HrNodal, the ascidian nodal-related gene, is expressed in the left side of the epidermis, and lies upstream of HrPitx

Dev Genes Evol. 2002 Oct;212(9):439-46. doi: 10.1007/s00427-002-0242-3. Epub 2002 Sep 4.


The nodal-related genes are well known for their fundamental roles during vertebrate development, including mesoderm induction, neural induction, and left-right axis formation, as several nodal-related genes show left-sided expression in mesodermal lineages. We have isolated the first non-vertebrate nodal-related gene, HrNodal, from the ascidian Halocynthia roretzi. During the late cleavage and gastrula stages, HrNodal is transiently and bilaterally expressed in several different cell lineages. Expression at the tailbud stage is observed asymmetrically in the left side, but unexpectedly only in the epidermis of the embryo. We also demonstrate the relationship of HrNodal with HrPitx, a Halocynthia homologue of the Pitx2 gene. HrNodal overexpression results in the disturbance of left-sided HrPitx expression. Our results demonstrate that left-right specification during ascidian embryogenesis involves the HrNodal gene, and that the left-sidedness of the expression is evolutionarily conserved throughout the chordate clade.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Body Patterning / genetics
  • Body Patterning / physiology
  • Epidermis / metabolism*
  • Gene Expression Regulation, Developmental
  • Homeodomain Proteins / genetics
  • Nodal Protein
  • Nuclear Proteins*
  • Organ Specificity
  • Transcription Factors / genetics
  • Transforming Growth Factor beta / genetics
  • Transforming Growth Factor beta / metabolism*
  • Up-Regulation
  • Urochordata / embryology
  • Urochordata / genetics
  • Urochordata / metabolism*


  • Homeodomain Proteins
  • Nodal Protein
  • Nuclear Proteins
  • Transcription Factors
  • Transforming Growth Factor beta
  • homeobox protein PITX2