Journal Article

rare DAT coding variant Val559 perturbs DA neuron function, changes behavior, and alters in vivo responses to psychostimulants

Paul J. Gresch, Gregg D. Stanwood, Marc A. Mergy, Stephanie C. Gantz, Maureen K. Hahn, Gwynne L. Davis, John Williams, Randy D. Blakely, Raajaram Gowrishankar, C. Austin Wheeler

2014

Overview

Despite the critical role of the presynaptic dopamine (DA) transporter (DAT, SLC6A3 ) in DA clearance and psychostimulant responses, evidence that DAT dysfunction supports risk for mental illness is indirect. Recently, we identified a rare, nonsynonymous Slc6a3 variant that produces the DAT substitution Ala559Val in two male siblings who share a diagnosis of attention-deficit hyperactivity disorder (ADHD), with other studies identifying the variant in subjects with bipolar disorder (BPD) and autism spectrum disorder (ASD). Previously, using transfected cell studies, we observed that although DAT Val559 displays normal total and surface DAT protein levels, and normal DA recognition and uptake, the variant transporter exhibits anomalous DA efflux (ADE) and lacks capacity for amphetamine (AMPH)-stimulated DA release. To pursue the significance of these findings in vivo, we engineered DAT Val559 knock-in mice, and here we demonstrate in this model the presence of elevated extracellular DA levels, altered somatodendritic and presynaptic D2 DA receptor (D2R) function, a blunted ability of DA terminals to support depolarization and AMPH-evoked DA release, and disruptions in basal and psychostimulant-evoked locomotor behavior. Together, our studies demonstrate an in vivo functional impact of the DAT Val559 variant, providing support for the ability of DAT dysfunction to impact risk for mental illness. Significance Dopamine (DA) signaling provides important, modulatory control of movement, at tention, and reward. Disorders linked to changes in DA signaling include Parkinson’s disease, attention-deficit hyperactivity disorder, schizophrenia, autism spectrum disorder, and addiction. We identified multiple, functional polymorphisms in the human DA transporter (DAT) gene and showed that one of these variants, which produces the amino acid substitution Val559 (wild-type DATs express Ala559), exhibits normal DA uptake accompanied by a spontaneous outward efflux of the neurotransmitter, reminiscent of the actions of the psychostimulant amphetamine. Here, we identify multiple biochemical, physiological, and behavioral perturbations that arise from DAT Val559 expression in vivo, supporting spontaneous DA efflux as a heretofore-unrecognized mechanism that may underlie multiple DA-linked neurobehavioral disorders.

• Publisher: National Academy of Sciences,National Acad Sciences
• Subject: Amino Acid Substitution / amphetamine / Amphetamine - pharmacology / Amphetamines / Animals / Attention deficit hyperactivity disorder / autism / behavior change / Behavior, Animal - drug effects / Biological Sciences / Bipolar disorder / Central Nervous System Stimulants - pharmacology / dopamine / Dopamine - genetics / Dopamine - metabolism / Dopamine Plasma Membrane Transport Proteins - genetics / Dopamine Plasma Membrane Transport Proteins - metabolism / Dopaminergic Neurons - metabolism / Dopaminergic Neurons - pathology / Female / genes / Humans / Male / Mental disorders / Mental Disorders - genetics / Mental Disorders - metabolism / Mental Disorders - pathology / Mental health / Mice / Mutation, Missense / neurons / Parkinson disease / PNAS Plus / Proteins / Receptors, Dopamine D2 - genetics / Receptors, Dopamine D2 - metabolism / Risk assessment / Rodents / schizophrenia