Elsevier

Brain Research

Volume 1190, 23 January 2008, Pages 78-85
Brain Research

Research Report
Motor coordination deficits in mice lacking RGS9

https://doi.org/10.1016/j.brainres.2007.11.017Get rights and content

Abstract

RGS9-2 is a striatum-enriched protein that negatively modulates dopamine and opioid receptor signaling. We examined the role of RGS9-2 in modulating complex behavior. Genetic deletion of RGS9-2 does not lead to global impairments, but results in selective abnormalities in certain behavioral domains. RGS9 knockout (KO) mice have decreased motor coordination on the accelerating rotarod and deficits in working memory as measured in the delayed-match-to-place version of the water maze. In contrast, RGS9 KO mice exhibit normal locomotor activity, anxiety-like behavior, cue and contextual fear conditioning, startle threshold, and pre-pulse inhibition. These studies are the first to describe a role for RGS9-2 in motor coordination and working memory and implicate RGS9-2 as a potential therapeutic target for motor and cognitive dysfunction.

Introduction

The regulators of G protein signaling (RGS) family of proteins negatively modulate heterotrimeric G protein signaling by stimulating the GTPase activity of G protein α subunits (Berman and Gilman, 1998) and can function as effector molecules in certain signaling networks (De Vries et al., 2000). RGS proteins also regulate cellular excitability via their indirect modulation of G protein-coupled inwardly rectifying K+ channels (GIRK) and voltage-dependent calcium channels (Berman et al., 1996, Chuang et al., 1998, Doupnik et al., 1997, Hollinger and Hepler, 2002, Sondek and Siderovski, 2001, Zhou et al., 2000).

The greater than 25 mammalian RGS proteins identified to date are defined by their 120 amino acid RGS domain and can be organized into subfamilies based on structural features and relative specificity for different G protein subunits (Traynor and Neubig, 2005). Numerous RGS genes are expressed in brain with highly region-specific expression patterns (Dohlman and Thorner, 1997). The biological role of specific RGS proteins is currently an area of active research.

The RGS9 gene gives rise to two splice forms RGS9-1 and RGS9-2 (Granneman et al., 1998, He et al., 1998, Rahman et al., 1999) that differ only at their C-terminus, where 18 C-terminal amino acid residues of RGS9-1 are replaced by a longer sequence of 209 amino acid residues. Furthermore, the 2 splice forms display highly specific and non-overlapping tissue distributions: RGS9-1 is expressed exclusively in retina, while RGS9-2 is highly enriched in striatal regions of the brain, with very low levels of expression seen throughout the remainder of the brain or in peripheral tissues (Granneman et al., 1998, Rahman et al., 1999, Thomas et al., 1998). The striatum, together with other neural structures of the basal ganglia, acts via multiple intrinsic and extrinsic circuits to control motor and cognitive functions. Moreover, one key feature of striatal neurons is their rich innervation by dopamine and high levels of expression of dopamine receptors (Aizman et al., 2000, Graybiel et al., 2000). Given the high expression of RGS9-2 in the striatum and its localization to medium spiny projection neurons (Kovoor and Lester, 2002, Rahman et al., 2003, Thomas et al., 1998), one would predict RGS9 to play a role in striatal dopamine-mediated behavior. Indeed, RGS9-2 over-expression diminishes sensitivity to the behavioral effects of DA agonists, while loss of RGS9 has the opposite effect (Rahman et al., 2003). In addition, RGS9 has been shown to be a critical negative regulator of opiate action in vivo (Zachariou et al., 2003). For instance, RGS9 KO mice show a 10-fold increase in sensitivity to the rewarding effects of morphine, as well as increased morphine analgesia, delayed development of analgesic tolerance, and severe morphine dependence and withdrawal.

