The p53 gene is widely expressed in embryo, tissues, and tumors, and its deficiency can rescue embryonic defects in certain genes null embryos. However, it is still poorly understood whether p53 is involved in myoblast and neuronal fate determination during embryogenesis. We established the ES cell clone in which p53 protein was persistently suppressed by stable expression of p53 RNAi, and GFP was expressed in a p53 RNAi transcription-independent manner. With the classical protocol in which the differentiation of ES cells into either neural or muscle cell is specifically modulated by different dosage retinoic acid (RA), we evaluated the function of p53 during myoblast and neuronal commitment. With RA treatment, silencing of p53 by RNAi in ES cells leads to dominant muscle cell production but lack of neuronal cell, indicating that p53 indeed plays a role during muscle and neuronal fate commitment. It thus provides a good model for investigating cross-talk between RA and p53 pathways during myogenesis and neurogenesis from ES cells. (C) 2005 Elsevier Inc. All rights reserved.