Identifying dominant-negative actions of a dopamine transporter variant in patients with parkinsonism and neuropsychiatric disease
Freja Herborg, … , Lena E. Hjermind, Ulrik Gether
Freja Herborg, … , Lena E. Hjermind, Ulrik Gether
Published August 10, 2021
Citation Information: JCI Insight. 2021;6(18):e151496. https://doi.org/10.1172/jci.insight.151496.
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Research Article Cell biology Neuroscience

Identifying dominant-negative actions of a dopamine transporter variant in patients with parkinsonism and neuropsychiatric disease

Abstract

Dysfunctional dopaminergic neurotransmission is central to movement disorders and mental diseases. The dopamine transporter (DAT) regulates extracellular dopamine levels, but the genetic and mechanistic link between DAT function and dopamine-related pathologies is not clear. Particularly, the pathophysiological significance of monoallelic missense mutations in DAT is unknown. Here, we use clinical information, neuroimaging, and large-scale exome-sequencing data to uncover the occurrence and phenotypic spectrum of a DAT coding variant, DAT-K619N, which localizes to the critical C-terminal PSD-95/Discs-large/ZO-1 homology–binding motif of human DAT (hDAT). We identified the rare but recurrent hDAT-K619N variant in exome-sequenced samples of patients with neuropsychiatric diseases and a patient with early-onset neurodegenerative parkinsonism and comorbid neuropsychiatric disease. In cell cultures, hDAT-K619N displayed reduced uptake capacity, decreased surface expression, and accelerated turnover. Unilateral expression in mouse nigrostriatal neurons revealed differential effects of hDAT-K619N and hDAT-WT on dopamine-directed behaviors, and hDAT-K619N expression in Drosophila led to impairments in dopamine transmission with accompanying hyperlocomotion and age-dependent disturbances of the negative geotactic response. Moreover, cellular studies and viral expression of hDAT-K619N in mice demonstrated a dominant-negative effect of the hDAT-K619N mutant. Summarized, our results suggest that hDAT-K619N can effectuate dopamine dysfunction of pathological relevance in a dominant-negative manner.

Authors

Freja Herborg, Kathrine L. Jensen, Sasha Tolstoy, Natascha V. Arends, Leonie P. Posselt, Aparna Shekar, Jenny I. Aguilar, Viktor K. Lund, Kevin Erreger, Mattias Rickhag, Matthew D. Lycas, Markus N. Lonsdale, Troels Rahbek-Clemmensen, Andreas T. Sørensen, Amy H. Newman, Annemette Løkkegaard, Ole Kjærulff, Thomas Werge, for the iPSYCH researchers, Lisbeth B. Møller, Heinrich J.G. Matthies, Aurelio Galli, Lena E. Hjermind, Ulrik Gether

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Figure 1

Identification of DAT-K619N in a patient with atypical parkinsonism and comorbid psychiatric disease.

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Identification of DAT-K619N in a patient with atypical parkinsonism and ...
(A) Snake diagram of DAT demonstrating the C-terminal location of the DAT-K619N mutation within a PDZ-binding domain. (B) Family tree with the index patient 1 shown in black shading. Only the patient’s parents were available for genetic analysis, which revealed paternal transmission of the DAT-K619N allele. It is unknown whether the father has neurological or psychological symptoms. (C) [123I]FP-CIT SPECT imaging of patient 1 carrying the DAT-K619N variant. Two [123I]FP-CIT SPECT scans, acquired 7 years apart, suggest progressive neurodegeneration. Images were taken with identical procedures on the same scanner at age 34 (in 2006, left) and age 43 (in 2013, right). Quantification of DAT availability is presented in Table 1.