Transient appearance of Strongylocentrotus purpuratus Otx in micromere nuclei: Cytoplasmic retention of SpOtx possibly mediated through an α- actinin interaction

Chin Kai Chuang, Athula H. Wikramanayake, Chai An Mao, Xiaotao Li, William H. Klein

Research output: Contribution to journalArticlepeer-review

43 Scopus citations

Abstract

At the 16-cell stage, the sea urchin embryo is partitioned along the animal-vegetal axis into eight mesomeres, four macromeres, and four micromeres. The micromeres, unlike the other blastomeres, are autonomously specified to produce skeletogenic mesenchymal cells and are also required to induce the vegetal-plate territory. A long-held belief is that micromeres inherit localized maternal determinants that endow them with their cell autonomous behavior and inducing capabilities. Here, we present evidence that an orthodenticle-related protein, SpOtx appears transiently in nuclei of micromeres but not in nuclei of mesomeres and macromeres. At later stages of development, SpOtx was translocated into nuclei of all cells. To address the possibility that SpOtx was retained in the cytoplasm at early developmental stages, we searched for cytoplasmic proteins that interact with SpOtx. A proline-rich region of SpOtx resembling an SH3-binding domain was used to screen an embryo cDNA expression library, and a cDNA clone was isolated and shown to be α-actinin. A yeast two-hybrid analysis showed a specific interaction between the proline-rich region of SpOtx and a putative SH3 domain of the sea urchin α-actinin. Because micromeres lack an actin-based cytoskeleton, the results suggested that, at the vegetal pole of the 16-cell stage embryo, SpOtx was translocated into micromere nuclei, whereas in other blastomeres SpOtx was actively retained in the cytoplasm by binding to α- actinin. The transient appearance of SpOtx in micromere nuclei may be associated with the specification of micromere cell fate.

Original languageEnglish (US)
Pages (from-to)231-237
Number of pages7
JournalDevelopmental Genetics
Volume19
Issue number3
DOIs
StatePublished - Dec 14 1996
Externally publishedYes

Keywords

  • α-actinin
  • micromeres
  • nuclear translocation
  • orthodenticle-related proteins
  • Sea urchin embryos

ASJC Scopus subject areas

  • Developmental Biology
  • Cell Biology
  • Genetics

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