Noggin signaling from Xenopus animal blastomere lineages promotes a neural fate in neighboring vegetal blastomere lineages

Dev Dyn. 2007 Jan;236(1):171-83. doi: 10.1002/dvdy.20944.

Abstract

In Xenopus, localized factors begin to regionalize embryonic fates prior to the inductive interactions that occur during gastrulation. We previously reported that an animal-to-vegetal signal that occurs prior to gastrulation promotes primary spinal neuron fate in vegetal equatorial (C-tier) blastomere lineages. Herein we demonstrate that maternal mRNA encoding noggin is enriched in animal tiers and at low concentrations in the C-tier, suggesting that the neural fates of C-tier blastomeres may be responsive to early signaling from their neighboring cells. In support of this hypothesis, experimental alteration of the levels of Noggin from animal equatorial (B-tier) or BMP4 from vegetal (D-tier) blastomeres significantly affects the numbers of primary spinal neurons derived from their neighboring C-tier blastomeres. These effects are duplicated in blastomere explants isolated at cleavage stages and cultured in the absence of gastrulation interactions. Co-culture with animal blastomeres enhanced the expression of zygotic neural markers in C-tier blastomere explants, whereas co-culture with vegetal blastomeres repressed them. The expression of these markers in C-tier explants was promoted when Noggin was transiently added to the culture during cleavage/morula stages, and repressed with the transient addition of BMP4. Reduction of Noggin translation in B-tier blastomeres by antisense morpholino oligonucleotides significantly reduced the efficacy of neural marker induction in C-tier explants. These experiments indicate that early anti-BMP signaling from the animal hemisphere recruits vegetal equatorial cells into the neural precursor pool prior to interactions that occur during gastrulation.

Publication types

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

MeSH terms

  • Animals
  • Blastomeres / cytology*
  • Blastomeres / metabolism*
  • Body Patterning / genetics
  • Body Patterning / physiology
  • Bone Morphogenetic Protein 4
  • Bone Morphogenetic Proteins / genetics
  • Bone Morphogenetic Proteins / metabolism
  • Carrier Proteins / genetics
  • Carrier Proteins / metabolism*
  • Cell Lineage
  • Embryonic Induction
  • Embryonic Stem Cells / metabolism
  • Gastrula / metabolism
  • Gene Expression Regulation, Developmental
  • Models, Biological
  • Motor Neurons / metabolism*
  • Signal Transduction*
  • Stem Cells / metabolism
  • Xenopus
  • Xenopus Proteins / genetics
  • Xenopus Proteins / metabolism*

Substances

  • Bone Morphogenetic Protein 4
  • Bone Morphogenetic Proteins
  • Carrier Proteins
  • Xenopus Proteins
  • bmp4 protein, Xenopus
  • noggin protein