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

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. Fibroblast cells were transduced with a vector carrying human MyoD gene and induced by tetracycline for expression. Dnase-seq, ChIP-seq and RNA-seq were used to identify transcription factors binding, differential chromtin structural change, and differential expression at on-target and off-target sites.