Altered adhesion efficiency and fibronectin content in fibroblasts from schizophrenic patients

Transcriptomic and Proteomic Analysis of CRISPR/Cas9-Mediated ARC-Knockout HEK293 Cells

Arc/Arg3.1 (activity-regulated cytoskeletal-associated protein (ARC)) is a critical regulator of long-term synaptic plasticity and is involved in the pathophysiology of schizophrenia. The functions and mechanisms of human ARC action are poorly understood and worthy of further investigation. To investigate the function of the ARC gene in vitro, we generated an ARC-knockout (KO) HEK293 cell line via CRISPR/Cas9-mediated gene editing and conducted RNA sequencing and label-free LC-MS/MS analysis to identify the differentially expressed genes and proteins in isogenic ARC-KO HEK293 cells. Furthermore, we used bioluminescence resonance energy transfer (BRET) assays to detect interactions between the ARC protein and differentially expressed proteins. Genetic deletion of ARC disturbed multiple genes involved in the extracellular matrix and synaptic membrane. Seven proteins (HSPA1A, ENO1, VCP, HMGCS1, ALDH1B1, FSCN1, and HINT2) were found to be differentially expressed between ARC-KO cells and ARC wild-type cells. BRET assay results showed that ARC interacted with PSD95 and HSPA1A. Overall, we found that ARC regulates the differential expression of genes involved in the extracellular matrix, synaptic membrane, and heat shock protein family. The transcriptomic and proteomic profiles of ARC-KO HEK293 cells presented here provide new evidence for the mechanisms underlying the effects of ARC and molecular pathways involved in schizophrenia pathophysiology.

Changes in the Brain Extracellular Matrix Composition in schizophrenia: A Pathophysiological Dysregulation and a Potential Therapeutic Target

The brain extracellular matrix (ECM) is involved in crucial processes of neural support, neuronal and synaptic plasticity, extrasynaptic transmission, and neurotransmission. ECM is a tridimensional fibrillary meshwork composed of macromolecules that determine its bioactivity and give it unique characteristics. The characterization of the brain ECM is critical to understand its dynamic in SZ. Thus, a comparative study was developed with 71 patients with schizophrenia (SZ) and 70 healthy controls. Plasma of participants was analysed by label-free liquid chromatography-tandem mass spectrometry, and the results were validated using the classical western blot method. Lastly, immunostaining of post-mortem human brain tissue was performed to analyse the distribution of the brain ECM proteins by confocal microscopy. The analysis identified four proteins: fibronectin, lumican, nidogen-1, and secreted protein acidic and rich in cysteine (SPARC) as components of the brain ECM. Statistical significance was found for fibronectin (P = 0.0166), SPARC (P = 0.0003), lumican (P = 0.0012), and nidogen-1 (P < 0.0001) that were decreased in the SZ group. Fluorescence imaging of prefrontal cortex (PFC) sections revealed a lower expression of ECM proteins in SZ. Our study proposes a pathophysiological dysregulation of proteins of the brain ECM, whose abnormal composition leads to a progressive neuronal impairment and consequently to neurodegenerative processes due to lack of neurophysiological support and dysregulation of neuronal homeostasis. Moreover, the brain ECM and its components are potential pharmacological targets to develop new therapeutic approaches to treat SZ.

Breakdown of the Paracellular Tight and Adherens Junctions in the Gut and Blood Brain Barrier and Damage to the Vascular Barrier in Patients with Deficit Schizophrenia

