Close associates: ER connection aids mitochondria in Neurospora crassa

Research Areas:

Gene regulation, Mitochondria, Neurospora crassa, Fluorescence microscopy

Imaging Needs:

Good signal-to-noise

Imaging System:
  • MitoTracker Green FM green-fluorescent mitochondrial stain
  • Olympus IX81 inverted microscope
  • 60X, NA1.42 oil objective lens
  • Yokogawa CSU-10 spinning disc confocal head modified
  • Quorum Technologies condenser lens in the optical path
  • Hamamatsu ORCA-R2 CCD camera
  • Molecular Devices MetaMorph software
Imaging cellular events in real time

Find out how Fang Huang, Jeorg Bewersdorf, and colleagues use the sCMOS technology in the ORCA-Flash4.0 camera to achieve video-rate imaging at nanometer scales. Read now.

THE QUESTION

How does association with the endoplasmic reticulum influence mitochondrial function?

The endoplasmic reticulum mitochondria encounter structure (ERMES) anchors mitochondria to the ER in the fungus Neurospora crassa. The four structural components of ERMES—the proteins Mmm1, Mmm2, Mdm10 and Mdm12—affect mitochondrial morphology, DNA, partitioning during inheritance, and assembly of some mitochondrial outer membrane proteins.

THE BARRIERS

Because disruption of individual ERMES components leads to a wide array of phenotuypes, it’s difficult to fully separate primary effects versus downstream ones, and understand the different roles of ERMES and its components.

THE SOLUTION

Analysis of Mutations in Neurospora crassa ERMES Components Reveals Specific Functions Related to β-Barrel Protein Assembly and Maintenance of Mitochondrial Morphology
Jeremy G. Wideman, Sebastian W. K. Lackey, Martin A. Srayko, Kacie A. Norton, Frank E. Nargang
PLoS One 2013 Aug 8(8): e71837. PMCID: PMC3733929.

To better assign primary roles for ERMES components, Wideman, et al,1 set out to define individual domains in each protein that mediate the different functions. They studied the effects of Gem1 (which some groups studying S. cervisiae believe to be part of ERMES) and ERMES component mutations and deletions on mitochondrial morphology and outer membrane proteins in N. crassa. For the morphology studies, fungi were stained with MitoTracker Green FM green-fluorescent mitochondrial stain and imaged using a Hamamatsu ORCA-R2 CCD camera.

The researchers found that Mmm1 or Mmm2 deletion leads to assembly defects in the protein Tom40, which enables protein entry into mitochondria, while deletion of any ERMES component causes a Tom22 assembly defect. In contrast, Gem1 deletion resulted in a small change in mitochondrial shape, but no other observed effects on ERMES-related characteristics. The authors conclude that Gem1 is different from the other ERMES proteins, if it is an ERMES component.

THE POSSIBILITIES

Wideman, et al, used Hamamatsu’s ORCA-R2 CCD camera to visualize shape changes in fungal mitochondria. Learn how newer cMOS detectors are making it possible to track intracellular events at video speeds with low-nanometer precision in Exciting Advances Push the Limits of Visualization.

References

  1. Wideman, et al. Analysis of Mutations in Neurospora crassa ERMES Components Reveals Specific Functions Related to β-Barrel Protein Assembly and Maintenance of Mitochondrial Morphology. PLoS One. 2013 Aug 8(8): e71837. PMCID: PMC3733929.
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