RAB4A and Down syndrome: Postmortem samples revealed that Rab4 is upregulated in patients with AD and mild cognitive disorder (Cataldo et al., 2000; Ginsberg et al., 2010), and Aβ is known to partially co-localize within Rab4 positive compartments in a mouse model of Down Syndrome (Arriagada et al., 2010) indicating that defects in endosomal sorting may underpin these disorders (Peric and Annaert, 2015).