Dataset Information

Pathogenesis of dominant-negative mutant GFI1B and associated proteomic abnormalities in megakaryocytes and platelets

ABSTRACT: Dominant-negative mutations in transcription factor Growth Factor Independence-1B (GFI1B) cause a bleeding disorder characterized by a plethora of megakaryocyte and platelet abnormalities. The deregulated molecular mechanisms and pathways are unknown. Here we show that normal and mutant GFI1B interacted most strongly with the LSD1-RCOR-HDAC corepressor complex in megakaryoblasts. Sequestration of this complex by mutant GFI1B and chemical separation of GFI1B from LSD1 induced abnormalities in normal megakaryocytes comparable to those seen in patients. Megakaryocytes derived from GFI1B-mutant induced pluripotent stem cells (iPSC) also phenocopied abnormalities seen in patients. Proteome studies on normal and mutant iPSC-derived megakaryocytes identified a multitude of deregulated pathways downstream of mutant GFI1B. Proteome studies on primary normal and GFI1B-mutant platelets showed reduced expression of proteins implicated in platelet function, and sustained expression of proteins normally downregulated during megakaryocyte differentiation. Thus, GFI1B regulates a broad developmental program during megakaryopoiesis. Mutant GFI1B deregulates this program through LSD1-RCOR-HDAC sequestering.

INSTRUMENT(S): Orbitrap Fusion

ORGANISM(S): Homo Sapiens (human)

TISSUE(S): Blood Platelet, Platelet, Primary Cell, Megakaryocyte

SUBMITTER: Johanna Koornneef

LAB HEAD: Alexander Meijer

PROVIDER: PXD009020 | Pride | 2019-01-25

REPOSITORIES: Pride

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Molecular mechanisms of bleeding disorderassociated GFI1B<sup>Q287*</sup> mutation and its affected pathways in megakaryocytes and platelets.

van Oorschot Rinske R Hansen Marten M Koornneef Johanna M JM Marneth Anna E AE Bergevoet Saskia M SM van Bergen Maaike G J M MGJM van Alphen Floris P J FPJ van der Zwaan Carmen C Martens Joost H A JHA Vermeulen Michiel M Jansen Pascal W T C PWTC Baltissen Marijke P A MPA Gorkom Britta A P Laros-van BAPL Janssen Hans H Jansen Joop H JH von Lindern Marieke M Meijer Alexander B AB van den Akker Emile E van der Reijden Bert A BA

Haematologica 20190117 7

Dominant-negative mutations in the transcription factor Growth Factor Independence-1B (GFI1B), such as GFI1B<sup>Q287*</sup>, cause a bleeding disorder characterized by a plethora of megakaryocyte and platelet abnormalities. The deregulated molecular mechanisms and pathways are unknown. Here we show that both normal and Q287* mutant GFI1B interacted most strongly with the lysine specific demethylase-1 - REST corepressor - histone deacetylase (LSD1-RCOR-HDAC) complex in megakaryoblasts. Sequestra ...[more]

PMID: 30655368

Similar Datasets

Project description:Background: Children with Down syndrome (DS) are predisposed to acute megakaryoblastic leukemia (AMKL, or AML M7) and a related myeloid disorder, referred to as transient myeloproliferative disorder (TMD), or transient leukemia (TL). Recently, acquired mutations in the erythroid/megakaryocytic lineage-specific transcription factor GATA-1 have been identified in megakaryoblasts from virtually all DS patients with AMKL (DS-AMKL), as well as in nearly all DS neonates with TMD. These mutations prevent synthesis of full-length GATA-1, but lead to synthesis of a truncated GATA-1 protein (GATA-1s) that lacks the N-terminal transactivation domain. To determine the in vivo requirement of GATA-1 N-terminal domain in hematopoiesis and to model DS megakaryocytic leukemia initiated by GATA-1 mutation, we generated a GATA-1 knockin allele with a truncation at this domain (GATA-1deltaN). ES cells bearing this mutant allele generated a unique type of large Thrombopoietin (Tpo)-dependent megakaryocytes-containing colonies, when differentiated in vitro. Fetal livers from mice carrying this mutant allele contained elevated numbers of CD41+ cells throughout embryonic development, especially during mid-gestation. In in vitro hematopoietic colony assays, mutant cells from yolk sacs and mid-gestation fetal livers gave rise to a large number of macroscopic hyperproliferative megakaryocytic colonies (CFU-MKs). Consistent with that, when mutant fetal liver progenitors were cultured in liquid medium in the presence of Tpo, the derived megakaryocytes displayed marked hyperproliferation and grew for longer period of time than WTs. Specific aims: To understand the molecular basis for the megakaryocytic hyperproliferation phenotype of the GATA-1deltaN mutants, we plan to profile gene expression patterns of fetal liver-derived primary megakaryocytes and megakaryocytic progenitors from the GATA-1deltaN mutants and compare them with WTs, as well as GATA-1deltaNeodeltaHS mutants (GATA-1megakaryocytes). Experimental design: E12.5 fetal livers were harvested from either GATA-1 WT and mutant embryos. Single cell suspensions were made from these livers and the cells were cultured in liquid medium in the presence of Tpo for 3 days. On day 3, primary megakaryocytes were enriched by a BSA gradient, and further enriched by anti-CD41 antibody and magnetic microbeads. Megakaryocytic progenitors were collected by FACS sorting for small cells in the same culture that express low level of CD41. Total RNAs were then prepared from these two populations and submitted for microarray profiling. Conclusions: When examining genes that are normally upregulated upon megakaryocyte differentiation (many of this class are megakaryocyte-specific genes), we found in GATA-1deltaN megakaryocytes, the majority of these genes are upregulated, although not to the full extent as seen in WTs. In contrast, this class of genes is largely not upregulated in GATA-1deltaNeodeltaHS megakaryocytes, which are blocked at an immature stage of differentiation. Genes that are downregulated during megakaryocyte differentiation include those that are normally repressed by GATA-1. Among genes that are not properly downregulated in GATA-1deltaN megakaryocytes, five transcription factors (Myc, Myb, GATA-2, PU.1, Ikaros) are of particular interest. Inadequate GATA-1s-mediated repression of transcription factors required for proliferation of hematopoietic progenitors (Myc, Myb and GATA-2) and for specifying lineage choices other than megakaryocyte/erythrocyte (PU.1 and Ikaros) may contribute to hyperproliferation of GATA-1deltaN megakaryocytes.

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