Figure 2.

DUX4 and target expression reveal temporal stages of the transcriptional cascade resulting from DUX4 activation. (A) Four distinct patterns identified by line scan fluorescence intensity analysis suggest that DUX4-activated target expression follows transient asynchronous pulses of DUX4 expression and can persist even after DUX4 is no longer detectable. (B) DUX4 protein originates from sentinel DUX4+ nuclei that do not express DUX4 targets (1), then diffuses to nearby nuclei in the shared cytoplasm of the myotube and activates target genes (2). This momentary expression of DUX4 followed by diffusion results in a gradient of the protein and its targets (3), followed by sustained target expression in nuclei previously exposed to DUX4 (4).