Fig. 1. Expression of human PSEN1 protein in transgenic mice under the control of the nestin intron 2 enhancer. Western blotting was performed on brain extracts from E12.5 nestin-Psen1 transgenic (Tg/+) embryos from line 9 and line 14, as well as non-transgenic controls (+/+). Blots were probed with NT.1 (upper panel) an antibody that recognizes the 30 kDa N-terminal fragment (NTF) of the transgenic human (Hu) PSEN1 but not the endogenous mouse (Mu) Psen1 (Wen et al., 2002b). The two wild-type (+/+) embryos are immunonegative. The lower panel was probed with a rabbit polyclonal antibody 222 that recognizes both the mouse and human NTFs (Wen et al., 2002b). Antibody 222 was raised against amino acids 2-12 of the human NTF, a region that contains one mismatch between the mouse and human proteins (Wen et al., 2002b). Thus, the apparent elevation in total Psen1 (Mu + Hu) in the transgenic (Tg/+) embryos may in part reflect a higher affinity of this antibody for the human protein.