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Incomplete MyoD-induced transdifferentiation is mediated by chromatin remodeling deficiencies [RNA-Seq]

ABSTRACT: MyoD is known to transdifferentiate fibroblasts into muscle-like cells. Despite phenotypic resemblance and expression of myogenic marker genes in transdifferentiated cells, our global gene expression data suggests that ~100 genes, many involved in muscle development and function, remain non-reprogrammed. To understand this incomplete reprogramming, we characterized genome-wide chromatin accessibility and MyoD binding in human primary myoblasts and in MyoD-induced skin fibroblast cells. Our analyses revealed thousands of sites with incomplete chromatin reprogramming.Combined analyses of gene expression and epigenetic profiles revealed that many myogenic genes not upregulated during the transdifferentiation process have undergone MyoD-dependent chromatin remodeling, but to a significantly lower extent than reprogrammed genes. Our findings suggest that incomplete MyoD-induced transdifferentiation is due to chromatin-remodeling deficiencies, and that additional factors are required to transdifferentiate cells into a state more similar to myoblasts.

ORGANISM(S): Homo sapiens

PROVIDER: GSE93263 | GEO | 2017/01/07

SECONDARY ACCESSION(S): PRJNA360449

REPOSITORIES: GEO

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Project description:Background: Similar to replicating myoblasts, many rhabdomyosarcoma cells express the myogenic determination gene MyoD. In contrast to myoblasts, rhabdomyosarcoma cells do not make the transition from a regulative growth phase to terminal differentiation. Previously we demonstrated that the forced expression of MyoD with its E-protein dimerization partner was sufficient to induce differentiation and suppress multiple growth-promoting genes, suggesting that the dimer was targeting a switch that regulated the transition from growth to differentiation. Our data also suggested that a balance existed between various inhibitory transcription factors and MyoD activity that kept rhabdomyosarcomas trapped in a proliferative state. Methods: Potential myogenic co-factors identified by analysis of high-throughput sequencing of chromatin immunoprecipitation experiments in normal myogenic cells were tested for their ability to drive differentiation in rhabdomyosarcoma cell culture models, and their relation to MyoD activity determined through molecular biological experiments. Results: Modulation of the transcription factors RUNX1 and ZNF238, factors with poorly delineated roles in myogenic development, can induce differentiation in rhabdomyosarcoma cells and their activity is integrated, at least in part, through the activation of miR-206, which acts as a genetic switch to transition the cell from a proliferative growth phase to differentiation. The inhibitory transcription factor MSC also plays a role in controlling miR-206, appearing to function by occluding a binding site for MyoD in the miR-206 promoter. Conclusions: These findings suggest that nested feed-forward circuits that proceed from MyoD, to RUNX1, to ZNF238, and finally to miR-206 function in both rhabdomyosarcomas as well as normal myogenesis to control the decision point of proliferation versus differentiation. Total RNA samples were collected from human RD cells transduced with lentivirus carrying RUNX1, RP58 (ZNF238), miR-206 or GFP (three biological replicates each) and allowed to differentiate for 72 hours.