FIGURE 1.

Expression of mouse OSK factors in tadpole muscle leads to GFP loss and cell mass appearance. A, somatic transgenesis in tadpole tail muscle of a GFP-reporter construct ± mouse OSK (200 ng/μl per plasmid). GFP expression was monitored at 3, 7, 14, and 21 dpi, increasing in controls (upper panels) but decreasing at 7 dpi in OSK-injected muscles (lower panels; arrowheads indicate the same myomeric units). Experiments were performed ≥5 times (n >10 for each time point), providing similar results. B, 200-μm-thick slice from OSK muscle at 11 dpi revealing a large, dense cell mass. C, residual GFP-positive fiber (*) near the mass (arrowhead). Scale bars, 500 μm.