nardilysin to facilitate platelet shedding. hiPSC-platelets showed properties of bona fide human platelets, including circulation and hemostasis capacities upon transfusion in two animal models. This study provides a concept in which a coordinated physico-chemical mechanism promotes platelet biogenesis and an innovative strategy for ex vivo platelet manufacturing.

10.
Cell Stem Cell ; 22(5): 713-725.e8, 2018 May 03.
Artigo em Inglês | MEDLINE | ID: mdl-29706577

RESUMO

Stem cell self-renewal is critical for tissue homeostasis, and its dysregulation can lead to organ failure or tumorigenesis. While obesity can induce varied abnormalities in bone marrow components, it is unclear how diet might affect hematopoietic stem cell (HSC) self-renewal. Here, we show that Spred1, a negative regulator of RAS-MAPK signaling, safeguards HSC homeostasis in animals fed a high-fat diet (HFD). Under steady-state conditions, Spred1 negatively regulates HSC self-renewal and fitness, in part through Rho kinase activity. Spred1 deficiency mitigates HSC failure induced by infection mimetics and prolongs HSC lifespan, but it does not initiate leukemogenesis due to compensatory upregulation of Spred2. In contrast, HFD induces ERK hyperactivation and aberrant self-renewal in Spred1-deficient HSCs, resulting in functional HSC failure, severe anemia, and myeloproliferative neoplasm-like disease. HFD-induced hematopoietic abnormalities are mediated partly through alterations to the gut microbiota. Together, these findings reveal that diet-induced stress disrupts fine-tuning of Spred1-mediated signals to govern HSC homeostasis.

11.
Br J Haematol ; 181(6): 791-802, 2018 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-29741776

RESUMO

Somatic mutations in the calreticulin (CALR) gene have been found in most patients with JAK2- and MPL-unmutated Philadelphia chromosome-negative myeloproliferative neoplasms (MPNs). It has recently been shown that mutant CALR constitutively activates the thrombopoietin receptor MPL and, thus, plays a causal role in the development of MPNs. However, the roles of mutant CALR in human haematopoietic cell differentiation remain predominantly elusive. To examine the impact of the 5-base insertion mutant CALR gene (Ins5) on haematopoietic cell differentiation, we generated induced pluripotent stem cells from an essential thrombocythaemia (ET) patient harbouring a CALR-Ins5 mutation and from a healthy individual (WT). Megakaryopoiesis was more prominent in Ins5-haematopoietic progenitor cells (Ins5-HPCs) than in WT-HPCs, implying that the system recapitulates megakaryocytosis observed in the bone marrow of CALR-mutant ET patients. Ins5-HPCs exhibited elevated expression levels of GATA1 and GATA2, suggesting a premature commitment to megakaryocytic differentiation in progenitor cells. We also demonstrated that 3-hydroxy anagrelide markedly perturbed megakaryopoiesis, but not erythropoiesis. Collectively, we established an in vitro model system that recapitulates megakaryopoiesis caused by mutant CALR. This system can be used to validate therapeutic compounds for MPN patients harbouring CALR mutations and in detailed studies on mutant CALR in human haematological cell differentiation.

12.
JCI Insight ; 3(8)2018 Apr 19.
Artigo em Inglês | MEDLINE | ID: mdl-29669932

RESUMO

Colon cancer is a complex disease affected by a combination of genetic and epigenetic factors. Here we demonstrate that nardilysin (N-arginine dibasic convertase; NRDC), a metalloendopeptidase of the M16 family, regulates intestinal tumorigenesis via its nuclear functions. NRDC is highly expressed in human colorectal cancers. Deletion of the Nrdc gene in ApcMin mice crucially suppressed intestinal tumor development. In ApcMin mice, epithelial cell-specific deletion of Nrdc recapitulated the tumor suppression observed in Nrdc-null mice. Moreover, epithelial cell-specific overexpression of Nrdc significantly enhanced tumor formation in ApcMin mice. Notably, epithelial NRDC controlled cell apoptosis in a gene dosage-dependent manner. In human colon cancer cells, nuclear NRDC directly associated with HDAC1, and controlled both acetylation and stabilization of p53, with alterations of p53 target apoptotic factors. These findings demonstrate that NRDC is critically involved in intestinal tumorigenesis through its epigenetic regulatory function, and targeting NRDC may lead to a novel prevention or therapeutic strategy against colon cancer.

