Human Molecular Genetics Advance Access originally published online on September 2, 2003
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Human Molecular Genetics, 2003, Vol. 12, No. 21 2789-2795
DOI: 10.1093/hmg/ddg300
© 2003 Oxford University Press
Regional differences of somatic CAG repeat instability do not account for selective neuronal vulnerability in a knock-in mouse model of SCA1
1Howard Hughes Medical Institute, 2Department of Molecular and Human Genetics, 3Program in Developmental Biology and 4Department of Pediatrics, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, USA and 5Institute of Human Genetics, University of Minnesota, Minneapolis, MN 55455, USA
Received June 16, 2003; Revised August 15, 2003; Accepted August 25, 2003
Expression of unstable translated CAG repeats is the mutational mechanism in nine different neurodegenerative disorders. Although the products of genes harboring these repeats are widely expressed, a subset of neurons is vulnerable in each disease accounting for the different phenotypes. Somatic instability of the expanded CAG repeat has been implicated as a factor mediating the selective striatal neurodegeneration in Huntington disease. It remains unknown, however, whether such a mechanism contributes to the selective neurodegeneration in other polyglutamine diseases or not. To address this question, we investigated the pattern of CAG repeat instability in a knock-in mouse model of spinocerebellar ataxia type 1 (SCA1). Small pool PCR analysis on DNA from various neuronal and non-neuronal tissues revealed that somatic repeat instability was most remarkable in the striatum. In the two vulnerable tissues, cerebellum and spinal cord, there were substantial differences in the profiles of mosaicism. These results suggest that in SCA1 there is no clear causal relationship between the degree of somatic instability and selective neuronal vulnerability. The finding that somatic instability is most pronounced in the striatum of various knock-in models of polyglutamine diseases highlights the role of trans-acting tissue- or cell-specific factors in mediating the instability.
* To whom correspondence should be addressed. Tel: +1 7137986558; Fax: +1 7137988728; Email: hzoghbi{at}bcm.tmc.edu
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