UBIQUITIN-RELATED CYTOSKELETAL ABNORMALITY IN FRONTOTEMPORAL DEMENTIA- IMMUNOHISTOCHEMICAL AND IMMUNOELECTRON MICROSCOPE STUDIES

Although reports of dementia lacking the distinctive non-Alzheimer-typ e histopathology have been increasing, the concept is still far from c lear. It has become apparent that this population shows neuropathologi cal heterogeneity, and some recent reports have proposed a classificat ion or criteria for these disease conditions. Of the reported cases, f rontotemporal dementia (FTD) of motor neuron disease is unique in that the neurons of the hippocampus and entorhinal cortex have ubiquitin-r elated abnormalities. Recently, a new ubiquitin-related abnormality, c haracterized by ubiquitinated inclusions in the neurites, has been fou nd in some FTD cases. Using immunoelectron microscopy with immunogold particles, we have found that in these two disease conditions ubiquiti nated inclusions consist of abnormal filaments of 10-15 nm in diameter . Our results support the speculation that there is a close relationsh ip between ubiquitin and abnormal filaments in these two types of FTD, indicating that cytoskeletal-related disorders may underlie certain t ypes of FTD.