Fig. 5

Loss of Blimp1 activity results in mis-regulation of slow as well as fast muscle genes in the precursors of the slow muscle lineage. (A, B) Expression of slow troponin-c in slow muscles of 24 hpf wild-type embryos. In B, staining in the superficial slow muscle layer is visible (arrow). (C, D) Expression of slow troponin-c is lost in 24 hpf ubo embryos. (E, F) Expression of slow myosin light chain in slow muscles of wild-type 24 hpf embryos. In (F) staining in the superficial slow muscle layer is visible (arrow). (G, H) Expression of slow myosin light chain is lost in 24 hpf ubo embryos. (I) mylz2 is not expressed in the adaxial cells of a 14 hpf wild-type embryo. (J) mylz2 is ectopically expressed in the adaxial cells of a blimp1 morphant embryo (arrowheads, n = 25/25). (K) Fast myosin light chain (green, detected with mAb F310) is normally expressed exclusively in fast muscle precursors in a 16 hpf wild-type embryo (arrow) and is absent from adaxial cells (arrowheads). (L) Fast myosin light chain protein is ectopically expressed at high levels in adaxial cells of a 16 hpf ubo embryo (arrowheads). Expression in fast muscle precursors is indicated (arrow). In K and L, “N” marks the position of the notochord. Panels A, C, E and G depict lateral views; panels B, D, F and H depict transverse sections; panels I–L show dorsal flat mounts. Scale bars = 25 μm. The scale bar in A is applicable for C, E and G, the scale bar in B applies to D, F and H. The scale bar in I is applicable in J and the scale bar in K is applicable in L.