Roles of Sox factors in neural determination: conserved signaling in evolution?

Neural differentiation in amphibian embryos is initiated by the neural indu cers emanating from the Spemann-Mangold organizer. The fate of uncommitted ectoderm is determined by graded BMP activity along the dorsal-ventral axis . Several transcriptional regulators acting in early neural differentiation have been identified, including Sox, Zic, Pou, HLH and Fox factors. In thi s paper, I review recent molecular studies on neural determination, focusin g mainly on Sox factors. I also discuss the possible conservation of regula tory factors in neural differentiation, comparing Xenopus and Drosophila co unterparts.