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Immunoprobe Localization by Correlative Microscopy.
1Department of Anatomy, Box 0452, University of California, San Francisco, CA 94143
Summary
Light microscopy can misidentify organelles in mammalian oocytes. This study shows gamma-tubulin and centrosome antigens localize to multivesicular aggregates, not standard microtubule organizing centers, in eggs.
Area of Science:
- Cell Biology
- Microscopy Techniques
- Oocyte Biology
Background:
- Mammalian oocytes are difficult to study with electron microscopy (EM) due to hydration and size.
- Light microscopy (LM) techniques like immunofluorescence are often used, but can lead to misinterpretations.
- Previous studies presumed standard microtubule organizing centers (MTOCs) house centrosome antigens.
Purpose of the Study:
- To investigate the accuracy of LM for predicting organelle ultrastructure in mammalian oocytes.
- To correlate light and electron microscopy data for centrosome and MTOC antigen localization.
- To clarify the identity and function of organelles containing these antigens.
Main Methods:
- Correlative light and electron microscopy (LM-EM) was employed.
- Immunofluorescence and post-embedding immuno-EM were used for antigen detection.
- Antibodies against 5051 and gamma-tubulin (a conserved MTOC element) were utilized, with Lowicryl embedding for optimal EM results.
Main Results:
- Prior to nuclear breakdown, 5051 and gamma-tubulin antigens were found exclusively in multivesicular aggregates (MVAs).
- MVAs bear no ultrastructural resemblance to standard MTOCs.
- Gamma-tubulin's presence suggests MVAs are precursors to centrosomes with a unique ultrastructure.
Conclusions:
- Light microscopy alone can lead to erroneous conclusions about organelle identity and function in mammalian oocytes.
- Multivesicular aggregates, not standard MTOCs, contain key centrosome/MTOC antigens before nuclear breakdown.
- MVAs represent a distinct organelle type serving as centrosomal precursors.