Two novel nodal-related genes initiate early inductive events in Xenopus Nieuwkoop center.
In vertebrates, Nodal-related protein plays crucial roles in mesoderm and endoderm induction. Here we describe two novel Xenopus nodal-related genes, Xnr5 and Xnr6, which are first zygotically expressed at the mid-blastula transition, in the dorsal-vegetal region including the Nieuwkoop center. Xnr5 and Xnr6 were isolated by expression screening of a library enriched with immediate-early-type transcripts, and are strong inducers of both mesoderm and endoderm. They also induce the other nodal-related genes in the animal cap. In embryos, cerberus-short (nodal-specific inhibitor) can inhibit Xnr1 and Xnr2 express to the same extent goosecoid, but not Xnr5 and Xnr6 transcription. Xnr5 and Xnr6 are regulated completely cell autonomously, differently from other Xnrs in the cell-dissociated embryos. The expression of Xnr5 and Xnr6 is regulated by maternal VegT and (beta)-catenin, but does not require TGF-(beta) signaling. Therefore, expression of Xnr5 and Xnr6 is controlled by different mechanisms from other Xnr family genes.
Takahashi
S
S
Department of Life Sciences (Biology), The University of Tokyo, Tokyo 153-8902, Japan.
Yokota
C
C
Takano
K
K
Tanegashima
K
K
Onuma
Y
Y
Goto
J
J
Asashima
M
M
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D003001:Cloning, Molecular; D003598:Cytoskeletal Proteins / Q000235:genetics; D017931:DNA Primers / Q000235:genetics; D004627:Embryonic Induction / Q000235:genetics; D004707:Endoderm / Q000378:metabolism; D005260:Female; D018507:Gene Expression Regulation, Developmental; D008648:Mesoderm / Q000378:metabolism; D008954:Models, Biological; D008969:Molecular Sequence Data; D055457:Nodal Protein; D055456:Nodal Signaling Ligands; D011506:Proteins / Q000235:genetics*; D017386:Sequence Homology, Amino Acid; D020825:T-Box Domain Proteins / Q000235:genetics; D015534:Trans-Activators; D016212:Transforming Growth Factor beta / Q000235:genetics; D029867:Xenopus Proteins; D014982:Xenopus laevis / Q000196:embryology* / Q000235:genetics*; D051176:beta Catenin
C495266:CTNNB1 protein, Xenopus; D003598:Cytoskeletal Proteins; D017931:DNA Primers; D055457:Nodal Protein; D055456:Nodal Signaling Ligands; D011506:Proteins; D020825:T-Box Domain Proteins; D015534:Trans-Activators; D016212:Transforming Growth Factor beta; C103966:VegT protein, Xenopus; D029867:Xenopus Proteins; D051176:beta Catenin; C512833:nodal1 protein, Xenopus; C418882:nodal5 protein, Xenopus; C418883:nodal6 protein, Xenopus