Neuroscience

Replenishing the Power Stations

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Science  24 Aug 2007:
Vol. 317, Issue 5841, pp. 1010
DOI: 10.1126/science.317.5841.1010a

Mitochondria—the microscopic powerhouses of the cell—contain their own vestigial genome (mtDNA), and each cell needs a collection of healthy organelles to survive. Mitochondria are highly dynamic and undergo both fission and fusion. They produce adenosine 5'-triphosphate by transferring electrons from organic substrates through a series of respiratory enzyme complexes to molecular oxygen. Chen et al. examined the function of the mitochondrial fusion protein mitofusin 2; mutations in the gene Mfn2 have been linked to the peripheral neuropathy Charcot-Marie-Tooth type 2A, in which the very long motor and sensory neurons of the lower leg die. They generated mice that lacked Mfn2 specifically in the cerebellum and found that the mutant mice suffered cerebellar degeneration. Mitochondrial distribution, morphology, and function were all compromised in Mfn2-deficient cells, and many mitochondria appeared to have lost their normal complement of mtDNA. The authors propose that a dynamic fusion capacity is required to maintain the genetic where-withal for each mitochondrion to synthesize adequate supplies of respiratory enzymes. Furthermore, it seems that the Purkinje cells of the cerebellum are particularly sensitive to changes in the distribution and respiratory activity of their mitochondria, perhaps as a consequence of their extensive ramifications. — SMH

Cell 130, 548 (2007).

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