Glia -- often called the 'support cells' of the brain -- contribute to neurodegeneration in the progressive disease spinocerebellar ataxia type 7 (SCA7) because a mutation they express interferes with the transport of a neurotransmitter, reports a paper in the October 2006 issue of Nature Neuroscience. This suggests that the death of neurons may not result from their self-programmed 'suicide', a finding that could influence researchers' approaches to treating this and other disorders.
Albert La Spada and colleagues created a mouse model of SCA7 that expressed a mutated protein -- ataxin-7, which causes the disease -- only in Bergmann glia of the cerebellum. The mice showed the characteristic gait impairment, or ataxia, that gives the disease its name, along with degeneration of Purkinje neurons in the cerebellum. A transporter molecule that normally removes the neurotransmitter glutamate was also found to be less abundant in the mice, which showed reduced glutamate transport function.
The authors conclude that reduced transport of glutamate into glial cells contributes to the degeneration of Purkinje neurons, as glutamate is known to be neurotoxic in large quantities. They speculate that this may be the process by which glial cells cause neuronal death in other neurodegenerative diseases, such as amyotrophic lateral sclerosis, Alzheimer disease, Huntington disease and prion disease, in which glia are implicated.
Albert R La Spada (University of Washington, Seattle, WA, USA)
Abstract available online.
(C) Nature Neuroscience press release.
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