【文章內(nèi)容簡介】 the UV The 2nd4th panel: the rescued embryos with dorsal structures in a dosagerelated fasion, when the defect embryo is injected with noggin mRNA The bottom: If too much noggin mRNA is injected, the embryo produces dorsal tissues at the expense of ventral and posterior tissue, being little more than a head. Model for the action of the Organizer in specifying the DV axis PSmad1 antibody staining shows the gradient of the BMP signaling along the DV axis in an early gastrulating Xenopus embryo A gradient of BMP4 signaling elicits the expression of different genes in a concentrationdependent fasion The diffusible signal proteins secreted by the Spemann anizer (II) The Organizer is able to secret the Wnt blockers Cerberus, Dickkopf and Frzb in the anterior portion of the embryo that generate a gradient of Wnt signaling. Thus, the Wnt signaling gradient specifies the AP axis. Cerberus, a secreted protein from the anizer is important for development of the most anterior head structures Injection of Cerberus mRNA into a vegetal ventral Xenopus blastomere at the 32cell stage induce ectopic head structures Frzb, another secreted protein from the anizer is important for development of the most anterior head structures The frzb is expressed in the head endomesoderm of the anizer The frzb mRNA: dark blue The chordin mRNA: brown Microinjection of frzb mRNA into the marginal zone leads to the inhibition of trunk formation, due to inactivation of the Wnt signaling The anizer is able to secret different sets of signal proteins that antagonize/block BMP and (or) Wnt signaling Mechanisms underlying role of the Spemann anizer in the body axis formation ? How was the anizer specified and formed? What caused the dorsal blastopore lip to differ from any other region of the embryo? ? What factors were being secreted from the anizer to create the antroposterior and dorsoventral axes? ? How did the patterning of the embryo along the body axes bee acpanied? The trunk mesoderm of a neurulastage embryo can be subdivided into four regions along the dorsoventral axis The trunk mesoderm of a neurulastage embryo can be subdivided into four regions along the dorsoventral axis Patterning the mesoderm along the dorsoventral axis (subdivision of the mesoderm) is controlled by the gradient of BMP4 signaling. High doses of BMP4 activate those genes (, Xvent1) for development of the lateral plate mesoderm Intermediate levels of BMP4 instruct formation of the intermediate mesoderm Low doses of BMP4 regulate the paraxial mesoderm differentiation through activating myf5 et al The mesoderm bees notochord tissue when no BMP4 activity is present in the most dorsal region The anteroposterior axial patterning in vertebrates Patterning of the vertebrate embryo along the AP axis will be focused on: Patterning of the dorsal mesoderm that forms the somites, the blocks of mesodermal cells that give rise to the skeleton and muscles of the trunk Patterning of the ectoderm that will develop into the nervous system. Patterning the body plan in animals 1 Development of the Drosophila body plan Specification of the anteroposterior and dorsoventral axis in Drosophila oocyte Setting up the body axes in Drosophila Patterning the Drosophila embryo 2 Patterning the vertebrate body plan Specification and setting up of the body axes in amphibians (Xenopus) Somite formation and anteroposterior patterning Patterning the vertebrate nervous system Specifying the leftright axis (leftright asymmetry of internal ans) Neural tube and somites seen by scanning electron microscopy Patterning of the somiteforming mesoderm along the anteroposterior axis ? Somites are blocks of mesodermal tissue that are formed af