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Fig. 3. Noggin + FGF generates neural tissue with anterior-posterior polarity. Ectoderm from stage 10.25 embryos was treated with increasing
doses of bFGF (2 ng/ml, 10 ng/ml, 50 ng/ml) either in the absence (A-C) or presence (D-F) of 1 mg/ml noggin. Explants were cultured until
control whole embryos (G) reached the late neurula stage (stage 18). Expression of otx2 and Hox B9 were analyzed by in situ hybridization.
Otx2 (light blue) is expressed at the anterior end, and Hox B9 (purple) is expressed at the posterior end of the control embryo (G; the dark color
at the anterior end is an effect of the embryo edge, and is not Hox B9 staining). Increasing bFGF dose increases Hox B9 expression (A-C). In
the presence of noggin, increasing bFGF dose(D-F) causes the explants to elongate and to express otx2 and Hox B9 on either end of the
elongated structure. Expression of a general neural marker, nrp-1 (purple) and muscle actin (blue) was examined in whole embryos (H) and in
explants treated with 1 mg/ml noggin (I), 50 ng/ml bFGF (J), and the combination of 1 mg/ml noggin and 50 ng/ml bFGF (K). Noggin alone
induces nrp-1 expression, bFGF alone induces both muscle actin and nrp-1, and the combination of the two induces only nrp-1, no muscle actin
expression is observed. |
