Via ScienceDaily, researchers postulate that the biochemical root of HPGS, or progeria, causes accelerated aging by affecting stem cell populations: "The cause of HGPS, a mutated protein called progerin, was identified in 2003. However, the mechanism by which progerin causes the widespread clinical effects of HGPS has been unclear. ... [researchers have now] found that progerin activates genes involved in the Notch signaling pathway, a major regulator of stem cell differentiation - the process by which stem cells give rise to the mature cells that make up different tissues. ... Their experiments revealed that progerin profoundly affects the fate of these stem cells, greatly skewing the rate at which they mature into different tissues. ... Progerin is present at low levels in the cells of healthy people. One could envision a scenario in which progerin's effects on the Notch pathway and, by extension, on adult stem cells could, over time, lead to many of the tissue changes we commonly associate with the aging process."