FGF8, Wnt8 and Myf5 are target genes of Tbx6 during anteroposterior specification in Xenopus embryo.
The T-box transcription factor Tbx6 is required for somite formation and loss-of-function or reduced activity of Tbx6 result in absence of posterior paraxial mesoderm or disorganized somites, but how it is involved in a regulatory hierarchy during Xenopus early development is not clear. We show here that Tbx6 is expressed in the lateral and ventral mesoderm of early gastrula, and it is necessary and sufficient to directly and indirectly regulate the expression of a subset of early mesodermal and endodermal genes. Ectopic expression of Tbx6 inhibits early neuroectodermal gene expression by strongly inducing the expression of posterior mesodermal genes, and expands the mesoderm territory at the expense of neuroectoderm. Conversely, overexpression of a dominant negative Tbx6 mutant in the ventral mesoderm inhibits the expression of several mesodermal genes and results in neural induction in a dose-dependent manner. Using a hormone-inducible form of Tbx6, we have identified FGF8, Xwnt8 and XMyf5 as immediate early responsive genes of Tbx6, and the induction of these genes by Tbx6 is independent of Xbra and VegT. These target genes act downstream and mediate the function of Tbx6 in anteroposterior specification. Our results therefore identify a regulatory cascade governed by Tbx6 in the specification of posterior mesoderm during Xenopus early development.
Li
Hong-Yan
HY
Groupe de Biologie Expérimentale, Laboratoire de Biologie du Développement, CNRS UMR 7622, Université Pierre et Marie-Curie, 9 quai Saint-Bernard, 75005 Paris, France.
Bourdelas
Audrey
A
Carron
Clémence
C
Gomez
Céline
C
Boucaut
Jean-Claude
JC
Shi
De-Li
DL
D000818:Animals; D019521:Body Patterning; D019070:Cell Lineage; D004305:Dose-Response Relationship, Drug; D004475:Ectoderm / Q000378:metabolism; D004707:Endoderm / Q000378:metabolism; D005260:Female; D018507:Gene Expression Regulation, Developmental; D005799:Genes, Dominant; D017403:In Situ Hybridization; D008648:Mesoderm / Q000378:metabolism; D008956:Models, Chemical; D009154:Mutation; D051787:Myogenic Regulatory Factor 5 / Q000502:physiology*; D009474:Neurons / Q000378:metabolism; D010641:Phenotype; D010957:Plasmids / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D020825:T-Box Domain Proteins; D014157:Transcription Factors / Q000378:metabolism / Q000502:physiology*; D051153:Wnt Proteins / Q000502:physiology*; D029867:Xenopus Proteins / Q000502:physiology*; D014982:Xenopus laevis
C497419:Myf5 protein, Xenopus; D051787:Myogenic Regulatory Factor 5; D012333:RNA, Messenger; D020825:T-Box Domain Proteins; C491181:Tbx6 protein, Xenopus; D014157:Transcription Factors; D051153:Wnt Proteins; C490602:Wnt8b protein, Xenopus; D029867:Xenopus Proteins