DUX4 and Facioscapulohumeral dystrophy: 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.