During myogenesis, transcriptional activities of two major myogenic factors, MyoD and myocyte enhancer factor 2 (Mef2) are regulated by histone modifications that switch on and off the target genes. However, the transition mechanism from repression to activation modes of histones has not been defined. Here we identify that lysine specific demethylase 1, (LSD1) is responsible for removing the repressive histone codes during C2C12 mouse myoblast differentiation. The potent role of LSD1 is suggested by the increment of its expression level during myogenic differentiation. Moreover, by performing co-immunoprecipitation and ChIP assay, physically interaction of LSD1 with MyoD and Mef2 on the target promoters was identified. Their interactions were resulted in upregulation of the transcription activities shown with increased luciferase activity. Interruption of demethylase activity of LSD1 using shRNA or chemical inhibitor, pargyline, treatment led to aberrant histone codes on myogenic promoters during skeletal muscle differentiation. We also demonstrate that inhibition of LSD1 impairs C2C12 mouse myoblast differentiation. Our results show for the first time the regulatory mechanism of myogenesis involving histone demethylase. Altogether, the present study suggests a de-repression model and expands the understanding on the dynamic regulation of chromatin during myogenesis. (C) 2010 Elsevier Inc. All rights reserved.