DUX4 and facioscapulohumeral muscular dystrophy: Specifically, as a first step to develop a new assay for DUX4 detection, we tested custom-made (but now available) RNAscope probes to detect overexpressed DUX4 in transfected HEK293s, and importantly, endogenous DUX4 transcripts in FSHD patient-derived myoblasts.