ZFIN ID: ZDB-PUB-010705-9
Role of the iroquois3 homeobox gene in organizer formation
Kudoh, T. and Dawid, I.B.
Date: 2001
Source: Proceedings of the National Academy of Sciences of the United States of America   98(14): 7852-7857 (Journal)
Registered Authors: Dawid, Igor B., Kudoh, Tetsuhiro
Keywords: none
MeSH Terms:
  • Amino Acid Sequence
  • Animals
  • Embryo, Nonmammalian/embryology
  • Embryo, Nonmammalian/physiology
  • Gene Expression Regulation, Developmental
  • Homeodomain Proteins/genetics*
  • Molecular Sequence Data
  • Organizers, Embryonic/embryology
  • Organizers, Embryonic/physiology*
  • Sequence Alignment
  • Transcription Factors/genetics*
  • Zebrafish/embryology*
  • Zebrafish/genetics
  • Zebrafish Proteins
PubMed: 11438735 Full text @ Proc. Natl. Acad. Sci. USA
In zebrafish, the organizer is thought to consist of two regions, the yolk syncytial layer (YSL) and the shield. The dorsal YSL appears to send signals that affect formation of the shield in the overlying mesendoderm. We show here that a domain of dorsal deep cells located between the YSL and the shield is marked by expression of the iro3 gene. As gastrulation proceeds, the iro3 positive domain involutes and migrates to the animal pole. Iro3 expression is regulated by Nodal and bone morphogenic protein antagonists. Overexpression of iro3 induced ectopic expression of shield-specific genes. This effect was mimicked by an Iro3-Engrailed transcriptional repressor domain fusion, whereas an Iro3-VP16 activator domain fusion behaved as a dominant negative or antimorphic form. These results suggest that Iro3 acts as a transcriptional repressor and further implicate the iro3 gene in regulating organizer formation. We propose that the iro3-expressing dorsal deep cells represent a distinct organizer domain that receives signals from the YSL and in turn sends signals to the forming shield, thereby influencing its expansion and differentiation.