Development

Messages on the Move

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Science  11 May 2001:
Vol. 292, Issue 5519, pp. 1025
DOI: 10.1126/science.292.5519.1025c

Correctly polarized epithelial cells are essential in developing tissues. Polarity is established by the asymmetric distribution of molecules to the apical and basolateral cell surfaces, enabling each to perform distinct functions. In many cases, cell polarity is achieved through differential protein trafficking. However, asymmetry can also be generated by the differential trafficking of messenger RNAs (mRNAs).

Two recent reports indicate that the distribution of Wingless (WG), a secreted glycoprotein implicated in developmental signaling events, is controlled via its mRNA. Using high-resolution in situ hybridization in fruit fly embryos, Simmonds et al. found that the apical cytoplasm of most epithelial cells is enriched in Wg mRNA and that this localization is critical for optimal signaling activity of the WG protein. Independently, Wilkie and Davis used time-lapse imaging to explore the mechanism by which Wg mRNA and other apically localized mRNAs reach their subcellular destination. The mRNAs are exported from the nucleus in all directions but then assemble into particles that are transported along microtubules to the apical cytoplasm. The transport is mediated by the motor protein dynein in association with dynactin. Such dynein-mediated transport may be a common mechanism for mRNA localization. — PAK

Cell105, 197; 209 (2001).

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