Deficit schizophrenia is characterized by leaky intestinal tight and adherens junctions and bacterial translocation. Here we examine whether (deficit) schizophrenia is accompanied by leaky paracellular, transcellular, and vascular barriers in the gut and blood-brain barriers. We measured IgA responses to occludin, claudin-5, E-cadherin, and β-catenin (paracellular pathway, PARA); talin, actin, vinculin, and epithelial intermediate filament (transcellular pathway, TRANS); and plasmalemma vesicle-associated protein (PLVAP, vascular pathway) in 78 schizophrenia patients and 40 controls. IgA responses to claudin-5, E-cadherin, and β-catenin, the sum of the four PARA proteins, and the ratio PARA/TRANS were significantly higher in deficit schizophrenia patients than in nondeficit schizophrenia patients and controls. A large part of the variance in PHEMN (psychosis, hostility, excitation, mannerism, and negative) symptoms, psychomotor retardation, formal thought disorders, verbal fluency, word list memory, word list recall, and executive functions was explained by the PARA/TRANS ratio coupled with plasma IgA responses to Gram-negative bacteria, IgM to malondialdehyde, CCL-11 (eotaxin), IgA levels of the ratio of noxious to more protective tryptophan catabolites (NOX/PRO TRYCATs), and a plasma immune activation index. Moreover, IgA levels to Gram-negative bacteria were significantly associated with IgA to E-cadherin, β-catenin, and PLVAP, while IgA levels to claudin-5 were significantly predicted by IgA to E-cadherin, NOX/PRO TRYCAT ratio, Gram-negative bacteria, and CCL11. The phenomenology of the deficit syndrome is to a large extent explained by the cumulative effects of lowered natural IgM, breakdown of the paracellular and vascular pathways, increased bacterial translocation, peripheral immune-inflammatory responses, and indices of BBB breakdown.

Extracellular matrix proteomics in schizophrenia and Alzheimer's disease

Brain extracellular matrix (ECM) is a highly organized system that consists of collagens, noncollagenous proteins, glycoproteins, hyaluronan, and proteoglycans. Recognized physiological roles of ECM include developmental regulation, tissue homeostasis, cell migration, cell proliferation, cell differentiation, neuronal plasticity, and neurite outgrowth. Aberrant ECM structure is associated with brain neurodegenerative conditions. This review focuses on two neurodegenerative conditions, schizophrenia and Alzheimer's disease, and summarizes recent findings of altered ECM components, including proteoglycans, glycosaminoglycans, proteins, and glycoproteins, and proteins and genes related to other brain components. The scope includes immunohistochemical, genomics, transcriptomics, proteomics, and glycomics studies, and a critical assessment of current state of proteomic studies for neurodegenerative disorders. The intent is to summarize the ECM molecular alterations associated with neurodegenerative pathophysiology. Graphical Abstract Brain extracellular matrix showing HSPGs, CSPGs, HA, collagens, and other glycoproteins.

Focal adhesion dynamics are altered in schizophrenia

BACKGROUND

Evidence from genetic association studies implicate genes involved in neural migration associated with schizophrenia risk. Neural stem/progenitor cell cultures (neurosphere-derived cells) from olfactory mucosa of schizophrenia patients have significantly dysregulated expression of genes in focal adhesion kinase (FAK) signaling, a key pathway regulating cell adhesion and migration. The aim of this study was to investigate whether olfactory neurosphere-derived cells from schizophrenia patients have altered cell adhesion, cell motility, and focal adhesion dynamics.

METHODS

Olfactory neurosphere-derived cells from nine male schizophrenia patients and nine male healthy control subjects were used. Cells were assayed for cell adhesion and cell motility and analyzed for integrins and FAK proteins. Focal adhesions were counted and measured in fixed cells, and time-lapse imaging was used to assess cell motility and focal adhesion dynamics.

RESULTS

Patient-derived cells were less adhesive and more motile than cells derived from healthy control subjects, and their motility was reduced to control cell levels by integrin-blocking antibodies and by inhibition of FAK. Vinculin-stained focal adhesion complexes were significantly smaller and fewer in patient cells. Time-lapse imaging of cells expressing FAK tagged with green fluorescent protein revealed that the disassembly of focal adhesions was significantly faster in patient cells.

CONCLUSIONS

The evidence for altered motility and focal adhesion dynamics in patient-derived cells is consistent with dysregulated gene expression in the FAK signaling pathway in these cells. Alterations in cell adhesion dynamics and cell motility could bias the trajectory of brain development in schizophrenia.

Identification of blood biomarkers for psychosis using convergent functional genomics

