title: An evolutionarily conserved kernel of gata5, gata6, otx2 and prdm1a operates in the formation of endoderm in zebrafish.
abstract: An evolutionarily conserved subcircuit (kernel) dedicated to a specific developmental function is found at the top of the gene regulatory networks (GRNs) hierarchy. Here we comprehensively demonstrate that a pan-deuterostome endoderm specification kernel exists in zebrafish. We analyzed interactions among gata5, gata6, otx2 and prdm1a using specific morpholino knockdowns and measured the gene expression profiles by quantitative real-time RT-PCR and in situ hybridization. The mRNA rescue experiment validated the specificity of the morpholino knockdown. We found that the interactions among gata5, gata6, otx2 and prdm1a determine the initial specification of the zebrafish endoderm. Although otx2 can activate both gata5 and gata6, and the prdm1a/krox homologue also activates some endoderm transcription factors, a feedback loop from Gata to otx2 and prdm1a is missing. Furthermore, we found the positive regulation between gata5 and gata6 to further lock-on the mesendoderm specification by the Gata family. Chromatin immunoprecipitation was used to further validate the recruitment of Otx2 to the gata5 and gata6 loci. Functional assays revealed that module B of gata6 and the basal promoter of gata5 drive the gene at the mesendoderm, and mutational analysis demonstrated that Otx2 and Gata5/6 contribute to reporter gene activation. This is the first direct evidence for evolutionarily conserved endoderm specification across echinoderms and vertebrates.
authors.affiliation: Institute of Molecular and Genomic Medicine, National Health Research Institutes, Zhunan Town, Miaoli County 350, Taiwan, ROC.
authors.forename: Wen-Fang
authors.initials: WF
authors.lastname: Tseng
authors.forename: Te-Hsuan
authors.initials: TH
authors.lastname: Jang
authors.forename: Chang-Ben
authors.initials: CB
authors.lastname: Huang
authors.forename: Chiou-Hwa
authors.initials: CH
authors.lastname: Yuh
mesh_terms: D000818:Animals; D001483:Base Sequence; D019521:Body Patterning / Q000187:drug effects / Q000235:genetics; D017124:Conserved Sequence / Q000235:genetics*; D004252:DNA Mutational Analysis; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D004707:Endoderm / Q000187:drug effects / Q000196:embryology* / Q000378:metabolism; D004843:Epistasis, Genetic / Q000187:drug effects; D019143:Evolution, Molecular; D050980:GATA Transcription Factors / Q000235:genetics / Q000378:metabolism; D050992:GATA5 Transcription Factor / Q000235:genetics / Q000378:metabolism; D020869:Gene Expression Profiling; D018507:Gene Expression Regulation, Developmental / Q000187:drug effects; D053263:Gene Regulatory Networks / Q000235:genetics*; D056426:Genetic Loci / Q000235:genetics; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism; D016376:Oligonucleotides, Antisense / Q000494:pharmacology; D051857:Otx Transcription Factors / Q000235:genetics / Q000378:metabolism; D000074462:Positive Regulatory Domain I-Binding Factor 1; D011485:Protein Binding; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D015203:Reproducibility of Results; D013997:Time Factors; D015027:Zebrafish / Q000196:embryology* / Q000235:genetics*; D029961:Zebrafish Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D004268:DNA-Binding Proteins; D050980:GATA Transcription Factors; D050992:GATA5 Transcription Factor; C525956:Gata6 protein, zebrafish; D009687:Nuclear Proteins; D016376:Oligonucleotides, Antisense; D051857:Otx Transcription Factors; D012333:RNA, Messenger; D029961:Zebrafish Proteins; C494754:gata5 protein, zebrafish; C497662:otx2b protein, zebrafish; D000074462:Positive Regulatory Domain I-Binding Factor 1; C513257:prdm1a protein, zebrafish