ABSTRACT
We have previously shown that the inhibition of fibroblast growth factor (FGF) signaling induced endodermal gene expression in the animal cap and caused the expansion of the endodermal mass in Xenopus embryos. However, we still do not know whether or not the alteration of FGF signaling controls embryonic cell fate, or when FGF signal blocking is required for endoderm formation in Xenopus. Here, we show that FGF signal blocking in embryonic cells causes their descendants to move into the endodermal region and to express endodermal genes. It is also interesting that blocking FGF signaling between fertilization and embryonic stage 10.5 promotes endoderm formation, but persistent FGF signaling blocking after stage 10.5 restricts endoderm formation and differentiation.
Subject(s)
Animals , Endoderm/drug effects , Fibroblast Growth Factors/antagonists & inhibitors , Gene Expression Regulation, Developmental/drug effects , In Situ Hybridization , Pyrroles/administration & dosage , Receptors, Fibroblast Growth Factor/genetics , Reverse Transcriptase Polymerase Chain Reaction , Signal Transduction/drug effects , Xenopus Proteins/antagonists & inhibitors , Xenopus laevis/embryologyABSTRACT
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.