Distribution of inclusions in neuronal nuclei and dystrophic neurites in Huntington disease brain

Recently, an N-terminal fragment of huntingtin was localized to neuronal intranuclear inclusions (NII), presumed to cause cellular dysfunction, and to inclusions in dystrophic neurites (IDN) in the neostriatum and neocortex of Huntington disease (HD) patients. In the present immunohistochemical study of autopsy brain of 2 juvenile-onset HD patients, 5 HD patients with adult-onset, and 5 controls, NII and IDN as stained with both N-terminal antiserum to huntingtin and ubiquitin antiserum were detected in the HD neostriatum, neocortex, and allocortex, but not in the HD pallidum, cerebellum, and substantia nigra nor in control brain. The frequency of NII in the HD neocortex was highest in the juvenile patients. Within the allocortex, NII and IDN were found in the entorhinal region, subiculum, and pyramidal cell layer of Ammon's horn. N-terminal huntingtin antiserum also labeled intranuclear granular structures adjacent to the neuronal nuclear membrane in 5 HD patients, one control with idiopathic epilepsy, and one with Alzheimer disease. Our results show that NII formation in HD involves the allocortex in addition to the neostriatum and neocortex. The development of NII in the neocortex and allocortex in HD brain might contribute to the emergence of the cognitive and behavioral symptoms of the disease.