13.
Rinsho Ketsueki ; 58(10): 2150-2159, 2017.
Artigo em Japonês | MEDLINE | ID: mdl-28978860

RESUMO

Blood products derived from iPS cells have been pursued as a blood donor-independent and genetically manipulative measure to complement or alternate current transfusion products. Erythrocytes and platelets are anucleate blood cells that are indispensable for oxygen delivery and hemostasis, respectively. Consequently, blood transfusions have been clinically established to treat severe anemia and thrombocytopenia. However, current blood products exhibit issues with regard to supply-demand imbalance and alloimmune responses and infections, and they also face a future shortage of donors in aging societies. While the production of erythrocytes from iPS cells has challenges to overcome, such as their differentiation into an adult-type phenotype and scalable production, platelet products are qualitatively and quantitatively approaching a clinically applicable level owing to advances in expandable megakaryocyte (MK) lines, platelet-producing bioreactors, and novel reagents. Currently, the establishment of guidelines that assure the quality of iPSC-derived blood products for clinical application is in progress. Considering the minimal risk of tumorigenicity and the expected significant demand of such products, the ex vivo production of iPSC-derived blood cells can be expected to lead iPSC-based regenerative medicine to become common clinical practice.


Assuntos
Células-Tronco Pluripotentes Induzidas , Guias de Prática Clínica como Assunto , Plaquetas/efeitos dos fármacos , Desenho de Drogas , Humanos , Inibidores da Agregação de Plaquetas/uso terapêutico , Trombopoese
14.
Transfusion ; 57(8): 2035-2044, 2017 08.
Artigo em Inglês | MEDLINE | ID: mdl-28681458

RESUMO

BACKGROUND: To bridge the gap between in vitro function and clinical efficacy of platelet (PLT) transfusion products, reliable in vivo PLT functional assays for hemostasis and survival in animal models are required. However, there are no standardized methods for assessing the in vivo quality of transfused human PLTs. STUDY DESIGN AND METHODS: Plasma-depleted human PLT concentrates (PCs; Day 3, Day 5, Day 7, Day 10, and damaged) were transfused into busulfan-induced rabbits with thrombocytopenia with prolonged bleeding times 1 day after treatment with ethyl palmitate (EP) to block their reticuloendothelial systems. The hemostatic effect of PC transfusion was evaluated by the ear fine vein bleeding time. For the in vivo survival assay, splenectomized EP-treated rabbits were transfused with human PCs, and viability of the human PLTs in the rabbits was determined by flow cytometry using human PLT-specific antibodies and Trucount tubes. RESULTS: The hemostatic effect of PCs was slightly reduced with increasing storage periods for early time points, but more dramatically reduced for later time points. PLT survival was similar after 3 and 7 days of storage, but PLTs stored for 10 days showed significantly poorer survival than those stored only 3 days. CONCLUSION: Our new and improved protocol for in vivo assessment of transfused PLTs is sufficiently sensitive to detect subtle changes in hemostatic function and viability of human PLTs transfused into rabbit models. This protocol could contribute to preclinical in vivo functional assessment and clinical quality assurance of emerging novel PLT products such as cultured cell-derived human PLTs.


Assuntos
Plaquetas/citologia , Sobrevivência Celular , Hemostasia , Testes de Função Plaquetária/métodos , Transfusão de Plaquetas , Animais , Preservação de Sangue/métodos , Citometria de Fluxo/métodos , Humanos , Métodos , Modelos Animais , Coelhos , Fatores de Tempo
15.
Stem Cells Transl Med ; 6(3): 720-730, 2017 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-28297575

