While the β-amyloid peptide in Alzheimer’s disease encompasses 42 residues, the smallest toxic peptide with only 14 residues is the prion protein PrP 113–126 (Brown, 2000 ▶; Murphy, 2002 ▶), which is on the same scale as the TIF2 peptide. Here, PRNP is linked to early-onset autosomal dominant Alzheimer disease.