Regulatory proteins in normal and malignant megakaryopoiesis and thrombopoiesis
Final Report Abstract
Among all cells circulating in the blood stream, platelets are not derived from a progenitor cell by maturation, but are anucleate cellular fragments that precursors in the bone marrow (megakaryocytes) shed across the endothelial barrier into the sinusoids. This process is not only biologically fascinating, as a single cell produces hundreds of virtually identical progeny, but also clinically important, since the number of blood platelets is kept within relatively small limits to prevent both thrombosis and bleeding. Recently, a series of structural proteins that support platelet formation have been identified. ?1-tubulin is a structurally divergent isotype that is crucial for normal platelet count and shape. The first aim addressed in this research project, was to characterize the role of RanBP10 for platelet biogenesis and function in vivo. RanBP10 was originally identified as a protein binding to the C-terminal domain of ?1-tubulin. We generated a mouse model for RanBP10 ablation and although mutant mice had almost normal platelet counts, we found an unexpected severe bleeding defect when challenged by a tail-cut assay. RanBP10 is dispensible for normal platelet counts, but plays an important role for platelet shape and function. Several lines of evidence, including aggregometry, flow cytometry, electron microscopy and immunoblotting suggest that lack of RanBP10 results in distorted microtubule filaments. This reduces the normal contraction of the marginal band microtubules preceding granule centralization and release. Based upon these results, we are currently testing the role of RanBP10 by in vivo thrombosis models and preliminary data suggest that our the RanBP10-null mouse might serve as an animal model for thrombus protection. In the second project addressed in this study, we used high resolution comparative genome hybridization to identify a microdeletion on chromosome 1q21 as essential, but not sufficient for thrombocytopenia-absent radii (TAR) syndrome, a rare congenital disorder. While all patients analyzed in the study harbored an until then unidentified loss of about 200 kb on one chromosome, the microdeletion was also present in some unaffected parents and family members, implying that TAR- syndrome must be considered a digenic disorder. Screening for the microdeletion provides now a basis for genetic counseling. In addition, PIAS3 is recognized as a candidate gene within the microdeleted region and current research focuses on the role of PIAS3, a negative regulator of the Jak-STAT pathway, downstream of TPO.
Publications
- "Making blood platelets in vivo: Mechanisms to study thrombocytopenia in mice and men." European Journal of Pediatrics 2006; 165(3): 218
Schulze H, Strauß G, Gaedicke G
- 42nd Workshop for Pediatric Research, Max-Planck-Institute for Experimental Medicine, Göttingen, 23.-24.02.2006: " Mechanisms to study thrombocytopenia in mice and men."
Schulze, H
- Physiologie der Megakaryopoese und des Thrombozyten. Monatsschrift Kinderheilkunde 2006; 154: 502-509
Dame C, Gaedicke G, Schulze H
- Some unsettled Questions in Childhood Thrombocytopenia Caused by Immunologic Platelet Destruction (Acute and Chronic ITP). Pediatric Blood Cancer 2006; 47: 668-670
Gaedicke G, Schulze H
- "A microdeletion on chromosome 1q21 is required but not sufficient for Thrombocytopenia-Absent Radii (TAR) Syndrome". Monatsschrift Kinderheilkunde 2007; 155: 400
Strauß G, Klopocki E, Mundlos S, Schulze H
- "Complex inheritance pattern involving a microdeletion in thrombocytopenia-absent radius (TAR) syndrome" Cellular Oncology 2007; 29 (2): 113
Klopocki E, Schulze H, Ott CE, Trotier F, Strauß G, Neumann LM, Ropers HH, Ullmann R, Horn D, Mundlos S
- An EF hand mutation in Stim1 causes premature platelet activation and bleeding in mice. J Clin Invest 2007; 117: 3540-3550
Grosse J, Braun A, Varga-Szabo D, Beyersdorf N, Schneider B, Zeitlmann L, Hanke, P, Schropp P, Mühlstedt S, Schmittwolf C, Jagla W, Yu P, Kerkau T, Schulze H, Nehls M, Nieswandt B
- Complex inheritance pattern resembling autosomale-recessive inheritance involving a microdeletion in chromosome in thrombocytopenia-absent radius (TAR) syndrome Am. J. Human Genet. 2007, 80: 232-240
Klopocki E, Schulze H, Strauß G, Ott CE, Hall J, Trotier F, Fleischhauer S, Greenhalgh L, Newbury-Ecob RA, Neumann LM, Habenicht R, König R, Seemanova E, Megarbane A, Ropers H, Ullmann R, Horn D, Mundlos S
- Gordon Research Conference: "Cell Biology of Megakaryocytes and Platelets", 4.- 9.3.2007:"A microdeletion on chromosome 1q21 is required but not sufficient for thrombocytopenia-absent radii (TAR)-syndrome"
Strauß G, Fleischhauer S, Klopocki E, Mundlos S, Schulze H
- XXIInd European Platelet Meeting, Lutherstadt Wittenberg, 11.-13.10.2007: "Visualization of blood platelet formation in the bone marrow of living mice."