There are to date no objective clinical laboratory blood tests for psychotic disease states. We provide proof of principle for a convergent functional genomics (CFG) approach to help identify and prioritize blood biomarkers for two key psychotic symptoms, one sensory (hallucinations) and one cognitive (delusions). We used gene expression profiling in whole blood samples from patients with schizophrenia and related disorders, with phenotypic information collected at the time of blood draw, then cross-matched the data with other human and animal model lines of evidence. Topping our list of candidate blood biomarkers for hallucinations, we have four genes decreased in expression in high hallucinations states (Fn1, Rhobtb3, Aldh1l1, Mpp3), and three genes increased in high hallucinations states (Arhgef9, Phlda1, S100a6). All of these genes have prior evidence of differential expression in schizophrenia patients. At the top of our list of candidate blood biomarkers for delusions, we have 15 genes decreased in expression in high delusions states (such as Drd2, Apoe, Scamp1, Fn1, Idh1, Aldh1l1), and 16 genes increased in high delusions states (such as Nrg1, Egr1, Pvalb, Dctn1, Nmt1, Tob2). Twenty-five of these genes have prior evidence of differential expression in schizophrenia patients. Predictive scores, based on panels of top candidate biomarkers, show good sensitivity and negative predictive value for detecting high psychosis states in the original cohort as well as in three additional cohorts. These results have implications for the development of objective laboratory tests to measure illness severity and response to treatment in devastating disorders such as schizophrenia.

Stem cell models for biomarker discovery in brain disease

Most brain diseases arise from interactions between complex genetic and environmental risk factors. Finding biomarkers for brain diseases will require appropriate cellular models to identify dysregulated cell functions and disease-associated biochemistries. Patient-derived stem cells hold great potential as models of brain diseases. Stem cells can proliferate and can be banked, stored, and thawed for genomic, proteomic, and functional studies. Patient-derived, induced pluripotent stem cells and adult stem cells from the olfactory organ in the nose are already giving novel insights into a number of brain diseases, including Parkinson's disease and schizophrenia. Biomarker discovery may be possible from investigating disease-associated cell biologies in patient-derived stem cells.

Disease-specific, neurosphere-derived cells as models for brain disorders

There is a pressing need for patient-derived cell models of brain diseases that are relevant and robust enough to produce the large quantities of cells required for molecular and functional analyses. We describe here a new cell model based on patient-derived cells from the human olfactory mucosa, the organ of smell, which regenerates throughout life from neural stem cells. Olfactory mucosa biopsies were obtained from healthy controls and patients with either schizophrenia, a neurodevelopmental psychiatric disorder, or Parkinson's disease, a neurodegenerative disease. Biopsies were dissociated and grown as neurospheres in defined medium. Neurosphere-derived cell lines were grown in serum-containing medium as adherent monolayers and stored frozen. By comparing 42 patient and control cell lines we demonstrated significant disease-specific alterations in gene expression, protein expression and cell function, including dysregulated neurodevelopmental pathways in schizophrenia and dysregulated mitochondrial function, oxidative stress and xenobiotic metabolism in Parkinson's disease. The study has identified new candidate genes and cell pathways for future investigation. Fibroblasts from schizophrenia patients did not show these differences. Olfactory neurosphere-derived cells have many advantages over embryonic stem cells and induced pluripotent stem cells as models for brain diseases. They do not require genetic reprogramming and they can be obtained from adults with complex genetic diseases. They will be useful for understanding disease aetiology, for diagnostics and for drug discovery.

Fibroblast and lymphoblast gene expression profiles in schizophrenia: are non-neural cells informative?

Lymphoblastoid cell lines (LCLs) and fibroblasts provide conveniently derived non-neuronal samples in which to investigate the aetiology of schizophrenia (SZ) using gene expression profiling. This assumes that heritable mechanisms associated with risk of SZ have systemic effects and result in changes to gene expression in all tissues. The broad aim of this and other similar studies is that comparison of the transcriptomes of non-neuronal tissues from SZ patients and healthy controls may identify gene/pathway dysregulation underpinning the neurobiological defects associated with SZ. Using microarrays consisting of 18,664 probes we compared gene expression profiles of LCLs from SZ cases and healthy controls. To identify robust associations with SZ that were not patient or tissue specific, we also examined fibroblasts from an independent series of SZ cases and controls using the same microarrays. In both tissue types ANOVA analysis returned approximately the number of differentially expressed genes expected by chance. No genes were significantly differentially expressed in either tissue when corrected for multiple testing. Even using relaxed parameters (p≤0.05, without multiple testing correction) there were still no differentially expressed genes that also displayed ≥2-fold change between the groups of SZ cases and controls common to both LCLs and fibroblasts. We conclude that despite encouraging data from previous microarray studies assessing non-neural tissues, the lack of a convergent set of differentially expressed genes associated with SZ using fibroblasts and LCLs indicates the utility of non-neuronal tissues for detection of gene expression differences and/or pathways associated with SZ remains to be demonstrated.

