Polymorphisms of Transferrin gene are associated with schizophrenia in Chinese Han population

Exploring Imaging Genetic Markers of Alzheimer's Disease Based on a Novel Nonlinear Correlation Analysis Algorithm

Alzheimer's disease (AD) is an irreversible neurological disorder characterized by insidious onset. Identifying potential markers in its emergence and progression is crucial for early diagnosis and treatment. Imaging genetics typically merges genetic variables with multiple imaging parameters, employing various association analysis algorithms to investigate the links between pathological phenotypes and genetic variations, and to unearth molecular-level insights from brain images. However, most existing imaging genetics algorithms based on sparse learning assume a linear relationship between genetic factors and brain functions, limiting their ability to discern complex nonlinear correlation patterns and resulting in reduced accuracy. To address these issues, we propose a novel nonlinear imaging genetic association analysis method, Deep Self-Reconstruction-based Adaptive Sparse Multi-view Deep Generalized Canonical Correlation Analysis (DSR-AdaSMDGCCA). This approach facilitates joint learning of the nonlinear relationships between pathological phenotypes and genetic variations by integrating three different types of data: structural magnetic resonance imaging (sMRI), single-nucleotide polymorphism (SNP), and gene expression data. By incorporating nonlinear transformations in DGCCA, our model effectively uncovers nonlinear associations across multiple data types. Additionally, the DSR algorithm clusters samples with identical labels, incorporating label information into the nonlinear feature extraction process and thus enhancing the performance of association analysis. The application of the DSR-AdaSMDGCCA algorithm on real data sets identified several AD risk regions (such as the hippocampus, parahippocampus, and fusiform gyrus) and risk genes (including VSIG4, NEDD4L, and PINK1), achieving maximum classification accuracy with the fewest selected features compared to baseline algorithms. Molecular biology enrichment analysis revealed that the pathways enriched by these top genes are intimately linked to AD progression, affirming that our algorithm not only improves correlation analysis performance but also identifies biologically significant markers.

Increased IL-6 Levels and the Upregulation of Iron Regulatory Biomarkers Contribute to the Progression of Japanese Encephalitis Virus Infection's Pathogenesis

Integrated analysis of iron regulatory biomarkers and inflammatory response could be an important strategy for Japanese encephalitis viral (JEV) infection disease management. In the present study, the inflammatory response was assessed by measuring serum Interleukin-6 (IL-6) levels using ELISA, and the transcription levels of iron homeostasis regulators were analyzed via RT-PCR. Furthermore, inter-individual variation in the transferrin gene was analyzed by PCR-RFLP and their association with clinical symptoms, susceptibility, severity, and outcomes was assessed through binary logistic regression and classification and regression tree (CART) analysis. Our findings revealed elevated levels of IL-6 in serum as well as increased expression of hepcidin (HAMP), transferrin (TF), and transferrin receptor-1 (TFR1) mRNA in JEV infection cases. Moreover, we found a genetic variation in TF (rs4481157) associated with clinical symptoms of meningoencephalitis. CART analysis indicates that individuals with the wild-type TF genotype are more susceptible to moderate JEV infection, while those with the homozygous type are in the high-risk group to develop a severe JEV condition. In summary, the study highlights that JEV infection induces alteration in both IL-6 levels and iron regulatory processes, which play pivotal roles in the development of JEV disease pathologies.

Association of Transferrin Gene Polymorphism with Cognitive Deficits and Psychiatric Symptoms in Patients with Chronic Schizophrenia

