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Kinesin I-dependent cortical exclusion restricts pole plasm to the oocyte posterior
Byeong-Jik Cha1, Laura R Serbus, Birgit S Koppetsch
1Program in Molecular Medicine, University of Massachusetts Medical School, Worcester, MA 01605, USA.
Abstract:
Microtubules and the plus-end-directed microtubule motor Kinesin I are required for the selective accumulation of oskar mRNA at the posterior cortex of the Drosophila melanogaster oocyte, which is essential to posterior patterning and pole plasm assembly. We present evidence that microtubule minus ends associate with the entire cortex, and that Kinesin and microtubules are not required for oskar mRNA association with the posterior pole, but prevent ectopic localization of this transcript and the pole plasm proteins Oskar and Vasa to other cortical regions. Cortical binding of oskar mRNA seems to be dependent on the actin cytoskeleton. We conclude that most of the actin-rich oocyte cortex can support pole plasm assembly, and propose that Kinesin restricts pole plasm formation to the posterior by moving oskar mRNA away from microtubule-rich lateral and anterior cortical regions.
Insights
Kinesin motor proteins and microtubules prevent oskar mRNA from localizing ectopically in Drosophila oocytes. Actin, not microtubules, binds oskar mRNA to the posterior pole.
Area of Science:
- Developmental Biology
- Cell Biology
- Genetics
Background:
- Oskar mRNA localization to the posterior pole of the Drosophila oocyte is crucial for establishing anterior-posterior polarity and germline development.
- Microtubules and the plus-end-directed motor Kinesin I have been implicated in this localization process.
Purpose of the Study:
- To investigate the precise roles of microtubules, Kinesin I, and the actin cytoskeleton in the localization of oskar mRNA and pole plasm proteins.
- To determine how oskar mRNA is selectively retained at the posterior pole.
Main Methods:
- Analysis of oskar mRNA and pole plasm protein localization in Drosophila oocytes under various experimental conditions.
- Investigation of the interaction between the actin cytoskeleton and oskar mRNA.
- Examination of microtubule organization and Kinesin I function.
Main Results:
- Microtubule minus ends are associated with the entire oocyte cortex.
- Kinesin I and microtubules are not essential for initial oskar mRNA binding to the posterior pole but prevent its ectopic localization to other cortical regions.
- Cortical binding of oskar mRNA appears to be dependent on the actin cytoskeleton.
Conclusions:
- The actin-rich cortex can support pole plasm assembly.
- Kinesin I functions to restrict pole plasm formation to the posterior pole by actively moving oskar mRNA away from anterior and lateral cortical regions rich in microtubules.