The role of XBtg2 in Xenopus neural development.

In early neural development, active cell proliferation and apoptosis take place concurrent with cell differentiation, but how these processes are coordinated remains unclear. In this study, we characterized the role of XBtg2 in Xenopus neural development. XBtg2 transcripts were detected at the edge of the anterolateral neural plate and the neural crest region at the midneurula stage, and in eyes and in part of the neural tube at the tailbud stage. Translational inhibition of XBtg2 affected anterior neural development and impaired eye formation. XBtg2 depletion altered the expression patterns of the early neural genes, Zic3 and SoxD, at the midneurula stage, but not at the early neurula stage. At the midneurula stage, XBtg2-depleted embryos exhibited a marked decrease in the expression of anterior neural genes, En2, Otx2, and Rx1, without any changes in neural crest genes, Slug and Snail, or an epidermal gene, XK81. These results suggest that XBtg2 is required for the differentiation of the anterior neural plate from the midneurula stage, but not for the specification of the fate and patterning of the neural plate. XBtg2-depleted embryos also exhibited an increase in both proliferation and apoptosis in the anterior neural plate; however, the altered expression patterns of neural markers were not reversed by inhibition of either the cell cycle or apoptosis. Based on these data, we propose that XBtg2 plays an essential role in the anterior neural development, by regulating neural cell differentiation, and, independently, cell proliferation and survival.