| Abstract: | Erythropoietin (EPO), the cytokine required for erythrocyte production, contributes to muscle progenitor cell proliferation and delay myogenic differentiation. However, the underlying mechanism is not yet fully understood. Here, we report that EPO changes the skeletal myogenic regulatory factor expression program and delays differentiation via induction of GATA-4 and the basic helix-loop-helix TAL1 and that knockdown of both factors promotes differentiation. EPO increases the Sirt1 level, a NAD(+)-dependent deacetylase, and also induces the NAD(+)/NADH ratio that further increases Sirt1 activity. Sirt1 knockdown reduced GATA-4 and TAL1 expression, impaired EPO effect on delayed myogenic differentiation, and the Sirt1 knockdown effect was abrogated when combined with overexpression of GATA-4 or TAL1. GATA-4 interacts with Sirt1 and targets Sirt1 to the myogenin promoter and represses myogenin expression, whereas TAL1 inhibits myogenin expression by decreasing MyoD binding to and activation of the myogenin promoter. Sirt1 was found to bind to the GATA-4 promoter to directly regulate GATA-4 expression and GATA-4 binds to the TAL1 promoter to regulate TAL1 expression positively. These data suggest that GATA-4, TAL1, and Sirt1 cross-talk each other to regulate myogenic differentiation and mediate EPO activity during myogenic differentiation with Sirt1 playing a role upstream of GATA-4 and TAL1. Taken together, our findings reveal a novel role for GATA-4 and TAL1 to affect skeletal myogenic differentiation and EPO response via cross-talk with Sirt1. |