Despite the growing literature on RGS9's role in dopamine signaling as a result of G protein modulation, little has been published on the role of RGS9-2 in dopamine modulated, striatum-dependent behaviors in the absence of prior pharmacologic manipulation. Thus, we have systematically examined the function of RGS9 in striatal-specific and dopamine-mediated behaviors, as well as other additional behavioral domains. Overall, our findings suggest that loss of this regulator of G protein signaling in the striatum leads to focal abnormalities in specific behavioral domains. In particular, RGS9 KO mice display deficits in motor coordination and working memory, but show normal performance in other tasks. Deficits in motor coordination and working memory are consistent with abnormal regulation of dopamine signaling in the striatum or prefrontal cortex, respectively (Fowler et al., 2002, Glickstein et al., 2002, Kellendonk et al., 2006). This is the first demonstration of the role of RGS9 in endogenously mediated complex behavior, as opposed to the effects of exogenously applied drugs of abuse. Our findings suggest that RGS9-2 is a potential therapeutic target for disorders involving motor or cognitive dysfunction.

Section snippets

Results

The creation of RGS9 KO mice is described in detail elsewhere (Chen et al., 2000). For all behavioral tests, 11 male pairs of RGS9 KO and WT littermate offspring of heterozygous matings after 4 backcrosses into the C57BL6 background were used.

Discussion

Our data represent the first demonstration of RGS9 function in endogenously mediated complex behavior. RGS9 KO mice have impaired motor coordination and deficits in working memory, as measured in the delayed-match-to-place version of the water maze. In contrast, RGS9 KO mice exhibit normal locomotor activity, emotional learning, anxiety-like behavior, startle amplitude, and pre-pulse inhibition. Our findings suggest that RGS9-2 may be a potential therapeutic target for disorders involving motor

Conclusions

We have systematically examined the function of RGS9 in complex behavior. Overall, our findings suggest that loss of RGS9-2 leads to focal abnormalities in specific behavioral domains. In particular, RGS9 KO mice display deficits in motor coordination and working memory, but show normal locomotor activity, anxiety-like behavior, startle threshold, and pre-pulse inhibition. Our findings suggest that manipulation of RGS9-2 may be a useful target for disorders with motor or cognitive dysfunction.

Genetic manipulations

To reduce genetic and experimental variability, male RGS9 KO and their male wild-type littermate control mice (Chen et al., 2000) were generated from heterozygous matings following 4 backcrosses into C57BL6 background. For all data presented we used 11 male pairs of RGS9 KO and their wild-type (WT), littermate controls. Mice were housed in a temperature- and humidity-controlled environment with a 12-h light/12-h dark cycle and had free access to food and water.

Behavioral overview

Experimenters were blind to

Acknowledgments

Supported by grants from the National Institute of Mental Health (K08 MH065975-04), NARSAD, and Autism Speaks (all to C.M.P.).

References (57)

  • KellendonkC. et al.

    Transient and selective overexpression of dopamine D2 receptors in the striatum causes persistent abnormalities in prefrontal cortex functioning

    Neuron.

    (2006)
  • KovoorA. et al.

    Gi Irks GIRKs

    Neuron.

    (2002)
  • KwonC.H. et al.

    Pten regulates neuronal arborization and social interaction in mice

    Neuron.

    (2006)
  • McDonaldR.J. et al.

    Parallel information processing in the water maze: evidence for independent memory systems involving dorsal striatum and hippocampus

    Behav. Neural. Biol.

    (1994)
  • MercuriN. et al.

    Dopamine decreases cell excitability in rat striatal neurons by pre- and postsynaptic mechanisms

    Brain Res.

    (1985)
  • NakazawaK. et al.

    Hippocampal CA3 NMDA receptors are crucial for memory acquisition of one-time experience

    Neuron.

    (2003)
  • PartiotA. et al.

    Delayed response tasks in basal ganglia lesions in man: further evidence for a striato-frontal cooperation in behavioural adaptation

    Neuropsychologia

    (1996)
  • PowellC.M. et al.

    The presynaptic active zone protein RIM1alpha is critical for normal learning and memory

    Neuron.

    (2004)
  • RahmanZ. et al.

    RGS9 modulates dopamine signaling in the basal ganglia

    Neuron.

    (2003)
  • RollsE.T. et al.

    Responses of striatal neurons in the behaving monkey. 3. effects of iontophoretically applied dopamine on normal responsiveness

    Neuroscience

    (1984)
  • SeemanP. et al.

