Integrative proteomic analysis of the NMDA NR1 knockdown mouse model reveals effects on central and peripheral pathways associated with schizophrenia and autism spectrum disorders

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.

Proteomic systems evaluation of the molecular validity of preclinical psychosis models compared to schizophrenia brain pathology

“…Sacrifice and tissue collection took place 30 min after the last injection on day 15. NR1-knockdown: NR1 transgenic mice were bred and genotyped as previously described (Halene et al, 2009;Mohn et al, 1999;Wesseling et al, 2014). 12 adult male homozygous mice and 12 wild-type littermates were used for this study.…”

Association of antibodies to the NR1 subunit of N-methyl-D-aspartate receptors with neuropsychiatric systemic lupus erythematosus

“…Consistently, anti-NR2 levels were increased in CSF from patients with diffuse NPSLE, suggesting that anti-NR2 might be involved in the pathogenesis of diffuse NPSLE [16,21]. Although perturbation of NR1 subunit has been shown to influence the functions of neuronal cells [23][24][25], it has been unclear whether autoantibodies to NR1 subunit might be expressed in NPSLE.…”

The involvement of <italic>N</italic>-methyl-d-aspartate receptor (NMDAR) subunit NR1 in the pathophysiology of schizophrenia

“…Neurotrophic factors and cytokines have been shown to be associated with schizophrenia. A multiplatform profiling study identified peripheral changes that are potentially linked to central alterations in synaptic plasticity and neuronal function associated with NMDAR-NR1 hypofunction [122]. Besides the abnormal behaviors similar to those described in other schizophrenia mouse model [123], reduction of NR1 subunits was observed in mice with heparin-binding epidermal growth factor (HB-EGF) disruption.…”