Intracellular green fluorescent protein-polyalanine aggregates are associated with cell death

Eight diseases, exemplified by Huntington's disease and spinocerebellar ata xia type 1, are caused by GAG-repeat expansion mutations. The GAG repeats a re translated into expanded polyglutamine tracts, which are associated with deleterious novel functions. While these diseases are characterized by int raneuronal aggregate formation, it is unclear whether the aggregates cause disease. We have addressed this debate by generating intracellular aggregat es with green fluorescent protein (GFP) fused to 19-37 alanines. No aggrega tes were seen in cells expressing native GFP or GFP fused to seven alanines . Aggregate-containing cells expressing GFP fused to 19-37 polyalanines sho w high rates of nuclear fragmentation compared with cells expressing the sa me constructs without aggregates, or cells expressing GFP fused to seven al anines. This suggests an association between aggregate formation and cell d eath.