Project description:Wnt signaling is intrinsic to mouse embryonic stem cell self-renewal. Therefore it is surprising that reprogramming of somatic cells to induced pluripotent stem cells (iPSCs) is not strongly enhanced by Wnt signaling. Here, we demonstrate that active Wnt signaling inhibits the early stage of reprogramming to iPSCs, while it is required and even stimulating during the late stage. Mechanistically, this biphasic effect of Wnt signaling is accompanied by a change in the requirement of all four of its transcriptional effectors: Tcf1, Lef1, Tcf3, and Tcf4. For example, Tcf3 and Tcf4 are stimulatory early but inhibitory late in the reprogramming process. Accordingly, ectopic expression of Tcf3 early in reprogramming combined with its loss-of-function late enables efficient reprogramming in the absence of ectopic Sox2. Together, our data indicate that the step-wise process of reprogramming to iPSCs is critically dependent on the stage-specific control and action of all four Tcfs and Wnt signaling.
Project description:Wnt signaling is intrinsic to mouse embryonic stem cell self-renewal. Therefore it is surprising that reprogramming of somatic cells to induced pluripotent stem cells (iPSCs) is not strongly enhanced by Wnt signaling. Here, we demonstrate that active Wnt signaling inhibits the early stage of reprogramming to iPSCs, while it is required and even stimulating during the late stage. Mechanistically, this biphasic effect of Wnt signaling is accompanied by a change in the requirement of all four of its transcriptional effectors: Tcf1, Lef1, Tcf3, and Tcf4. For example, Tcf3 and Tcf4 are stimulatory early but inhibitory late in the reprogramming process. Accordingly, ectopic expression of Tcf3 early in reprogramming combined with its loss-of-function late enables efficient reprogramming in the absence of ectopic Sox2. Together, our data indicate that the step-wise process of reprogramming to iPSCs is critically dependent on the stage-specific control and action of all four Tcfs and Wnt signaling. For genome wide expression analysis: A. Tcf3 wt and ko OSK iPS cells were analyzed (ko was performed from 2 different cell lines). B. Tcf3 ko OCK iPS cells were analyzed (2 different cell lines) C. Tcf3 wt and ko OCK reprogramming timecourse was analyzed at the indicated days after the beginning of the reprogramming. D. OCK partial iPS cell clone treated with control siRNA or 2 independent Tcf3 siRNA and RNA were analyzed 48hr after siRNA treatment.
Project description:Sivakumar2011_WntSignalingPathway
The secreted protein Wnt activates the
heptahelical receptor Frizzled on nieghboring cells. Activation of
Frizzled causes the recruitment of additional membrane proteins
which in turn result in 1) the activation of the protein
Dishevelled via phosphorylation and 2) the activation of a
heterotrimeric G protein of unknown type. Activation of Dishevelled
results in the down-regulation of the Beta-Catenin destruction
complex which causes ubiquitination of Beta-Catenin and its
ultimate degradation via the proteasome. Inhibition of the
Beta-Catenin destruction complex yields a higher cytosolic
concentration of Beta-Catenin, which enters the nucleus, binds
various transcriptional regulatory molecules including the TCF/LEF
class of proteins, and results in the transcription of TCF/LEF
target genes. Activation of the heterotrimeric G-protein pathway in
turn activates Phospholipase C which in turn catalyzes the
catalysis of PI(4,5)P2 into DAG and IP3.
Reference:
The Wnt
signalling pathway.
You Wnt
some, you lose some: oncogenes in the Wnt signaling
pathway.
Wnt
signaling pathway.
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 2011 Oct; 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.
This model is hosted on
BioModels Database
and identified by:
BIOMD0000000397.
To cite BioModels Database, please use:
BioModels Database:
An enhanced, curated and annotated resource for published
quantitative kinetic models.
To the extent possible under law, all copyright and related or
neighbouring rights to this encoded model have been dedicated to
the public domain worldwide. Please refer to
CC0
Public Domain Dedication for more information.
Project description:Although transcriptional programs associated with T-cell specification and commitment have been described, the functional hierarchy and the roles of key regulators in structuring/ orchestrating these programs remain unclear. Activation of Notch signaling in uncommitted precursors by the thymic stroma initiates the T-cell differentiation program. One regulator first induced in these precursors is the DNA binding protein Tcf-1, a T-cell specific mediator of Wnt signaling. Yet the specific contribution of Tcf-1 to early T-cell development and the signals inducing it in these cells remain unclear. Here we assign functional significance to Tcf-1 as a gatekeeper of T-cell fate. We show that Tcf-1 is directly activated by Notch signals. Tcf-1 is required at the earliest phase of Tcell determination for progression beyond the early thymic progenitor (ETP) stage. The global expression profile of Tcf-1 deficient progenitors indicates that basic processes of DNA metabolism are downregulated in its absence and the blocked T-cell progenitors become abortive and die by apoptosis. Our data thus add an important functional relationship to the roadmap of T-cell development. We used microarrays to detail the global programme of gene expression of mouse ETP thymocyte after Ikaros inactivation with dominant negative of Ik at different stage. 6 samples (mouse ETP thymocytes from wt, and Tcf1 inactivation) are analyzed Mouse Microarray Expression platforms, Affymetrix Mouse 430 2.0,
Project description:The canonical Wnt signaling pathway is critical for myogenesis and can induce muscle progenitors to switch from proliferation to differentiation; how Wnt signals integrate with muscle specific regulatory factors in this process is poorly understood. We previously demonstrated that the Barx2 homeobox protein promotes differentiation in cooperation with the muscle regulatory factor (MRF) MyoD. Pax7, another important muscle homeobox factor represses differentiation. We now identify Barx2,MyoD,and Pax7 as novel components of the Wnt effector complex, providing a new molecular pathway for regulation of muscle progenitor differentiation. Canonical Wnt signaling induces Barx2 expression in muscle progenitors and perturbation of Barx2 leads to misregulation of Wnt target genes. Barx2 activates two endogenous Wnt target promoters as well as the Wnt reporter gene TOPflash, the latter synergistically with MyoD. Moreover, Barx2 interacts with the core Wnt effectors β-catenin and TCF, is recruited to TCF/LEF sites, and promotes recruitment of β-catenin. In contrast, Pax7 represses the Wnt reporter gene and antagonizes the activating effect of Barx2. Pax7 also binds β-catenin suggesting that Barx2 and Pax7 may compete for interaction with the core Wnt effector complex. Overall, the data show for the first time that Barx2, Pax7, and MRFs can act as direct transcriptional effectors of Wnt signals in myoblasts and that Barx2 and Wnt signaling participate in a regulatory loop. We propose that antagonism between Barx2 and Pax7 in regulation of Wnt signaling may help mediate the switch from myoblast proliferation to differentiation. RNA-Seq analyses was used to characterize gene expression in primary myoblasts from wild-type and Barx2 knockout mice.
