TY - JOUR A1 - Stegner, David A1 - van Eeuwijk, Judith M.M. A1 - Angay, Oğuzhan A1 - Gorelashvili, Maximilian G. A1 - Semeniak, Daniela A1 - Pinnecker, Jürgen A1 - Schmithausen, Patrick A1 - Meyer, Imke A1 - Friedrich, Mike A1 - Dütting, Sebastian A1 - Brede, Christian A1 - Beilhack, Andreas A1 - Schulze, Harald A1 - Nieswandt, Bernhard A1 - Heinze, Katrin G. T1 - Thrombopoiesis is spatially regulated by the bone marrow vasculature JF - Nature Communications N2 - In mammals, megakaryocytes (MKs) in the bone marrow (BM) produce blood platelets, required for hemostasis and thrombosis. MKs originate from hematopoietic stem cells and are thought to migrate from an endosteal niche towards the vascular sinusoids during their maturation. Through imaging of MKs in the intact BM, here we show that MKs can be found within the entire BM, without a bias towards bone-distant regions. By combining in vivo two-photon microscopy and in situ light-sheet fluorescence microscopy with computational simulations, we reveal surprisingly slow MK migration, limited intervascular space, and a vessel-biased MK pool. These data challenge the current thrombopoiesis model of MK migration and support a modified model, where MKs at sinusoids are replenished by sinusoidal precursors rather than cells from a distant periostic niche. As MKs do not need to migrate to reach the vessel, therapies to increase MK numbers might be sufficient to raise platelet counts. KW - bone marrow KW - megakaryocytes KW - thrombopoiesis Y1 - 2017 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-170591 VL - 8 IS - 127 ER - TY - JOUR A1 - Schuhmann, Michael K. A1 - Kraft, Peter A1 - Bieber, Michael A1 - Kollikowski, Alexander M. A1 - Schulze, Harald A1 - Nieswandt, Bernhard A1 - Pham, Mirko A1 - Stegner, David A1 - Stoll, Guido T1 - Targeting platelet GPVI plus rt-PA administration but not α2β1-mediated collagen binding protects against ischemic brain damage in mice JF - International Journal of Molecular Science N2 - Platelet collagen interactions at sites of vascular injuries predominantly involve glycoprotein VI (GPVI) and the integrin α2β1. Both proteins are primarily expressed on platelets and megakaryocytes whereas GPVI expression is also shown on endothelial and integrin α2β1 expression on epithelial cells. We recently showed that depletion of GPVI improves stroke outcome without increasing the risk of cerebral hemorrhage. Genetic variants associated with higher platelet surface integrin α2 (ITGA2) receptor levels have frequently been found to correlate with an increased risk of ischemic stroke in patients. However until now, no preclinical stroke study has addressed whether platelet integrin α2β1 contributes to the pathophysiology of ischemia/reperfusion (I/R) injury. Focal cerebral ischemia was induced in C57BL/6 and Itga2\(^{−/−}\) mice by a 60 min transient middle cerebral artery occlusion (tMCAO). Additionally, wild-type animals were pretreated with anti-GPVI antibody (JAQ1) or Fab fragments of a function blocking antibody against integrin α2β1 (LEN/B). In anti-GPVI treated animals, intravenous (IV) recombinant tissue plasminogen activator (rt-PA) treatment was applied immediately prior to reperfusion. Stroke outcome, including infarct size and neurological scoring was determined on day 1 after tMCAO. We demonstrate that targeting the integrin α2β1 (pharmacologic; genetic) did neither reduce stroke size nor improve functional outcome on day 1 after tMCAO. In contrast, depletion of platelet GPVI prior to stroke was safe and effective, even when combined with rt-PA treatment. Our results underscore that GPVI, but not ITGA2, is a promising and safe target in the setting of ischemic stroke. KW - ischemic stroke KW - integrin α2 KW - glycoprotein VI KW - recombinant tissue-type plasminogen activator KW - intracranial bleeding KW - transient middle cerebral artery occlusion Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-201700 SN - 1422-0067 VL - 20 IS - 8 ER - TY - JOUR A1 - Herrmann, Johannes A1 - Notz, Quirin A1 - Schlesinger, Tobias A1 - Stumpner, Jan A1 - Kredel, Markus A1 - Sitter, Magdalena A1 - Schmid, Benedikt A1 - Kranke, Peter A1 - Schulze, Harald A1 - Meybohm, Patrick A1 - Lotz, Christopher T1 - Point of care diagnostic of