DSCAM and Down syndrome: As observed in Xenopus midbrain neurons [39], DSCAM knockdown also increases the complexity of proximal dendritic branching of in vitro mouse cortical neurons [38], whereas DSCAM overexpression inhibits dendritic branching of in vitro mouse hippocampal neurons [40], thus suggesting that DSCAM overexpression could contribute to the reduced dendritic arborization of cortical and hippocampal neurons of Down syndrome patients [41,42,43].