Posterior cells of the Xenopus neural plate undergo neurogenesis at the end of gastrulation, whereas cells of the anterior region continue to proliferate and differentiate at a later stage. Unlike posterior neurogenesis,the factors that regulate proliferation and differentiation of the anterior neuroectoderm are poorly understood. Now, on , Andreazzoli and coworkers report that the homeobox gene Xrx1, which functions during eye and anterior brain development, is a crucial regulator of the balance between proliferation and neurogenesis of the anterior neuroectoderm. Activated by chordin and hedgehog signalling, Xrx1 is expressed over the whole anterior neural plate and promotes proliferation by repressing the cell-cycle inhibitor p27Xic1. Xrx1 also activates two anti-neurogenic transcription factors, Xhairy2 and Zic2, and, in so doing, represses several genes associated with neurogenesis.
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