A large amount of recent literature has focused on impaired iron homeostasis in the pathophysiology of schizophrenia. Specifically, microarray analysis has illustrated associations between the transferrin locus and schizophrenia. To elaborate on the effects of transferrin on schizophrenia and its psychiatric phenotypes, our study aimed to investigate whether transferrin gene polymorphism was correlated with cognitive deficits and clinical symptoms in schizophrenia. We recruited 564 patients with chronic schizophrenia and 422 healthy controls (HCs) in a Han Chinese population, collected phenotypic data, and genotyped the rs3811655 polymorphism of the transferrin gene. Our results showed that the rs3811655 polymorphism was related to cognitive performance in both patients and HCs, as well as negative symptoms in patients (all p < 0.05), and patients carrying at least one G-allele showed worsened cognition/severe negative symptoms (all p < 0.05). Further analyses also found that the rs3811655 polymorphism in combination with cognition may exert small but significant contributions to the negative (β = −0.10, t = −2.48, p < 0.05) or total psychiatric symptoms (β = −0.08, t = −1.92, p < 0.05) in patients. Our findings indicated that the rs3811655 polymorphism may be implicated in the cognitive deficits of schizophrenia and HCs as well as psychiatric symptoms in patients, which suggested the possible iron regulatory mechanism in the pathology of schizophrenia.

Insights into myelin dysfunction in schizophrenia and bipolar disorder

Schizophrenia and bipolar disorder are disabling psychiatric disorders with a worldwide prevalence of approximately 1%. Both disorders present chronic and deteriorating prognoses that impose a large burden, not only on patients but also on society and health systems. These mental illnesses share several clinical and neurobiological traits; of these traits, oligodendroglial dysfunction and alterations to white matter (WM) tracts could underlie the disconnection between brain regions related to their symptomatic domains. WM is mainly composed of heavily myelinated axons and glial cells. Myelin internodes are discrete axon-wrapping membrane sheaths formed by oligodendrocyte processes. Myelin ensheathment allows fast and efficient conduction of nerve impulses through the nodes of Ranvier, improving the overall function of neuronal circuits. Rapid and precisely synchronized nerve impulse conduction through fibers that connect distant brain structures is crucial for higher-level functions, such as cognition, memory, mood, and language. Several cellular and subcellular anomalies related to myelin and oligodendrocytes have been found in postmortem samples from patients with schizophrenia or bipolar disorder, and neuroimaging techniques have revealed consistent alterations at the macroscale connectomic level in both disorders. In this work, evidence regarding these multilevel alterations in oligodendrocytes and myelinated tracts is discussed, and the involvement of proteins in key functions of the oligodendroglial lineage, such as oligodendrogenesis and myelination, is highlighted. The molecular components of the axo-myelin unit could be important targets for novel therapeutic approaches to schizophrenia and bipolar disorder.

Polymorphism of Transferrin Gene Impacts the Mediating Effects of Psychotic Symptoms on the Relationship between Oxidative Stress and Cognition in Patients with Chronic Schizophrenia

A series of studies indicated that iron distribution that partly derives from transferrin-bound iron in the peripheral nervous system in the brain may act in processes such as myelination and brain development. However, the relationship between schizophrenia, its psychotic symptoms, and the transferrin (TF) gene has not been systematically explored. Our study aimed to investigate how a particular polymorphism of the transferrin gene, rs3811655, affects the superoxide dismutase (SOD), malondialdehyde (MDA), psychotic symptoms, cognition, or the mediation model between antioxidant enzymes and cognition via symptoms. A total of 564 patients with chronic schizophrenia and 468 healthy control subjects were recruited. The psychotic symptoms and cognition were assessed by the Positive and Negative Syndrome Scale (PANSS) and the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS), respectively. Furthermore, the serum SOD, MDA activity, and transferrin gene polymorphism were measured in patients. Our results demonstrated that patients with the G allele possessed more severe negative symptoms, worse cognitive performance with respect to attention, and higher serum Mn-SOD activity. Additionally, the rs3811655 polymorphism may act as a moderator in the association between Cu/Zn-SOD activity and cognition, as well as psychotic symptoms in patients suffering from schizophrenia. According to this study, the single nucleotide polymorphism (SNP) rs3811655 polymorphism may fail to contribute to the susceptibility of schizophrenia in an individual but is involved in the iron-induced oxidative stress disturbance and cognitive impairment in schizophrenia. This deepens our understanding of the critical role of iron-induced oxidative stress that might underlie the pathophysiology of schizophrenia.

