A novel Cripto-related protein reveals an essential role for EGF-CFCs in Nodal signalling in Xenopus embryos

Dev Biol. 2006 Apr 15;292(2):303-16. doi: 10.1016/j.ydbio.2006.01.006. Epub 2006 Feb 21.


The location, timing and intensity of Nodal signalling are all critical for proper patterning of the vertebrate embryo. Genetic evidence from mouse and zebrafish indicates that EGF-CFC family members are essential for Nodal ligands to signal. However, the Xenopus EGF-CFC, FRL1, has been implicated in Wnt signalling and in activation of Erk MAP kinase. Here, we identify two additional Xenopus EGF-CFCs, XCR2 and XCR3. We have focused on the role of XCR1/FRL1 and XCR3, which are both expressed at gastrula stages when Nodal signalling is active. We demonstrate spatial and temporal regulation of XCR1 protein expression, whereas XCR3 appears to be expressed ubiquitously. Using gain and loss of function approaches, we show that XCR1 and XCR3 are required for Nodal-related ligands to signal during early Xenopus development. Moreover, different Nodal-related ligands require different XCRs to signal. When both XCR1 and XCR3 are knocked down, activation of the Nodal intracellular signal transducer, Smad2, is severely inhibited and neither gastrulation nor mesendoderm formation occurs. Together our results indicate that the XCRs are important for modulation of the timing and intensity of Nodal signalling in Xenopus embryos.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Conserved Sequence
  • Down-Regulation
  • Embryo, Nonmammalian
  • GPI-Linked Proteins
  • Gastrula
  • Gene Expression Regulation, Developmental
  • Homeodomain Proteins / chemistry
  • Homeodomain Proteins / metabolism*
  • Intercellular Signaling Peptides and Proteins
  • Membrane Proteins / chemistry
  • Membrane Proteins / genetics
  • Membrane Proteins / metabolism*
  • Models, Biological
  • Molecular Sequence Data
  • Nodal Protein
  • Oligonucleotides, Antisense / pharmacology
  • Protein Structure, Tertiary
  • RNA, Messenger / metabolism
  • Receptors, Cell Surface / metabolism
  • Sequence Homology, Amino Acid
  • Smad2 Protein / antagonists & inhibitors
  • Transcription Factors / chemistry
  • Transcription Factors / metabolism*
  • Transforming Growth Factor beta / metabolism*
  • Xenopus / embryology*
  • Xenopus / metabolism*
  • Xenopus Proteins / antagonists & inhibitors
  • Xenopus Proteins / chemistry
  • Xenopus Proteins / genetics
  • Xenopus Proteins / metabolism*


  • GPI-Linked Proteins
  • Homeodomain Proteins
  • Intercellular Signaling Peptides and Proteins
  • Membrane Proteins
  • Nodal Protein
  • Nodal protein, mouse
  • Oligonucleotides, Antisense
  • RNA, Messenger
  • Receptors, Cell Surface
  • Smad2 Protein
  • Smad2 protein, Xenopus
  • Transcription Factors
  • Transforming Growth Factor beta
  • Xenopus Proteins
  • tdgf1.1 protein, Xenopus
  • tdgf1.2 protein, Xenopus
  • tdgf1.3 protein, Xenopus