Inhibition of erythropoiesis by Smad6 in human cord blood hematopoietic stem cells
ABSTRACT Bone morphogenetic proteins (BMPs) that belong to the transforming growth factor-β (TGF-β) superfamily cytokines, play crucial roles in hematopoiesis. However, roles of Smad6 in hematopoiesis remained unknown in contrast to the other inhibitory Smad (I-Smad), Smad7. Here we show that Smad6 inhibits erythropoiesis in human CD34(+) cord blood hematopoietic stem cells (HSCs). Smad6 was specifically expressed in CD34(+) cord blood HSCs, which was correlated with the expression of BMP2/4/6/7 and BMP type I receptor (BMPRI). BMP-specific receptor-regulated Smads (R-Smads), Smad1 and Smad5 in cooperation with Smad4 induced transcription of the Smad6 gene. Instead of affecting cell cycle, apoptosis, self-renewal, and stemness of CD34(+) cells, Smad6 knockdown enhanced, whereas Smad6 overexpression suppressed erythropoiesis in stem cell culture and colony formation assay. Consistently, Smad6 suppressed the expression of the genes essential for erythropoiesis, such as Kruppel-like factor 1 (erythroid) (KLF1/EKLF) and GATA binding protein 2 (GATA-2). Promoter analyses showed that Smad6 repressed Smad5/4-induced transcription of the Klf1 gene. Thus, our data suggest that Smad6 indirectly maintains stemness by preventing spontaneous erythropoiesis in HSCs.
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ABSTRACT: Background Iron nanoparticles (FeNPs) have attracted increasing attention over the past two decades owing to their promising application as biomedical agents. However, to ensure safe application, their potential nanotoxicity should be carefully and thoroughly evaluated. Studies on the effects of FeNPs on cells at the transcriptomic level will be helpful for identifying any potential nanotoxicity of FeNPs and providing valuable mechanistic insights into various FeNPs-induced nanotoxicities.ResultsThis study investigated the effects of an 11-nm dimercaptosuccinic acid-coated magnetite nanoparticle on the gene expression profiles of two human cell lines, THP-1 and HepG2. It was found that the expression of hundreds of genes was significantly changed by a 24-h treatment with the nanoparticles at two doses, 50 ¿g/mL and 100 ¿g/mL, in the two cell types. By identifying the differentially expressed genes and annotating their functions, this study characterized the general and cell-specific effects of the nanoparticles on two cell types at the gene, biological process and pathway levels. At these doses, the overall effects of the nanoparticle on the THP-1 cells were the induction of various responses and repression of protein translation, but in the HepG2 cells, the main effects were the promotion of cell metabolism, growth and mobility. In combination with a previous study, this study also characterized the common genes, biological processes and pathways affected by the nanoparticle in two human and mouse cell lines and identified Id3 as a nanotoxicity biomarker of the nanoparticle.Conclusion The studied FeNPs exerted significant effects on the gene expression profiles of human cells. These effects were highly dependent on the innate biological functions of cells, i.e., the cell types. However, cells can also show some cell type-independent effects such as repression of Id3 expression. Id3 can be used as a nanotoxicity biomarker for iron nanoparticles.Journal of Nanobiotechnology 01/2015; 13(1):3. DOI:10.1186/s12951-014-0063-3 · 4.08 Impact Factor
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ABSTRACT: The roles of DHHC-containing proteins in embryonic cell fate specification are not well defined, nor are the underlying mechanisms of their activity well understood. Here, we compared the embryonic function of zinc finger DHHC-type containing (Zdhhc13) in zebrafish embryos and in an in vitro cell model. Zdhhc13, a critical regulator of bone morphogenetic protein (BMP) signaling, specifically bound to Smad6 to induce its perinuclear accumulation and degradation through a mechanism independent of its palmitoyltransferase activity. We showed Zdhhc13 played a crucial role during zebrafish embryogenesis in the control of germ layer specification, particularly in ectoderm and mesoderm differentiation homeostasis. Depletion of Zdhhc13 led to the neuralization of ectoderm and dorsalization of mesoderm in zebrafish embryos. Moreover, Zdhhc13 antagonized Smad6 during BMP-dependent signaling and early lineage decisions in our in vitro cell model. Our results extended the cellular role of Zdhhc13, suggesting that it acts as a regulator in BMP signaling, and established that the embryonic function of Zdhhc13 is in lineage specification.Stem cells and development 04/2014; DOI:10.1089/scd.2014.0068 · 4.15 Impact Factor
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ABSTRACT: The erythroblastic island provides an important nutritional and survival support niche for efficient erythropoietic differentiation. Island integrity is reliant on adhesive interactions between erythroid and macrophage cells. We show that erythroblastic islands can be formed from single progenitor cells present in differentiating embryoid bodies, and that these correspond to erythro-myeloid progenitors (EMPs) that first appear in the yolk sac of the early developing embryo. Erythroid Krüppel-like factor (EKLF; KLF1), a crucial zinc finger transcription factor, is expressed in the EMPs, and plays an extrinsic role in erythroid maturation by being expressed in the supportive macrophage of the erythroblastic island and regulating relevant genes important for island integrity within these cells. Together with its well-established intrinsic contributions to erythropoiesis, EKLF thus plays a coordinating role between two different cell types whose interaction provides the optimal environment to generate a mature red blood cell.Development 06/2014; 141(11):2245-54. DOI:10.1242/dev.103960 · 6.27 Impact Factor