Association of EPHB1 rs11918092 and EFNB2 rs9520087 with psychopathological symptoms of schizophrenia in Chinese Zhuang and Han populations

Two single-nucleotide polymorphisms (SNPs) (rs11918092 and rs9520087) were genotyped in Chinese Zhuang and Han populations. Symptoms of schizophrenic patients were assessed by the Positive and Negative Syndrome Scale. No association of any SNP with schizophrenic susceptibility was found. However, associations of rs9520087 with the total scale score (P = 0.014), positive scale score (P = 0.013), negative scale score (P = 0.032), and general psychopathology scale score (P = 0.031) were found in Zhuang patients. Additionally, rs11918092 was associated with positive scale score (P = 0.035) in Han patients. The two SNPs might influence symptoms of schizophrenia.

Elevated serum immunoinflammation-related protein complexes are associated with psychosis

Emerging evidence suggests an underlying immune and inflammatory response for a variety of psychiatric disorders. Herein, we employed an optimized native-polyacrylamide gel electrophoresis to isolate psychosis-related serum immunoinflammation-related protein complexes (IIRPCs) from 147 patients with schizophrenia (SCH), 158 patients with bipolar disorder (BPD), 132 patients with other psychosis, and 145 normal controls. All participants could be classified into four categories based on serum IIRPCs, which correspond to 290, 215, 70, and 7 serum samples, correspondingly. For each category, significantly enhanced levels of serum IIRPCs in patients with SCH, BPD, and other psychosis groups were observed compared with normal controls. Receiver operating characteristic analysis indicated that serum IIRPCs have excellent diagnostic performance to differentiate SCH, BPD, and other psychosis groups from normal controls, with high sensitivities and specificities of >85%. Total serum amounts of IgG, IgA, and IgM in all patients were significantly decreased compared with normal controls.

Glial cells as key players in schizophrenia pathology: recent insights and concepts of therapy

The past decade has witnessed an explosion of knowledge on the impact of glia for the neurobiological foundation of schizophrenia. A plethora of studies have shown structural and functional abnormalities in all three types of glial cells. There is convincing evidence of reduced numbers of oligodendrocytes, impaired cell maturation and altered gene expression of myelin/oligodendrocyte-related genes that may in part explain white matter abnormalities and disturbed inter- and intra-hemispheric connectivity, which are characteristic signs of schizophrenia. Earlier reports of astrogliosis could not be confirmed by later studies, although the expression of a variety of astrocyte-related genes is abnormal in psychosis. Since astrocytes play a key role in the synaptic metabolism of glutamate, GABA, monoamines and purines, astrocyte dysfunction may contribute to certain aspects of disturbed neurotransmission in schizophrenia. Finally, increased densities of microglial cells and aberrant expression of microglia-related surface markers in schizophrenia suggest that immunological/inflammatory factors are of considerable relevance for the pathophysiology of psychosis. This review describes current evidence for the multifaceted role of glial cells in schizophrenia and discusses efforts to develop glia-directed therapies for the treatment of the disease.

Schizophrenia: susceptibility genes and oligodendroglial and myelin related abnormalities

Given that the genetic risk for schizophrenia is highly polygenic and the effect sizes, even for rare or de novo events, are modest at best, it has been suggested that multiple biological pathways are likely to be involved in the etiopathogenesis of the disease. Most efforts in understanding the cellular basis of schizophrenia have followed a “neuron-centric” approach, focusing on alterations in neurotransmitter systems and synapse cytoarchitecture. However, multiple lines of evidence coming from genetics and systems biology approaches suggest that apart from neurons, oligodendrocytes and potentially other glia are affected from schizophrenia risk loci. Neurobiological abnormalities linked with genetic association signal could identify abnormalities that are more likely to be primary, versus environmentally induced changes or downstream events. Here, we summarize genetic data that support the involvement of oligodendrocytes in schizophrenia, providing additional evidence for a causal role with the disease. Given the undeniable evidence of both neuronal and glial abnormalities in schizophrenia, we propose a neuro-glial model that invokes abnormalities at the node of Ranvier as a functional unit in the etiopathogenesis of the disease.