Psychiatric genetics in Australia

Australian research in psychiatric genetics covers molecular genetic studies of depression, anxiety, alcohol dependence, Alzheimer's disease, bipolar disorder, schizophrenia, autism, and attention deficit hyperactivity disorder. For each disorder, a variety of clinical cohorts have been recruited including affected sib pair families, trios, case/controls, and twins from a large population-based twin registry. These studies are taking place both independently and in collaboration with international groups. Microarray studies now complement DNA investigations, while animal models are in development. An Australian government genome facility provides a high throughput genotyping and mutation detection service to the Australian scientific community, enhancing the contribution of Australian psychiatric genetics groups to gene discovery.

Association study between the fibronectin gene and schizophrenia

Fibronectin is one of the cell adhesion proteins. Adhesion molecules play an important role in neural and synaptic genesis, and their dysfunction may result in neurodevelopmental abnormalities, which have been assumed to be a factor in the pathogenesis of schizophrenia. To examine the possible involvement of fibronectin in the etiology of schizophrenia, we analyzed six polymorphisms, located in introns 2, 21, 24, and 26, and exons 20 and 28, in the human fibronectin gene (FN1) of schizophrenic patients in the Japanese population (n = 104) and age-and gender-matched controls (n = 104). No significant positive association was observed between either of the polymorphisms and schizophrenia, nor was an association found between either of the polymorphisms and any subtypes of schizophrenia. These data did not provide evidence for a contribution of the FN1 gene to susceptibility to schizophrenia.

A novel mechanism to explain protein abnormalities in schizophrenia based on the flavivirus resistance gene

The geographical distribution of schizophrenia was previously shown to correlate with the global distribution of tick-borne flaviviruses. The correlation suggests a natural resistance gene to flaviviruses could be involved in schizophrenia. The flavivirus resistance gene, Flv, a gene found in wild mice and certain in-bred strains, confers resistance to flaviviruses through the interaction of cellular proteins with the flaviviral 3' untranslated regions (UTRs). Although the sequence and product of Flv are unknown, translation elongation factor alpha-1 (EF-1) is a protein known to interact with the 3' UTR flavivirus RNA, forming some complexes with long half-lives that inhibit RNA growth. A study was performed to assess the homology between flaviviral UTRs, subunits of EF-1, and selected proteins reported as abnormal in schizophrenia. The UTRs of four flaviviruses with wide geographical and phylogenic distribution were manually translated. Using the National Biomedical Research Foundation protein databank, the amino acid sequences were correlated with the amino acid sequences of selected proteins. The amino acid sequences of the EF-1 subunits were then correlated with the same proteins. Similar amino acid correlations between the proteins, EF-1 subunits and viral UTRs suggest that translational pathophysiology resulting from the product of Flv can be postulated as the cause of protein abnormalities observed in schizophrenia.

Altered adhesion, proliferation and death in neural cultures from adults with schizophrenia

The causes of schizophrenia are unknown, but there is evidence linking subtle deviations in neural development with schizophrenia. Embryonic brain development cannot be studied in an adult with schizophrenia, but neurogenesis and early events in neuronal differentiation can be investigated throughout adult life in the human olfactory epithelium. Our past research has demonstrated that neuronal cultures can be derived from biopsy of the human adult olfactory epithelium. In the present study, we examined mechanisms related to neurogenesis and neuronal differentiation in adults with schizophrenia versus well controls. Forty biopsies were collected under local anaesthesia from ten individuals with DSM III-R schizophrenia and ten age- and sex-matched well controls. All patients, except one, were receiving antipsychotic medication at the time of the biopsy. Immunostaining for neuronal markers indicated that neurogenesis occurred in the biopsies from both patients and controls since all contained cells expressing tubulin and/or olfactory marker protein. The major findings of this study are: 1. biopsies from patients with schizophrenia showed a significantly reduced ability to attach to the culture slide: 29.9% of patient biopsies attached compared to 73.5% of control biopsies; 2. biopsies from patients with schizophrenia had a significantly greater proportion of cells undergoing mitosis: 0.69% in the patients compared to 0.29% in the controls; and 3. dopamine (10 microM) significantly increased the proportion of apoptotic cells in the control cultures but significantly decreased the proportion in patients' cultures.