Western blot showing strong dystrophin (Dp427) downregulation in myotubes treated with siRNA targeting dystrophin (D2). The samples were obtained directly from those used for gene expression arrays. Untr.: Untreated myotubes. GL2: Myotubes treated with siRNA targeting firefly luciferase. D2: Myotubes treated with an optimal siRNA targeting dystrophin (referred to as D2 in a previous study ). mdx: Myotubes prepared from muscles from mdx mice. Nedd-4: loading control.