Missense dopamine transporter mutations associate with adult parkinsonism and ADHD
Freja H. Hansen, … , Lisbeth B. Møller, Ulrik Gether
Freja H. Hansen, … , Lisbeth B. Møller, Ulrik Gether
Published June 9, 2014
Citation Information: J Clin Invest. 2014;124(7):3107-3120. https://doi.org/10.1172/JCI73778.
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Research Article Neuroscience

Missense dopamine transporter mutations associate with adult parkinsonism and ADHD

Abstract

Parkinsonism and attention deficit hyperactivity disorder (ADHD) are widespread brain disorders that involve disturbances of dopaminergic signaling. The sodium-coupled dopamine transporter (DAT) controls dopamine homeostasis, but its contribution to disease remains poorly understood. Here, we analyzed a cohort of patients with atypical movement disorder and identified 2 DAT coding variants, DAT-Ile312Phe and a presumed de novo mutant DAT-Asp421Asn, in an adult male with early-onset parkinsonism and ADHD. According to DAT single-photon emission computed tomography (DAT-SPECT) scans and a fluoro-deoxy-glucose-PET/MRI (FDG-PET/MRI) scan, the patient suffered from progressive dopaminergic neurodegeneration. In heterologous cells, both DAT variants exhibited markedly reduced dopamine uptake capacity but preserved membrane targeting, consistent with impaired catalytic activity. Computational simulations and uptake experiments suggested that the disrupted function of the DAT-Asp421Asn mutant is the result of compromised sodium binding, in agreement with Asp421 coordinating sodium at the second sodium site. For DAT-Asp421Asn, substrate efflux experiments revealed a constitutive, anomalous efflux of dopamine, and electrophysiological analyses identified a large cation leak that might further perturb dopaminergic neurotransmission. Our results link specific DAT missense mutations to neurodegenerative early-onset parkinsonism. Moreover, the neuropsychiatric comorbidity provides additional support for the idea that DAT missense mutations are an ADHD risk factor and suggests that complex DAT genotype and phenotype correlations contribute to different dopaminergic pathologies.

Authors

Freja H. Hansen, Tina Skjørringe, Saiqa Yasmeen, Natascha V. Arends, Michelle A. Sahai, Kevin Erreger, Thorvald F. Andreassen, Marion Holy, Peter J. Hamilton, Viruna Neergheen, Merete Karlsborg, Amy H. Newman, Simon Pope, Simon J.R. Heales, Lars Friberg, Ian Law, Lars H. Pinborg, Harald H. Sitte, Claus Loland, Lei Shi, Harel Weinstein, Aurelio Galli, Lena E. Hjermind, Lisbeth B. Møller, Ulrik Gether

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Figure 7

Amphetamine- and cocaine-induced amperometric currents and MPP+ efflux.

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Amphetamine- and cocaine-induced amperometric currents and MPP+ efflux. ...
HEK293 cells were transiently transfected with WT, DAT-I312F, or DAT-D421N. (A) Representative amperometric currents; arrows indicate the application of amphetamine (10 μM). (B) Quantification of the amphetamine-induced peak amperometric currents. (C) Amperometric data are reported as the amphetamine-induced amperometric current recorded 10 minutes after amphetamine application. Data are the means ± SEM; n = 7–9. **P < 0.01 and ***P < 0.001 by Mann-Whitney U test. (D) Quantification of amphetamine-induced [3H]MPP+ efflux presented as the AUC of MPP+ efflux. [3H]MPP+ release was calculated by subtracting the basal release from total release during the first 8 minutes following amphetamine exposure. Data are the means ± SEM; n = 4–5. *P < 0.025 by Mann-Whitney U test. (E) Representative amperometric currents following cocaine exposure (50 μM) of HEK293 cells transiently expressing WT DAT or DAT-D421N. (F) Amperometric data are reported as the cocaine-induced amperometric current 10 minutes after cocaine application. Data are the means ± SEM; n = 3. *P < 0.05 by 1-tailed t test. (G) Quantification of cocaine-induced [3H]MPP+ efflux presented as the AUC of MPP+ efflux. Cocaine treatments led to a significantly higher reduction in MPP+ efflux from cells expressing DAT-D421N compared with WT. *P < 0.05 by Mann-Whitney U test, consistent with a constitutive leak of dopamine.