Fig. 5. Inhibition of macho-1 function is enough to allow endoderm formation in the absence of cell interaction. (A-D) B4.1 blastomeres were isolated from eight-cell embryos and cultured as partial embryos. Embryos were treated with DMSO as controls. Expression of ALP and myosin was detected to monitor the formation of endoderm and muscle cells. (E-H) The partial embryos were treated with a MEK inhibitor, U0126, to inhibit MEK-MAPK signaling. In F, every constituent cell expressed myosin. (A,B,E,F) Control morpholino antisense oligonucleotide (MO) was injected into fertilized eggs. (C,D,G,H) Antisense MO complementary to macho-1 mRNA was injected to inhibit macho-1 translation. Slight staining in D and H is background caused by mitochondria. Muscle formation was totally suppressed. In G, ALP expression is visible even when embryos were treated with MEK inhibitor. Scale bar: 100 µm.

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