Xenopus embryonic E2F is required for the formation of ventral and posterior cell fates during early embryogenesis

Using an expression cloning approach, we have unveiled a novel function for the transcription factor E2F. We demonstrate that Xenopus E2F (xE2F) is re quired for patterning of the Xenopus embryonic axis. Overexpression of xE2F in embryos induces ectopic expression of ventral and posterior markers, in cluding selected members of the Hox genes, and suppresses the development o f dorsoanterior structures. Loss of xE2F function in embryos leads to the e limination of ventral and posterior structures. These observations suggest that xE2F acts as an important regulator of region-specific gene expression and in the formation of the embryonic axis. This study provides evidence f or an additional embryonic function for E2F, independent of its well-docume nted role in cell cycle regulation, and suggests a novel mechanism of regio n-specific gene expression during vertebrate embryogenesis.