No change in HIF-1α levels in Psen1-/- embryonic brain. HIF-1α levels were determined by Western blotting of extracts from E14.5 (A) or E18.5 (B) brain from wild type (wt) or homozygous (-/-) Psen1 mutant mice. Representative experiments are shown. Lower panels show the same blots reprobed for β-tubulin. HIF-1α levels were quantitated as a ratio to β-tubulin at E14.5 (C) and E18.5 (D) (n = 4 wild type and 2 Psen1-/- at each age). There were no differences between wild type (wt) and Psen1-/- at either age (unpaired t-tests).