ABSTRACT
Our previous results showed that FGF signaling, which is important for the mesoderm and neuroectoderm induction, should be blocked for the endoderm formation in Xenopus. Here, Xenopus embryos were collected according to the two time points of MBT or stage 10.5. FGF signal was blocked with SU5402, chemical inhibitor of FGF signal, in the stage-specific embryos, to understand the role of FGF signal during the endoderm formation in the stage-specific embryos. Embryos subjected with the blocking of FGF signal before stage 10.5 showed the expanded abdominal volume in which endodermal mass was increased about 2 times but abdominal organs were not found. The tissue recombinant experiment showed that mesodermal tissue was necessary for the differentiation of endoderm. Embryos subjected with the blocking of FGF signal after stage 10.5 showed that abdomen was not expanded, the neural tube was opened instead. Our data indicate that blocking of FGF signal before stage 10.5 may be necessary for the endoderm induction and signals from neighboring endoderm tissue and mesoderm are required for the endoderm differentiation.