ACTIVIN INDUCES THE EXPRESSION OF THE XENOPUS HOMOLOG OF SONIC HEDGEHOG DURING MESODERM FORMATION IN XENOPUS EXPLANTS

The Xenopus homologue of sonic hedgehog (Xhh) was detected in Xenopus embryos at stages 13 and 31 by RT-PCR, but it was not expressed in exp lants isolated from the animal hemisphere of Xenopus embryos at stage 8-9. Treatment of the animal cap with activin (1-100 ng/ml) induced th e expression of Xhh. However, it was not induced by 100 ng/ml basic fi broblast growth factor (bFGF). Whole mount in situ hybridization confi rmed the expression of Xhh in the animal cap treated with activin. The expression of Xhh induced by activin was not inhibited in the presenc e of cycloheximide, suggesting that Xhh is an early response gene indu ced by activin. (C) 1995 Academic Press, Inc.