hypercoagulability and platelet function in COVID-19 induced acute respiratory distress syndrome: a retrospective observational study JF - Thrombosis Journal N2 - Background Coronavirus disease 2019 (COVID-19) associated coagulopathy (CAC) leads to thromboembolic events in a high number of critically ill COVID-19 patients. However, specific diagnostic or therapeutic algorithms for CAC have not been established. In the current study, we analyzed coagulation abnormalities with point-of-care testing (POCT) and their relation to hemostatic complications in patients suffering from COVID-19 induced Acute Respiratory Distress Syndrome (ARDS). Our hypothesis was that specific diagnostic patterns can be identified in patients with COVID-19 induced ARDS at risk of thromboembolic complications utilizing POCT. Methods This is a single-center, retrospective observational study. Longitudinal data from 247 rotational thromboelastometries (Rotem®) and 165 impedance aggregometries (Multiplate®) were analysed in 18 patients consecutively admitted to the ICU with a COVID-19 induced ARDS between March 12th to June 30th, 2020. Results Median age was 61 years (IQR: 51–69). Median PaO2/FiO2 on admission was 122 mmHg (IQR: 87–189), indicating moderate to severe ARDS. Any form of hemostatic complication occurred in 78 % of the patients with deep vein/arm thrombosis in 39 %, pulmonary embolism in 22 %, and major bleeding in 17 %. In Rotem® elevated A10 and maximum clot firmness (MCF) indicated higher clot strength. The delta between EXTEM A10 minus FIBTEM A10 (ΔA10) > 30 mm, depicting the sole platelet-part of clot firmness, was associated with a higher risk of thromboembolic events (OD: 3.7; 95 %CI 1.3–10.3; p = 0.02). Multiplate® aggregometry showed hypoactive platelet function. There was no correlation between single Rotem® and Multiplate® parameters at intensive care unit (ICU) admission and thromboembolic or bleeding complications. Conclusions Rotem® and Multiplate® results indicate hypercoagulability and hypoactive platelet dysfunction in COVID-19 induced ARDS but were all in all poorly related to hemostatic complications.. KW - COVID-19 KW - acute Respiratory Distress Syndrome KW - point of care testing KW - thromboelastometry KW - impedance aggregometry; WHOLE-BLOOD THROMBOELASTOMETRY; DEFINITION; DISEASE Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-260739 VL - 19 IS - 1 ER - TY - JOUR A1 - Manukjan, Georgi A1 - Wiegering, Verena A1 - Reindl, Tobias A1 - Strauß, Gabriele A1 - Klopocki, Eva A1 - Schulze, Harald A1 - Andres, Oliver T1 - Novel variants in FERMT3 and RASGRP2 - Genetic linkage in Glanzmann-like bleeding disorders JF - Pediatric Blood & Cancer N2 - Defects of platelet intracellular signaling can result in severe platelet dysfunction. Several mutations in each of the linked genes FERMT3 and RASGRP2 on chromosome 11 causing a Glanzmann‐like bleeding phenotype have been identified so far. We report on novel variants in two unrelated pediatric patients with severe bleeding diathesis—one with leukocyte adhesion deficiency type III due to a homozygous frameshift in FERMT3 and the other with homozygous variants in both, FERMT3 and RASGRP2 . We focus on the challenging genetic and functional variant assessment and aim to accentuate the risk of obtaining misleading results due to the phenomenon of genetic linkage. KW - bleding disorders other than hemophilia KW - hematology KW - hemostasis and thrombosis KW - platelet disorders Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-208129 VL - 67 IS - 2 ER - TY - JOUR A1 - Kunz, Meik A1 - Wolf, Beat A1 - Schulze, Harald A1 - Atlan, David A1 - Walles, Thorsten A1 - Walles, Heike A1 - Dandekar, Thomas T1 - Non-Coding RNAs in Lung Cancer: Contribution of Bioinformatics Analysis to the Development of Non-Invasive Diagnostic Tools JF - Genes N2 - Lung cancer is currently the leading cause of cancer related mortality due to late diagnosis and limited treatment intervention. Non-coding RNAs are not translated into proteins and have emerged as fundamental regulators of gene expression. Recent studies reported that microRNAs and long non-coding RNAs are involved in lung cancer development and progression. Moreover, they appear as new promising non-invasive biomarkers