The invention relates to a novel method for treating a variety of diseases and disorders, including polyglutamine expansion diseases such as Huntington's disease, neurological degeneration, psychiatric disorders, and protein aggregation disorders and diseases, comprising administering to patients in need thereof a therapeutically effective amount of one or more deacetylase inhibitors. The invention is also directed to a transgenic fly useful as a model of polyglutamine expansion diseases, which may be used to test potential therapeutic agents.