Human Molecular Genetics Advance Access originally published online on October 29, 2008
Human Molecular Genetics 2009 18(2):328-340; doi:10.1093/hmg/ddn359
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Twinkle mutations associated with autosomal dominant progressive external ophthalmoplegia lead to impaired helicase function and in vivo mtDNA replication stalling
1 Institute of Medical Technology and Tampere University Hospital, Biokatu 6, 33014, Tampere, Finland 2 Research Program of Molecular Neurology, Biomedicum-Helsinki, University of Helsinki, Helsinki, Finland 3 Department of Neurology, Helsinki University Central Hospital, Helsinki, Finland
* To whom correspondence should be addressed Tel: +358 335518598; Fax: +358 335517710; Email: hans.spelbrink{at}uta.fi
Received September 19, 2008; Accepted October 27, 2008
Mutations in the mitochondrial helicase Twinkle underlie autosomal dominant progressive external ophthalmoplegia (PEO), as well as recessively inherited infantile-onset spinocerebellar ataxia and rare forms of mitochondrial DNA (mtDNA) depletion syndrome. Familial PEO is typically associated with the occurrence of multiple mtDNA deletions, but the mechanism by which Twinkle dysfunction induces deletion formation has been under debate. Here we looked at the effects of Twinkle adPEO mutations in human cell culture and studied the mtDNA replication in the Deletor mouse model, which expresses a dominant PEO mutation in Twinkle and accumulates multiple mtDNA deletions during life. We show that expression of dominant Twinkle mutations results in the accumulation of mtDNA replication intermediates in cell culture. This indicated severe replication pausing or stalling and caused mtDNA depletion. A strongly enhanced accumulation of replication intermediates was evident also in six-week-old Deletor mice compared with wild-type littermates, even though mtDNA deletions accumulate in a late-onset fashion in this model. In addition, our results in cell culture pointed to a problem of transcription that preceded the mtDNA depletion phenotype and might be of relevance in adPEO pathophysiology. Finally, in vitro assays showed functional defects in the various Twinkle mutants and broadly agreed with the cell culture phenotypes such as the level of mtDNA depletion and the level of accumulation of replication intermediates. On the basis of our results we suggest that mtDNA replication pausing or stalling is the common consequence of Twinkle PEO mutations that predisposes to multiple deletion formation.
Present address: Department of Medical Biochemistry and Cell Biology, Göteborg University, Göteborg, Sweden.
CiteULike 
Connotea 
Del.icio.us What's this?
This article has been cited by other articles:
|
|
 |
|
  J. P. Duxin, B. Dao, P. Martinsson, N. Rajala, L. Guittat, J. L. Campbell, J. N. Spelbrink, and S. A. Stewart Human Dna2 Is a Nuclear and Mitochondrial DNA Maintenance Protein Mol. Cell. Biol., August 1, 2009; 29(15): 4274 - 4282. [Abstract] [Full Text] [PDF]
|
|