Project description:Sp1 and Sp3 belong to the Specificity proteins (Sp)/Krüppel-like transcription factor family. They are closely related, ubiquitously expressed and recognize G-rich DNA motifs. They are thought to regulate generic processes such as cell cycle and growth control, metabolic pathways and apoptosis. Ablation of Sp1 or Sp3 in mice is lethal, and combined haploinsufficiency results in hematopoietic defects during the fetal stages. Here, we show that in adult mice conditional ablation of either Sp1 or Sp3 has minimal impact on hematopoiesis, while the simultaneous loss of Sp1 and Sp3 results in severe macrothrombocytopenia and platelet dysfunction. We employed flow cytometry, cell culture and electron microscopy and show that although megakaryocyte numbers are normal in bone marrow and spleen, they display a less compact demarcation membrane system and a striking inability to form proplatelets. Through megakaryocyte transcriptomics and platelet proteomics we identified several cytoskeleton-related proteins and downstream effector kinases, including Mylk, that were downregulated upon Sp1/Sp3 depletion, providing an explanation for the observed defects in megakaryopoiesis. We show that Mylk is required for proplatelet formation and stabilization and for ITAM-receptor mediated platelet aggregation. Our data highlights the specific vs generic role of these ubiquitous transcription factors in the highly specialized megakaryocytic lineage. Megakaryocyte mRNA profiles of Sp1fl/fl::Sp3fl/fl (WTlox) and Pf4-Cre::Sp1fl/fl::Sp3fl/fl (dKO) mice were generated by deep sequencing, in triplicate.
Project description:Sp1 and Sp3 belong to the Specificity proteins (Sp)/Krüppel-like transcription factor family. They are closely related, ubiquitously expressed and recognize G-rich DNA motifs. They are thought to regulate generic processes such as cell cycle and growth control, metabolic pathways and apoptosis. Ablation of Sp1 or Sp3 in mice is lethal, and combined haploinsufficiency results in hematopoietic defects during the fetal stages. Here, we show that in adult mice conditional ablation of either Sp1 or Sp3 has minimal impact on hematopoiesis, while the simultaneous loss of Sp1 and Sp3 results in severe macrothrombocytopenia and platelet dysfunction. We employed flow cytometry, cell culture and electron microscopy and show that although megakaryocyte numbers are normal in bone marrow and spleen, they display a less compact demarcation membrane system and a striking inability to form proplatelets. Through megakaryocyte transcriptomics and platelet proteomics we identified several cytoskeleton-related proteins and downstream effector kinases, including Mylk, that were downregulated upon Sp1/Sp3 depletion, providing an explanation for the observed defects in megakaryopoiesis. We show that Mylk is required for proplatelet formation and stabilization and for ITAM-receptor mediated platelet aggregation. Our data highlights the specific vs generic role of these ubiquitous transcription factors in the highly specialized megakaryocytic lineage.
Project description:To investigate the function of transcription factors Sp1 and Sp3 in the regulation of endothelial functions, we established tamoxifen-induced endothelial Sp1/Sp3 knockout mice and isolated the MLECs We then performed gene expression profiling analysis using data obtained from RNA-seq of MLECs from endothelial Sp1/Sp3 knockout mice and their control mice
Project description:Investigation of the binding behaviour of Sp1, Sp2, Sp3 and NF-ya, NF-yb and NF-yc in mouse embryonic fibroblasts and of Sp1, Sp2 and Sp3 in HEK-293 cells reveals distinct binding of the seemingly similar transcription factors Sp1/3 and Sp2.
Project description:Development requires the cooperation of tissue-specifically and ubiquitously expressed transcription factors, such as Sp-family members. However, the molecular details of how ubiquitous factors participate in developmental processes are still unclear. We previously showed that during the differentiation of embryonic stem cells lacking Sp1 DNA binding activity (Sp1DDBD/DDBD cells), early blood progenitors are formed. However, gene expression during differentiation becomes progressively deregulated and terminal differentiation is blocked. Here we studied the cooperation of Sp1 and its homologue Sp3 in hematopoietic development and demonstrate that Sp1 and Sp3 binding sites largely overlap. Sp3 cooperates with Sp1DDBD/DDBD cells but is unable to support hematopoiesis in the complete absence of Sp1. Using single cell gene expression analysis, we show that the lack of Sp1 DNA binding leads to a distortion of cell fate decision timing, indicating that stable chromatin binding of Sp1 is required to maintain robust differentiation trajectories.
Project description:Development requires the cooperation of tissue-specific and ubiquitously expressed transcription factors, such as Sp-family members. However, the molecular details of how ubiquitous factors participate in developmental processes are still unclear. We previously showed that during the differentiation of embryonic stem cells lacking Sp1 DNA binding activity (Sp1deltaDBD/deltaDBD cells), early blood progenitors are formed. However, gene expression during differentiation becomes progressively deregulated and terminal differentiation is severely compromised. Here we studied the cooperation of Sp1 and its closest paralogue Sp3 in hematopoietic development and demonstrate that Sp1 and Sp3 binding sites largely overlap. Sp3 cooperates with Sp1deltaDBD/deltaDBD but is unable to support hematopoiesis in the complete absence of Sp1. Using single cell gene expression analysis, we show that the lack of Sp1 DNA binding leads to a distortion of cell fate decision timing, indicating that stable chromatin bi nding of Sp1 is required to maintain robust differentiation trajectories.
