MYOG and chronic obstructive pulmonary disease: In the group of patients with COPD and preserved muscle mass, the increased expression of Myf5 (proliferation), which is paralleled by a decrease in the expression of Myogenin and MRF4 (differentiation) suggests that the switch between Notch (proliferation) and Wnt (differentiation) signaling pathway is dysfunctional leading to a sustained proliferative state, a finding that is corroborated by a previous study [40].