Evolutionary modification of T-brain (tbr) expression patterns in sand dollar

Keiko Minemura, Masaaki Yamaguchi, Takuya Minokawa

Research output: Contribution to journalArticlepeer-review

13 Citations (Scopus)


The sand dollars are a group of irregular echinoids that diverged from other regular sea urchins approximately 200 million years ago. We isolated two orthologs of T-brain (tbr), Smtbr and Pjtbr, from the indirect developing sand dollar Scaphechinus mirabilis and the direct developing sand dollar Peronella japonica, respectively. The expression patterns of Smtbr and Pjtbr during early development were examined by whole mount in situ hybridization. The expression of Smtbr was first detected in micromere descendants in early blastula stage, similar to tbr expression in regular sea urchins. However, unlike in regular sea urchin, Smtbr expression in middle blastula stage was detected in micromere-descendent cells and a subset of macromere-descendant cells. At gastrula stage, expression of Smtbr was detected in part of the archenteron as well as primary mesenchyme cells. A similar pattern of tbr expression was observed in early Peronella embryos. A comparison of tbr expression patterns between sand dollars and other echinoderm species suggested that broader expression in the endomesoderm is an ancestral character of echinoderms. In addition to the endomesoderm, Pjtbr expression was detected in the apical organ, the animal-most part of the ectoderm.

Original languageEnglish
Pages (from-to)468-474
Number of pages7
JournalGene Expression Patterns
Issue number7
Publication statusPublished - 2009 Oct


  • Ambulacraria
  • Clypeasteroida
  • Direct development
  • Echinoderm
  • Echinoid
  • Echinoida
  • Evolution
  • Hemichordate
  • Indirect development
  • Peronella japonica
  • Sand dollar
  • Scaphechinus mirabilis
  • Sea urchin
  • T-brain
  • tbr


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