Project description:Development requires the cooperation of tissue-specific and ubiquitously expressed transcription factors, such as Sp-family members. However, the molecular details of how ubiquitous factors participate in developmental processes are still unclear. We previously showed that during the differentiation of embryonic stem cells lacking Sp1 DNA binding activity (Sp1deltaDBD/deltaDBD cells), early blood progenitors are formed. However, gene expression during differentiation becomes progressively deregulated and terminal differentiation is severely compromised. Here we studied the cooperation of Sp1 and its closest paralogue Sp3 in hematopoietic development and demonstrate that Sp1 and Sp3 binding sites largely overlap. Sp3 cooperates with Sp1deltaDBD/deltaDBD but is unable to support hematopoiesis in the complete absence of Sp1. Using single cell gene expression analysis, we show that the lack of Sp1 DNA binding leads to a distortion of cell fate decision timing, indicating that stable chromatin bi nding of Sp1 is required to maintain robust differentiation trajectories.
Project description:Development requires the cooperation of tissue-specific and ubiquitously expressed transcription factors, such as Sp-family members. However, the molecular details of how ubiquitous factors participate in developmental processes are still unclear. We previously showed that during the differentiation of embryonic stem cells lacking Sp1 DNA binding activity (Sp1deltaDBD/deltaDBD cells), early blood progenitors are formed. However, gene expression during differentiation becomes progressively deregulated and terminal differentiation is severely compromised. Here we studied the cooperation of Sp1 and its closest paralogue Sp3 in hematopoietic development and demonstrate that Sp1 and Sp3 binding sites largely overlap. Sp3 cooperates with Sp1deltaDBD/deltaDBD but is unable to support hematopoiesis in the complete absence of Sp1. Using single cell gene expression analysis, we show that the lack of Sp1 DNA binding leads to a distortion of cell fate decision timing, indicating that stable chromatin bi nding of Sp1 is required to maintain robust differentiation trajectories.
Project description:Members of the Sp family of transcription factors regulate gene expression via binding GC boxes within promoter regions. Unlike Sp1, which stimulates transcription, the closely related Sp3 can either repress or activate gene expression and is required for perinatal survival in mice. Here we use RNAseq and cellular phenotyping to show how Sp3 regulates murine fetal cell differentiation and proliferation. Homozygous Sp3-/- mice were smaller than WT and Sp+/- littermates, died soon after birth, and had abnormal lung morphogenesis. RNAseq of Sp3-/- fetal lung mesenchymal cells identified alterations in extracellular matrix production, developmental signaling pathways, and myofibroblast/lipofibroblast differentiation. The lungs of Sp3-/- mice contained multiple structural defects, with abnormal endothelial cell morphology, lack of elastic fiber formation, and accumulation of lipid droplets within mesenchymal lipofibroblasts. Sp3-/- cells and mice also displayed cell cycle arrest, with accumulation in G0/G1 and reduced expression of numerous cell cycle regulators including Ccne1. These data detail the global impact of Sp3 on in vivo mouse gene expression and development. Development • Accepted manuscript lung mesenchymal cells identified alterations in extracellular matrix production, developmental signaling pathways, and myofibroblast/lipofibroblast differentiation. The lungs of Sp3-/- mice contained multiple structural defects, with abnormal endothelial cell morphology, lack of elastic fiber formation, and accumulation of lipid droplets within mesenchymal lipofibroblasts. Sp3-/- cells and mice also displayed cell cycle arrest, with accumulation in G0/G1 and reduced expression of numerous cell cycle regulators including Ccne1. These data detail the global impact of Sp3 on in vivo mouse gene expression and development.
Project description:Srf is a MADS-box transcription factor that is critical for muscle differentiation. Its function in hematopoiesis has not yet been revealed. Mkl1, a cofactor of Srf, is part of the t(1;22) translocation in acute megakaryoblastic leukemia, and plays a critical role in megakaryopoiesis. In order to test the role of Srf in megakaryocyte development, we crossed Pf4-Cre mice, which express Cre recombinase in cells committed to the megakaryocytic lineage, to SrfF/F mice in which functional Srf is no longer expressed after Cre-mediated excision. Pf4-Cre/SrfF/F (KO) mice are born with normal mendelian frequency, but have significant macrothrombocytopenia with approximately 50% reduction in platelet count. In contrast, the BM has increased numbers and percentages of CD41+ megakaryocytes (WT: 0.41+/-0.06%; KO: 1.92+/-0.12%) with significantly reduced ploidy. KO mice show significantly increased megakaryocyte progenitors in the BM by both FACS analysis and CFU-Mk. Megakaryocytes lacking Srf have abnormal stress fiber and demarcation membrane formation and platelets lacking Srf have abnormal actin distribution. In vitro and in vivo assays reveal platelet function defects in KO mice. Critical actin cytoskeletal genes are downregulated in KO megakaryocytes. Thus, Srf is required for normal megakaryocyte maturation and platelet production, due at least in part, to regulation of cytoskeletal genes. C-kit+CD41+ megakaryocyte progenitors from PF4-Cre/SRF C57BL/6 SRF WT (3) and C57BL/6 SRF KO (3) mice were sorted by flow cytometry and cultured for three days in thrombopoietin.