Schizophrenia patient-derived olfactory neurosphere-derived cells do not respond to extracellular reelin

Reelin Signaling and Synaptic Plasticity in Schizophrenia

Recent research emphasizes the significance of studying the quality of life of schizophrenia patients, considering the complex nature of the illness. Identifying neuronal markers for early diagnosis and treatment is crucial. Reelin (RELN) stands out among these markers, with genetic studies highlighting its role in mental health. Suppression of RELN expression may contribute to cognitive deficits by limiting dendritic proliferation, affecting neurogenesis, and leading to improper neuronal circuits. Although the physiological function of reelin is not fully understood, it plays a vital role in hippocampal cell stratification and neuroglia formation. This analysis explores reelin's importance in the nervous system, shedding light on its impact on mental disorders such as schizophrenia, paving the way for innovative therapeutic approaches, and at the same time, raises the following conclusions: increased methylation levels of the RELN gene in patients with a diagnosis of schizophrenia results in a multiple decrease in the expression of reelin, and monitoring of this indicator, i.e., methylation levels, can be used to monitor the severity of symptoms in the course of schizophrenia.

Directional Persistence of Cell Migration in Schizophrenia Patient-Derived Olfactory Cells

Cell migration is critical for brain development and linked to several neurodevelopmental disorders, including schizophrenia. We have shown previously that cell migration is dysregulated in olfactory neural stem cells from people with schizophrenia. Although they moved faster than control cells on plastic substrates, patient cells were insensitive to regulation by extracellular matrix proteins, which increase the speeds of control cells. As well as speed, cell migration is also described by directional persistence, the straightness of movement. The aim of this study was to determine whether directional persistence is dysregulated in schizophrenia patient cells and whether it is modified on extracellular matrix proteins. Directional persistence in patient-derived and control-derived olfactory cells was quantified from automated live-cell imaging of migrating cells. On plastic substrates, patient cells were more persistent than control cells, with straighter trajectories and smaller turn angles. On most extracellular matrix proteins, persistence increased in patient and control cells in a concentration-dependent manner, but patient cells remained more persistent. Patient cells therefore have a subtle but complex phenotype in migration speed and persistence on most extracellular matrix protein substrates compared to control cells. If present in the developing brain, this could lead to altered brain development in schizophrenia.

Altered gene regulation as a candidate mechanism by which ciliopathy gene SDCCAG8 contributes to schizophrenia and cognitive function

Mutations in genes that encode centrosomal/ciliary proteins cause severe cognitive deficits, while common single-nucleotide polymorphisms in these genes are associated with schizophrenia (SZ) and cognition in genome-wide association studies. The role of these genes in neuropsychiatric disorders is unknown. The ciliopathy gene SDCCAG8 is associated with SZ and educational attainment (EA). Genome editing of SDCCAG8 caused defects in primary ciliogenesis and cilium-dependent cell signalling. Transcriptomic analysis of SDCCAG8-deficient cells identified differentially expressed genes that are enriched in neurodevelopmental processes such as generation of neurons and synapse organization. These processes are enriched for genes associated with SZ, human intelligence (IQ) and EA. Phenotypic analysis of SDCCAG8-deficent neuronal cells revealed impaired migration and neuronal differentiation. These data implicate ciliary signalling in the aetiology of SZ and cognitive dysfunction. We found that centrosomal/ciliary genes are enriched for association with IQ, suggesting altered gene regulation as a general model for neurodevelopmental impacts of centrosomal/ciliary genes.

Functional patient-derived cellular models for neuropsychiatric drug discovery

Mental health disorders are a leading cause of disability worldwide. Challenges such as disease heterogeneity, incomplete characterization of the targets of existing drugs and a limited understanding of functional interactions of complex genetic risk loci and environmental factors have compromised the identification of novel drug candidates. There is a pressing clinical need for drugs with new mechanisms of action which address the lack of efficacy and debilitating side effects of current medications. Here we discuss a novel strategy for neuropsychiatric drug discovery which aims to address these limitations by identifying disease-related functional responses ('functional cellular endophenotypes') in a variety of patient-derived cells, such as induced pluripotent stem cell (iPSC)-derived neurons and organoids or peripheral blood mononuclear cells (PBMCs). Disease-specific alterations in cellular responses can subsequently yield novel drug screening targets and drug candidates. We discuss the potential of this approach in the context of recent advances in patient-derived cellular models, high-content single-cell screening of cellular networks and changes in the diagnostic framework of neuropsychiatric disorders.

