Expression cloning of Siamois, a Xenopus homeobox gene expressed in dorsal-vegetal cells of blastulae and able to induce a complete secondary axis

Cell. 1995 Apr 7;81(1):85-94. doi: 10.1016/0092-8674(95)90373-9.


Using an expression cloning strategy that relies on a functional assay, we have cloned a novel Xenopus homeobox-containing gene, Siamois. Embryos injected in a ventral-vegetal blastomere with as little as 5 pg of Siamois mRNA develop a complete secondary axis, but the progeny of the injected cells do not participate in the secondary axis formation. In normal development, Siamois mRNA is first detected shortly after the midblastula transition, which is earlier than mRNAs for goosecoid or Xbrachyury, and is present most abundantly in the dorsal endoderm of early gastrulae. The activation of this gene can be obtained cell autonomously in dispersed embryo cells. These results indicate that Siamois may play an important role in the formation of the Nieuwkoop center.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Base Sequence
  • Blastocyst / metabolism*
  • Blastomeres
  • Carrier Proteins
  • Cloning, Molecular
  • DNA-Binding Proteins / biosynthesis
  • DNA-Binding Proteins / genetics
  • Endoderm / chemistry
  • Fetal Proteins / biosynthesis
  • Fetal Proteins / genetics
  • Gastrula / chemistry
  • Gene Expression Regulation, Developmental*
  • Genes, Homeobox*
  • Goosecoid Protein
  • Homeodomain Proteins / biosynthesis
  • Homeodomain Proteins / genetics*
  • Microinjections
  • Molecular Sequence Data
  • Proteins / genetics
  • Proto-Oncogene Proteins / genetics
  • RNA, Messenger / analysis
  • Repressor Proteins*
  • Sequence Analysis, DNA
  • T-Box Domain Proteins*
  • Transcription Factors*
  • Wnt Proteins
  • Xenopus Proteins
  • Xenopus laevis
  • Zebrafish Proteins*


  • Carrier Proteins
  • DNA-Binding Proteins
  • Fetal Proteins
  • Goosecoid Protein
  • Homeodomain Proteins
  • Proteins
  • Proto-Oncogene Proteins
  • RNA, Messenger
  • Repressor Proteins
  • SIA1 protein, Xenopus
  • T-Box Domain Proteins
  • Transcription Factors
  • Wnt Proteins
  • Xenopus Proteins
  • Zebrafish Proteins
  • noggin protein
  • Brachyury protein

Associated data

  • GENBANK/Z48606