%0 Journal Article
%T Correct anteroposterior patterning of the zebrafish neurectoderm in the absence of the early dorsal organizer
%A M¨¢t¨¦ Varga
%A Shingo Maegawa
%A Eric S Weinberg
%J BMC Developmental Biology
%D 2011
%I BioMed Central
%R 10.1186/1471-213x-11-26
%X Using the ventralized, maternal effect ichabod (ich) mutant, and by inhibiting BMP signaling in ich embryos, we provide conclusive evidence that AP patterning is independent of the organizer in zebrafish, and is governed by TGF¦Â, FGF, and Wnt signals emanating from the germ-ring. The expression patterns of neurectodermal markers in embryos with impaired BMP signaling show that the directionality of such signals is oriented along the animal-vegetal axis, which is essentially concordant with the AP axis. In addition, we find that in embryos inhibited in both Wnt and BMP signaling, the AP pattern of such markers is unchanged from that of the normal untreated embryo. These embryos develop radially organized trunk and head tissues, with an outer neurectodermal layer containing diffusely positioned neuronal precursors. Such organization is reflective of the presumed eumetazoan ancestor and might provide clues for the evolution of centralization in the nervous system.Using a zebrafish mutant deficient in the induction of the embryonic organizer, we demonstrate that the AP patterning of the neuroectoderm during gastrulation is independent of DV patterning. Our results provide further support for Nieuwkoop's "two step model" of embryonic induction. We also show that the zebrafish embryo can form a radial diffuse neural sheath in the absence of both BMP signaling and the early organizer.The body plan of developing animal embryos is initially generated by establishment of the anteroposterior (AP) and dorsoventral (DV) axes. The dorsal organizer (i.e., Spemann organizer and homologous structures) is clearly important in formation of the DV axis (reviewed in [1-3]), but its role in AP axis development has been controversial (reviewed in [4,5]). Failure to form the Spemann organizer in frogs and fish [6-8] results not only in the absence of dorsal tissues, but also in the loss of anterior regions of the embryo. Nevertheless, there is also evidence that at least some degree of pro
%U http://www.biomedcentral.com/1471-213X/11/26