The antero-posterior and dorso-ventral axes of the <i>Drosophila</i> embryo are set up during oogenesis. These axes of polarity are the results of several symmetry-breaking steps that characterise the development of the <i>Drosophila</i> oocyte. During my PhD, I have studied two of these steps. Oocyte determination. During early oogenesis, one cell is selected to become the oocyte within a cyst of 16 germ cells. These 16 germ cells are all siblings and share the same cytoplasm. By using several oocyte-specific markers, I have found that there at least three different pathways to restrict the oocyte fate to one cell. The restriction of cytoplasmic proteins depends on the microtubules and on the activity of the Egl/BicD complex. The restriction of meiosis also depends on the same complex but is independent of the microtubules. Finally, the restriction of the centrosomes is independent of both the microtubules and the Egl/BicD complex. From this analysis, I also concluded that the selection of the oocyte does not depend on the microtubules and that the oocyte is probably selected while the cyst is still dividing, as shown by the asymmetric inheritance of the fusome. By homology with the polarisation of the C. elegans one cell embryo, I have shown that the <i>Drosophila</i> homologues of <i>par-1, par-3 </i>and <i>par-6</i> are required for the first polarisation of the oocyte. This polarisation is then required to maintain the oocyte fate. Oocyte polarisation. During mid-oogenesis, the A/P and D/V axes of the oocyte are defined by the asymmetric localisation of several mRNAs. I have conducted a germline clone screen to find lethal genes involved in this polarisation. In particular, I report here that one of the major <i>Drosophila</i> hnRNP, <i>hrp48</i>, is required for the localisation of <i>oskar</i> mRNA within the oocyte.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:604905 |
| Date | January 2003 |
| Creators | Huynh, J. R. |
| Publisher | University of Cambridge |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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