Notch-1 is a protein that influences cell fate decisions, with its expression 
occurring primarily during embryogenesis and development. However, Notch-1 is 
also expressed in the adult brain, in regions with high synaptic plasticity, 
particularly the hippocampus. Its role in adults is unknown; however, it may 
impact neurite outgrowth or cell differentiation in adult brain regions 
undergoing neurogenesis. Notch-1 is increased in Alzheimer's disease (AD); 
however, its expression in other CNS degenerative diseases has not been 
described. To begin to define the range of degenerative disorders where Notch-1 
expression is altered, we examined Notch-1 immunoreactivity in a variety of 
neurodegenerative diseases to determine whether its increase is selective for 
AD. We examined sections of hippocampus from 13 AD, 13 classical Pick's disease 
(PiD; with Pick bodies), 4 dementia lacking distinctive histopathology (DLDH) 
and 8 control brains, emphasizing hippocampal (dentate gyrus) pathology. We 
determined that Notch-1 immunoexpression is increased in AD and PiD relative to 
control cases. DLDH cases were not significantly different than control cases 
with respect to Notch-1 expression. Given the increase in Notch-1 
immunoexpression in AD and PiD, two diseases where abnormal tau aggregates are 
present, and the lack of Notch-1 immunoexpression in DLDH (where tau aggregates 
are absent), we cannot rule out the possibility that tau aggregates are 
associated with Notch-1 expression in neurodegenerative diseases.