TR-FRET-Based Duplex Immunoassay Reveals an Inverse Correlation of Soluble and Aggregated Mutant huntingtin in Huntingtonʹs Disease Original Research Article

Huntingtonʹs disease (HD) is an inherited neurodegenerative disorder caused by the amplification of a polyglutamine stretch at the N terminus of the huntingtin protein. N-terminal fragments of the mutant huntingtin (mHtt) aggregate and form intracellular inclusions in brain and peripheral tissues. Aggregates are an important hallmark of the disease, translating into a high need to quantify them in vitro and in vivo. We developed a one-step TR-FRET-based immunoassay to quantify soluble and aggregated mHtt in cell and tissue homogenates. Strikingly, quantification revealed a decrease of soluble mHtt correlating with an increase of aggregated protein in primary neuronal cell cultures, transgenic R6/2, and HdhQ150 knock-in HD mice. These results emphasize the assayʹs efficiency for highly sensitive and quantitative detection of soluble and aggregated mHtt and its application in high-throughput screening and characterization of HD models.