PRPSAP2 and early-onset autosomal dominant Alzheimer disease: Similarly, on making synonymous substitutions in the A3G substrate PRPSAP2 by changing −1C>G (CCcC>CCgC; P267P) and −4C>G (GCcCCCC>GCgCCCC; A266A) (mutated residue in lower case) (Fig. 1D, M1P and M2P, respectively), there is a drastic reduction in RNA editing (CGG>UGG; R268W) that causes a missense alteration in PRPSAP2. Mutations in the APP gene have been linked to Alzheimer’s disease.