Zebrafish Dkk1, induced by the pre-MBT Wnt signaling, is secreted from the prechordal plate and patterns the anterior neural plate.
mRNA injection into the ventral blastomeres of Xenopus embryos of mRNA encoding Wnt pathway genes induces a secondary axis with complete head structures. To identify target genes of the pre-MBT dorsalization pathway that might be responsible for head formation in zebrafish, we have cloned zebrafish dickkopf1 (dkk1), which is expressed in tissues implicated in head patterning. We found that dkk1 blocks the post-MBT Wnt signaling and dkk1 is a target of the pre-MBT Wnt signaling. Dkk1 overexpression in the prechordal plate suggests that Dkk1, secreted from the prechordal plate, expands the forebrain at the expense of the midbrain in the anterior neural plate. Furthermore, dkk1 acts in parallel to the homeobox gene bozozok and bozozok is required for the maintenance of dkk1 expression. The nodal gene squint is also required for the maintenance of dkk1 expression. Among the mutually dependent target genes of the pre-MBT Wnt signaling, dkk1 plays an important role in patterning the anterior head of zebrafish.
Shinya
M
M
Abteilung für Entwicklungsbiologie, Institut für Biologie I, Universität Freiburg, D-79104, Freiburg, Germany.
Eschbach
C
C
Clark
M
M
Lehrach
H
H
Furutani-Seiki
M
M
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001755:Blastocyst / Q000378:metabolism; D019521:Body Patterning / Q000235:genetics / Q000502:physiology; D001921:Brain / Q000196:embryology; D004247:DNA / Q000235:genetics; D018507:Gene Expression Regulation, Developmental; D005801:Genes, Homeobox; D017403:In Situ Hybridization; D036341:Intercellular Signaling Peptides and Proteins; D008954:Models, Biological; D008969:Molecular Sequence Data; D009420:Nervous System / Q000196:embryology; D011506:Proteins / Q000235:genetics* / Q000502:physiology*; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D012689:Sequence Homology, Nucleic Acid; D015398:Signal Transduction; D051153:Wnt Proteins; D015027:Zebrafish / Q000196:embryology* / Q000235:genetics* / Q000378:metabolism; D029961:Zebrafish Proteins
D036341:Intercellular Signaling Peptides and Proteins; D011506:Proteins; D011518:Proto-Oncogene Proteins; D012333:RNA, Messenger; D051153:Wnt Proteins; D029961:Zebrafish Proteins; C501128:dkk1b protein, zebrafish; C094522:wnt8b protein, zebrafish; D004247:DNA