The present invention relates to compositions and methods for expressing mini-dystrophin peptides. In particular, the present invention provides compositions comprising nucleic acid sequences that are shorter than wild-type dystrophin cDNA and that express mini-dystrophin peptides that function in a similar manner as wild-type dystrophin proteins. The present invention also provides compositions comprising mini-dystrophin peptides, and methods for expressing mini-dystrophin peptides in target cells.