Project description:Notch signaling regulates several cellular processes including cell fate decisions and proliferation in both invertebrates and mice. However, comparatively less is known about the role of Notch during early human development. Here, we examined the function of Notch signaling during hematopoietic lineage specification from human pluripotent stem cells (hPSCs) of both embryonic and adult fibroblast origin. Using immobilized Notch ligands and siRNA to Notch receptors we have demonstrated that Notch1, but not Notch2 activation, induced HES1 expression and generation of committed hematopoietic progenitors. Using gain and loss of function approaches, this was shown to be attributed to Notch signaling regulation through HES1, that dictated cell fate decisions from bipotent precursors either to the endothelial or hematopoietic lineages at the clonal level. Our study reveals a previously unappreciated role for the Notch pathway during early human hematopoiesis, whereby Notch signaling via HES1 represents a toggle switch of hematopoietic vs. endothelial fate specification. Human pluripotent stem cells (hPSCs) have differentiation potential into three embryonic germ layers including blood. Notch signaling is one of important signaling pathways involved in blood differentiation of hPSCs. Thus, in order to examine the effect of Notch signaling pathways during hematopoietic differentiation of hPSCs, embryoid bodies (EBs) were formed and cultured for 10 days in the combination of cytokines and growth factors (Chadwick, Blood, 2003; 300 ng/ml of SCF, 300 ng/ml of Flt-3L, 10 ng/ml of IL-3, 10 ng/ml of IL-6, and 50 ng/ml of G-CSF) to induce differentiation into blood. Additionally, CD31+CD45- bipotent hemogenic precursors were isolated from day10 hematopoietic EBs (Wang et al., Immunity, 2004)
Project description:Sivakumar2011 - Notch Signaling Pathway
Notch is a transmembrane receptor that mediates local cell-cell communication and coordinates a signaling cascade. It plays a key role in modulating cell fate decisions throughout the development of invertebrate and vertebrate species and the misregulation leads to a number of human diseases.
References:
Notch signaling: from the outside in.
Notch signaling in hematopoiesis and early lymphocyte development.
An overview of the Notch signalling pathway.
Notch and cancer: best to avoid the ups and downs.
Notch signaling: control of cell communication and cell fate.
This model is described in the article:
A systems biology approach to model neural stem cell regulation by notch, shh, wnt, and EGF signaling pathways.
Sivakumar KC, Dhanesh SB, Shobana S, James J, Mundayoor S.
Omics: a Journal of Integrative Biology. 2011; 15(10):729-737
Abstract:
The Notch, Sonic Hedgehog (Shh), Wnt, and EGF pathways have long been known to influence cell fate specification in the developing nervous system. Here we attempted to evaluate the contemporary knowledge about neural stem cell differentiation promoted by various drug-based regulations through a systems biology approach. Our model showed the phenomenon of DAPT-mediated antagonism of Enhancer of split [E(spl)] genes and enhancement of Shh target genes by a SAG agonist that were effectively demonstrated computationally and were consistent with experimental studies. However, in the case of model simulation of Wnt and EGF pathways, the model network did not supply any concurrent results with experimental data despite the fact that drugs were added at the appropriate positions. This paves insight into the potential of crosstalks between pathways considered in our study. Therefore, we manually developed a map of signaling crosstalk, which included the species connected by representatives from Notch, Shh, Wnt, and EGF pathways and highlighted the regulation of a single target gene, Hes-1, based on drug-induced simulations. These simulations provided results that matched with experimental studies. Therefore, these signaling crosstalk models complement as a tool toward the discovery of novel regulatory processes involved in neural stem cell maintenance, proliferation, and differentiation during mammalian central nervous system development. To our knowledge, this is the first report of a simple crosstalk map that highlights the differential regulation of neural stem cell differentiation and underscores the flow of positive and negative regulatory signals modulated by drugs.
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Project description:A transcriptome study in mouse hematopoietic stem cells was performed using a sensitive SAGE method, in an attempt to detect medium and low abundant transcripts expressed in these cells. Among a total of 31,380 unique transcript, 17,326 (55%) known genes were detected, 14,054 (45%) low-copy transcripts that have no matches to currently known genes. 3,899 (23%) were alternatively spliced transcripts of the known genes and 3,754 (22%) represent anti-sense transcripts from known genes.
