Huntington’s disease, a devastating neurodegenerative disorder, is caused by a mutation that inserts a repeated DNA sequence into the gene encoding the huntingtin protein. The mutant protein may damage neurons by directly interfering with their mitochondria, report Tim Greenamyre and colleagues in the August issue of Nature Neuroscience. This new finding may lead to treatments that would slow the progression of Huntington’s disease, as well as other diseases caused by mutations that insert the same repeated DNA sequence into different genes.
The authors isolated mitochondria, the energy-producing machinery of cells, from patients with Huntington’s disease or from mice engineered to express a mutant form of huntingtin. Both types of mitochondria responded to unusually small amounts of calcium. These mitochondrial defects were apparent when the mice were only 3–4 months old, well before they start to develop the movement disorders and neurodegeneration characteristic of Huntington’s disease (6–12 months). Finally, the authors found that they could reproduce the abnormalities that they observed in mitochondria from patients or mutant mice by directly applying proteins containing the mutant repeat to mitochondria from normal subjects. These results suggest that a direct interaction of mutant huntingtin with mitochondria may be centrally involved in causing the disease. Future studies will have to identify how the abnormal polyglutamine regions of huntingtin interfere with mitochondrial function. One suggestion consistent with the authors’ observations is that these repeating regions may be able to insert into mitochondrial membranes and essentially poke holes in them.
Dr. J. Timothy Greenamyre
Center for Neurodegenerative Diseases
Tel: +1 404 727 3727
Additional contact for comment on paper:
Dr. Elena Cattaneo
Department of Pharmacological Sciences
University of Milan, Italy
Tel: +39 02 58358333
Article available online.
(C) Nature Neuroscience press release.
Message posted by: Trevor M. D'Souza