DUXA and facioscapulohumeral muscular dystrophy: Single-nucleus RNA-seq demonstrated the heterogeniety and disease-specific transcriptomic changes of patient myotube nuclei with high or low expression of DUX4 and FSHD-induced genes.Our results provide strong evidence that DUX4 transcript expression in one or two nuclei can result in a high expression of downstream target genes in the entire myotube, which may be mediated by DUX4 protein spreading to multiple nuclei as well as signal amplification by downstream target transcription factors, such as DUXA.