P24. A mechanism coordinating the establishment of the dorsal–ventral and anterior–posterior axes during early Xenopus embryogenesis

Abstract

The formation of the dorsal–ventral (DV) and anterior–posterior (AP) axes is fundamental to the body plan of animals and regulated by several groups of polypeptide growth factor families including the TGF-β, FGF, and Wnt families. In order to ensure the correct formation of body plan, there must be genetic and developmental mechanisms that link and coordinately regulate the establishment of the DV and AP axes. However, the molecular mechanisms responsible for these interactions remain unclear. Here we demonstrate that the forkhead box transcription factor FoxB1, which is upregulated by the neuralizing factor XOct-25 (Takebayashi-Suzuki et al., Mech. Dev., 2007), plays an essential role for the formation of the DV and AP axes. Overexpression of FoxB1 promotes neural induction and inhibits BMP-dependent epidermal differentiation in ectodermal explants, thereby regulating the DV patterning of the ectoderm. In addition, FoxB1 was also found to promote the formation of posterior neural tissue, and the posteriorizing effects of FoxB1 require Wnt signal activation, indicating that FoxB1 is also involved in AP axis patterning via the Wnt pathway. Loss-of-function analysis of FoxB1 confirmed that FoxB1 regulates the establishment of the DV and AP axes in Xenopus ectoderm. Importantly, we show evidence that FoxB1 functionally interacts with its upstream factor XOct-25 and plays an essential role in induction and/or maintenance of neural tissue. Our results suggest that FoxB1 contributes to a mechanism that fine tunes and leads to the coordinated formation of the DV and AP axes during early development.