SYNJ1 and Down syndrome: Brain autopsy of Down syndrome (DS) patients revealed an excessive expression of the Synj1 protein, that is encoded on the triplicated chromosome 21, and it was shown that the overexpression of Synj1 leads to PI(4,5)P2 deficiency and learning deficits in Down syndrome model mice (Voronov et al., 2008; Arai et al., 2002).