for early lung cancer diagnosis. Here, we highlight their potential as biomarker in lung cancer and present how bioinformatics can contribute to the development of non-invasive diagnostic tools. For this, we discuss several bioinformatics algorithms and software tools for a comprehensive understanding and functional characterization of microRNAs and long non-coding RNAs. KW - lung cancer KW - non-invasive biomarkers KW - miRNAs KW - lncRNAs KW - bioinformatics KW - early diagnosis KW - algorithm Y1 - 2016 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-147990 VL - 8 IS - 1 ER - TY - JOUR A1 - Westbury, Sarah K A1 - Turro, Ernest A1 - Greene, Daniel A1 - Lentaigne, Claire A1 - Kelly, Anne M A1 - Bariana, Tadbir K A1 - Simeoni, Ilenia A1 - Pillois, Xavier A1 - Attwood, Antony A1 - Austin, Steve A1 - Jansen, Sjoert BG A1 - Bakchoul, Tamam A1 - Crisp-Hihn, Abi A1 - Erber, Wendy N A1 - Favier, Rémi A1 - Foad, Nicola A1 - Gattens, Michael A1 - Jolley, Jennifer D A1 - Liesner, Ri A1 - Meacham, Stuart A1 - Millar, Carolyn M A1 - Nurden, Alan T A1 - Peerlinck, Kathelijne A1 - Perry, David J A1 - Poudel, Pawan A1 - Schulman, Sol A1 - Schulze, Harald A1 - Stephens, Jonathan C A1 - Furie, Bruce A1 - Robinson, Peter N A1 - van Geet, Chris A1 - Rendon, Augusto A1 - Gomez, Keith A1 - Laffan, Michael A A1 - Lambert, Michele P A1 - Nurden, Paquita A1 - Ouwehand, Willem H A1 - Richardson, Sylvia A1 - Mumford, Andrew D A1 - Freson, Kathleen T1 - Human phenotype ontology annotation and cluster analysis to unravel genetic defects in 707 cases with unexplained bleeding and platelet disorders JF - Genome Medicine N2 - Background: Heritable bleeding and platelet disorders (BPD) are heterogeneous and frequently have an unknown genetic basis. The BRIDGE-BPD study aims to discover new causal genes for BPD by high throughput sequencing using cluster analyses based on improved and standardised deep, multi-system phenotyping of cases. Methods: We report a new approach in which the clinical and laboratory characteristics of BPD cases are annotated with adapted Human Phenotype Ontology (HPO) terms. Cluster analyses are then used to characterise groups of cases with similar HPO terms and variants in the same genes. Results: We show that 60% of index cases with heritable BPD enrolled at 10 European or US centres were annotated with HPO terms indicating abnormalities in organ systems other than blood or blood-forming tissues, particularly the nervous system. Cases within pedigrees clustered closely together on the bases of their HPO-coded phenotypes, as did cases sharing several clinically suspected syndromic disorders. Cases subsequently found to harbour variants in ACTN1 also clustered closely, even though diagnosis of this recently described disorder was not possible using only the clinical and laboratory data available to the enrolling clinician. Conclusions: These findings validate our novel HPO-based phenotype clustering methodology for known BPD, thus providing a new discovery tool for BPD of unknown genetic basis. This approach will also be relevant for other rare diseases with significant genetic heterogeneity. KW - disease KW - thrombocytopenia KW - guidelines KW - complex Y1 - 2015 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-143329 VL - 7 IS - 36 ER - TY - JOUR A1 - Cullmann, Katharina A1 - Jahn, Magdalena A1 - Spindler, Markus A1 - Schenk, Franziska A1 - Manukjan, Georgi A1 - Mucci, Adele A1 - Steinemann, Doris A1 - Boller, Klaus A1 - Schulze, Harald A1 - Bender, Markus A1 - Moritz, Thomas A1 - Modlich, Ute T1 - Forming megakaryocytes from murine‐induced pluripotent stem cells by the inducible overexpression of supporting factors JF - Research and Practice in Thrombosis and Haemostasis N2 - Background Platelets are small anucleate cells that circulate in the blood in a resting state but can be activated by external cues. In case of need, platelets from blood donors can be transfused. As an alternative source, platelets can be produced from induced pluripotent stem cells (iPSCs); however, recovered numbers are low. Objectives To optimize megakaryocyte (MK) and platelet output from murine iPSCs, we investigated overexpression of the transcription factors GATA‐binding factor 1 (GATA1); nuclear factor, erythroid 