bicoid mRNA localises to the Drosophila oocyte anterior by random Dynein-mediated transport and anchoring

Trovisco V, Belaya K, Nashchekin D, Irion U, Sirinakis G, Butler R, Lee JJ, Gavis ER and St Johnston D. (2016) eLife 2016;10.7554/eLife.17537 [Epub ahead of print]

The polarised body axis of the fruitlfy is created by the presence of different proteins at different ends of the developing oocyte. This study sought to discover how the messenger RNA for Bicoid, one of two crucial signals for anterior-posterior body axis formation in Drosophila, becomes specifically localised at the oocyte anterior. By following labelled bicoid mRNA with live imaging and super-resolution microscopy, the team show that the mRNA movements within the cell are random but the anchoring occurs only at the cell's anterior, allowing the packaged granules of bicoid mRNA to become localised there.  

Abstract from the paper

bicoid mRNA localises to the Drosophila oocyte anterior from stage 9 of oogenesis onwards to provide a local source for Bicoid protein for embryonic patterning. Live imaging at stage 9 reveals that bicoid mRNA particles undergo rapid Dynein-dependent movements near the oocyte anterior, but with no directional bias. Furthermore, bicoid mRNA localises normally in shot2A2, which abolishes the polarised microtubule organisation. FRAP and photo-conversion experiments demonstrate that the RNA is stably anchored at the anterior, independently of microtubules. Thus, bicoid mRNA is localised by random active transport and anterior anchoring. Super-resolution imaging reveals that bicoid mRNA forms 110-120nm particles with variable RNA content, but constant size. These particles appear to be well-defined structures that package the RNA for transport and anchoring.

Abstract and figure excerpt reproduced under CC-BY-4.0 licence.

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