Fig. 8. Inactivation of the Mef2c skeletal muscle enhancer by individual mutations in the MEF2 binding site and E-box. Mutations of the (A-C) MEF2 site (MEF2 mut) and (D-F) E-box (E-box mut), shown in Fig. 7B, were introduced individually in the context of the nucleotide region from -512 bp to +41 bp fused to hsp68-lacZ and F₀ transgenic embryos were generated. Embryos were analyzed for ß-galactosidase expression at E9.5 (A,B,D,E) and E11.5 (C,F). (B,E) Enlargements of the regions indicated by the boxes in A,D, respectively. (A,B) Only the MEF2 mut-hsp68-lacZ construct was weakly active in somites at E9.5. Constructs were inactive at all other time points. Arrows, somitic expression.