CAG-polyglutamine-repeat mutations: independence from gene context

Several neurological disorders have been attributed to the inheritance of long CAG–polyglutamine repeats. Unlike classical mutations, whose deleterious effects are totally dependent on the context of the gene in which they reside, these translated CAG repeat mutations have been shown to cause neurotoxicity and neuronal intranuclear inclusions when expressed outside their natural gene context. We provide a description of mice with different lengths of repeat in the foreign context of the murine Hprt locus, focusing on aspects of the phenotype that provide an insight into the mechanism by which this unusual mutation might cause toxicity.