Dynactin suppresses the retrograde movement of apically localized mRNA in <i>Drosophila</i> blastoderm embryos

Vendra, Georgia; Hamilton, Russell S.; Davis, Ilan

doi:10.1261/rna.509007

Cited by 15 publications

(20 citation statements)

References 45 publications

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“…We found that all movement of bcd *GFP particles is completely eliminated in Dhc mutant oocytes, including both unidirectional and bidirectional motility (Movie S6). These observations are consistent with recent evidence that Dynein can mediate both minus- and plus-end directed transport [9–11]. The minimal amount of bcd detected at the anterior cortex could be due to residual Dynein function of the hypomorphic alleles used, which is sufficient at least to permit oogenesis (Figure 2D–2F).…”

Section: Resultssupporting

confidence: 91%

Changes in bicoid mRNA Anchoring Highlight Conserved Mechanisms during the Oocyte-to-Embryo Transition

et al. 2008

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Summary Intracellular mRNA localization directs protein synthesis to particular subcellular domains to establish embryonic polarity in a wide range of vertebrates and invertebrates. In Drosophila, bicoid (bcd) mRNA is pre-localized at the anterior of the oocyte. After fertilization, this RNA is translated to produce a Bcd protein gradient that determines anterior cell fates [1, 2]. Recent analysis of bcd mRNA during late stages of oogenesis led to a model for steady-state localization of bcd by continual active transport [3]. Here, we elucidate the path and mechanism of sustained bcd mRNA transport by direct observation of bcd RNA particle translocation in living oocytes. However, this mechanism cannot explain maintenance of bcd localization throughout the end of oogenesis, when microtubules disassemble in preparation for embryogenesis [4, 5] or retention of bcd at the anterior in mature oocytes, which can remain dormant, but developmentally competent, for weeks prior to fertilization [6]. Through temporal analysis of bcd RNA particle dynamics, we show that bcd mRNA shifts from continuous active transport to stable actin-dependent anchoring at the end of oogenesis, ensuring the developmental integrity of the oocyte during dormancy. Egg activation triggers release of bcd from the anterior cortex for proper deployment in the fertilized egg, probably through reorganization of the actin cytoskeleton. These findings uncover a surprising parallel between flies and frogs, as cortically tethered Xenopus Vg1mRNA undergoes a similar redistribution during oocyte maturation [7]. Our results highlight a conserved mechanism used by invertebrates and vertebrates to regulate mRNA anchoring and redeployment during the oocyte-to-embryo transition.

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Section: Resultssupporting

confidence: 91%

Changes in bicoid mRNA Anchoring Highlight Conserved Mechanisms during the Oocyte-to-Embryo Transition

et al. 2008

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“…When published, the functional significance of the interaction was unknown, but our data supports the hypothesis that it may be important. Our recent work[24]establishes that plus-end droplet motion is driven by kinesin-1, so it is unlikely that the effects of BicD on plus-end motion are simply due to its effects on dynein, although recent work suggests that this may be the case for some mRNA transport[25]. Second, the large phase IIb run length peak is absent in the t = 3 null, consistent with the hypothesis that BicD can acutely up-regulate both directions of transport.…”

Section: Discussionsupporting

confidence: 77%

BicaudalD Actively Regulates Microtubule Motor Activity in Lipid Droplet Transport

Larsen

Cermelli

et al. 2008

PLoS ONE

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BackgroundA great deal of sub-cellular organelle positioning, and essentially all minus-ended organelle transport, depends on cytoplasmic dynein, but how dynein's function is regulated is not well understood. BicD is established to play a critical role in mediating dynein function—loss of BicD results in improperly localized nuclei, mRNA particles, and a dispersed Golgi apparatus—however exactly what BicD's role is remains unknown. Nonetheless, it is widely believed that BicD may act to tether dynein to cargos. Here we use a combination of biophysical and biochemical studies to investigate BicD's role in lipid droplet transport during Drosophila embryogenesis.Methodology/Principal FindingsFunctional loss of BicD impairs the embryo's ability to control the net direction of droplet transport; the developmentally controlled reversal in transport is eliminated. We find that minimal BicD expression (near-BicDnull) decreases the average run length of both plus and minus end directed microtubule (MT) based transport. A point mutation affecting the BicD N-terminus has very similar effects on transport during cellularization (phase II), but in phase III (gastrulation) motion actually appears better than in the wild-type.Conclusions/SignificanceIn contrast to a simple static tethering model of BicD function, or a role only in initial dynein recruitment to the cargo, our data uncovers a new dynamic role for BicD in actively regulating transport. Lipid droplets move bi-directionally, and our investigations demonstrate that BicD plays a critical—and temporally changing—role in balancing the relative contributions of plus-end and minus-end motors to control the net direction of transport. Our results suggest that while BicD might contribute to recruitment of dynein to the cargo it is not absolutely required for such dynein localization, and it clearly contributes to regulation, helping activation/inactivation of the motors.

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“…The mechanism of localization of MS2x6 RNA by this fusion protein was reminiscent of that exhibited by endogenous apical transcripts in wild-type embryos, being sensitive to preinjection of functionblocking antibodies to dynein subunits (Fig. 1B) (Wilkie and Davis 2001) and driven by rapid bidirectional movements with an overall bias in the minus-end direction (Supplemental Movie 1; Bullock et al 2006;Vendra et al 2007). Thus, in flies, as in mammals (Hoogenraad et al 2003), the role of the BicD CTD in dynein transport can be functionally substituted by a heterologous recognition motif.…”

Section: A Conserved Role Of the Ctd Of Drosophila Bicd In Recruitingmentioning

confidence: 93%

Egalitarian is a selective RNA-binding protein linking mRNA localization signals to the dynein motor

Dienstbier¹,

Boehl²,

Li³

et al. 2009

Genes Dev.

191

318

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Cytoplasmic sorting of mRNAs by microtubule-based transport is widespread, yet very little is known at the molecular level about how specific transcripts are linked to motor complexes. In Drosophila, minus-end-directed transport of developmentally important transcripts by the dynein motor is mediated by seemingly divergent mRNA elements. Here we provide evidence that direct recognition of these mRNA localization signals is mediated by the Egalitarian (Egl) protein. Egl and the dynein cofactor Bicaudal-D (BicD) are the only proteins from embryonic extracts that are abundantly and specifically enriched on RNA localization signals from transcripts of gurken, hairy, K10, and the I factor retrotransposon. In vitro assays show that, despite lacking a canonical RNAbinding motif, Egl directly recognizes active localization elements. We also reveal a physical interaction between Egl and a conserved domain for cargo recruitment in BicD and present data suggesting that Egl participates selectively in BicD-mediated transport of mRNA in vivo. Our work leads to the first working model for a complete connection between minus-end-directed mRNA localization signals and microtubules and reveals molecular strategies that are likely to be of general relevance for cargo transport by dynein.[Keywords: Drosophila; dynein; mRNA localization; microtubule-based transport; stem-loop] Supplemental material is available at http://www.genesdev.org.

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Dynactin suppresses the retrograde movement of apically localized mRNA in Drosophila blastoderm embryos

Cited by 15 publications

References 45 publications

Changes in bicoid mRNA Anchoring Highlight Conserved Mechanisms during the Oocyte-to-Embryo Transition

Changes in bicoid mRNA Anchoring Highlight Conserved Mechanisms during the Oocyte-to-Embryo Transition

BicaudalD Actively Regulates Microtubule Motor Activity in Lipid Droplet Transport

Egalitarian is a selective RNA-binding protein linking mRNA localization signals to the dynein motor

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