PSEN1 and familial Alzheimer disease: In addition, unexpected substitutions resulted in the generation of Psen1-T116I (n = 1, 1.3%), Psen1-T116N (n = 2, 2.6%), Psen1-P117A (n = 2, 3.9%), and Psen1-P117R (n = 1, 1.3%) mutations, which also cause fAD (Supplementary Fig. 9).