Polar transport in the Drosophila oocyte requires Dynein and Kinesin I cooperation.
BACKGROUND
The cytoskeleton and associated motors play an important role in the establishment of intracellular polarity. Microtubule-based transport is required in many cell types for the asymmetric localization of mRNAs and organelles. A striking example is the Drosophila oocyte, where microtubule-dependent processes govern the asymmetric positioning of the nucleus and the localization to distinct cortical domains of mRNAs that function as cytoplasmic determinants. A conserved machinery for mRNA localization and nuclear positioning involving cytoplasmic Dynein has been postulated; however, the precise role of plus- and minus end-directed microtubule-based transport in axis formation is not yet understood.


RESULTS
Here, we show that mRNA localization and nuclear positioning at mid-oogenesis depend on two motor proteins, cytoplasmic Dynein and Kinesin I. Both of these microtubule motors cooperate in the polar transport of bicoid and gurken mRNAs to their respective cortical domains. In contrast, Kinesin I-mediated transport of oskar to the posterior pole appears to be independent of Dynein. Beside their roles in RNA transport, both motors are involved in nuclear positioning and in exocytosis of Gurken protein. Dynein-Dynactin complexes accumulate at two sites within the oocyte: around the nucleus in a microtubule-independent manner and at the posterior pole through Kinesin-mediated transport.


CONCLUSIONS
The microtubule motors cytoplasmic Dynein and Kinesin I, by driving transport to opposing microtubule ends, function in concert to establish intracellular polarity within the Drosophila oocyte. Furthermore, Kinesin-dependent localization of Dynein suggests that both motors are components of the same complex and therefore might cooperate in recycling each other to the opposite microtubule pole.
Januschke
Jens
J
Laboratory of Developmental Biology, Institut Jacques Monod, 2 place Jussieu, 75251 Paris Cedex 05, France.
Gervais
Louis
L
Dass
Sajith
S
Kaltschmidt
Julia A
JA
Lopez-Schier
Hernan
H
St Johnston
Daniel
D
Brand
Andrea H
AH
Roth
Siegfried
S
Guichet
Antoine
A
D000818:Animals; D002467:Cell Nucleus / Q000502:physiology; D016764:Cell Polarity; D004330:Drosophila / Q000502:physiology*; D029721:Drosophila Proteins / Q000235:genetics; D004398:Dyneins / Q000235:genetics / Q000502:physiology*; D005089:Exocytosis; D005260:Female; D017403:In Situ Hybridization; D016547:Kinesins / Q000235:genetics / Q000502:physiology*; D008870:Microtubules / Q000502:physiology; D016296:Mutagenesis; D009865:Oocytes / Q000166:cytology / Q000502:physiology*; D012333:RNA, Messenger / Q000235:genetics; D014158:Transcription, Genetic
D029721:Drosophila Proteins; D012333:RNA, Messenger; D004398:Dyneins; D016547:Kinesins