    Dopamine partial agonist action of (−)OSU6162 is consistent with dopamine hyperactivity in psychosis

    Eur. J. Pharmacol.

    (2007)
  • SeifG.I. et al.

    Effects of distraction and stress on delayed matching-to-place performance in aged rats

    Physiol. Behav.

    (2004)
  • ShuklaK. et al.

    Learning-induced glutamate receptor phosphorylation resembles that induced by long term potentiation

    J. Biol. Chem.

    (2007)
  • SondekJ. et al.

    Ggamma-like (GGL) domains: new frontiers in G-protein signaling and beta-propeller scaffolding

    Biochem. Pharmacol.

    (2001)
  • Abi-DarghamA. et al.

    Increased baseline occupancy of D2 receptors by dopamine in schizophrenia

    Proc. Natl. Acad. Sci. U. S. A.

    (2000)
  • AizmanO. et al.

    Anatomical and physiological evidence for D1 and D2 dopamine receptor colocalization in neostriatal neurons

    Nat. Neurosci.

    (2000)
  • BattigK. et al.

    Comparison of the effects of frontal and caudate lesions on delayed response and alternation in monkeys

    J. Comp. Physiol. Psychol.

    (1960)
  • BirrellJ.M. et al.

    Medial frontal cortex mediates perceptual attentional set shifting in the rat

    J. Neurosci.

    (2000)
  • Cited by (44)

    • In silico identification of the potential molecular mechanisms involved in protective effects of prolactin on motor and memory deficits induced by 1,2-Diacetylbenzene in young and old rats

      2022, NeuroToxicology
      Citation Excerpt :

      RGS9–2 is a striatum-enriched protein that inhibits the signaling of dopamine and opioid receptors. RGS9 knockout mice showed poor motor coordination and working memory problems in the delayed-match to place version of the water maze (Blundell et al., 2008). Our study observed that DAB was related to an RGS9 mRNA expression decrease, while prolactin showed the opposite effect in young rats.

    • Two for the Price of One: G Protein-Dependent and -Independent Functions of RGS6 in Vivo

      2015, Progress in Molecular Biology and Translational Science
      Citation Excerpt :

      Similarly, RGS7 is unable to regulate 5-HT1AR-mediated inhibition of AC in vitro62 consistent with the primary function of RGS6 in regulating this receptor population. Mice lacking RGS9 exhibit no changes in anxiety, though their behavior has only been evaluated in the open field test.63 Because mice lacking RGS7 or RGS11 have not been evaluated in the behavioral paradigms described in this work, it is unknown whether these R7 family members have any role in modulating anxiety and depression.

    • Effects of gender on locomotor sensitivity to amphetamine, body weight, and fat mass in regulator of G protein signaling 9 (RGS9) knockout mice

      2015, Physiology and Behavior
      Citation Excerpt :

      In retina, RGS9-1 controls photosensitivity by regulating the half-life of activated transducin (Gαt) [5,6]. However brain RGS9-2 is enriched in the striatum where it influences locomotor and motivational behaviors via unknown mechanisms [7–12]. Although it is well-established that RGS9 KO mice exhibit greater levels of behavioral sensitization to psychostimulants such as cocaine and morphine [7,8], the underlying mechanism for this phenomenon remains unclear.

    • Regulator of G protein signaling 6 (RGS6) protein ensures coordination of motor movement by modulating GABA <inf>B</inf> receptor signaling

      2012, Journal of Biological Chemistry
      Citation Excerpt :

      RGS proteins are known to modulate GPCR pathways involving GIRK channel activation. In particular, loss of RGS9–2 results in deficits in motor coordination and working memory (13) due to its essential role in accelerating the termination of dopamine D2 receptor-mediated activation of GIRK channels (14–16). RGS2 is known to play a similar role in dopaminergic neurons of the ventral tegmental area where it contributes to low GABAB-GIRK signaling sensitivity (17).

    View all citing articles on Scopus
    [1]

    Current address: Merck Research Laboratories, Rahway, NJ 07065, USA.

    View full text