Induction of tooth and eye by transplantation of activin A-treated, undifferentiated presumptive ectodermal Xenopus cells into the abdomen

Activin A can induce the Xenopus presumptive ectoderm (animal cap) to form different types of mesoderm and endoderm at different concentrations and the animal cap treated with activin can function as an organizer during early development. The dissociated Xenopus animal cap cells treated with activin form an aggregate and it develops into various tissues in vitro. In this study, to induce jaw cartilage from undifferentiated cells effectively, we developed a culture method to manipulate body patterning in vitro, using activin A and dissociated animal cap cells. An aggregate consisting only of activin A-treated dissociated cells developed into endodermal tissues. However, when activin A-treated cells were mixed with untreated cells at a ratio of 1:5, the aggregate developed cartilage with the maxillofacial regional marker genes, goosecoid, Xenopus Distal-less 4 and X-Hoxa2. When this aggregate was transplanted into the abdominal region of host embryos, maxillofacial structures containing cartilage and eye developed. We raised these embryos to adulthood and found that tooth germ had developed in the transplanted tissue. Here, we show the induction of jaw cartilage, tooth germ and eye structures from animal caps using activin A in the aggregation culture method. This differentiation system will help to promote a better understanding of the regulating mechanisms of body patterning and tooth induction in vertebrates.