Zebrafish Dkk1 functions in forebrain specification and axial mesendoderm formation

Hashimoto, H., Itoh, M., Yamanaka, Y., Yamashita, S., Shimizu, T., Solnica-Krezel, L., Hibi, M., and Hirano, T.
Developmental Biology   217(1): 138-152 (Journal)
Registered Authors
Hashimoto, Hisashi, Hibi, Masahiko, Itoh, Motoyuki, Shimizu, Takashi, Solnica-Krezel, Lilianna, Yamanaka, Yojiro, Yamashita, Susumu
Dickkopf1; forebrain; bozozok; dharma; squint; one-eyed pinhead
MeSH Terms
  • Amino Acid Sequence
  • Animals
  • Base Sequence
  • DNA Primers
  • Embryonic Development
  • Endoderm
  • Eye/embryology
  • Gene Expression Regulation, Developmental
  • Intercellular Signaling Peptides and Proteins
  • Mesoderm
  • Molecular Sequence Data
  • Mutation
  • Nodal Protein
  • Phenotype
  • Prosencephalon/embryology*
  • Proteins/chemistry
  • Proteins/genetics
  • Proteins/physiology*
  • Sequence Homology, Amino Acid
  • Signal Transduction
  • Transforming Growth Factor beta/metabolism
  • Zebrafish/embryology*
  • Zebrafish Proteins
10625541 Full text @ Dev. Biol.
We identified a zebrafish homologue of Dickkopf-1 (Dkk1), which was previously identified in Xenopus as a Wnt inhibitor with potent head-inducing activity. Zebrafish dkk1 is expressed in the dorsal marginal blastoderm and also in the dorsal yolk syncytial layer after mid-blastula transition. At later blastula stages, the expression expands to the entire blastoderm margin. During gastrulation, dkk1-expressing cells are confined to the embryonic shield and later to the anterior axial mesendoderm, prospective prechordal plate. Embryos, in which dkk1 was ectopically expressed, exhibited enlarged forebrain, eyes, and axial mesendoderm such as prechordal plate and notochord. dkk1 expression in the dorso-anterior mesendoderm during gastrulation was prominently reduced in zebrafish mutants bozozok (boz), squint (sqt), and one-eyed pinhead (oep), which all display abnormalities in the formation and function of the Spemann organizer and axial mesendoderm. dkk1 expression was normal in these embryos during the blastula period, indicating that zygotic functions of these genes are required for maintenance but not establishment of dkk1 expression. Overexpression of dkk1 suppressed defects in the development of forebrain, eyes, and notochord in boz mutants. Overexpression of dkk1 promoted anterior neuroectoderm development in the embryos injected with antivin RNA, which lack most of the mesoderm and endoderm, suggesting that Dkk1 can affect regionalization of neuroectoderm independently of dorso-anterior mesendoderm. These data indicate that Dkk1, expressed in dorsal mesendoderm, functions in the formation of both the anterior nervous system and the axial mesendoderm in zebrafish.
Genes / Markers
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Mutations / Transgenics
Human Disease / Model
Sequence Targeting Reagents
Engineered Foreign Genes