Identification and investigation of mitochondria lacking cytochrome c oxidase activity in axons
J Zambonin1, S Engeham, G R Campbell
1Mitochondrial Research Group, Institute for Ageing and Health, The Medical School, Newcastle University, Framlington Place, Newcastle upon Tyne NE2 4HH, UK.
Abstract:
Mitochondrial defects have been implicated in the degeneration of axons in a number of CNS disorders, including multiple sclerosis. Uniquely, mitochondria harbor the only non-nuclear DNA (mitochondrial DNA or mtDNA), which encodes functionally important subunits of the respiratory chain. The pattern of mitochondrial respiratory chain subunit expression provides important clues to the underlying mechanism of mitochondrial injury. In snap frozen tissue mitochondrial respiratory chain complex IV or cytochrome c oxidase (COX) activity may be determined using a well-established histochemical technique, COX histochemistry. Lack of COX activity may be the result of mtDNA mutations, degradation of transcripts of subunits, modification of subunits or inhibition of complexes. Mitochondria lacking complex IV activity, however, have not been further explored within axons in CNS disorders. By combining COX histochemistry with immunofluorescent labeling of mitochondrial proteins we describe a method to identify mitochondria lacking complex IV activity in CNS tissue and locate inactive mitochondria to axons using confocal microscopy. Inactive axonal mitochondria may then be further investigated using confocal microscopy to define the pattern of mitochondrial respiratory chain complex subunit expression. Our technique may be used to gain important clues to the underlying mechanisms of mitochondrial injury within axons in a number of CNS disorders and relevant animal models.
Insights
Mitochondrial defects in axons are linked to CNS disorders. A new method identifies inactive mitochondria in axons, revealing insights into mitochondrial injury mechanisms in neurological diseases.
Area of Science:
- Neuroscience
- Cell Biology
- Genetics
Background:
- Mitochondrial defects contribute to axonal degeneration in CNS disorders like multiple sclerosis.
- Mitochondria contain non-nuclear DNA (mtDNA) crucial for respiratory chain function.
- Understanding respiratory chain subunit expression patterns aids in elucidating mitochondrial injury mechanisms.
Purpose of the Study:
- To develop and validate a method for identifying mitochondria lacking cytochrome c oxidase (COX) activity within CNS axons.
- To investigate the pattern of respiratory chain subunit expression in inactive axonal mitochondria.
- To provide insights into the mechanisms of axonal mitochondrial injury in CNS disorders.
Main Methods:
- Combined COX histochemistry with immunofluorescent labeling of mitochondrial proteins.
- Utilized confocal microscopy to identify and localize COX-deficient mitochondria in CNS tissue.
- Analyzed the expression of respiratory chain subunits in inactive axonal mitochondria.
Main Results:
- Successfully identified mitochondria lacking COX activity within CNS axons.
- Demonstrated the ability to investigate the respiratory chain subunit expression pattern in these inactive axonal mitochondria.
- Established a novel technique for exploring axonal mitochondrial dysfunction.
Conclusions:
- The developed method allows for the identification and characterization of inactive axonal mitochondria.
- This technique offers valuable insights into the mechanisms of mitochondrial injury in axons across various CNS disorders.
- Further investigation of inactive axonal mitochondria can elucidate disease pathogenesis and inform therapeutic strategies.
