β-catenin Signaling and Axis Specification
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This animation provides a representation of the β-catenin signaling pathway in response to fertilization and the process of axis specification that occurs early in development. The process shown is based on analysis of embryos of the amphibian Xenopus. Prior to fertilization components of the Wnt/β-catenin pathway, Dishevelled (Dsh), glycogen synthase kinase-3 (GSK-3) binding protein (GBP), and β-catenin (β-CAT) are uniformly distributed in the egg and β-CAT is degraded by a ubiquitin (U)-proteasome process following phosphorylation (P) by casein kinase 1 (not shown) and GSK-3. Sperm entry causes a calcium wave and then the microtubules become oriented with the plus ends pointing away from the sperm entry point. Dsh accumulates in the side opposite sperm entry, which will become the anterior and dorsal structures, possibly by association with GBP, which in turn binds protein motors that move along the oriented microtubules. The accumulation of Dsh promotes the stabilization and dorsal accumulation of β-CAT, which then activates direct target genes, including the homeobox genes siamois and twinned. Activation of these genes on the prospective dorsal side is necessary and sufficient for formation of the gastrula organizer (Spemann Organizer), which organizes the embryonic germ layers and axes.
This animation would be useful in illustrating events that occur early in embryogenesis and how embryos become polarized as a consequence of localized signaling processes.
The animation was created by Cameron Slayden with the scientific oversight of Randall Moon.
Learning Resource Type: Animation
Context: Undergraduate upper division, graduate, professional (degree program)
Intended Users: Teacher, learner
Intended Educational Use: Teach, learn
Discipline: Developmental biology, cell biology, reproductive biology
Keywords: signal transduction, cytoskeleton, reproduction, gene expression, movie
Format: Shockwave Flash Object (swf file)
Size: 91 kb
Requirements: Macromedia Flash 5 or higher (http://www.macromedia.com/downloads/)
Connections Map: R. T. Moon, Xenopus egg Wnt/beta-catenin pathway. Sci. STKE (Connections Map, as seen June 2004), http://stke.sciencemag.org/cgi/cm/stkecm;CMP_6031. [Specific Pathway]
Limits for Use
Rights: This material may be downloaded, printed, linked to, and/or redistributed without modification for noncommercial, course-teaching purposes only, provided credit to STKE is included by listing the citation for the teaching resource.
Citation: R. T. Moon, β-catenin signaling and axis specification. Sci. STKE2004, tr6 (2004).