Hormone-Inducible Transport Reporter Assay to Study Nuclear Import Defects in Neurodegenerative Diseases

In the recent years, defective nuclear import has emerged as an important pathomechanism of neurodegenerative diseases, particularly in amyotrophic lateral sclerosis (ALS). Here, specific nuclear RNA binding proteins (RBPs) mislocalize and aggregate in the cytoplasm of neurons and glial cells in degenerating brain regions. Bona fide transport assays that measure nuclear import in a quantitative manner allow one to distinguish whether disease-linked RBP mutations that cause cytosolic RBP mislocalization directly result in reduced nuclear import or cause increased cytoplasmic localization of the RBP through other mechanisms. Here we describe the quantitative analysis of nuclear import rates of RBPs using a hormone-inducible system by live cell imaging.