Regulative development of the sea urchin embryo: signalling cascades and morphogen gradients.
Differentiation of sea urchin embryo ectoderm, endoderm and mesenchyme cells, whose anlagen are arrayed along the animal-vegetal axis, relies on both maternally regulated localized transcription factor activities and cell-cell signalling. Classic models proposed that fates are determined by opposing animal and vegetal morphogenetic gradients, whereas current models emphasize unidirectional and sequential vegetal-to-animal signalling cascades between adjacent blastomeres. Recent data support aspects of both models: the vegetal micromeres send one or more signals, which depend on a nuclear beta-catenin-dependent pathway, that both activate Notch signalling required for secondary mesenchyme fate and promote endoderm differentiation and gastrulation. This is opposed by an animalizing domain of BMP4 signals that regulates ectodermal cell fates and establishes the ectoderm-endoderm border.
Angerer
L M
LM
Department of Biology, University of Rochester, Rochester, NY 14627, USA.
Angerer
R C
RC
D000818:Animals; D019521:Body Patterning; D019485:Bone Morphogenetic Proteins / Q000502:physiology; D002450:Cell Communication / Q000502:physiology; D002454:Cell Differentiation / Q000502:physiology; D003598:Cytoskeletal Proteins / Q000502:physiology; D004625:Embryo, Nonmammalian / Q000196:embryology*; D008565:Membrane Proteins / Q000502:physiology; D008954:Models, Biological; D009024:Morphogenesis / Q000502:physiology; D051880:Receptors, Notch; D012617:Sea Urchins / Q000196:embryology* / Q000502:physiology; D015398:Signal Transduction / Q000502:physiology*; D015534:Trans-Activators; D014158:Transcription, Genetic; D051176:beta Catenin
D019485:Bone Morphogenetic Proteins; D003598:Cytoskeletal Proteins; D008565:Membrane Proteins; D051880:Receptors, Notch; D015534:Trans-Activators; D051176:beta Catenin