Fig. 1. lame duck (lmd) mutant embryos exhibit severe defects within the somatic muscle lineage. Wild-type and mutant embryos (trans-heterozygous for lmd¹ and Df(3R)M95A)were stained with an antibody against MEF2 (A-D) or MHC (E-H). (A,B) Lateral views of stage 13 embryos. When compared with control embryo (A), mutant embryo shows a dramatic reduction in MEF2 expression in somatic mesodermal cells. (C,D) Dorsal views of stage 16 embryos with normal MEF2 expression in cardioblasts (cb; arrowheads) but a reduced number of MEF2-positive somatic muscle nuclei (arrows in D). (E,F) Multinucleate MHC-positive fibers are present in late stage 15 control embryo (E) while only elongated, mononucleate MHC-expressing muscle cells are detected in mutant embryo (arrows in F). (G,H) MHC expression in cardioblasts and gut muscles is normal.