Huntington's disease (HD) is one of an increasing number of neurodegenerative disorders caused by a CAG/polyglutamine repeat expansion. Mice have been generated that are transgenic for the 5' end of the human HD gene carrying (CAG)115-(CAG)150 repeat expansions. In three lines, the transgene is ubiquitously expressed at both mRNA and protein level. Transgenic mice exhibit a progressive neurological phenotype that exhibits many of the features of HD, including choreiform-like movements, involuntary stereotypic movements, tremor, and epileptic seizures, as well as nonmovement disorder components. This transgenic model will greatly assist in an eventual understanding of the molecular pathology of HD and may open the way to the testing of intervention strategies.

The cause of neurodegeneration in Huntington's disease (HD) is unknown. Patients with HD have an expanded NH2-terminal polyglutamine region in huntingtin. An NH2-terminal fragment of mutant huntingtin was localized to neuronal intranuclear inclusions (NIIs) and dystrophic neurites (DNs) in the HD cortex and striatum, which are affected in HD, and polyglutamine length influenced the extent of huntingtin accumulation in these structures. Ubiquitin was also found in NIIs and DNs, which suggests that abnormal huntingtin is targeted for proteolysis but is resistant to removal. The aggregation of mutant huntingtin may be part of the pathogenic mechanism in HD.