Alternative splicing of Amyloid precursor-like protein 2 (Aplp2) is known to regulate inclusion of a bovine pancreatic trypsin inhibitor (BPTI) Kunitz domain (Sandbrink et al., 1997) and this domain is known to regulate proteolysis of the related protein APP, the amyloid precursor protein implicated in Alzheimer’s disease (Beckmann et al., 2016). Here, APLP2 is linked to early-onset autosomal dominant Alzheimer disease.