Essential role of the transcription factor Ets-2 in Xenopus early development

The fibroblast growth factor (FGF)/MAPK pathway plays an important role in early Xenopus developmental processes, including mesoderm patterning. The activation of the MAPK pathway leads to induction of Xenopus Brachyury (Xbra), which regulates the transcription of downstream mesoderm-specific genes in mesoderm patterning. However, the link between the FGF/MAPK pathway and the induction of Xbra has not been fully understood. Here we present evidence suggesting that Ets-2 is involved in the induction of Xbra and thus in the development of posterior mesoderm during early embryonic development. Overexpression of Ets-2 caused posteriorized embryos and led to the induction of mesoderm in ectodermal explants. Expression of a dominant-negative form of Ets-2 or injection of antisense morpholino oligonucleotides against Ets-2 inhibited the formation of the trunk and tail structures. Overexpression of Ets-2 resulted in the induction of Xbra, and expression of the dominant-negative Ets-2 inhibited FGF- or constitutively active MEK-induced Xbra expression. Moreover, overexpression of Ets-2 up-regulated the transcription from Xbra promoter reporter gene constructs. Ets-2 bound to the Xbra promoter region in vitro. These results taken together indicate that Xenopus Ets-2 plays an essential role in mesoderm patterning, lying between the FGF/MAPK pathway and the Xbra transcription.