The Xcad-2 gene can provide a ventral signal independent of BMP-4

Graciela Pillemer, Ronit Yelin, Michal Epstein, Linda Gont, Yaara Frumkin, Joel K. Yisraeli, Herbert Steinbeisser, Abraham Fainsod*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

29 Scopus citations

Abstract

Patterning of the marginal zone in the Xenopus embryo has been attributed to interactions between dorsal genes expressed in the organizer and ventral-specific genes. In this antagonistic interplay of activities, BMP-4, a gene that is not expressed in the organizer, provides a strong ventralizing signal. The Xenopus caudal type homeobox gene, Xcad-2, which is expressed around the blastopore with a gap over the dorsal lip, was analyzed as part of the ventral signal. Xcad-2 was shown to efficiently repress during early gastrula stages the dorsal genes gsc, Xnot-2, Otx-2, XFKH1 and Xlim-I, while it positively regulates the ventral genes, xvent-1 and Xvent-2, with Xpo exhibiting a strong positive response to Xcad-2 overexpression. Xcad-2 was also capable of inducing BMP-4 expression in the organizer region. Support for a ventralizing role for Xcad-2 was obtained from co-injection experiments with the dominant negative BMP receptor which was used to block BMP-4 signaling. Under lack-of-BMP-signaling conditions Xcad-2 could still regulate dorsal and ventral gene expression and restore normal development, suggesting that it can act downstream of BMP-4 signaling or independently of it. Xcad-2 could also inhibit secondary axis formation and dorsalization induced by the dominant negative BMP receptor. Xcad-2 was also shown to efficiently reverse the dorsalizing effects of LiCl. These results place Xcad-2 as part of the ventralizing gene program which acts during early gastrula stages and can execute its ventralizing function in the absence of BMP signaling.

Original languageAmerican English
Pages (from-to)133-143
Number of pages11
JournalMechanisms of Development
Volume74
Issue number1-2
DOIs
StatePublished - Jun 1998

Bibliographical note

Funding Information:
Drs. T. Sargent for the Xpo probe, C. Niehrs for the Xvent-1 and Xvent-2 probes, D. Kimelman for the Vox probe, D. Melton for the dominant negative BMP receptor construct. This work was funded in part by a grant from the Council of Tobacco Research USA to A.F.

Keywords

  • Anterior-posterior axis
  • Axis patterning
  • BMP-4
  • Caudal genes
  • Dorsoventral axis
  • Gastrulation
  • Homeobox
  • Spemann's organizer
  • Xcad- 2
  • Xenopus embryo

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