Network-based prediction of polygenic disease genes involved in cell motility

Background

Schizophrenia and autism are examples of polygenic diseases caused by a multitude of genetic variants, many of which are still poorly understood. Recently, both diseases have been associated with disrupted neuron motility and migration patterns, suggesting that aberrant cell motility is a phenotype for these neurological diseases.

Results

We formulate the Polygenic Disease Phenotype Problem which seeks to identify candidate disease genes that may be associated with a phenotype such as cell motility. We present a machine learning approach to solve this problem for schizophrenia and autism genes within a brain-specific functional interaction network. Our method outperforms peer semi-supervised learning approaches, achieving better cross-validation accuracy across different sets of gold-standard positives. We identify top candidates for both schizophrenia and autism, and select six genes labeled as schizophrenia positives that are predicted to be associated with cell motility for follow-up experiments.

Conclusions

Candidate genes predicted by our method suggest testable hypotheses about these genes’ role in cell motility regulation, offering a framework for generating predictions for experimental validation.

Electronic supplementary material

The online version of this article (10.1186/s12859-019-2834-1) contains supplementary material, which is available to authorized users.

Cell migration in schizophrenia: Patient-derived cells do not regulate motility in response to extracellular matrix

Schizophrenia is a highly heritable psychiatric disorder linked to a large number of risk genes. The function of these genes in disease etiology is not fully understood but pathway analyses of genomic data suggest developmental dysregulation of cellular processes such as neuronal migration and axon guidance. Previous studies of patient-derived olfactory cells show them to be more motile than control-derived cells when grown on a fibronectin substrate, motility that is dependent on focal adhesion kinase signaling. The aim of this study was to investigate whether schizophrenia patient-derived cells are responsive to other extracellular matrix (ECM) proteins that bind integrin receptors. Olfactory neurosphere-derived cells from nine patients and nine matched controls were grown on ECM protein substrates at increasing concentrations and their movement was tracked for 24h using automated high-throughput imaging. Control-derived cells increased their motility as the ECM substrate concentration increased, whereas patient-derived cell motility was little affected by ECM proteins. Patient and control cells had appropriate integrin receptors for these ECM substrates and detected them as shown by increases in focal adhesion number and size in response to ECM proteins, which also induced changes in cell morphology and cytoskeleton. These observations indicate that patient cells failed to translate the detection of ECM proteins into appropriate changes in cell motility. In a sense, patient cells act like a moving car whose accelerator is jammed, moving at the same speed without regard to the external environment. This focuses attention on cell motility regulation rather than speed as key to impairment of neuronal migration in the developing brain in schizophrenia.

DNA methylation in schizophrenia in different patient-derived cell types

DNA methylation of gene promoter regions represses transcription and is a mechanism via which environmental risk factors could affect cells during development in individuals at risk for schizophrenia. We investigated DNA methylation in patient-derived cells that might shed light on early development in schizophrenia. Induced pluripotent stem cells may reflect a “ground state” upon which developmental and environmental influences would be minimal. Olfactory neurosphere-derived cells are an adult-derived neuro-ectodermal stem cell modified by developmental and environmental influences. Fibroblasts provide a non-neural control for life-long developmental and environmental influences. Genome-wide profiling of DNA methylation and gene expression was done in these three cell types from the same individuals. All cell types had distinct, statistically significant schizophrenia-associated differences in DNA methylation and linked gene expression, with Gene Ontology analysis showing that the differentially affected genes clustered in networks associated with cell growth, proliferation, and movement, functions known to be affected in schizophrenia patient-derived cells. Only five gene loci were differentially methylated in all three cell types. Understanding the role of epigenetics in cell function in the brain in schizophrenia is likely to be complicated by similar cell type differences in intrinsic and environmentally induced epigenetic regulation.

Schizophrenia-associated differences in the DNA methylation status of patient-derived cells suggest it could affect early brain development. Mechanisms that control gene expression without altering the genetic code, such as DNA methylation, could explain how environmental risk factors contribute to schizophrenia in genetically susceptible individuals. Alan Mackay-Sim and colleagues from Griffith University, Australia, carried out genome-wide comparisons of DNA methylation in induced pluripotent stem (iPS) cells, olfactory neurosphere-derived cells and fibroblasts from patients and controls. Differences in the DNA methylation pattern between patient and control iPS cells, which could reflect what happens in the embryo, suggest a disease-associated effect very early on in development. Only five genes were differentially methylated in all three patient-derived cell types compared to controls. None of these genes has previously been associated with schizophrenia and may represent new targets for future research.