title: Temporal alteration of dose-dependent response to activin in newt animal-cap explants.
abstract: In this study, we examined the dose-dependent responses of animal-pole cells of the Japanese newt, Cynops pyrrhogaster, to activin. Cynops has a slower developmental rate and a simpler animal cap structure than Xenopus. These features enable temporal differences in animal-cap competence to be identified more easily and relatively sharp dose-response profiles can be obtained without cell dissociation. When Cynops caps were excised at the mid-blastula stage and transcript levels of marker genes were examined at the early gastrula stage, the strongest induction of brachyury occurred at a low activin dose, suggesting that cells can recognize changing concentrations of an inducing signal in the embryo. Furthermore, the time course of brachyury expression revealed that caps from the mid-blastula stage exposed to a high dose of activin maintained a low expression level after induction. This suggests that Cynops animal-pole cells can assess activin concentration in a simple and direct manner. In addition, we found that animal-cap competence significantly changes during the blastula stage. The data presented here suggest that this change does not autonomously occur within animal-pole cells but requires signals that emanate from other germ layers.
authors.affiliation: Graduate School of Human Informatics, Nagoya University, Nagoya 464-01, Japan, , , , , , JP.
authors.forename: Kiyoaki
authors.initials: K
authors.lastname: Sone
authors.affiliation: Radioisotope Research Center, Nagoya University, Nagoya 464-01, Japan, , , , , , JP.
authors.forename: Kazuhito
authors.initials: K
authors.lastname: Takeshima
authors.affiliation: Biohistory Research Hall, Takatsuki, Osaka 569-11, Japan, , , , , , JP.
authors.forename: Tadashi C
authors.initials: TC
authors.lastname: Takahashi
authors.affiliation: Radioisotope Research Center, Nagoya University, Nagoya 464-01, Japan, , , , , , JP.
authors.forename: T
authors.initials: T
authors.lastname: Takabatake
keywords: Activin; Brachyury; Dose-dependent response; Goosecoid; Key words Cynops pyrrhogaster