Abstract
BackgroundOver the last decade, the transgenic N-methyl-D-aspartate receptor (NMDAR) NR1-knockdown mouse (NR1neo−/−) has been investigated as a glutamate hypofunction model for schizophrenia. Recent research has now revealed that the model also recapitulates cognitive and negative symptoms in the continuum of other psychiatric diseases, particularly autism spectrum disorders (ASD). As previous studies have mostly focussed on behavioural readouts, a molecular characterisation of this model will help to identify novel biomarkers or potential drug targets.MethodsHere, we have used multiplex immunoassay analyses to investigate peripheral analyte alterations in serum of NR1neo−/− mice, as well as a combination of shotgun label-free liquid chromatography mass spectrometry, bioinformatic pathway analyses, and a shotgun-based 40-plex selected reaction monitoring (SRM) assay to investigate altered molecular pathways in the frontal cortex and hippocampus. All findings were cross compared to identify translatable findings between the brain and periphery.ResultsMultiplex immunoassay profiling led to identification of 29 analytes that were significantly altered in sera of NR1neo−/− mice. The highest magnitude changes were found for neurotrophic factors (VEGFA, EGF, IGF-1), apolipoprotein A1, and fibrinogen. We also found decreased levels of several chemokines. Following this, LC-MSE profiling led to identification of 48 significantly changed proteins in the frontal cortex and 41 in the hippocampus. In particular, MARCS, the mitochondrial pyruvate kinase, and CamKII-alpha were affected. Based on the combination of protein set enrichment and bioinformatic pathway analysis, we designed orthogonal SRM-assays which validated the abnormalities of proteins involved in synaptic long-term potentiation, myelination, and the ERK-signalling pathway in both brain regions. In contrast, increased levels of proteins involved in neurotransmitter metabolism and release were found only in the frontal cortex and abnormalities of proteins involved in the purinergic system were found exclusively in the hippocampus.ConclusionsTaken together, this multi-platform profiling study has identified peripheral changes which are potentially linked to central alterations in synaptic plasticity and neuronal function associated with NMDAR-NR1 hypofunction. Therefore, the reported proteomic changes may be useful as translational biomarkers in human and rodent model drug discovery efforts.
Highlights
Over the last decade, the transgenic N-methyl-D-aspartate receptor (NMDAR) NR1-knockdown mouse (NR1neo−/−) has been investigated as a glutamate hypofunction model for schizophrenia
Serum characterisation – Quantitative serum immunoassay profiling We evaluated the peripheral adaption to the systemically reduced NMDAR-NR1 expression by analysing 75 analytes (Additional file 1: Table S2) in serum using a multiplex immunoassay platform
Brain characterisation – quantitative LC-MSE proteomic profiling of frontal cortex and hippocampus LC-MSE analysis resulted in the identification of 11,345 distinct peptides (563 proteins) in the frontal cortex and 14,775 distinct peptides (883 proteins) in the hippocampus after filtering the data using the criteria described in the Materials and Methods section
Summary
The transgenic N-methyl-D-aspartate receptor (NMDAR) NR1-knockdown mouse (NR1neo−/−) has been investigated as a glutamate hypofunction model for schizophrenia. NR1neo−/− mice display hyperlocomotion and increased stereotypic behaviour, which represent standard behavioural readouts for the evaluation of animal models of SZ These behavioural effects can be attenuated by the typical antipsychotic drug haloperidol, a potent highly specific D2dopamine receptor antagonist [6], and by the atypical antipsychotic drug clozapine [1], which affects a broader spectrum of neurotransmission systems [7,8]. In addition to these behavioural changes, NR1neo−/− mice show significant impairments in spatial cognitive performance [9], reduced social interaction, escape behaviours, and actively avoid interaction with intruder males. Administration of clozapine has been found to ameliorate all of these symptoms [1], which are thought to predominantly reflect the negative and cognitive symptoms of SZ
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
