MLC3 regulatory elements are transcriptionally active in chicken skeletal muscle but not cardiac muscle primary cultures. Cardiac (A, A') and skeletal (B, B') muscle chick primary cultures were co-transfected with the MLC3 lentiviral construct and a CAG-GFP reporter construct. Three independent experiments were carried out and a representative field is shown. A, B: GFP fluorescence A'B': X-gal staining of primary cultures. Large myotubes are stained in B'.