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PSTPIP2 dysregulation contributes to aberrant terminal differentiation in GATA-1-deficient megakaryocytes by activating LYN.

ABSTRACT: GATA1 mutations are tightly associated with transient myeloproliferative disorder (TMD) and acute megakaryoblstic leukemia (AMKL) in children with Down syndrome. Numerous genes are altered in GATA-1-deficient megakaryocytes, which may contribute to the hyperproliferation and abnormal terminal differentiation of these malignant cells. In this study, we demonstrate that Pstpip2 is a GATA-1-repressed gene that controls megakaryopoiesis. Ectopic expression of PSTPIP2 impaired megakaryocytic differentiation as evidenced by a decrease of CD41 expression and reduced DNA content in K562 cells. PSTPIP2 overexpression also caused enhanced activation of Src family kinases and subsequently reduced ERK phosphorylation. Consistently, PSTPIP2 knockdown showed the opposite effect on differentiation and signaling. Moreover, the W232A mutant of PSTPIP2, defective in its interaction with PEST family phosphatases that recruit c-Src terminal kinase (CSK) to suppress Src family kinases, failed to inhibit differentiation and lost its ability to enhance Src family kinases or reduce ERK phosphorylation. In fact, the W232A mutant of PSTPIP2 promoted megakaryocyte differentiation. These observations suggest that PSTPIP2 recruiting PEST phosphatases somehow blocked CSK activity and led to enhanced activation of Src family kinases and reduced ERK phosphorylation, which ultimately repressed megakaryocyte differentiation. Supporting this idea, PSTPIP2 interacted with LYN and the expression of a dominant negative LYN (LYN DN) overwhelmed the inhibitory effect of PSTPIP2 on differentiation and ERK signaling. In addition, a constitutively active LYN (LYN CA) normalized the enhanced megakaryocyte differentiation and repressed ERK signaling in PSTPIP2 knockdown cells. Finally, we found that PSTPIP2 repressed ERK signaling, differentiation, and proliferation and verified that PSTPIP2 upregulation repressed megakaryocyte development in primary mouse bone marrow cells. Our study thus reveals a novel mechanism by which dysregulation of PSTPIP2 due to GATA-1 deficiency may contribute to abnormal megakaryocyte proliferation and differentiation in pathogenesis of related diseases.

SUBMITTER: Liu L

PROVIDER: S-EPMC4040682 | biostudies-literature | 2014

REPOSITORIES: biostudies-literature

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PSTPIP2 dysregulation contributes to aberrant terminal differentiation in GATA-1-deficient megakaryocytes by activating LYN.

Liu L L Wen Q Q Gong R R Gilles L L Stankiewicz M J MJ Li W W Guo M M Li L L Sun X X Li W W Crispino J D JD Huang Z Z

Cell death & disease 20140109

GATA1 mutations are tightly associated with transient myeloproliferative disorder (TMD) and acute megakaryoblstic leukemia (AMKL) in children with Down syndrome. Numerous genes are altered in GATA-1-deficient megakaryocytes, which may contribute to the hyperproliferation and abnormal terminal differentiation of these malignant cells. In this study, we demonstrate that Pstpip2 is a GATA-1-repressed gene that controls megakaryopoiesis. Ectopic expression of PSTPIP2 impaired megakaryocytic differen ...[more]

PMID: 24407241

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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-1– megakaryocytes). 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. Keywords = GATA-1 Keywords = megakaryocyte Keywords = mouse model Keywords: other

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PSTPIP2 dysregulation contributes to aberrant terminal differentiation in GATA-1-deficient megakaryocytes by activating LYN.

Publications

PSTPIP2 dysregulation contributes to aberrant terminal differentiation in GATA-1-deficient megakaryocytes by activating LYN.

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