Schulze, H
- "Modulation of plasma cell homeostasis by megakaryopoiesis in the bone marrow". Wiener Klinische Wochenschrift 2008; 120 Suppl.1: 168-169
Winter O, Moser K, Schulze H, Szyska M, Radbruch A, Manz RA
- "The beta1-tubulin binding protein RanBP10 plays a critical role for platelet discoid shape and Hemostasis". Blood 2008; 112 (11): 158
Schulze H, Fleischhauer S, Meyer I, Wannack M, Kunert S
- 3rd Europaediatrics Conference, Istanbul, 14.-17.06.2008: "New Insights into cellular and molecular biology of Megakaryopoiesis and Thrombocytopoiesis."
Schulze, H
- 50th Annual Meeting of the American Society of Hematology San Francisco, 6.- 9.12.2008: "The beta1-tubulin binding protein RanBP10 plays a critical role for platelet discoid shape and Hemostasis".
Schulze, H
- 52. Jahrestagung der Gesellschaft für Thrombose- und Hämostaseforschung (GTH) 20.-23.2.2008: " Defective Rap1-Activation is involved in Leukocyte Adhesion Deficiency Type III / Type I-variant"
Schulze, H
- 71. Wissenschaftliche Halbjahrestagung der Gesellschaft für Pädiatrische Onkologie und Hämatologie (GPOH), Berlin, 16.-17.05.2008: "Die Geburt von Thrombozyten: Neue Aspekte der Thrombozytopoese in vivo."
Schulze, H
- Impaired Rap1 activation in platelets from Leukocyte Adhesion Deficiency type III or type-I/variant in association with mutations in the Rap1 exchange factor CalDAG-GEFI
Strauss G, Salanova B, Fleischhauer S, Kettritz R, Crittenden J, Graybiel AM, Meyer O, Seeger K, Bergmeier W, Schulze H
- Jahrestagung der Ständigen Kommission Pädiatrie der GTH, Tübingen, 9.- 11.10.2008: " Neue Aspekte der Thrombozytopoese in vivo für die Messung von neuen automatisierten Thrombozytenparametern."
Schulze, H
- Platelets 2008 International Symposioum, Woods Hole 15.-18.10.2008: "The microtubule modulator RanBP10 plays a critical role for platelet discoid shape and hemostasis".
Schulze H, Meyer I, Fleischhauer S, Kunert S
- RanBP10 is a cytoplasmic guanine nucleotide-exchange factor that modulates noncentrosomal microtubules. Journal of Biological Chemistry 2008; 283 (20): 14109-14119
Schulze H, Dose M, Korpal M, Meyer I, Italiano JE Jr., Shivdasani RA
- Seminars in Biomembranes, Institute for Biomembranes, Utrecht, Niederlande, 07.02.2008: " Dynamic visualization of thrombopoiesis in vivo."
Schulze, H
- The microtubule modulator RanBP10 plays a critical role in regulation of platelet discoid shape and degranulation. Blood 2009; 114 (27): 5412-3
Kunert S, Meyer I, Fleischhauer S, Wannack M, Fiedler J, Shivdasani RA, Schulze H
