Notch3 is a single pass transmembrane protein belonging to the Notch receptor 
family. Notch proteins are involved in a very conserved signaling system (Notch 
signaling) with a broad spectrum of functions, from cell proliferation and 
differentiation to apoptosis. Mutations in Notch3 gene are linked to cerebral 
autosomal dominant arteriopathy with subcortical infarcts and 
leukoencephalopathy (CADASIL), a disorder characterized by stroke and dementia 
in young adults. Studies evaluating Notch3 expression in human differentiated 
cells and adult tissues have shown high Notch3 levels only in vascular smooth 
muscle cells (VSMC). However, it has been hypothesized that Notch3 is 
ubiquitously expressed in adult human tissues. Our aim was to evaluate Notch3 
expression in human peripheral blood lymphocytes (PBLs) and fibroblasts from 
normal healthy subjects. In both cell types, we examined the expression of 
Notch3 by reverse transcriptase-polymerase chain reaction (RT-PCR) and 
quantitative real-time polymerase chain reaction (qRT-PCR). Moreover, we 
assessed Notch3 protein expression by Western blot analysis. RT-PCR and qRT-PCR 
analysis showed the presence of Notch3 mRNA in both cell types. Western blot 
analysis confirmed Notch3 protein expression in PBLs and fibroblasts though 
showing different profiles. Our data support the expression of Notch3 in adult 
human cell types, and suggests that PBLs and fibroblasts could provide readily 
available cells for the study of the role of Notch3 expression in the 
pathogenetic mechanisms leading to different human disease.