Autonomous and non-autonomous differentiation of ectoderm in different sea urchin species

A. H. Wikramanayake, B. P. Brandhorst, W. H. Klein

Research output: Contribution to journalArticlepeer-review

49 Scopus citations

Abstract

During early embryogenesis, the highly regulative sea urchin embryo relies extensively on cell-cell interactions for cellular specification. Here, the role of cellular interactions in the temporal and spatial expression of markers for oral and aboral ectoderm in Strongylocentrotus purpuratus and Lytechinus pictus was investigated. When pairs of mesomeres or animal caps, which are fated to give rise to ectoderm, were isolated and cultured they developed into ciliated embryoids that were morphologically polarized. In animal explants from S. purpuratus, the aboral ectoderm-specific Spec1 gene was activated at the same time as in control embryos and at relatively high levels. The Spec1 protein was restricted to the squamous epithelial cells in the embryoids suggesting that an oral-aboral axis formed and aboral ectoderm differentiation occurred correctly. However, the Ecto V protein, a marker for oral ectoderm differentiation, was detected throughout the embryoid and no stomodeum or ciliary band formed. These results indicated that animal explants from S. purpuratus were autonomous in their ability to form an oral-aboral axis and to differentiate aboral ectoderm, but other aspects of ectoderm differentiation require interaction with vegetal blastomeres. In contrast to S. purpuratus, aboral ectoderm-specific genes were not expressed in animal explants from L. pictus even though the resulting embryoids were morphologically very similar to those of S. purpuratus. Recombination of the explants with vegetal blastomeres or exposure to the vegetalizing agent LiCl restored activity of aboral ectoderm-specific genes, suggesting the requirement of a vegetal induction for differentiation of aboral ectoderm cells. These results demonstrate that differences exist in aboral ectoderm differentiation between S. purpuratus and L. pictus and suggest that the formation of a cell type may occur by alternative mechanisms in two related species.

Original languageEnglish (US)
Pages (from-to)1497-1505
Number of pages9
JournalDevelopment
Volume121
Issue number5
StatePublished - Jan 1 1995
Externally publishedYes

Keywords

  • Animal cap
  • Ectoderm differentiation
  • Sea urchin development
  • Spec genes

ASJC Scopus subject areas

  • Cell Biology
  • Anatomy

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