Indeed, DUX4 may typically be present in only a small percentage (0.1%–0.01%) of myonuclei from FSHD patient cell lines (Snider et al. 2010), and this relative scarcity has posed challenges for detecting DUX4 messenger RNA or DUX4 protein reliably using methods like PCR, western blotting or immunohistochemistry in vivo. This evidence concerns the gene DUX4 and facioscapulohumeral muscular dystrophy.