Nature Neuroscience Reports on Possible HD Mechanism
Study Zeroes in on Causes of Huntington's Disease
Thu Aug 1, 2:01 PM ET
NEW YORK (Reuters Health) - A possible mechanism for the degeneration of brain cells in people with Huntington's disease has been identified by a group of researchers.
Huntington's disease is a fatal hereditary disease that causes certain cells in the brain to become dysfunctional and eventually die. Symptoms gradually develop between the ages of 30 and 50 and include memory lapses, depression, irritability and movement problems.
Researchers have identified the cause of the disease as a mutated gene that produces an abnormal protein called huntingtin. But how this defect leads to the degenerative effects of the disease has been a mystery.
Now, a team led by Dr. J. Timothy Greenamyre from Emory University in Atlanta, Georgia, reports that the mutant huntingtin protein seems to throw a wrench in the cellular machinery that processes calcium, which results in abnormally high levels of calcium. Too much calcium can damage brain cells. A report on the findings appears in the advance online edition of the journal Nature Neuroscience.
The researchers took blood samples from patients with Huntington's and healthy individuals and examined structures called mitochondria, which provide the energy needed by cells to function. Compared to the samples taken from healthy individuals, those from Huntington's patients showed signs of abnormalities in mitochondria.
When the researchers studied mice that had been genetically engineered to have the mutant huntingtin gene, they detected similar mitochondrial abnormalities involved in calcium processing. The abnormalities appeared when the mice were around 3 to 4 months old, several months before symptoms typically appear in mice. This suggests that the problems with the mitochondria may cause, at least in part, the symptoms of Huntington's disease, according to the report.
The defect in calcium processing "may play a pivotal role" in the development of Huntington's disease, the authors conclude. However, they point out that it remains uncertain how the defect causes the specific symptoms of the disease.
"Elucidation of the responsible mechanisms and the consequences of this defect should provide new targets for neuroprotective therapeutic intervention," Greenamyre and colleagues report.
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