The Dlk1-Dio3 noncoding RNA cluster coordinately regulates mitochondrial respiration and chromatin structure to establish proper cell state for muscle differentiation

The coordinate regulation of metabolic activity and epigenetics to establish cell state-specific gene expression patterns during lineage progression is among the most important aspects of cell differentiation. Cell states are defined by their epigenetic landscape and have cell state-specific metabolic demands. Defining the regulatory factors involved in the interplay between metabolism and cell state would represent a significant step forward in understanding the genetic circuitry that drives differentiation of progenitor cells into highly specialized cell types for proper tissue formation. Expression levels of the imprinted Dlk1-Dio3 noncoding RNA (ncRNA) mega-cluster have been shown to correlate with distinct metabolic profiles in a variety of progenitor cells, suggesting it functions as a key regulator of metabolism and cell state. Here, we directly demonstrate that the Dlk1-Dio3 ncRNA locus is a central player coordinating mitochondrial metabolic activity and genome-wide epigenetic changes in myoblasts and differentiated myotubes. Stable muscle cell lines were generated harboring two distinct deletions in the proximal promoter region resulting in either greatly upregulated or severely attenuated transcription of the entire mega-cluster of Dlk1-Dio3 ncRNAs. Both mutant lines displayed impaired myotube formation along with perturbed mitochondrial respiration and widespread changes in chromatin accessibility and histone methylation. Global gene expression patterns and pathway analyses indicated a reprogramming of cell state which created a differentiated-like molecular profile in proliferating myoblasts. Our results strongly suggest that the Dlk1-Dio3 ncRNA locus is a nodal regulator coordinating metabolic activity and the epigenome to maintain proper cell state in the myogenic lineage.