The unique function of Runx1 in skeletal muscle differentiation and regeneration is mediated by an ETS interaction domain

Abstract

AbstractThe conserved Runt-related (RUNX) transcription factor family are well-known master regulators of developmental and regenerative processes.Runx1andRunx2are both expressed in satellite cells (SC) and skeletal myotubes. Conditional deletion ofRunx1in adult SC negatively impacted self-renewal and impaired skeletal muscle maintenance.Runx1-deficient SC retainRunx2expression but cannot support muscle regeneration in response to injury. To determine the unique molecular functions of Runx1 that cannot be compensated by Runx2 we deletedRunx1in C2C12 that retainRunx2expression and established that myoblasts differentiation was blockedin vitrodue in part to ectopic expression ofMef2c,a target repressed byRunx1. 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 fromRunx1(T-cells, muscle) versusRunx2(preosteoblasts) dependent tissue identified enrichment for a Ets:Runx composite site inRunx1-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 ofRunx1.