CELLULAR SNACK PACK: An axon in the optic nerve of a mouse packs mitochondria (pink) into bite-size parcels for degradation by adjacent astrocytes. KEUN-YOUNG KIM, MARK ELLISMAN, NICHOLAS MARSH-ARMSTRONG


The paper
C.O. Davis et al., “Transcellular degradation of axonal mitochondria,” PNAS, 111:9633-38, 2014.

The background
Most cells clean up their own damaged mitochondria by transporting the organelles into lysosomes, where they are digested internally. Lysosomes are located in the cell body, so neurons with long axons were thought to shuttle far-off axonal mitochondria back to the cell bodies for disposal. Nicholas Marsh-Armstrong of Johns Hopkins University School of Medicine and colleagues observed that in mice, retinal glial cells called astrocytes, clustered around the head of the optic nerve, were constantly chomping up cellular parcels extruded by axons in the nerve, leading Marsh-Armstrong to wonder what the neurons might be exporting for degradation.

The discovery

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