Florey Department of Neuroscience and Mental Health - Research Publications
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ItemA neuroligin-3 mutation implicated in autism causes abnormal aggression and increases repetitive behavior in mice(BMC, 2015-11-14)BACKGROUND: Aggression is common in patients with autism spectrum disorders (ASD) along with the core symptoms of impairments in social communication and repetitive behavior. Risperidone, an atypical antipsychotic, is widely used to treat aggression in ASD. In order to understand the neurobiological underpinnings of these challenging behaviors, a thorough characterisation of behavioral endophenotypes in animal models is required. METHODS: We investigated aggression in mice containing the ASD-associated R451C (arginine to cysteine residue 451 substitution) mutation in neuroligin-3 (NL3). Furthermore, we sought to verify social interaction impairments and assess olfaction, anxiety, and repetitive and restrictive behavior in NL3(R451C) mutant mice. RESULTS: We show a pronounced elevation in aggressive behavior in NL3(R451C) mutant mice. Treatment with risperidone reduced this aggression to wild-type (WT) levels. Juvenile and adult social interactions were also investigated, and subtle differences in initiation of interaction were seen in juvenile NL3(R451C) mice. No genotype differences in olfactory discrimination or anxiety were observed indicating that aggression was not dependent on altered olfaction, stress response, or social preference. We also describe repetitive behavior in NL3(R451C) mice as assessed by a clinically relevant object exploration task. CONCLUSIONS: The presence of aberrant aggression and other behavioral phenotypes in NL3(R451C) mice consistent with clinical traits strengthen face validity of this model of ASD. Furthermore, we demonstrate predictive validity in this model through the reversal of the aggressive phenotype with risperidone. This is the first demonstration that risperidone can ameliorate aggression in an animal model of ASD and will inform mechanistic and therapeutic research into the neurobiology underlying abnormal behaviors in ASD.
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ItemDecreased expression of mGluR5 within the dorsolateral prefrontal cortex in autism and increased microglial number in mGluR5 knockout mice: Pathophysiological and neurobehavioral implications(ACADEMIC PRESS INC ELSEVIER SCIENCE, 2015-10)Metabotropic glutamate receptor 5 (mGluR5) and microglial abnormalities have been implicated in autism spectrum disorder (ASD). However, controversy exists as to whether the receptor is down or upregulated in functioning in ASD. In addition, whilst activation of mGluR5 has been shown to attenuate microglial activation, its role in maintaining microglial homeostasis during development has not been investigated. We utilised published microarray data from the dorsolateral prefrontal cortex (DLPFC) of control (n=30) and ASD (n=27) individuals to carry out regression analysis to assess gene expression of mGluR5 downstream signalling elements. We then conducted a post-mortem brain stereological investigation of the DLPFC, to estimate the proportion of mGluR5-positive neurons and glia. Finally, we carried out stereological investigation into numbers of microglia in mGluR5 knockout mice, relative to wildtype littermates, together with assessment of changes in microglial somal size, as an indicator of activation status. We found that gene expression of mGluR5 was significantly decreased in ASD versus controls (p=0.018) as well as downstream elements SHANK3 (p=0.005) and PLCB1 (p=0.009) but that the pro-inflammatory marker NOS2 was increased (p=0.047). Intensity of staining of mGluR5-positive neurons was also significantly decreased in ASD versus controls (p=0.016). Microglial density was significantly increased in mGluR5 knockout animals versus wildtype controls (p=0.011). Our findings provide evidence for decreased expression of mGluR5 and its signalling components representing a key pathophysiological hallmark in ASD with implications for the regulation of microglial number and activation during development. This is important in the context of microglia being considered to play key roles in synaptic pruning during development, with preservation of appropriate connectivity relevant for normal brain functioning.