Netrin signaling is similarly implicated in synaptogenesis [55], synaptic plasticity [73], Alzheimer's disease [74–76], schizophrenia [77], and brain tumor cell biology [78–81], suggesting that the significance of netrin-1 signaling via Cdc42 likely extends beyond roles directing chemotropic axon guidance. Here, NTN1 is linked to early-onset autosomal dominant Alzheimer disease.