2; and pre–B‐cell leukemia transcription factor 1 (Pbx1) and a hyperactive variant of the small guanosine triphosphatase RhoA (RhoAhc). Methods To avoid off‐target effects, we generated iPSCs carrying the reverse tetracycline‐responsive transactivator M2 (rtTA‐M2) in the Rosa26 locus and expressed the factors from Tet‐inducible gammaretroviral vectors. Differentiation of iPSCs was initiated by embryoid body (EB) formation. After EB dissociation, early hematopoietic progenitors were enriched and cocultivated on OP9 feeder cells with thrombopoietin and stem cell factor to induce megakaryocyte (MK) differentiation. Results Overexpression of GATA1 and Pbx1 increased MK output 2‐ to 2.5‐fold and allowed prolonged collection of MK. Cytologic and ultrastructural analyses identified typical MK with enlarged cells, multilobulated nuclei, granule structures, and an internal membrane system. However, GATA1 and Pbx1 expression did not improve MK maturation or platelet release, although in vitro–generated platelets were functional in spreading on fibrinogen or collagen‐related peptide. Conclusion We demonstrate that the use of rtTA‐M2 transgenic iPSCs transduced with Tet‐inducible retroviral vectors allowed for gene expression at later time points during differentiation. With this strategy we could identify factors that increased in vitro MK production. KW - genetic modification KW - iPS cells KW - megakaryocytes KW - retroviral vectors KW - Tet‐inducible system Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-224565 VL - 5 IS - 1 SP - 111 EP - 124 ER - TY - JOUR A1 - Rommel, Marcel G. E. A1 - Milde, Christian A1 - Eberle, Regina A1 - Schulze, Harald A1 - Modlich, Ute T1 - Endothelial–platelet interactions in influenza‐induced pneumonia: A potential therapeutic target JF - Anatomia, Histologia, Embryologia N2 - Every year, influenza viruses spread around the world, infecting the respiratory systems of countless humans and animals, causing illness and even death. Severe influenza infection is associated with pulmonary epithelial damage and endothelial dysfunction leading to acute lung injury (ALI). There is evidence that an aggressive cytokine storm and cell damage in lung capillaries as well as endothelial/platelet interactions contribute to vascular leakage, pro‐thrombotic milieu and infiltration of immune effector cells. To date, treatments for ALI caused by influenza are limited to antiviral drugs, active ventilation or further symptomatic treatments. In this review, we summarize the mechanisms of influenza‐mediated pathogenesis, permissive animal models and histopathological changes of lung tissue in both mice and men and compare it with histological and electron microscopic data from our own group. We highlight the molecular and cellular interactions between pulmonary endothelium and platelets in homeostasis and influenza‐induced pathogenesis. Finally, we discuss novel therapeutic targets on platelets/endothelial interaction to reduce or resolve ALI. KW - endothelial cell KW - influenza KW - interaction KW - laboratory animals KW - lung injury KW - platelet KW - pneumonia KW - therapy Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-213610 VL - 49 IS - 5 SP - 606 EP - 619 ER - TY - JOUR A1 - Laukner, Anna A1 - Truchet, Laura A1 - Manukjan, Georgi A1 - Schulze, Harald A1 - Langbein-Detsch, Ines A1 - Mueller, Elisabeth A1 - Leeb, Tosso A1 - Kehl, Alexandra T1 - Effects of cocoa genotypes on coat color, platelets and coagulation parameters in French Bulldogs JF - Genes N2 - A nonsense variant in HPS3, c.2420G>A or p.Trp807*, was recently discovered as the cause for a brown coat color termed cocoa in French Bulldogs. Here, we studied the genotype–phenotype correlation regarding coat color in HPS3 mutant dogs that carried various combinations of mutant alleles at other coat color genes. Different combinations of HPS3, MLPH and TYRP1 genotypes resulted in subtly different shades of brown coat colors. As HPS3 variants in humans cause the Hermansky–Pudlak syndrome type 3, which in addition to oculocutaneous albinism is characterized by a storage pool deficiency leading to bleeding tendency, we also investigated the phenotypic consequences of the HPS3 variant in French Bulldogs on hematological