Chromatin wide and transcriptome profiling integration uncovers p38a MAPK as a global regulator of skeletal muscle differentiation
BackgroundExtracellular stimuli induce gene expression responses through intracellular signaling mediators. The p38 signaling pathway is a paradigm of the mitogen activated protein kinase (MAPK) family that, although originally identified as stress response mediator, contributes to establishing stem cell differentiation fates. p38a is central for induction of the differentiation fate of the skeletal muscle stem cells (satellite cells) through not fully characterized mechanisms.MethodsTo investigate the global gene transcription program regulated by p38a during satellite cell differentiation (myogenesis) and to specifically address whether this regulation occurs through direct action of p38a on gene promoters, we performed a combination of microarray gene expression and genome wide binding analyses. For experimental robustness, two myogenic cellular systems with genetic and chemical loss of p38a function were used: (1) satellite cells derived from mice with muscle specific deletion of p38a, and (2) the C2C12 murine myoblast cell line cultured in the absence or presence of the p38a/b inhibitor SB203580. Analyses were performed at cell proliferation and early differentiation stages.ResultsWe show that p38a binds to a large set of active promoters during the transition of myoblasts from proliferation to differentiation stages. p38a bound promoters are enriched with binding motifs for several transcription factors, with Sp1, Tcf3/E47, Lef1, FoxO4, MyoD, and NFATc standing out in all experimental conditions. p38a association with chromatin correlates very well with high levels of transcription, in agreement with its classical function as an activator of myogenic differentiation. Interestingly, p38a also associates with genes repressed at the onset of differentiation, thus highlighting the relevance of p38 dependent chromatin regulation for transcriptional activation and repression during myogenesis.ConclusionsThese results uncover p38a association and function on chromatin at novel classes of target genes during skeletal muscle cell differentiation. This is consistent with this MAPK isoform being a transcriptional regulator.
Skeletal Muscle