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Mouse Oocyte Microinjection, Maturation and Ploidy Assessment
Published on: July 23, 2011
Centrosome precursors in the acentriolar mouse oocyte
1University of California, San Francisco 94143, USA. calarco@itsa.ucsf.edu
Microscopy Research and Technique
|June 8, 2000
Summary
Before mouse oocyte maturation, unique gamma-tubulin-positive structures called multivesicular aggregates (MVA) form. These structures, distinct from microtubule organizing centers (MTOC), are identified as potential precursors to MTOC.
Area of Science:
- Cell Biology
- Developmental Biology
- Reproductive Biology
Background:
- Centrioles are absent in mature mouse oocytes.
- Multiple microtubule organizing centers (MTOC) form spindle and mitotic poles during oocyte maturation and early cleavage.
- The precursors to these MTOCs in early oogenesis remain unidentified.
Purpose of the Study:
- To identify and characterize the structures present before the formation of multiple MTOCs in mouse oocytes.
- To describe the location and microtubule (MT)-nucleating ability of these pre-maturation structures.
Main Methods:
- Correlative confocal, immunofluorescence, and electron microscopy were employed.
- Mouse oocytes were collected at "time zero" (ovaries released into 2% paraformaldehyde).
- Characterization of gamma-tubulin-positive structures and their ultrastructure was performed.
Main Results:
- Two large (10 microm diameter), gamma-tubulin-positive structures, termed multivesicular aggregates (MVA), were identified in the oocyte cortex.
- MVAs do not morphologically resemble MTOCs and do not appear to nucleate MTs.
- Ultrastructural analysis revealed vesicular structures, including ~25 nm rings, within MVAs.
Conclusions:
- MVAs are identified as unique centrosomal precursors in immature mouse oocytes.
- The unique ultrastructure of MVAs may explain the function of MTOCs in the prematuration oocyte.
- MVAs migrate and break down into smaller units during maturation, with some forming functional MTOCs.
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