Project description:The objective of this study was to identify genes regulated by Sonic Hedgehog pathway stimulation in neural progenitors. Paired (parallel culture) triplicates of neuralized embryoid body cultures with and without Shh pathway stimulation (Ag1.3-treatment)
Project description:Nkx2.2, Nkx6.1, and Olig2 are transcriptional repressors regulating somatic motor neuron and interneuron subtypes in neural progenitors. The purpose of this study was to identify their target genes and to elucidate their gene regulatory mechanisms, including their relationship to Sonic Hedgehog/Gli pathway.
Project description:The morphogen and mitogen, Sonic Hedgehog, activates a Gli1-dependent transcription program that drives proliferation of granule neuron progenitors (GNPs) within the external germinal layer of the postnatally developing cerebellum. Medulloblastomas with mutations activating the Sonic Hedgehog signaling pathway preferentially arise within the external germinal layer, and the tumor cells closely resemble GNPs. Atoh1/Math1, a basic helix-loop-helix transcription factor essential for GNP histogenesis, does not induce medulloblastomas when expressed in primary mouse GNPs that are explanted from the early postnatal cerebellum and transplanted back into the brains of naïve mice. However, enforced expression of Atoh1 in primary GNPs enhances the oncogenicity of cells overexpressing Gli1 by almost three orders of magnitude. Unlike Gli1, Atoh1 cannot support GNP proliferation in the absence of Sonic Hedgehog signaling and does not govern expression of canonical cell cycle genes. Instead, Atoh1 maintains GNPs in a Sonic Hedgehog-responsive state by regulating genes that trigger neuronal differentiation, including many expressed in response to bone morphogenic protein-4. Therefore, by targeting multiple genes regulating the differentiation state of GNPs, Atoh1 collaborates with the pro-proliferative Gli1-dependent transcriptional program to influence medulloblastoma development. Keywords: disease state analysis 14 samples, 1 time series, 2 engineered Medulloblastoma tumors
Project description:Sivakumar2011 - Hedgehog Signaling Pathway
This is the current model for the Hedgehog signaling pathway. The best data for mechanism of signaling has been worked out in Drosophila, so this model is based largely on Drosophila data. Hedgehog target genes vary from tissue to tissue, so the identities of individual target genes have not been listed. The main difference between the Drosophila and mammalian Hedgehog signaling pathways is the fact that there are three mammalian homologs of Cubitus interruptus, Gli1 Gli2 and Gli3. Some or all of the mammalian homologs may be proteolytically processed, but the data are controversial. There are two mammalian Ptc genes and three mammalian Hedgehog genes as well. The pathway for Sonic Hedgehog appears to be most similar to the Drosophila hedgehog pathway.
References:
Hedgehog signaling in animal development: paradigms and principles.
Sonic hedgehog in the nervous system: functions, modifications and mechanisms.
Hedgehog signal transduction: recent findings.
Hedgehog signaling: Costal-2 bridges the transduction gap.
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.
This model is hosted on BioModels Database and identified by: BIOMD0000000395.
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:We report that Hedgehog signaling is a heterochronic pathway that determines the timing of the transition from specified cardiac progenitor to differentiated cardiomyocyte, a function distinct from its previously described roles affecting cellular patterning or proliferation. Hedgehog signaling was required to prevent premature differentiation and disruption of cardiac morphogenesis in vivo and the Hedgehog signaling transcription factor GLI1 was sufficient to delay differentiation in stem cell-derived cardiac progenitors in vitro. GLI1 directly activated a de novo progenitor-specific network in vitro that inhibited the induction of the cardiac differentiation program. The GLI1-driven gene regulatory network is sufficient to induce Hedgehog-naive in vitro cardiac progenitors to adopt an epigenomic state reminiscent of second heart field cardiac progenitors in vivo. A Hh-dependent GLI transcription factor switch functions as a differentiation timer, restricting activity of the progenitor network to the second heart field and permitting cardiomyocyte differentiation in the heart. GLI1 expression is broadly associated with the progenitor state, and its activity also delayed the differentiation of specified neural progenitors in vitro. We posit that Hedgehog signaling functions as a heterochronic regulator that transiently maintains diverse progenitor populations for complex organ development and that may explain diverse Hedgehog signaling-dependent phenomena.
