Although this assumption needs to be experimentally validated, it may explain why Aβ in App KI or APP-Tg mice can be extracted by GuHCl (Kawarabayashi et al, 2001; Saito et al, 2014), whereas that in AD brains requires formic acid for Aβ extraction (Harigaya et al, 1995; Saido et al, 1995; Kawarabayashi et al, 2001). Here, APP is linked to Alzheimer disease.