Enhanced MyoD-induced transdifferentiation to a myogenic lineage by fusion to a potent transactivation domain.
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ABSTRACT:
SUBMITTER: Kabadi AM
PROVIDER: S-EPMC4475448 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:Synthetic transcription factors can be applied to many areas of biotechnology, medicine, and basic research. Currently, the most common method for engineering synthetic transcription factors has been based on programmable DNA-binding domains of zinc finger proteins, Transcription Activator-Like Effectors (TALEs), and most recently the CRISPR/Cas9 system. These transcription factor platforms consist of the DNA-binding domain fused to potent transcriptional activation domains, most commonly the tetramer of the minimal transactivation domain of the VP16 protein from herpes simplex virus, referred to as VP64. Although many applications are well-suited for the targeted activation of a single gene, genetic reprogramming requires the coordinated regulation of many nodes of natural gene networks as is typically performed by naturally occurring reprogramming factors. Thus we sought to combine principles from each of these approaches by attaching potent transcriptional activation domains to a natural reprogramming factor to increase the efficiency and/or rate of cell fate conversion. In this study, we evaluated the effects of fusing potent activation domains to the transcription factor MyoD, the master regulator of the skeletal myoblast lineage. In certain non-myogenic lineages, MyoD overexpression causes upregulation of the myogenic gene network and conversion to a myoblast phenotype including cell fusion into multinucleated myotubes. Compared to wild-type MyoD, the VP64-MyoD fusion protein induced greater overall reprogramming of global gene expression. This simple approach for increasing the potency of natural reprogramming factors circumvents the need for screening engineered proteins and leads to a more robust cellular reprogramming compared to treatment with the wild type transcription factor. Human dermal fibroblasts were transduced with a single tet inducible lentivirus that expresses either WT-MyoD or VP64-MyoD in response to treatment with doxycycline. Untreated human dermal fibroblast served as the negative control. Gene expression was measured using mRNA-seq, and differential expression was calculated using DESeq. All experiments were performed in biological duplicates.
2014-12-11 | E-GEOD-62448 | biostudies-arrayexpress
Project description:Synthetic transcription factors can be applied to many areas of biotechnology, medicine, and basic research. Currently, the most common method for engineering synthetic transcription factors has been based on programmable DNA-binding domains of zinc finger proteins, Transcription Activator-Like Effectors (TALEs), and most recently the CRISPR/Cas9 system. These transcription factor platforms consist of the DNA-binding domain fused to potent transcriptional activation domains, most commonly the tetramer of the minimal transactivation domain of the VP16 protein from herpes simplex virus, referred to as VP64. Although many applications are well-suited for the targeted activation of a single gene, genetic reprogramming requires the coordinated regulation of many nodes of natural gene networks as is typically performed by naturally occurring reprogramming factors. Thus we sought to combine principles from each of these approaches by attaching potent transcriptional activation domains to a natural reprogramming factor to increase the efficiency and/or rate of cell fate conversion. In this study, we evaluated the effects of fusing potent activation domains to the transcription factor MyoD, the master regulator of the skeletal myoblast lineage. In certain non-myogenic lineages, MyoD overexpression causes upregulation of the myogenic gene network and conversion to a myoblast phenotype including cell fusion into multinucleated myotubes. Compared to wild-type MyoD, the VP64-MyoD fusion protein induced greater overall reprogramming of global gene expression. This simple approach for increasing the potency of natural reprogramming factors circumvents the need for screening engineered proteins and leads to a more robust cellular reprogramming compared to treatment with the wild type transcription factor.
2014-12-11 | GSE62448 | GEO
Project description:Our current understanding of cellular transdifferentiation systems is limited. It is oftentimes unknown, at a genome-wide scale, how much transdifferentiated cells differ quantitatively from both the starting cells and the target cells. Focusing on transdifferentiation of primary human skin fibroblasts by forced expression of myogenic transcription factor MyoD, we performed quantitative analyses of gene expression and chromatin accessibility profiles of transdifferentiated cells compared to fibroblasts and myoblasts. In this system, we find that while many of the early muscle marker genes are reprogrammed, global gene expression and accessibility changes are still incomplete when compared to myoblasts. In addition, we find evidence of epigenetic memory in the transdifferentiated cells, with reminiscent features of fibroblasts being visible both in chromatin accessibility and gene expression. Quantitative analyses revealed a continuum of changes in chromatin accessibility induced by MyoD, and a strong correlation between chromatin-remodeling deficiencies and incomplete gene expression reprogramming. Classification analyses identified genetic and epigenetic features that distinguish reprogrammed from non-reprogrammed sites, and suggested ways to potentially improve transdifferentiation efficiency. Our approach for combining gene expression, DNA accessibility, and protein-DNA binding data to quantify and characterize the efficiency of cellular transdifferentiation on a genome-wide scale can be applied to any transdifferentiation system.
