HBEGF and attention deficit-hyperactivity disorder: Social withdrawal, cognitive and psychiatric abnormalities exhibited by Hbegf cKO mice are similar to those observed in mice lacking neurexin-1α gene (well characterized in autism and schizophrenia) [59], synaptosomal-associated protein 25 (SNAP-25) gene (Coloboma mouse mutant) [60] and dopamine active transporter (DAT) KO mice (animal model of ADHD) [61].