There is evidence that APP degradation products (including Aβ and also cleavage products upstream of Aβ such as the β-C-terminal fragment) can interfere with this process at multiple stages (reviewed extensively in [4]), and previous work in DS models has shown that the presence of an extra APP gene alone is necessary for the early endosomal abnormalities seen in DS [3]. This evidence concerns the gene APP and Dravet syndrome.