| S-EPMC5714206 | biostudies-literature
Project description:The presence of tetraplex structures in the promoter region of the myogenic differentiation 1 gene (MyoD1) was investigated with a specific tetraplex-binding porphyrin (TMPyP4), to test its influence on the expression of MyoD1 itself and downstream-regulated genes during myogenic differentiation. TMPyP4-exposed C2C12 myoblasts, blocking MyoD1 transcription, proliferated reaching confluence and fused forming elongated structures, resembling myotubes, devoid of myosin heavy chain 3 (MHC) expression. Besides lack of MHC, upon MyoD1 inhibition, other myogenic gene expressions were also affected in treated cells, while untreated control cell culture showed normal myotube formation expressing MyoD1, Myog, MRF4, Myf5, and MHC. Unexpectedly, the myomaker (Mymk) gene expression was not affected upon TMPyP4 exposure during C2C12 myogenic differentiation. At the genomic level, the bioinformatic comparison of putative tetraplex sites found that three tetraplexes in MyoD1 and Myog are highly conserved in mammals, while Mymk and MHC did not show any conserved tetraplexes in the analysed regions. Thus, here, we report for the first time that the inhibition of the MyoD1 promoter function, stabilizing the tetraplex region, affects downstream myogenic genes by blocking their expression, while leaving the expression of Mymk unaltered. These results reveal the existence of two distinct pathways: one leading to cell fusion and one guaranteeing correct myotube differentiation.
| S-EPMC5964432 | biostudies-literature
Project description:A major difficulty of producing induced pluripotent stem cells (iPSCs) has been the low efficiency of reprogramming differentiated cells into pluripotent cells. We previously showed that 5% of mouse embryonic fibroblasts (MEFs) were reprogrammed into iPSCs when they were transduced with a fusion gene composed of Oct4 and the transactivation domain of MyoD (called M(3)O), along with Sox2, Klf4 and c-Myc (SKM). In addition, M(3)O facilitated chromatin remodeling of pluripotency genes in the majority of transduced MEFs, including cells that did not become iPSCs. These observations suggested the possibility that more than 5% of cells had acquired the ability to become iPSCs given more favorable culture conditions. Here, we raised the efficiency of making mouse iPSCs with M(3)O-SKM to 26% by culturing transduced cells at low density in serum-free culture medium. In contrast, the efficiency increased from 0.1% to only 2% with the combination of wild-type Oct4 and SKM (OSKM) under the same culture condition. For human iPSCs, M(3)O-SKM achieved 7% efficiency under a similar serum-free culture condition, in comparison to 1% efficiency with OSKM. This study highlights the power of combining the transactivation domain of MyoD with a favorable culture environment.
| S-EPMC3316619 | biostudies-literature
Project description:The generation of myotubes from fibroblasts upon forced MyoD expression is a classic example of transcription factor-induced reprogramming. We recently discovered that additional modulation of signaling pathways with small molecules facilitates reprogramming to more primitive induced myogenic progenitor cells (iMPCs). Here, we dissected the transcriptional and epigenetic dynamics of mouse fibroblasts undergoing reprogramming to either myotubes or iMPCs using a MyoD-inducible transgenic model. Induction of MyoD in fibroblasts combined with small molecules generated Pax7+ iMPCs with high similarity to primary muscle stem cells. Analysis of intermediate stages of iMPC induction revealed that extinction of the fibroblast program preceded induction of the stem cell program. Moreover, key stem cell genes gained chromatin accessibility prior to their transcriptional activation, and these regions exhibited a marked loss of DNA methylation dependent on the Tet enzymes. In contrast, myotube generation was associated with few methylation changes, incomplete and unstable reprogramming, and an insensitivity to Tet depletion. Finally, we showed that MyoD's ability to bind to unique bHLH targets was crucial for generating iMPCs but dispensable for generating myotubes. Collectively, our analyses elucidate the role of MyoD in myogenic reprogramming and derive general principles by which transcription factors and signaling pathways cooperate to rewire cell identity.
