Spine-tingling new role for Sall4

Wnt, Fgf and retinoic acid signalling play a key role in patterning the posterior neural plate to form the midbrain, hindbrain and spinal cord. Despite intense study of Wnt signalling and neural patterning, only a few target transcription factors that mediate spinal cord development have been identified and the mechanism remains unclear. In this issue (p. 1683), Richard Harland and colleagues reveal a role for Spalt-like 4 (Sall4) in promoting the differentiation of neural progenitor cells in Xenopus via the repression of pou5f3 (oct4). Morpholino-induced knockdown of Sall4 results in defects in neural tube closure and neural differentiation in the embryo, while morpholino injection at the 4-cell stage reduces expression of spinal cord markers hoxb9, hoxc10 and hoxd10 without affecting pan-neuronal identity. The authors find that when Sall4 activity is disrupted, expression of pou5f3 increases, while overexpression of pou5f3 disrupts the expression of key spinal cord identity genes. These data uncover a novel role for Sall4 in neural patterning, with a specific role in spinal cord differentiation.