Determination of gene promoter activity in skeletal muscles in vivo

The use of nonviral (plasmid DNA) gene delivery into skeletal muscle has increased significantly in recent years. The procedure is used to overexpress wild-type proteins, express mutant proteins, or knock down endogenous proteins. These manipulations can identify the role of a specific protein in muscle cell biology and physiology. The same procedure of plasmid DNA gene delivery can be used to introduce a gene promoter reporter construct. Such constructs contain a defined sequence of a gene promoter that regulates the expression of a "reporter." This reporter is easily measured and reflects the in vivo transcriptional activity of the gene promoter sequence under study. The gene promoter can be mutated at known transcription factor-binding sites, truncated to identify specific regions of the gene promoter that are required for transcription, or introduced into skeletal muscle with an expression plasmid for a protein believed to regulate the gene's transcription. Therefore, the use of such gene promoter reporters allows for an in-depth physiological assessment of the gene's transcriptional regulation.