CAG expansion affects the expression of mutant huntingtin in the Huntington's disease brain

Neil Aronin, Kathryn Chase, Christine Young, Ellen Sapp, Cordula Schwarz, Nahida Matta, Ruth Kornreich, Bernhard Lanwehrmeyer, Edward Bird, M. Flint Beal, Jean Paul Vonsattel, Tom Smith, Robert Carraway, Frederick M. Boyce, Anne B. Young, John B. Penney, Marian DiFiglia

Research output: Contribution to journalArticlepeer-review

159 Scopus citations

Abstract

A trinucleotide repeat (CAG) expansion in the huntingtin gene causes Huntington's disease (HD). In brain tissue from HD heterozygotes with adult onset and more clinically severe juvenile onset, where the largest expansions occur, a mutant protein of equivalent intensity to wild-type huntingtin was detected in cortical synaptosomes, indicating that a mutant species is synthesized and transported with the normal protein to nerve endings. The increased size of mutant huntingtin relative to the wild type was highly correlated with CAG repeat expansion, thereby linking an altered electrophoretic mobility of the mutant protein to its abnormal function. Mutant huntingtin appeared in gray and white matter with no difference in expression in affected regions. The mutant protein was broader than the wild type and in 6 of 11 juvenile cases resolved as a complex of bands, consistent with evidence at the DNA level for somatic mosaicism. Thus, HD pathogenesis results from a gain of function by an aberrant protein that is widely expressed in brain and is harmful only to some neurons.

Original languageEnglish
Pages (from-to)1193-1201
Number of pages9
JournalNeuron
Volume15
Issue number5
DOIs
StatePublished - Nov 1995
Externally publishedYes

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