Figure 1.
The MEF3 motif is crucial for myogenin promoter activation during embryogenesis. One mouse founder embryo carrying the nls-β-galactosidase reporter under the control of a wild-type myogenin −184 promoter (a) and one F1 transgenic mouse carrying the β-galactosidase reporter under the control of a mutated MEF3 myogenin −184 promoter (b) were sacrificed at E11.5. At E11.5 the control transgene (a) gives a β-galactosidase activity in the limbs and in the jaws muscles (arrow heads), which is not observed with the mutated promoter. The transgenic mouse harboring the −184mutMEF3 transgene (b) was one of those with a faint expression of the transgene in a small stripe of cells in the myotomes and an additional stripe of cells in the lateral part of the myotome between fore and hind limbs. The ectopic expression in the brain was not reproduced in other independent transgenic lines.