Fig. 4. Effects of inhibiting MAP Kinase function on the gene expression program of the PMCs. Embryos were placed into MFSW containing DMSO (control) or 10 µM U0126 starting at the two-cell stage. After fixation at the desired stage, in situ hybridization was then performed with the following probes ets1 (A-F), alx1 (G-L), skeT (M-R) and msp130 (S-X). Control embryos on the left, U0126-treated embryos on the right of the figure. These experiments were repeated several times with different batches of embryos. Representative embryos are shown. U0126 treatment reduces the level of alx1, skeT and msp130 transcripts. Expression of ets1 remains unaffected by the treatment. HB, hatching blastula; lB, late blastula; mB, mesenchyme blastula; eG, early gastrula; lG, late gastrula; vv, vegetal view; ov, oral view.