Analysis of the spatial, temporal and tissue-specific transcription of gamma-sarcoglycan gene using a transgenic mouse.

To evaluate the promoter function of the 5'-flanking sequence of mouse gamma-sarcoglycan (gamma-SG) gene in vivo, we generated transgenic mice harboring this sequence fused with enhanced green fluorescent protein reporter gene. The reporter expression was restricted in striated muscles and particularly strong in all myofibers in skeletal muscles. Using these mice, we examine the spatial and temporal transcriptional patterns of the gamma-SG gene during mouse skeletal muscle development. The expression of basic helix loop helix transcriptional factors preceded that of the reporter. Differences between the expression of reporter and endogenous gamma-SG genes in non-muscle tissues suggested the existence of additional promoter elements in the endogenous gene, and the analysis of endogenous mRNAs demonstrated the existence of a novel upstream exon and promoter active in non-muscle tissues.