Related Experiment Video
Updated: May 15, 2025
Visualization of ATP Synthase Dimers in Mitochondria by Electron Cryo-tomography
Published on: September 14, 2014
Snapshots of mitochondrial fission imaged by cryo-scanning transmission electron tomography
Peter Kirchweger1,2, Sharon Grayer Wolf3, Neta Varsano3
1Department of Chemical and Biological Physics, Weizmann Institute of Sciences, 7610001 Rehovot, Israel.
Abstract:
Mitochondria undergo constant remodeling via fission, fusion, extension and degradation. Fission, in particular, depends on the accumulation of mitochondrial fission factor (MFF) and subsequent recruitment of the dynamin-related protein DRP1 (also known as DNM1L). We used cryo-scanning transmission electron tomography (cryo-STET) to investigate mitochondrial morphologies in MFF mutant (MFF-/-) mouse embryonic fibroblast (MEF) cells in ATP-depleting conditions that normally induce fission. The capability of cryo-STET to image through the cytoplasmic volume to a depth of 1 µm facilitated visualization of intact mitochondria and their surroundings. We imaged changes in mitochondrial morphology and cristae structure, as well as contacts with the endoplasmic reticulum (ER), degradative organelles and the cytoskeleton at stalled fission sites. We found disruption of the outer mitochondrial membrane at contact sites with the ER and degradative organelles at sites of mitophagy. We identified fission sites where the inner mitochondrial membrane is already separated while the outer membrane is still continuous. Although MFF is a general fission factor, these observations demonstrate that mitochondrial fission can proceed to the final stage in its absence. The use of cryo-STET allays concerns about the loss of structures due to sample thinning required for tomography using cryo-transmission electron microscopy.
Insights
Mitochondrial fission, crucial for cell remodeling, can occur even without the mitochondrial fission factor (MFF). Cryo-STET imaging revealed fission processes proceeding to completion in MFF-deficient cells.
Area of Science:
- Cell Biology
- Mitochondrial Dynamics
- Electron Microscopy
Background:
- Mitochondria are dynamic organelles undergoing constant remodeling, including fission, fusion, and degradation.
- Mitochondrial fission is primarily mediated by the mitochondrial fission factor (MFF) and dynamin-related protein 1 (DRP1).
Purpose of the Study:
- To investigate mitochondrial morphologies and fission processes in MFF-deficient cells using cryo-scanning transmission electron tomography (cryo-STET).
- To visualize intact mitochondria and their interactions with cellular components at stalled fission sites.
Main Methods:
- Cryo-scanning transmission electron tomography (cryo-STET) was employed to image mitochondrial structures in MFF mutant mouse embryonic fibroblast (MEF) cells under ATP-depleting conditions.
- High-resolution imaging allowed visualization of mitochondrial morphology, cristae, and contacts with the endoplasmic reticulum (ER) and degradative organelles.
Main Results:
- Mitochondrial fission was observed to proceed to completion in the absence of MFF.
- Disruption of the outer mitochondrial membrane at contact sites with the ER and degradative organelles was noted during mitophagy.
- Fission sites were identified where the inner mitochondrial membrane separated before the outer membrane.
Conclusions:
- Mitochondrial fission can occur independently of MFF, challenging the established model.
- Cryo-STET provides high-resolution, in situ structural information without sample thinning artifacts.
- This study offers new insights into the complex mechanisms of mitochondrial fission and mitophagy.
More Related Videos
Related Concept Videos
01:07Electron Microscope Tomography and Single-particle Reconstruction
Electron Tomography
Electron tomography can be performed either in TEM or STEM (scanning transmission...
01:28Cryo-electron Microscopy