Abstract
In zebrafish, endoderm induction occurs in marginal blastomeres and requires Casanova (Cas), the first endoderm-specific factor expressed in the embryo. Whereas the transcription factors Gata5 and Bon are necessary and sufficient for cas expression in marginal blastomeres, Bon and Gata5 are unable to induce cas in animal pole cells, suggesting that cas expression requires an additional, unidentified factor(s). Here, we show that cas expression depends upon the T box transcription factor Eomesodermin (Eomes), a maternal determinant that is localized to marginal blastomeres. Eomes synergizes potently with Bon and Gata5 to induce cas, even in animal pole blastomeres. We show that Eomes is required for endogenous endoderm induction, acting via an essential binding site in the cas promoter. Direct physical interactions between Eomes, Bon, and Gata5 suggest that Eomes promotes endoderm induction in marginal blastomeres by facilitating the assembly of a transcriptional activating complex on the cas promoter.
Publication types
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, Non-P.H.S.
MeSH terms
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Animals
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Embryonic Induction*
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Endoderm / cytology
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Endoderm / physiology*
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GATA5 Transcription Factor / genetics
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GATA5 Transcription Factor / metabolism
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Gene Expression Regulation, Developmental
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High Mobility Group Proteins / genetics
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High Mobility Group Proteins / metabolism*
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Homeodomain Proteins / genetics
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Homeodomain Proteins / metabolism
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In Situ Hybridization
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Nodal Protein
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Oligoribonucleotides, Antisense / genetics
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Oligoribonucleotides, Antisense / metabolism
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Promoter Regions, Genetic
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Protein Binding
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SOX Transcription Factors
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T-Box Domain Proteins / genetics
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T-Box Domain Proteins / metabolism*
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Transcription Factors / genetics
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Transcription Factors / metabolism*
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Transcription, Genetic
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Transforming Growth Factor beta / genetics
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Transforming Growth Factor beta / metabolism
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Zebrafish / anatomy & histology
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Zebrafish / embryology*
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Zebrafish Proteins / genetics
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Zebrafish Proteins / metabolism*
Substances
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GATA5 Transcription Factor
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High Mobility Group Proteins
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Homeodomain Proteins
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Nodal Protein
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Oligoribonucleotides, Antisense
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SOX Transcription Factors
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T-Box Domain Proteins
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Transcription Factors
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Transforming Growth Factor beta
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Zebrafish Proteins
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eomesa protein, zebrafish
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gata5 protein, zebrafish
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mixl1 protein, zebrafish
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sox32 protein, zebrafish