Two-dimensional morphogen gradient in Xenopus: boundary formation and real-time transduction response.
Morphogen gradients play an important role in pattern formation in embryo. However, the interpretation of position in a morphogen gradient is not well understood. Because it is hard to analyze morphogen gradients especially in opaque embryos such as those of Xenopus, it is necessary to fix and section the embryo, thereby eliminating the possibility of real-time observation, and making more difficult the interpretation of events that take place in three dimensions. We describe here a two-dimensional preparation of cells from a Xenopus blastula animal cap, in which an activin concentration gradient appears to be formed and interpreted at the same rate and in the same way as in normal embryos. We use two-dimensional preparations of this kind to contribute the following new information about gradient formation and interpretation in embryo. We determine the dynamics of formation of an activin activity gradient in real time. We demonstrate that this gradient is established by diffusion of activin through intercellular space and does not require internalization of receptor or ligand. We also show that the generation of a boundary of gene expression depends on the interpretation, rather than a change of composition, of the concentration gradient.
Kinoshita
T
T
Developmental Biology, Faculty of Science and Technology, Kwansei Gakuin University, Sanda, Japan. tom@ksc.kwansei.ac.jp
Jullien
J
J
Gurdon
J B
JB
D000818:Animals; D030801:Animals, Genetically Modified; D019521:Body Patterning; D018507:Gene Expression Regulation, Developmental; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D017403:In Situ Hybridization; D028322:Inhibin-beta Subunits / Q000235:genetics / Q000378:metabolism; D018613:Microscopy, Confocal; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D020825:T-Box Domain Proteins / Q000235:genetics; D046509:Tissue Culture Techniques; D014981:Xenopus / Q000196:embryology* / Q000235:genetics / Q000502:physiology; D029867:Xenopus Proteins / Q000235:genetics / Q000378:metabolism
D011993:Recombinant Fusion Proteins; D020825:T-Box Domain Proteins; C116765:TBXT protein, Xenopus; D029867:Xenopus Proteins; D049452:Green Fluorescent Proteins; D028322:Inhibin-beta Subunits