RESUMO

Donor-independent platelet concentrates for transfusion can be produced in vitro from induced pluripotent stem cells (iPSCs). However, culture at 37°C induces ectodomain shedding on platelets of glycoprotein Ibα (GPIbα), the von Willebrand factor receptor critical for adhesive function and platelet lifetime in vivo, through temperature-dependent activation of a disintegrin and metalloproteinase 17 (ADAM17). The shedding can be suppressed by using inhibitors of panmetalloproteinases and possibly of the upstream regulator p38 mitogen-activated protein kinase (p38 MAPK), but residues of these inhibitors in the final platelet products may be accompanied by harmful risks that prevent clinical application. Here, we optimized the culture conditions for generating human iPSC-derived GPIbα+ platelets, focusing on culture temperature and additives, by comparing a new and safe selective ADAM17 inhibitor, KP-457, with previous inhibitors. Because cultivation at 24°C (at which conventional platelet concentrates are stored) markedly diminished the yield of platelets with high expression of platelet receptors, 37°C was requisite for normal platelet production from iPSCs. KP-457 blocked GPIbα shedding from iPSC platelets at a lower half-maximal inhibitory concentration than panmetalloproteinase inhibitor GM-6001, whereas p38 MAPK inhibitors did not. iPSC platelets generated in the presence of KP-457 exhibited improved GPIbα-dependent aggregation not inferior to human fresh platelets. A thrombus formation model using immunodeficient mice after platelet transfusion revealed that iPSC platelets generated with KP-457 exerted better hemostatic function in vivo. Our findings suggest that KP-457, unlike GM-6001 or p38 MAPK inhibitors, effectively enhances the production of functional human iPSC-derived platelets at 37°C, which is an important step toward their clinical application. Stem Cells Translational Medicine 2017;6:720-730.

16.
Blood Adv ; 1(7): 468-476, 2017 Feb 28.
Artigo em Inglês | MEDLINE | ID: mdl-29296963

RESUMO

Signaling by thrombopoietin (TPO) in complex with its receptor, c-MPL, is critical for hematopoietic stem cell (HSC) homeostasis and platelet generation. Here we show that TA-316, a novel chemically synthesized c-MPL agonist (CMA), is useful for ex vivo platelet generation from human-induced pluripotent stem (iPS) cell-derived immortalized megakaryocyte progenitor cell lines (imMKCLs). Moreover, the generation is clinically applicable, because self-renewal expansion and platelet release is tightly controllable. TA-316 but not eltrombopag, another CMA, promoted both the self-renewal and maturation of imMKCLs, leading to more than a twofold higher platelet production than that achieved with recombinant human TPO (rhTPO). Interestingly, TA-316 seemed to favor MK-biased differentiation from bone marrow CD34+ HSC/progenitors and imMKCLs through the upregulation of vascular endothelial growth factor A and fibroblast growth factor 2. This result suggests TA-316 could facilitate the development of an efficient and useful system to expand platelets from imMKCLs.

17.
Development ; 143(12): 2039-43, 2016 06 15.
Artigo em Inglês | MEDLINE | ID: mdl-27302394

RESUMO

Ten years ago, the discovery that mature somatic cells could be reprogrammed into induced pluripotent stem cells (iPSCs) redefined the stem cell field and brought about a wealth of opportunities for both basic research and clinical applications. To celebrate the tenth anniversary of the discovery, the International Society for Stem Cell Research (ISSCR) and Center for iPS Cell Research and Application (CiRA), Kyoto University, together held the symposium 'Pluripotency: From Basic Science to Therapeutic Applications' in Kyoto, Japan. The three days of lectures examined both the mechanisms and therapeutic applications of iPSC reprogramming. Here we summarize the main findings reported, which are testament to how far the field has come in only a decade, as well as the enormous potential that iPSCs hold for the future.


Assuntos
Células-Tronco Pluripotentes Induzidas/citologia , Células-Tronco Pluripotentes Induzidas/transplante , Transplante de Células-Tronco , Animais , Diferenciação Celular , Doença , Humanos
18.
Rinsho Ketsueki ; 57(3): 308-14, 2016 Mar.
Artigo em Japonês | MEDLINE | ID: mdl-27076243

RESUMO

Platelet transfusion is indispensable for current medical treatments of hematological disorders. However, alternative platelet sources are urgently needed due to the inadequate donor blood supply, particularly of HLA/HPA-matched platelets. The advent of 'iPS cell (iPSC) technology' was considered in light of this problem, which yielded the idea of iPSC-derived platelet production. The safety of iPSC-derived cell therapy is critical, but platelets can be gamma-irradiated prior to their use. Thus, there is an advantage in terms of clinical application. The remaining developmental aim of the in vitro iPSC-derived platelet generation process is to further scale up industrialized culture and production for the packaging of washed-type platelet concentrates, and a laboratory scale production system has already been optimized in preparation for meeting this goal.


