Coordinated activation of the secretory pathway during notochord formation in the Xenopus embryo

Development. 2009 Nov;136(21):3543-8. doi: 10.1242/dev.036715. Epub 2009 Sep 30.


We compared the transcriptome in the developing notochord of Xenopus laevis embryos with that of other embryonic regions. A coordinated and intense activation of a large set of secretory pathway genes was observed in the notochord, but not in notochord precursors in the axial mesoderm at early gastrula stage. The genes encoding Xbp1 and Creb3l2 were also activated in the notochord. These two transcription factors are implicated in the activation of secretory pathway genes during the unfolded protein response, where cells react to the stress of a build-up of unfolded proteins in their endoplasmic reticulum. Xbp1 and Creb3l2 are differentially expressed but not differentially activated in the notochord. Reduction of expression of Xbp1 or Creb3l2 by injection of antisense morpholinos led to strong deficits in notochord but not somitic muscle development. In addition, the expression of some, but not all, genes encoding secretory proteins was inhibited by injection of xbp1 morpholinos. Furthermore, expression of activated forms of Xbp1 or Creb3l2 in animal explants could activate a similar subset of secretory pathway genes. We conclude that coordinated activation of a battery of secretory pathway genes mediated by Xbp1 and Creb/ATF factors is a characteristic and necessary feature of notochord formation.

Publication types

  • Research Support, N.I.H., Intramural

MeSH terms

  • Animals
  • Basic-Leucine Zipper Transcription Factors / metabolism
  • Embryo, Nonmammalian / metabolism
  • Endoplasmic Reticulum / metabolism
  • Gene Expression Regulation, Developmental
  • Notochord / embryology
  • Protein Folding
  • Secretory Pathway*
  • Xenopus / embryology*
  • Xenopus / metabolism
  • Xenopus Proteins / metabolism


  • Basic-Leucine Zipper Transcription Factors
  • Xbp1 protein, Xenopus
  • Xenopus Proteins