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Fig. 4. SCL expression responds to BMP-4 signaling. (a) BMP-4 induces SCL expression in primitive ectoderm. Embryos were injected with BMP-4 mRNA (1 ng per embryo in the animal pole region). Animal pole explants were removed at stage 8 and treated with soluble growth factors (activin at 100 pM (Genentech); human basic FGF at 50 ng/ml; Gibco BRL) and cultured to mid-neurula stage (stage 19). Sibling whole embryo was used as a positive control. Whole embryo −RT (without reverse transcriptase) was used as a negative control. SCL and EF-1α sequences were amplified from first strand cDNA, separated on polyacrylamide gels and visualized by autoradiography. (b) Ectopic expression for BMP-4 or Mix.1 induces SCL expression in the whole embryo. Embryos were injected with either BMP-4 or Mix.1 mRNA (500 pg per blastomere at the two cell stage) and cultured to sibling tailbud stage. SCL expression was assayed by whole-mount in situ hybridization. Expression of either BMP-4 or Mix.1 caused ventralization and increased expression of SCL. |
