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Review

Morphogens and the Control of Cell Proliferation and Patterning in the Spinal Cord

Fausto Ulloa and James Briscoe

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The development of animal embryos depends on accurate coordination of the growth and specification of precursor cells. Morphogens, extracellular signals that act at a distance to control cell fate, are crucial in the patterning of embryonic tissues. One of the most extensively studied examples of a morphogen patterned tissue is the developing vertebrate spinal cord. The distribution of distinct neuronal subtypes along the dorsoventral (DV) axis of the spinal cord is determined by counteracting gradients of long-range signals. Wnt and BMP signals promote dorsal identities, while Shh signaling induces ventral identities. Simultaneous to their specification, neural progenitors proliferate, facilitating the growth of the neural tube. In this review we discuss evidence indicating that the signals governing progenitor specification also control proliferation and survival of progenitor cells. Moreover, evidence of reciprocal transcriptional interactions and cross-talk between the signaling pathways has emerged from recent studies. Together these studies suggest ways in which patterning and growth may be coordinated in the spinal cord. One level of interaction is an inhibitory regulation of repressor forms of the transcription factor Gli3—generated in the absence of Shh—on β-catenin activity, the transcription factor activated by Wnt signaling. This interaction may also be relevant in other tissues and situations in which the two signaling pathways are known to participate.

Authors

Fausto Ulloa

Institut d’ Investigaciò Médica Parc de Recerca Biomedica; Barcelona, Spain

James Briscoe

National Institute for Medical Research; Mill Hill, London UK

Purchase article for $19

Subscribe to this journal for $129/year