The Disabled-1 (Dab1) gene encodes a key regulator of Reelin signaling. Reelin is a large glycoprotein secreted by neurons of the developing brain, particularly Cajal-Retzius cells. DAB1 functions downstream of Reln in a signaling pathwaythat controls cell positioning in the developing brain and during adult neurogenesis. It docks to the intracellular part of the Reelin very low density lipoprotein receptor (VLDLR) and apoE receptor type 2 (ApoER2) and becomes tyrosine-phosphorylated following binding of Reelin to cortical neurons. In mice, mutations of Dab1 and Reelin generate identical phenotypes. In humans, Reelin mutations are associated with brain malformations and mental retardation. In mice, Dab1 mutation results in the scrambler mouse phenotype.