We used the 9A12 mouse monoclonal anti-DUX4 antibody [7] and also produced mouse and rabbit monoclonal antibodies to the amino-terminal and carboxyterminal portion of the DUX4 protein [10], but were unable to detect DUX4 protein in western analysis of FSHD muscle cultures, consistent with the very low amounts of DUX4 mRNA. Here, DUX4 is linked to facioscapulohumeral muscular dystrophy.