Self-regulation of the head-inducing properties of the Spemann organizer

Masafumi Inui, Marco Montagner, Danny Ben-Zvi, Graziano Martello, Sandra Soligo, Andrea Manfrin, Mariaceleste Aragona, Elena Enzo, Luca Zacchigna, Francesca Zanconato, Luca Azzolin, Sirio Dupont, Michelangelo Cordenonsi, Stefano Piccolo*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

21 Scopus citations

Abstract

The Spemann organizer stands out from other signaling centers of the embryo because of its broad patterning effects. It defines development along the anteroposterior and dorsoventral axes of the vertebrate body, mainly by secreting antagonists of growth factors. Qualitative models proposed more than a decade ago explain the organizer's region-specific inductions (i.e., head and trunk) as the result of different combinations of antagonists. For example, head induction is mediated by extracellular inhibition of Wnt, BMP, and Nodal ligands. However, little is known about how the levels of these antagonists become harmonized with those of their targets and with the factors initially responsible for germ layers and organizer formation, including Nodal itself. Here we show that key ingredients of the head-organizer development, namely Nodal ligands, Nodal antagonists, and ADMP ligands reciprocally adjust each other's strength and range of activity by a self-regulating network of interlocked feedback and feedforward loops. A key element in this cross-talk is the limited availability of ACVR2a, for which Nodal and ADMP must compete. By trapping Nodal extracellularly, the Nodal antagonists Cerberus and Lefty are permissive for ADMP activity. The system self-regulates because ADMP/ACVR2a/Smad1 signaling in turn represses the expression of the Nodal antagonists, reestablishing the equilibrium. In sum, this work reveals an unprecedented set of interactions operating within the organizer that is critical for embryonic patterning.

Original languageAmerican English
Pages (from-to)15354-15359
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Volume109
Issue number38
DOIs
StatePublished - 18 Sep 2012
Externally publishedYes

Keywords

  • Morphogen gradients
  • Xenopus leavis

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