parameters. HPS3 mutant dogs had a significantly lowered platelet dense granules abundance. However, no increased bleeding tendencies in daily routine were reported by dog owners. We therefore conclude that in dogs, the phenotypic effect of the HPS3 variant is largely restricted to pigmentation. While an effect on platelet morphology is evident, we did not obtain any indications for major health problems associated with the cocoa coat color in French Bulldogs. Further studies will be necessary to definitely rule out very subtle effects on visual acuity or a clinically relevant bleeding disorder. KW - Canis lupus familiaris KW - dog KW - thrombocyte KW - pigmentation KW - hematology KW - platelet Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-242745 SN - 2073-4425 VL - 12 IS - 7 ER - TY - JOUR A1 - Stritt, Simon A1 - Nurden, Paquita A1 - Favier, Remi A1 - Favier, Marie A1 - Ferioli, Silvia A1 - Gotru, Sanjeev K. A1 - van Eeuwijk, Judith M.M. A1 - Schulze, Harald A1 - Nurden, Alan T. A1 - Lambert, Michele P. A1 - Turro, Ernest A1 - Burger-Stritt, Stephanie A1 - Matsushita, Masayuki A1 - Mittermeier, Lorenz A1 - Ballerini, Paola A1 - Zierler, Susanna A1 - Laffan, Michael A. A1 - Chubanov, Vladimir A1 - Gudermann, Thomas A1 - Nieswandt, Bernhard A1 - Braun, Attila T1 - Defects in TRPM7 channel function deregulate thrombopoiesis through altered cellular Mg\(^{2+}\) homeostasis and cytoskeletal architecture JF - Nature Communications N2 - Mg\(^{2+}\) plays a vital role in platelet function, but despite implications for life-threatening conditions such as stroke or myocardial infarction, the mechanisms controlling [Mg\(^{2+}\)]i in megakaryocytes (MKs) and platelets are largely unknown. Transient receptor potential melastatin-like 7 channel (TRPM7) is a ubiquitous, constitutively active cation channel with a cytosolic α-kinase domain that is critical for embryonic development and cell survival. Here we report that impaired channel function of TRPM7 in MKs causes macrothrombocytopenia in mice (Trpm7\(^{fl/fl-Pf4Cre}\)) and likely in several members of a human pedigree that, in addition, suffer from atrial fibrillation. The defect in platelet biogenesis is mainly caused by cytoskeletal alterations resulting in impaired proplatelet formation by Trpm7\(^{fl/fl-Pf4Cre}\) MKs, which is rescued by Mg\(^{2+}\) supplementation or chemical inhibition of non-muscle myosin IIA heavy chain activity. Collectively, our findings reveal that TRPM7 dysfunction may cause macrothrombocytopenia in humans and mice. KW - Cytoskeleton KW - homeostasisIon channels KW - thrombopoiesis Y1 - 2016 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-173843 VL - 7 ER - TY - JOUR A1 - Rosa, Annabelle A1 - Butt, Elke A1 - Hopper, Christopher P. A1 - Loroch, Stefan A1 - Bender, Markus A1 - Schulze, Harald A1 - Sickmann, Albert A1 - Vorlova, Sandra A1 - Seizer, Peter A1 - Heinzmann, David A1 - Zernecke, Alma T1 - Cyclophilin a is not acetylated at lysine-82 and lysine-125 in resting and stimulated platelets JF - International Journal of Molecular Sciences N2 - Cyclophilin A (CyPA) is widely expressed by all prokaryotic and eukaryotic cells. Upon activation, CyPA can be released into the extracellular space to engage in a variety of functions, such as interaction with the CD147 receptor, that contribute to the pathogenesis of cardiovascular diseases. CyPA was recently found to undergo acetylation at K82 and K125, two lysine residues conserved in most species, and these modifications are required for secretion of CyPA in response to cell activation in vascular smooth muscle cells. Herein we addressed whether acetylation at these sites is also required for the release of CyPA from platelets based on the potential for local delivery of CyPA that may exacerbate cardiovascular disease events. Western blot analyses confirmed the presence of CyPA in human and mouse platelets. Thrombin stimulation resulted in CyPA release from platelets; however, no acetylation was observed—neither in cell lysates nor in supernatants of both untreated and activated platelets, nor after immunoprecipitation of CyPA from platelets. Shotgun proteomics detected two CyPA peptide precursors in the recombinant protein, acetylated at K28, but again, no acetylation was