Re-examination of the secretory compartments in the study of transport organelles in mitotic cells with correlative light, immune and three-dimensional electron microscopy

Session

LSA.6 - Applications of correlative microscopy of biological systems

Authors

Dr. Galina Beznoussenko (1), Anna Mironov (2), Sara Barozzi (1), Dario Parazzoli (1), Dr. Alexander Mironov (1)

Affiliations

1. The FIRC Institute of Molecular Oncology
2. Universita Vita-Salute San Raffaele

Keywords

Electron microscopy, Correlative microscopy, Electron tomography, mitosis

Abstract text

Summary

Recent development of the modern electron microscopy (EM) and in particular three-dimensional EM, correlative light EM (CLEM) and immune EM (IEM) creates the necessity for the re-evaluation of so-called established facts. 

 

Introduction

For instance, according to the current consensus, during mitosis, the Golgi complex (GC) undergoes fragmentation and then COPI-dependent vesiculation. Many 52-nm COPI-coated vesicles are accumulated in the cytosol. ER-Golgi transport is blocked and COPII-coated buds disappear. These observations were made without application of 3DEM and should be verified.

 

Methods/Materials

We used CLEM, IEM and 3DEM of the culture cells.

 

Results and Discussion

We found that that above mentioned facts are not precise. For instance, during prophase and metaphase, we found short non-polarized Golgi stacks containing Golgi glycosylation enzymes and inter-cisternal connections. Polarization of Golgi stacks started to form only during telophase and cytokinesis. 52-nm presumably COPI-dependent vesicles were rare, they were uncoated and did not contain Golgi enzymes. The clusters of round profile observed on routine EM sections appeared as aggregates of irregular disks and beaded partially coated membrane tubules. Membrane buds with cross diameter of more than 65 nm in diameter were coated with the unusual coat possessing the EM features similar to the COPII-coat. However, instead of the standard 12-nm thickness this coat was thicker (up to 25 nm in thickness). Also isolated clathrin-coated vesicles were accumulated during cytokinesis. These observations are discussed from the point of view of different models of intracellular transport.

 

Conclusion 

Vesicular model describing Golgi behaviour during mitosis should be reconsidered or adapted.

References