OCD candidate gene SLC1A1 /EAAT3 impacts basal ganglia-mediated activity and stereotypic behavior

Abstract

Obsessive-compulsive disorder (OCD) is a chronic, disabling condition with inadequate treatment options that leave most patients with substantial residual symptoms. Structural, neurochemical, and behavioral findings point to a significant role for basal ganglia circuits and for the glutamate system in OCD. Genetic linkage and association studies in OCD point to , which encodes the neuronal glutamate/aspartate/cysteine transporter excitatory amino acid transporter 3 (EAAT3)/excitatory amino acid transporter 1 (EAAC1). However, no previous studies have investigated EAAT3 in basal ganglia circuits or in relation to OCD-related behavior. Here, we report a model of loss based on an excisable STOP cassette that yields successful ablation of EAAT3 expression and function. Using amphetamine as a probe, we found that EAAT3 loss prevents expected increases in () locomotor activity, () stereotypy, and () immediate early gene induction in the dorsal striatum following amphetamine administration. Further, -STOP mice showed diminished grooming in an SKF-38393 challenge experiment, a pharmacologic model of OCD-like grooming behavior. This reduced grooming is accompanied by reduced dopamine D receptor binding in the dorsal striatum of -STOP mice.-STOP mice also exhibit reduced extracellular dopamine concentrations in the dorsal striatum both at baseline and following amphetamine challenge. Viral-mediated restoration of /EAAT3 expression in the midbrain but not in the striatum results in partial rescue of amphetamine-induced locomotion and stereotypy in-STOP mice, consistent with an impact of EAAT3 loss on presynaptic dopaminergic function. Collectively, these findings indicate that the most consistently associated OCD candidate gene impacts basal ganglia-dependent repetitive behaviors.

Neuronal glutamate transporters control dopaminergic signaling and compulsive behaviors

“…The findings that EAAC1 −/− mice show reduced D1R expression is consistent with recent radiolabeling assays, showing decreased D1R density in the DLS of mice with constitutively reduced EAAC1 expression via prolonged exposure to amphetamine (Zike et al, 2017). The DARPP-32 phosphoprotein is abundantly but not exclusively expressed in D1-MSNs (Ouimet et al, 1984; Anderson and Reiner, 1991) and is known to integrate glutamatergic and dopaminergic transmission in the striatum (Svenningsson et al, 2004).…”

“…The neuronal glutamate transporter EAAC1 accounts for a small fraction of all glutamate transporters in the brain (Holmseth et al, 2012). As a consequence, its functional role has long remained enigmatic (Scimemi et al, 2009; Holmseth et al, 2012), despite evidence of genetic association between polymorphisms in the gene encoding EAAC1 and OCD (Dickel et al, 2006; Porton et al, 2013; Zike et al, 2017). In the hippocampus, EAAC1 limits extra-synaptic GluN activation by rapidly binding synaptically-released glutamate (Scimemi et al, 2009).…”

Enhanced Social Dominance and Altered Neuronal Excitability in the Prefrontal Cortex of Male KCC2b Mutant Mice

“…Anxiety‐like behavior was measured in the elevated zero maze (EZM) for 5 min, as previously described [Zike et al, ]. ANY‐maze software (Stoelting, Wood Dale, IL) was used to analyze movement in the maze, including time spent in each arm of the maze, and total distance traveled and entries into arms as measures of total activity.…”

“…HomeCageScan (Clever Sys, Reston, VA) was used as previously described [Veenstra‐VanderWeele et al, ; Zike et al, ] to assess time spent in various activities over a 24‐hr period in the home cage, including sleeping, consuming food or water, rearing, grooming, hanging, remaining low, sniffing, stretching, twitching, and walking. A two‐way repeated measures analysis of variance (ANOVA) was used to analyze the array of behaviors (GraphPad Prism 6).…”

“…Spontaneous grooming was assessed as previously described [Zike et al, ], for 10 min in an empty cage.…”