1) Identify the regulatory sequences responsible for the fiber type-specific expression of muscle genes by progressive deletions and site directed mutagenesis. Constructs containing portions of the 5' flanking regions of a gene expressed in slow muscle fibers, (the myosin light chain 2 slow/ventricular gene), and a gene expressed in fast fibers (the MyHC-2X gene), will be linked to reporter genes and used for direct injection of plasmid DNA into fast and slow regenerating skeletal muscles that will be subsequently analyzed.
2)Determine the capacity of skeletal muscle to produce and deliver systemically recombinant serum factors. Appropriate promoter/enhancer combinations are essential for a successful gene therapy. The information obtained from 1) will be used to determine the role of muscle-specific regulatory sequences (alone or with viral promoters/enhancers), in driving the expression of the rat growth hormone gene. This gene will be transfered into muscles of hypophysectomized rats and blood levels of GH and its effects on body growth will be determined.