Insight into broken record genetic diseases

Those of us who are old enough to remember vinyl records will recall how a scratch can cause the same sounds to repeat many times. A similar type of genetic glitch causes neurodegenerative diseases such as Huntington’s and several forms of spinocerebellar ataxia.

Huntington’s and the spinocerebellar ataxias are known as “polyglutamine” diseases. In each, the affected gene has a stretch where the same three DNA letters are repeated several times — more than usual. As a result, the protein encoded by the affected gene has a patch, where only the building block glutamine can be found, disrupting that protein’s usual functions in the body.

Geneticist Xiao-Jiang Li and colleagues recently published a paper in Cell Reports that may explain why more aggressive juvenile-onset forms of polyglutamine diseases have different symptoms and pathology.

Li’s findings, in a mouse model of spinocerebellar ataxia 17 (SCA17), are most applicable to SCA17, which is very rare in humans, but may also explain aspects of Huntington’s and other spinocerebellar ataxias. They observe that larger polyglutamine repeats selectively poison muscle tissue, in addition to the nervous system (see figure).fx1

SCA17 affects the gene encoding TBP, a protein important for the vital process of transcription. Polyglutamine patches appear to interfere with TBP’s interaction with MyoD, a muscle-specific transcription factor.

Figure from Cell Reports (open access/Creative Commons).

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Posted on by Quinn Eastman in Neuro Leave a comment

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Quinn Eastman

Science Writer, Research Communications
qeastma@emory.edu
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