found in CyPA derived from resting or stimulated platelets. Our findings suggest that acetylation of CyPA is not a major protein modification in platelets and that CyPA acetylation is not required for its secretion from platelets. KW - Cyclophilin A KW - acetylation KW - platelets KW - CD147 KW - EMMPRIN Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-284011 SN - 1422-0067 VL - 23 IS - 3 ER - TY - JOUR A1 - Wagner, Nicole A1 - Mott, Kristina A1 - Upcin, Berin A1 - Stegner, David A1 - Schulze, Harald A1 - Ergün, Süleyman T1 - CXCL12-abundant reticular (CAR) cells direct megakaryocyte protrusions across the bone marrow sinusoid wall JF - Cells N2 - Megakaryocytes (MKs) release platelets into the lumen of bone marrow (BM) sinusoids while remaining to reside within the BM. The morphogenetic events of this complex process are still not fully understood. We combined confocal laser scanning microscopy with transmission and serial block-face scanning electron microscopy followed by 3D-reconstruction on mouse BM tissue sections. These analyses revealed that MKs in close vicinity to BM sinusoid (BMS) wall first induce the lateral retraction of CXCL12-abundant reticular (CAR) cells (CAR), followed by basal lamina (BL) degradation enabling direct MK-sinusoidal endothelial cells (SECs) interaction. Subsequently, an endothelial engulfment starts that contains a large MK protrusion. Then, MK protrusions penetrate the SEC, transmigrate into the BMS lumen and form proplatelets that are in direct contact to the SEC surface. Furthermore, such processes are induced on several sites, as observed by 3D reconstructions. Our data demonstrate that MKs in interaction with CAR-cells actively induce BMS wall alterations, including CAR-cell retraction, BL degradation, and SEC engulfment containing a large MK protrusion. This results in SEC penetration enabling the migration of MK protrusion into the BMS lumen where proplatelets that are adherent to the luminal SEC surface are formed and contribute to platelet release into the blood circulation. KW - megakaryocytes KW - microvasculature KW - CXCL12-abundant reticular (CAR)-cells Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-234180 SN - 2073-4409 VL - 10 IS - 4 ER - TY - JOUR A1 - Dütting, Sebastian A1 - Gaits-Iacovoni, Frederique A1 - Stegner, David A1 - Popp, Michael A1 - Antkowiak, Adrien A1 - van Eeuwijk, Judith M.M. A1 - Nurden, Paquita A1 - Stritt, Simon A1 - Heib, Tobias A1 - Aurbach, Katja A1 - Angay, Oguzhan A1 - Cherpokova, Deya A1 - Heinz, Niels A1 - Baig, Ayesha A. A1 - Gorelashvili, Maximilian G. A1 - Gerner, Frank A1 - Heinze, Katrin G. A1 - Ware, Jerry A1 - Krohne, Georg A1 - Ruggeri, Zaverio M. A1 - Nurden, Alan T. A1 - Schulze, Harald A1 - Modlich, Ute A1 - Pleines, Irina A1 - Brakebusch, Cord A1 - Nieswandt, Bernhard T1 - A Cdc42/RhoA regulatory circuit downstream of glycoprotein Ib guides transendothelial platelet biogenesis JF - Nature Communications N2 - Blood platelets are produced by large bone marrow (BM) precursor cells, megakaryocytes (MKs), which extend cytoplasmic protrusions (proplatelets) into BM sinusoids. The molecular cues that control MK polarization towards sinusoids and limit transendothelial crossing to proplatelets remain unknown. Here, we show that the small GTPases Cdc42 and RhoA act as a regulatory circuit downstream of the MK-specific mechanoreceptor GPIb to coordinate polarized transendothelial platelet biogenesis. Functional deficiency of either GPIb or Cdc42 impairs transendothelial proplatelet formation. In the absence of RhoA, increased Cdc42 activity and MK hyperpolarization triggers GPIb-dependent transmigration of entire MKs into BM sinusoids. These findings position Cdc42 (go-signal) and RhoA (stop-signal) at the centre of a molecular checkpoint downstream of GPIb that controls transendothelial platelet biogenesis. Our results may open new avenues for the treatment of platelet production disorders and help to explain the thrombocytopenia in patients with Bernard–Soulier syndrome, a bleeding disorder caused by defects in GPIb-IX-V. KW - megakaryocytes KW - blood platelets KW - regulatory circuit downstream KW - glycoprotein Ib Y1 - 2017 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-170797 VL - 8 IS - 15838 ER -