Project description:We report that Hedgehog signaling is a heterochronic pathway that determines the timing of the transition from specified cardiac progenitor to differentiated cardiomyocyte, a function distinct from its previously described roles affecting cellular patterning or proliferation. Hedgehog signaling was required to prevent premature differentiation and disruption of cardiac morphogenesis in vivo and the Hedgehog signaling transcription factor GLI1 was sufficient to delay differentiation in stem cell-derived cardiac progenitors in vitro. GLI1 directly activated a de novo progenitor-specific network in vitro that inhibited the induction of the cardiac differentiation program. The GLI1-driven gene regulatory network is sufficient to induce Hedgehog-naive in vitro cardiac progenitors to adopt an epigenomic state reminiscent of second heart field cardiac progenitors in vivo. A Hh-dependent GLI transcription factor switch functions as a differentiation timer, restricting activity of the progenitor network to the second heart field and permitting cardiomyocyte differentiation in the heart. GLI1 expression is broadly associated with the progenitor state, and its activity also delayed the differentiation of specified neural progenitors in vitro. We posit that Hedgehog signaling functions as a heterochronic regulator that transiently maintains diverse progenitor populations for complex organ development and that may explain diverse Hedgehog signaling-dependent phenomena.
Project description:We report that Hedgehog signaling is a heterochronic pathway that determines the timing of the transition from specified cardiac progenitor to differentiated cardiomyocyte, a function distinct from its previously described roles affecting cellular patterning or proliferation. Hedgehog signaling was required to prevent premature differentiation and disruption of cardiac morphogenesis in vivo and the Hedgehog signaling transcription factor GLI1 was sufficient to delay differentiation in stem cell-derived cardiac progenitors in vitro. GLI1 directly activated a de novo progenitor-specific network in vitro that inhibited the induction of the cardiac differentiation program. The GLI1-driven gene regulatory network is sufficient to induce Hedgehog-naive in vitro cardiac progenitors to adopt an epigenomic state reminiscent of second heart field cardiac progenitors in vivo. A Hh-dependent GLI transcription factor switch functions as a differentiation timer, restricting activity of the progenitor network to the second heart field and permitting cardiomyocyte differentiation in the heart. GLI1 expression is broadly associated with the progenitor state, and its activity also delayed the differentiation of specified neural progenitors in vitro. We posit that Hedgehog signaling functions as a heterochronic regulator that transiently maintains diverse progenitor populations for complex organ development and that may explain diverse Hedgehog signaling-dependent phenomena.
Project description:We report that Hedgehog signaling is a heterochronic pathway that determines the timing of the transition from specified cardiac progenitor to differentiated cardiomyocyte, a function distinct from its previously described roles affecting cellular patterning or proliferation. Hedgehog signaling was required to prevent premature differentiation and disruption of cardiac morphogenesis in vivo and the Hedgehog signaling transcription factor GLI1 was sufficient to delay differentiation in stem cell-derived cardiac progenitors in vitro. GLI1 directly activated a de novo progenitor-specific network in vitro that inhibited the induction of the cardiac differentiation program. The GLI1-driven gene regulatory network is sufficient to induce Hedgehog-naive in vitro cardiac progenitors to adopt an epigenomic state reminiscent of second heart field cardiac progenitors in vivo. A Hh-dependent GLI transcription factor switch functions as a differentiation timer, restricting activity of the progenitor network to the second heart field and permitting cardiomyocyte differentiation in the heart. GLI1 expression is broadly associated with the progenitor state, and its activity also delayed the differentiation of specified neural progenitors in vitro. We posit that Hedgehog signaling functions as a heterochronic regulator that transiently maintains diverse progenitor populations for complex organ development and that may explain diverse Hedgehog signaling-dependent phenomena.
Project description:We report that Hedgehog signaling is a heterochronic pathway that determines the timing of the transition from specified cardiac progenitor to differentiated cardiomyocyte, a function distinct from its previously described roles affecting cellular patterning or proliferation. Hedgehog signaling was required to prevent premature differentiation and disruption of cardiac morphogenesis in vivo and the Hedgehog signaling transcription factor GLI1 was sufficient to delay differentiation in stem cell-derived cardiac progenitors in vitro. GLI1 directly activated a de novo progenitor-specific network in vitro that inhibited the induction of the cardiac differentiation program. The GLI1-driven gene regulatory network is sufficient to induce Hedgehog-naive in vitro cardiac progenitors to adopt an epigenomic state reminiscent of second heart field cardiac progenitors in vivo. A Hh-dependent GLI transcription factor switch functions as a differentiation timer, restricting activity of the progenitor network to the second heart field and permitting cardiomyocyte differentiation in the heart. GLI1 expression is broadly associated with the progenitor state, and its activity also delayed the differentiation of specified neural progenitors in vitro. We posit that Hedgehog signaling functions as a heterochronic regulator that transiently maintains diverse progenitor populations for complex organ development and that may explain diverse Hedgehog signaling-dependent phenomena.