Project description:A transcriptome study in mouse hematopoietic stem cells was performed using a sensitive SAGE method, in an attempt to detect medium and low abundant transcripts expressed in these cells. Among a total of 31,380 unique transcript, 17,326 (55%) known genes were detected, 14,054 (45%) low-copy transcripts that have no matches to currently known genes. 3,899 (23%) were alternatively spliced transcripts of the known genes and 3,754 (22%) represent anti-sense transcripts from known genes. Mouse hematopoietic stem cells were purified from bone marrow cells using negative and positive selection with a Magnetic-Activated Cell Sorter (MACS). total RNA and mRNA were purified from the purified cells using Trizol reagent and magnetic oligo dT beads. Double strand cDNAs were synthesized using a cDNA synthesis kit and anchored oligo dT primers. After NlaIII digestion, 3’ cDNAs were isolated and amplified through 16-cycle PCR. SAGE tags were released from the 3’ cDNA after linker ligation. Ditags were formed, concatemerized and cloned into a pZERO vector. Sequencing reactions were performed with the ET sequencing terminator kit. Sequences were collected using a Megabase 1000 sequencer. SAGE tag sequences were extracted using SAGE 2000 software.
Project description:Although Notch signaling has been clearly implicated in lymphoid differentiation, its role in myeloid lineages differentiation is unclear. Expression data from hematopoietic stem cells plated on OP9 stroma expressing or not the Notch ligand Delta-like1. Results provide insight into the role of Notch signalling in megakaryocyte fate specification. Keywords: Gene expression array-based (RNA / in situ oligonucleotide)
Project description:Notch signaling defines a conserved, fundamental pathway, responsible for determination in metazoan development and is widely recognized as an essential component of lineage specific differentiation and stem cell self-renewal in many tissues including the hematopoietic system. Until recently, the majority of studies in the hematopoietic system focused on Notch signaling in lymphocyte differentiation and knowledge of individual Notch receptor roles in early hematopoiesis has been limited due to a paucity of genetic tools available To fate-map Notch receptor expression and pathway activity in the hematopoietic system we used tamoxifen-inducible CreER knock-in mice for individual Notch receptors in combination to a novel Notch reporter strain (Hes1GFP) and a conditional gain of function allele of Notch2 receptor (Rosa-lsl-ICN2). Bone marrow lineage negative, cKit+, Sca1- cells were sorted from Hes-GFP mice for RNA extraction and hybridization on Affymetrix microarrays
Project description:Notch signaling defines a conserved, fundamental pathway, responsible for determination in metazoan development and is widely recognized as an essential component of lineage specific differentiation and stem cell self-renewal in many tissues including the hematopoietic system. Until recently, the majority of studies in the hematopoietic system focused on Notch signaling in lymphocyte differentiation and knowledge of individual Notch receptor roles in early hematopoiesis has been limited due to a paucity of genetic tools available To fate-map Notch receptor expression and pathway activity in the hematopoietic system we used tamoxifen-inducible CreER knock-in mice for individual Notch receptors in combination to a novel Notch reporter strain (Hes1GFP) and a conditional gain of function allele of Notch2 receptor (Rosa-lsl-ICN2). Bone marrow lineage negative, cKit+, Sca1+ cells were sorted from Hes-GFP mice for RNA extraction and hybridization on Affymetrix microarrays
Project description:Recently, we identified and characterized specific endothelial progenitors with varying hemogenic potential during human pluripotent stem cell differentiation. Based on these studies we established a platform on which we can manipulate NOTCH signaling on these subsets to elucidate the specific role of this signaling pathway during hemogenic endothelial specification, endothelial-to-hematopoietic transition, and definitive hematopoietic specification.
Project description:Notch signaling defines a conserved, fundamental pathway, responsible for determination in metazoan development and is widely recognized as an essential component of lineage specific differentiation and stem cell self-renewal in many tissues including the hematopoietic system. Until recently, the majority of studies in the hematopoietic system focused on Notch signaling in lymphocyte differentiation and knowledge of individual Notch receptor roles in early hematopoiesis has been limited due to a paucity of genetic tools available To fate-map Notch receptor expression and pathway activity in the hematopoietic system we used tamoxifen-inducible CreER knock-in mice for individual Notch receptors in combination to a novel Notch reporter strain (Hes1GFP) and a conditional gain of function allele of Notch2 receptor (Rosa-lsl-ICN2). E13.5 Foetal Liver lineage negative, cKit+, Sca1+ cells were sorted from Hes-GFP mice for RNA extraction and hybridization on Affymetrix microarrays