Project description:Pig induced pluripotent stem cells (piPSCs) have significant biomedical and agricultural applications. We analyzed the transcriptional profiles of pig iPSC lines derived from different labs using Affymetrix GeneChip Pig Genome Array and published microarray datasets of mouse and human iPSCs. Our results demonstrated that cell surface proteins of EpCAM (epithelial cells adhesion molecule) were significantly upregulated in complete fully reprogrammed pig iPSCs, but not in partially reprogrammed cells. EpCAM could be markers for evaluating pig cell reprogramming and selecting successful reprogramming. We analyzed gene expression levels of the six key developmental signaling pathways, including JAK-STAT, NOTCH, TGF-M-NM-2b, WNT, MAPK and VEGF in pig, human and mouse iPSCs, respectively. The result demonstrates that the core transcriptional network to maintain pluripotency and self-renewal in pig are different from mouse and human. Pig iPSCs lacked expression of specific naM-CM-/ve state markers (e.g. Klf family genes Klf2/4/5, Tbx3), but expressed unregulated primed state markers (e.g. Otx2 and Fabp7). Dlk1-Dio3 domain was silenced in piPSCs as previously seen in mouse and human iPSCs, which explantsexplains rare success of generation of pig chimeric and cloned offspring. Our analyses decipher pig somatic cells undergoes reprogramming into a primed state and maintains its regulatory network with define feature with human iPSCs and mouse EpiSCs. We compare gene expression profiles of pig iPS cell lines generated by our lab with cell lines derived from other labs with different levels of marker expression and plasticity.
Project description:Dysregulation of Wnt signaling is involved in carcinogenesis, mainly through activation of beta-catenin/TCF target genes. Although aberrant activation of several Wnt target genes, including CCND1 and MYC, has been reported as promoting proliferation of cancer cells, it is hardly enough to understand malignant phenotypes of cancer cells with aberrant Wnt signaling. To elucidate the transcriptional regulation of beta-catenin/TCF target genes, we examined binding of beta-catenin (BC) to DNA by chromatin immunoprecipitation linked to genome tiling array (ChIP-on-chip).
Project description:The WNT-TCF signaling pathway participates in adult tissue homeostasis and repair, and is hyperactive in a number of human diseases including cancers of the colon. Whereas to date there are no antagonists approved for patient use, a potential problem for their sustained use is the blockade of WNT signaling in healthy tissues, thus provoking potentially serious co-lateral damage. Here we have screened a library of plant and microorganism small molecules for novel WNT signaling antagonists and describe withanolide F as a potent WNT-TCF response blocker. This steroidal lactone inhibits TCF-dependent colon cancer xenograft growth and mimics the effects of genetic blockade of TCF and of ivermectin, a previously reported WNT-TCF blocker. However, withanolide F is unique in that it imposes a long-lasting repression of tumor growth, WNT-TCF targets and cancer stem cell clonogenicity long after drug treatment
Project description:Although transcriptional programs associated with T-cell specification and commitment have been described, the functional hierarchy and the roles of key regulators in structuring/ orchestrating these programs remain unclear. Activation of Notch signaling in uncommitted precursors by the thymic stroma initiates the T-cell differentiation program. One regulator first induced in these precursors is the DNA binding protein Tcf-1, a T-cell specific mediator of Wnt signaling. Yet the specific contribution of Tcf-1 to early T-cell development and the signals inducing it in these cells remain unclear. Here we assign functional significance to Tcf-1 as a gatekeeper of T-cell fate. We show that Tcf-1 is directly activated by Notch signals. Tcf-1 is required at the earliest phase of Tcell determination for progression beyond the early thymic progenitor (ETP) stage. The global expression profile of Tcf-1 deficient progenitors indicates that basic processes of DNA metabolism are downregulated in its absence and the blocked T-cell progenitors become abortive and die by apoptosis. Our data thus add an important functional relationship to the roadmap of T-cell development. We used microarrays to detail the global programme of gene expression of mouse ETP thymocyte after Ikaros inactivation with dominant negative of Ik at different stage.
Project description:Dysregulation of Wnt/TCF signaling is closely associated with cancers arising from the gastrointestinal tract, inlcluding colon cancer and liver cancer. The goal of this study is to understand the transcriptional programs underlying Wnt/TCF activation in gastrointestinal cancers. We examined the transcriptional responses to TCF inhibition in cultured human colon cancer cells and liver cancer cells that are characteristic of Wnt pathway activation. Human liver cancer cell line HepG2 and colon cancer cell line LS174T with or without expression of a dominant negative form of TCF4