Activating and repressing signals in head development: The role of Xotx1 and Xotx2

Massimiliano Andreazzoli, Maria Pannese, Edoardo Boncinelli

Research output: Contribution to journalArticlepeer-review


Xotx1 and Xotx2 are two Xenopus homologues of the Drosophila orthodenticle gene that are specifically expressed in presumptive head regions that do not undergo convergent extension movements during gastrulation. We studied the function of Xotx1 and compared it with that of Xotx2. Ectopic expression of each of the two genes has similar effects in impairing trunk and tail development. Experimental evidence suggests that posterior deficiencies observed in microinjected embryos are due to negative interference with convergent extension movements. Transplantations of putative tail-forming regions showed that, while Xotx1 overexpression inhibits tail organizer activity, Xotx2 overexpression is able to turn a tail organizer into a head organizer. Finally, Xotx1 and Xotx2 are activated by factors involved in head formation and repressed by a posteriorizing signal like retinoic acid. Taken together, these data suggest that Xotx genes are involved in head-organizing activity, They also suggest that the head organizer may act not only stimulating the formation of anterior regions, but also repressing the formation of posterior structures.

Original languageEnglish
Pages (from-to)1733-1743
Number of pages11
Issue number9
Publication statusPublished - May 1997


  • Convergent extension
  • Head organizer
  • Homeobox
  • Otx1
  • Otx2
  • Tail organizer
  • Xenopus laevis

ASJC Scopus subject areas

  • Anatomy
  • Cell Biology


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