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| Cell Polarity: Can Wnt Act as a Positional Cue? |
| M. Roh,1 A. Mikels,2 R. Nusse,2 B. Goldstein1; 1Biology, University of North Carolina, Chapel Hill, NC, 2Developmental Biology, Stanford University, Stanford, CA |
| Presentation Number: 1926 |
| Poster Board Number: B525 |
| Establishing cell polarity is essential for normal development. Cell polarity requires intricate cell-cell signalling and remodeling of the underlying cytoskeleton - all phenomena that remain under-explored. The Wnt pathway is a conserved pathway, known to play a role in establishing cell polarity in a variety of organisms. Although this is a well-studied pathway, an outstanding question that remains is whether a Wnt signal can act as a positional cue. To address this, we are studying the four-cell stage C. elegans embryo. At this stage, signals from one cell to its neighbour result in polarization of the responding cell such that the responding cell divides asymmetrically. Two signals, MES-1 and MOM-2/Wnt, are sent from the signalling cell to polarize the responding cell and align the mitotic spindle as well as regulate gene expression. Although both pathways are required for polarized division, cell manipulation experiments suggest that it is the position of the Wnt signal that dictates spindle positioning (Goldstein et al., 2006). However, it remains elusive whether this is a direct effect of Wnt, or an indirect downstream effect. To address this issue, we use a novel approach in which beads coated with purified MOM-2/Wnt proteins are used to manipulate the position of the MOM-2/Wnt source on an isolated responding cell. We have also constructed a transgenic strain containing GFP-tagged tubulin in a mom-2/Wnt background. Thus, the effects of a local MOM-2/Wnt signal on spindle dynamics can be analyzed in real-time. Combining these cell manipulation experiments with live and fixed cell imaging, our goal is to determine definitively whether a Wnt signal can directly act as a positional cue during cell polarization. In addition, we hope to extend this approach to investigate the effects of Wnt signalling on downstream cell polarity proteins by high resolution microscopy in C. elegans. |
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