Construction and expression of cardiomyocyte-specific sarcoglycan transgenes. (A) Full-length murine γ-sarcoglycan (γ-sg) or δ-sarcoglycan (δ-sg) cDNA was ligated into a vector containing the 5.6-kb murine α-MHC promoter (15) to create MHG or MHD, respectively. Transgenic mice with the MHG transgene were crossed with γ-sarcoglycan–null (gsg^–/–) mice to generate gsg^–/–/MHG mice. Transgenic mice with the MHD transgene were crossed with δ-sarcoglycan–null (dsg^–/–) mice generating dsg^–/–/MHD mice. pA, polyadenylation signals. (B) Immunoblot of whole heart extracts from normal, gsg^–/–, dsg^–/–, gsg^–/–/MHG, and dsg^–/–/MHD animals at 12 weeks of age using γ-sarcoglycan Ab showed γ-sarcoglycan expression was absent in the hearts of gsg^–/– and dsg^–/– animals, but was restored in transgenic animals. Quantitative Western blot analysis determined the level of γ-sarcoglycan expression in gsg^–/–/MHG animals to be sevenfold above normal. (C) δ-Sarcoglycan expression was restored to normal levels by expression of the MHD transgene in dsg^–/–/MHD hearts. Expression of δ-sarcoglycan from the MHD transgene also resulted in recovery of γ-sarcoglycan to normal levels (last lane). (D) Immunoblots for the remaining sarcoglycan subunits showed that α-sarcoglycan (ASG) expression is recovered in hearts with either γ- or δ-sarcoglycan transgene expression. β-Sarcoglycan protein (BSG) is increased to normal levels, and ζ-sarcoglycan protein (ZSG) levels are not significantly different in transgenic hearts. Loading control is shown for B, C, and D. Coom., Coomassie blue.