Cooperative roles of Bozozok/Dharma and Nodal-related proteins in the formation of the dorsal organizer in zebrafish.
In vertebrates, specification of the dorso-ventral axis requires Wnt signaling, which leads to formation of the Nieuwkoop center and the Spemann organizer (dorsal organizer), through the nuclear accumulation of beta-catenin. Zebrafish bozozok/dharma (boz) and squint (sqt), which encode a homeodomain protein and a Nodal-related protein, respectively, are required for the formation of the dorsal organizer. The zygotic expression of boz and sqt in the dorsal blastoderm and dorsal yolk syncytial layer (YSL) was dependent on the maternally derived Wnt signal, and their expression at the late blastula and early gastrula stages was dependent on the zygotic expression of their own genes. The dorsal organizer genes, goosecoid (gsc) and chordin (din), were ectopically expressed in wild-type embryos injected with boz or sqt RNA. The expression of gsc strictly depended on both boz and sqt while the expression of din strongly depended on boz but only partially depended on sqt and cyclops (cyc, another nodal-related gene). Overexpression of boz in embryos defective in Nodal signaling elicited the ectopic expression of din but not gsc and resulted in dorsalization, implying that boz could induce part of the organizer, independent of the Nodal proteins. Furthermore, boz; sqt and boz;cyc double mutants displayed a severely ventralized phenotype with anterior truncation, compared with the single mutants, and boz;sqt;cyc triple mutant embryos exhibited an even more severe phenotype, lacking the anterior neuroectoderm and notochord, suggesting that Boz/Dharma and the Nodal-related proteins cooperatively regulate the formation of the dorsal organizer.
Shimizu
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T
Division of Molecular Oncology (C7), Biomedical Research Center, Osaka University Graduate School of Medicine, 2-2 Yamada-oka, Suita, Osaka, Japan.
Yamanaka
Y
Y
Ryu
S L
SL
Hashimoto
H
H
Yabe
T
T
Hirata
T
T
Bae
Y K
YK
Hibi
M
M
Hirano
T
T
D000818:Animals; D001755:Blastocyst / Q000502:physiology; D019521:Body Patterning / Q000502:physiology*; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000235:genetics / Q000378:metabolism; D003598:Cytoskeletal Proteins / Q000235:genetics / Q000378:metabolism; D005775:Gastrula / Q000502:physiology; D018507:Gene Expression Regulation, Developmental; D038362:Glycogen Synthase Kinase 3; D006023:Glycoproteins; D051956:Goosecoid Protein; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism*; D036341:Intercellular Signaling Peptides and Proteins; D047908:Intracellular Signaling Peptides and Proteins; D055456:Nodal Signaling Ligands; D011506:Proteins / Q000235:genetics; D012097:Repressor Proteins; D013997:Time Factors; D015534:Trans-Activators; D014157:Transcription Factors; D016212:Transforming Growth Factor beta / Q000235:genetics / Q000378:metabolism*; D015027:Zebrafish / Q000196:embryology* / Q000502:physiology; D029961:Zebrafish Proteins; D051176:beta Catenin
D003598:Cytoskeletal Proteins; D006023:Glycoproteins; D051956:Goosecoid Protein; D018398:Homeodomain Proteins; D036341:Intercellular Signaling Peptides and Proteins; D047908:Intracellular Signaling Peptides and Proteins; D055456:Nodal Signaling Ligands; D011506:Proteins; D012097:Repressor Proteins; D015534:Trans-Activators; D014157:Transcription Factors; D016212:Transforming Growth Factor beta; D029961:Zebrafish Proteins; D051176:beta Catenin; C495269:ctnnb1 protein, zebrafish; C113874:dharma protein, zebrafish; C497995:gsc protein, zebrafish; C485171:ndr1 protein, zebrafish; C512832:ndr2 protein, zebrafish; C054234:chordin; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D038362:Glycogen Synthase Kinase 3