| S-EPMC8415322 | biostudies-literature
Project description:Background and purposeThe bioflavonoid, hesperedin, promotes osteoblast differentiation in human mesenchymal stem cells, indicating an anabolic effect of hesperedin on bone metabolism. Murine bone marrow mesenchymal stem cells undergo myogenic differentiation as well as osteogenic differentiation. We therefore explored whether hesperedin modulates muscle cell differentiation.Experimental approachMyoblast C2C12 cells were differentiated into muscle cells in the presence or absence of hesperedin. The effects of hesperedin on myogenic differentiation were determined by analysing specific muscle markers in vitro using reporter gene assays, immunoblotting, RT-PCR and DNA pull-down assays. In vivo, the effects of hesperedin were assessed using the freeze injury-induced muscle regeneration model in mice and daily injections of hesperedin for 6 days.Key resultsHesperedin promoted myogenic differentiation, in a dose-dependent manner, by increasing myogenin gene expression. MyoD-induced myogenin gene transcription was enhanced by hesperedin, as this bioflavonoid augmented the nuclear localization and myogenin promoter-binding of MyoD. In addition, hesperedin increased myogenin and muscle creatine kinase gene expression during myogenic differentiation from C3H10T1/2 mesenchymal stem cells in a MyoD-dependent manner and accelerated in vivo muscle regeneration induced by muscle injury.Conclusions and implicationsOur results demonstrate that hesperedin promoted myogenic differentiation in vitro and in vivo through activation of MyoD-mediated myogenin expression, suggesting a beneficial role in promoting muscle regeneration, following injury.
| S-EPMC3101621 | biostudies-literature
Project description:Induced pluripotent stem cells (iPSCs) can be created by reprogramming differentiated cells through introduction of defined genes, most commonly Oct4, Sox2, Klf4, and c-Myc (OSKM). However, this process is slow and extremely inefficient. Here, we demonstrate radical acceleration of iPSC creation with a fusion gene between Oct4 and the powerful transactivation domain (TAD) of MyoD (M(3)O). Transduction of M(3) O as well as Sox2, Klf4, and c-Myc into fibroblasts effectively remodeled patterns of DNA methylation, chromatin accessibility, histone modifications, and protein binding at pluripotency genes, raising the efficiency of making mouse and human iPSCs more than 50-fold in comparison to OSKM. These results identified that one of the most critical barriers to iPSC creation is poor chromatin accessibility and protein recruitment to pluripotency genes. The MyoD TAD has a capability of overcoming this problem. Our approach of fusing TADs to unrelated transcription factors has far-reaching implications as a powerful tool for transcriptional reprogramming beyond application to iPSC technology.
| S-EPMC3431196 | biostudies-literature
Project description:AimsFibroblasts can be directly reprogrammed to cardiomyocyte-like cells by introducing defined genes. However, the reprogramming efficiency remains low, delaying the clinical application of this strategy to regenerative cardiology. We previously showed that fusion of the MyoD transactivation domain to the pluripotency transcription factor Oct4 facilitated the transcriptional activity of Oct4, resulting in highly efficient production of induced pluripotent stem cells. We examined whether the same approach can be applied to cardiac transcription factors to facilitate cardiac reprogramming.Methods and resultsWe fused the MyoD domain to Mef2c, Gata4, Hand2, and Tbx5 and transduced these genes in various combinations into mouse non-cardiac fibroblasts. Transduction of the chimeric Mef2c with the wild-types of the other three genes produced much larger beating clusters of cardiomyocyte-like cells faster than the combination of the four wild-type genes, with an efficiency of 3.5%, >15-fold greater than the wild-type genes.ConclusionFusion of a powerful transactivation domain to heterologous factors can increase the efficiency of direct reprogramming of fibroblasts to cardiomyocytes.
| S-EPMC3778960 | biostudies-literature
Project description:Skeletal myogenesis is associated with the activation of four muscle regulatory factors (MRFs): Myf5, MyoD, Myogenin and MRF4. Here we report that p38 mitogen-activated protein kinase represses the transcriptional activity of MRF4 (involved in late stages of myogenesis), resulting in downregulation of specific muscle genes. MRF4 is phosphorylated in vitro and in vivo by p38 on two serines (Ser31 and Ser42) located in the N-terminal transactivation domain, resulting in reduced MRF4-mediated transcriptional activity. In contrast, nonphosphorylatable MRF4 mutants display increased transcriptional activity and are able to advance both myoblast fusion and differentiation. We also show that expression of desmin and alpha-actin, but not muscle creatin kinase, decreased at late stages of muscle differentiation, correlating with the induction of MRF4 and p38 activation. Accordingly, inhibition of p38 during late myogenesis results in the upregulation of both desmin and alpha-actin. We propose that repression of MRF4 activity by p38 phosphorylation may represent a new mechanism for the silencing of specific muscle genes at the terminal stages of muscle differentiation.
| S-EPMC1271762 | biostudies-literature