Assuntos
Células-Tronco Pluripotentes Induzidas , Transfusão de Plaquetas , Antígenos HLA/imunologia , Hematopoese , Humanos , Células-Tronco Pluripotentes Induzidas/citologia
19.
Blood ; 127(10): 1234-41, 2016 Mar 10.
Artigo em Inglês | MEDLINE | ID: mdl-26787737

RESUMO

Thrombocytopenia is defined as a status in which platelet numbers are reduced. Imbalance between the homeostatic regulation of platelet generation and destruction is 1 potential cause of thrombocytopenia. In adults, platelet generation is a 2-stage process entailing the differentiation of hematopoietic stem cells into mature megakaryocytes (MKs; known as megakaryopoiesis) and release of platelets from MKs (known as thrombopoiesis or platelet biogenesis). Until recently, information about the genetic defects responsible for congenital thrombocytopenia was only available for a few forms of the disease. However, investigations over the past 15 years have identified mutations in genes encoding >20 different proteins that are responsible for these disorders, which has advanced our understanding of megakaryopoiesis and thrombopoiesis. The underlying pathogenic mechanisms can be categorized as (1) defects in MK lineage commitment and differentiation, (2) defects in MK maturation, and (3) defect in platelet release. Using these developmental stage categories, we here update recently described mechanisms underlying megakaryopoiesis and thrombopoiesis and discuss the association between platelet generation systems and thrombocytopenia.


Assuntos
Doenças Genéticas Inatas , Células-Tronco Hematopoéticas , Megacariócitos , Mutação , Trombocitopenia , Trombopoese/genética , Adulto , Animais , Doenças Genéticas Inatas/genética , Doenças Genéticas Inatas/metabolismo , Doenças Genéticas Inatas/patologia , Células-Tronco Hematopoéticas/metabolismo , Células-Tronco Hematopoéticas/patologia , Humanos , Megacariócitos/metabolismo , Megacariócitos/patologia , Trombocitopenia/genética , Trombocitopenia/metabolismo , Trombocitopenia/patologia
20.
Proc Natl Acad Sci U S A ; 112(41): 12800-5, 2015 Oct 13.
Artigo em Inglês | MEDLINE | ID: mdl-26417084

RESUMO

Phosphatidylserine (PtdSer) exposure on the surface of activated platelets requires the action of a phospholipid scramblase(s), and serves as a scaffold for the assembly of the tenase and prothrombinase complexes involved in blood coagulation. Here, we found that the activation of mouse platelets with thrombin/collagen or Ca(2+) ionophore at 20 °C induces PtdSer exposure without compromising plasma membrane integrity. Among five transmembrane protein 16 (TMEM16) members that support Ca(2+)-dependent phospholipid scrambling, TMEM16F was the only one that showed high expression in mouse platelets. Platelets from platelet-specific TMEM16F-deficient mice exhibited defects in activation-induced PtdSer exposure and microparticle shedding, although α-granule and dense granule release remained intact. The rate of tissue factor-induced thrombin generation by TMEM16F-deficient platelets was severely reduced, whereas thrombin-induced clot retraction was unaffected. The imaging of laser-induced thrombus formation in whole animals showed that PtdSer exposure on aggregated platelets was TMEM16F-dependent in vivo. The phenotypes of the platelet-specific TMEM16F-null mice resemble those of patients with Scott syndrome, a mild bleeding disorder, indicating that these mice may provide a useful model for human Scott syndrome.


Assuntos
Plaquetas/metabolismo , Micropartículas Derivadas de Células/metabolismo , Fosfatidilserinas/metabolismo , Proteínas de Transferência de Fosfolipídeos/metabolismo , Ativação Plaquetária , Animais , Anoctaminas , Coagulação Sanguínea/genética , Transtornos da Coagulação Sanguínea/genética , Transtornos da Coagulação Sanguínea/metabolismo , Transtornos da Coagulação Sanguínea/patologia , Plaquetas/patologia , Cálcio/metabolismo , Micropartículas Derivadas de Células/genética , Modelos Animais de Doenças , Humanos , Camundongos , Camundongos Mutantes , Fosfatidilserinas/genética , Proteínas de Transferência de Fosfolipídeos/genética , Trombina/genética , Trombina/metabolismo
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