Basal levels of HIF-1α are decreased in Psen1-/- fibroblasts. Shown are prolonged exposures of Western blots from non-stimulated Psen1+/+ and Psen1-/- fibroblasts. A representative experiment that was performed multiple times is shown in panel A. In panel B, the experiment in (A) is quantified (asterisk indicates p = 0.0005, unpaired t-test). In panel C, levels of HIF-1α RNA were determined in Psen1 +/+ and Psen1-/- fibroblasts by qPCR (n = 3 cultures per group). Samples were run in triplicate and normalized to the geometric mean of Ppia and Gusb. Asterisk (*) indicates p = 0.0008.