TY - JOUR
T1 - Zebrafish Dkk1 functions in forebrain specification and axial mesendoderm formation
AU - Hashimoto, Hisashi
AU - Itoh, Motoyuki
AU - Yamanaka, Yojiro
AU - Yamashita, Susumu
AU - Shimizu, Takashi
AU - Solnica-Krezel, Lilianna
AU - Hibi, Masahiko
AU - Hirano, Toshio
N1 - Funding Information:
We are grateful to K. Fekany for critical reading of the manuscript. We thank Dr. M. Mishina for providing us otx2 cDNA, Dr. M. Kobayashi for six3 cDNA, Dr. T. Jowett for krox20, Dr. H. Takeda for pax2.1, Dr. R. Moon for wnt8 and wnt8b cDNAs, Drs. C. Thisse and B. Thisse for hgg1 and antivin cDNAs, Dr. M. Halpern for chordin cDNA, Drs. M. Rebagliati and I. Dawid for squint cDNA, Dr. W. S. Talbot for cyclops and squint fish and Drs. M. Furutani-Seiki and H. Takeda for one-eyed pinhead fish. We also thank Y. Kuga for her excellent technical assistance. This work was supported by a grant and a Grant-in-Aid for Center of Excellence (COE) Research from the Ministry of Education, Science, Sports, and Culture in Japan.
PY - 2000/1/1
Y1 - 2000/1/1
N2 - 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.
AB - 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.
KW - Bozozok
KW - Dharma
KW - Dickkopf1
KW - Forebrain
KW - One-eyed pinhead
KW - Squint
UR - http://www.scopus.com/inward/record.url?scp=0033980024&partnerID=8YFLogxK
U2 - 10.1006/dbio.1999.9537
DO - 10.1006/dbio.1999.9537
M3 - Article
C2 - 10625541
AN - SCOPUS:0033980024
SN - 0012-1606
VL - 217
SP - 138
EP - 152
JO - Developmental Biology
JF - Developmental Biology
IS - 1
ER -