The Unique Function of Runx1 in Skeletal Muscle Differentiation and Regeneration is Mediated by an ETS Interaction Domain (RNA-Seq)
The conserved Runt-related (RUNX) transcription factor family are well-known master regulators of developmental and regenerative processes. Both Runx1 and Runx2 are expressed in satellite cells (SC) and skeletal myotubes. Conditional deletion of Runx1 in adult SC negatively impacted self-renewal, and skeletal muscle maintenance was impaired; Runx1-deficient SC cannot support muscle regeneration in response to injury. To determine the unique molecular functions of Runx1 that cannot be compensated by Runx2 we deleted Runx1 in C2C12 that retain Runx2 expression and established that myoblasts differentiation was blocked in vitro due in part to ectopic expression of Mef2c, a target repressed by Runx1. Structure-function analysis demonstrated that the Ets-interacting MID/EID region of Runx1 absent from Runx2 is critical to regulating myoblasts proliferation, differentiation, and fusion. Analysis of in-house and published ChIP-seq datasets from Runx1 (T-cells, muscle) versus Runx2 (preosteoblasts) dependent tissue identified enrichment for a Ets:Runx composite site in Runx1-dependent tissues. Comparing ATACseq datasets from WT and Runx1KO C2C12 cells showed that the Ets:Runx composite motif was enriched in peaks open exclusively in WT cells compared to peaks unique to Runx1KO cells. Thus, engagement of a set of targets by the RUNX1/ETS complex define the non-redundant functions of Runx1 Overall design: RNA was collected from control and Runx1KO C2C12 cells in triplicate in growth media (20% FBS) or during differentiation in low serum (2% horse serum) media at 1 day , 3 days or 5 days. Differential gene expression was determined comparing control vs Runx1KO in growth media or at each timepoint. Additionally, gene expression during differentiation was determined by comparing gene expression of the timepoint versus growth media.