Opposing Nodal/Vg1 and BMP signals mediate axial patterning in embryos of the basal chordate amphioxus.
The basal chordate amphioxus resembles vertebrates in having a dorsal, hollow nerve cord, a notochord and somites. However, it lacks extensive gene duplications, and its embryos are small and gastrulate by simple invagination. Here we demonstrate that Nodal/Vg1 signaling acts from early cleavage through the gastrula stage to specify and maintain dorsal/anterior development while, starting at the early gastrula stage, BMP signaling promotes ventral/posterior identity. Knockdown and gain-of-function experiments show that these pathways act in opposition to one another. Signaling by these pathways is modulated by dorsally and/or anteriorly expressed genes including Chordin, Cerberus, and Blimp1. Overexpression and/or reporter assays in Xenopus demonstrate that the functions of these proteins are conserved between amphioxus and vertebrates. Thus, a fundamental genetic mechanism for axial patterning involving opposing Nodal and BMP signaling is present in amphioxus and probably also in the common ancestor of amphioxus and vertebrates or even earlier in deuterostome evolution.
Onai
Takayuki
T
Marine Biology Research Division, Scripps Institution of Oceanography, University of California San Diego, La Jolla, CA 92093-0202, USA.
Yu
Jr-Kai
JK
Blitz
Ira L
IL
Cho
Ken W Y
KW
Holland
Linda Z
LZ
D000818:Animals; D036703:Blastula / Q000378:metabolism; D019521:Body Patterning; D019485:Bone Morphogenetic Proteins / Q000378:metabolism*; D002816:Chordata, Nonvertebrate / Q000235:genetics* / Q000502:physiology*; D005775:Gastrula / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D017930:Genes, Reporter; D036341:Intercellular Signaling Peptides and Proteins / Q000378:metabolism; D008954:Models, Biological; D055457:Nodal Protein / Q000378:metabolism*; D012097:Repressor Proteins / Q000378:metabolism; D015398:Signal Transduction; D014981:Xenopus; D029867:Xenopus Proteins / Q000378:metabolism
D019485:Bone Morphogenetic Proteins; D036341:Intercellular Signaling Peptides and Proteins; D055457:Nodal Protein; C402290:PRDM1 protein, Xenopus; D012097:Repressor Proteins; D029867:Xenopus Proteins; C100866:cer1 protein, Xenopus