Human Molecular Genetics Advance Access originally published online on June 27, 2009
Human Molecular Genetics 2009 18(18):3407-3416; doi:10.1093/hmg/ddp281
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Inhibition of mitochondrial fission favours mutant over wild-type mitochondrial DNA
1 Neuroscience Department, University of Padova, Padova, Italy and 2 MRC-Mitochondrial Biology Unit Wellcome Trust/MRC Building, Hills Road, Cambridge, UK
* To whom correspondence should be addressed. Email: lodovica.vergani{at}unipd.it or holt{at}mrc-mbu.cam.ac.uk
Received March 13, 2009; Revised June 5, 2009; Accepted June 11, 2009
Biased segregation of mitochondrial DNA variants has been widely documented, but little was known about its molecular basis. We set out to test the hypothesis that altering the balance between mitochondrial fusion and fission could influence the segregation of mutant and wild-type mtDNA variants, because it would modify the number of organelles per cell. Therefore human cells heteroplasmic for the pathological A3243G mitochondrial DNA mutation were transfected with constructs designed to silence Drp1 or hFis1, whose gene products are required for mitochondrial fission. Drp1 and hFis1 gene silencing were both associated with increased levels of mutant mitochondrial DNA. Thus, the extent of the mitochondrial reticular network appears to be an important factor in determining mutant load. The fact that the level of mutant and wild-type mitochondrial DNA can be manipulated by altering the expression of nuclear encoded factors involved in mitochondrial fission suggests new interventions for mitochondrial DNA disorders.