Stem cells are central to the development and maintenance of many tissues. This 
is due to their capacity for extensive proliferation and differentiation into 
effector cells. More recently it has been shown that the proliferative and 
differentiative ability of stem cells decreases with age, suggesting that this 
may play a role in tissue aging. Down syndrome (DS), is associated with many of 
the signs of premature tissue aging including T-cell deficiency, increased 
incidence of early Alzheimer-type, Myelodysplastic-type disease and leukaemia. 
Previously we have shown that both hematopoietic (HSC) and neural stem cells 
(NSC) in patients affected by DS showed signs of accelerated aging. In this 
study we tested the hypothesis that changes in gene expression in HSC and NSC of 
patients affected by DS reflect changes occurring in stem cells with age. The 
profiles of genes expressed in HSC and NSC from DS patients highlight pathways 
associated with cellular aging including a downregulation of DNA repair genes 
and increases in proapoptotic genes, s-phase cell cycle genes, inflammation and 
angiogenesis genes. Interestingly, Notch signaling was identified as a potential 
hub, which when deregulated may drive stem cell aging. These data suggests that 
DS is a valuable model to study early events in stem cell aging.