Neuroimaging, nutrition, and iron-related genes

Several dietary factors and their genetic modifiers play a role in neurological disease and affect the human brain. The structural and functional integrity of the living brain can be assessed using neuroimaging, enabling large-scale epidemiological studies to identify factors that help or harm the brain. Iron is one nutritional factor that comes entirely from our diet, and its storage and transport in the body are under strong genetic control. In this review, we discuss how neuroimaging can help to identify associations between brain integrity, genetic variations, and dietary factors such as iron. We also review iron's essential role in cognition, and we note some challenges and confounds involved in interpreting links between diet and brain health. Finally, we outline some recent discoveries regarding the genetics of iron and its effects on the brain, suggesting the promise of neuroimaging in revealing how dietary factors affect the brain.

Viral infection, inflammation and schizophrenia

Schizophrenia is a severe neurodevelopmental disorder with genetic and environmental etiologies. Prenatal viral/bacterial infections and inflammation play major roles in the genesis of schizophrenia. In this review, we describe a viral model of schizophrenia tested in mice whereby the offspring of mice prenatally infected with influenza at E7, E9, E16, and E18 show significant gene, protein, and brain structural abnormalities postnatally. Similarly, we describe data on rodents exposed to bacterial infection or injected with a synthetic viral mimic (PolyI:C) also demonstrating brain structural and behavioral abnormalities. Moreover, human serologic data has been indispensible in supporting the viral theory of schizophrenia. Individuals born seropositive for bacterial and viral agents are at a significantly elevated risk of developing schizophrenia. While the specific mechanisms of prenatal viral/bacterial infections and brain disorder are unclear, recent findings suggest that the maternal inflammatory response may be associated with fetal brain injury. Preventive and therapeutic treatment options are also proposed. This review presents data related to epidemiology, human serology, and experimental animal models which support the viral model of schizophrenia.

Roles of glial cells in schizophrenia: possible targets for therapeutic approaches

Glial cells consisting of oligodendrocytes, astrocytes, microglia, and NG2 positive cells are major cell populations in the central nervous system, number-wise. They function as effectors and modulators of neurodevelopment through a wide variety of neuron-glial cell interactions in brain development and functions. Glial cells can be affected by both genetic and environmental factors, leading to their dysfunctions in supporting neuronal development and functions. These in turn can affect neuronal cells, causing alterations at the circuitry level that manifest as behavioral characteristics associated with schizophrenia in late teens-early twenties. Glial cells are also involved in neuroinflammatory processes, which sometimes have deleterious effects on the normal brain development. If the glial involvement plays significant roles in schizophrenia, the processes involving glial cells can become possible therapeutic targets for schizophrenia. A number of known antipsychotics are shown to have beneficial effects on glial cells, but other drugs targeting glial cell functions may also have therapeutic effects on schizophrenia. The latter can be taken into consideration for future drug development for schizophrenia.

White matter abnormalities and animal models examining a putative role of altered white matter in schizophrenia

Schizophrenia is a severe mental disorder affecting about 1% of the population worldwide. Although the dopamine (DA) hypothesis is still keeping a dominant position in schizophrenia research, new advances have been emerging in recent years, which suggest the implication of white matter abnormalities in schizophrenia. In this paper, we will briefly review some of recent human studies showing white matter abnormalities in schizophrenic brains and altered oligodendrocyte-(OL-) and myelin-related genes in patients with schizophrenia and will consider abnormal behaviors reported in patients with white matter diseases. Following these, we will selectively introduce some animal models examining a putative role of white matter abnormalities in schizophrenia. The emphasis will be put on the cuprizone (CPZ) model. CPZ-fed mice show demyelination and OLs loss, display schizophrenia-related behaviors, and have higher DA levels in the prefrontal cortex. These features suggest that the CPZ model is a novel animal model of schizophrenia.

The A Allele of the -576G>A polymorphism of the transferrin gene is associated with the increased risk of age-related macular degeneration in smokers

Age-related macular degeneration (AMD) is the leading cause of blindness among the elderly in developed countries, and its pathogenesis is underlined by genetic and environmental factors. Oxidative stress is a major environmental risk factor of AMD; namely, AMD is associated with the increased level of reactive oxygen species, which may be produced in reactions catalyzed by iron present in the retina. Therefore, variability of the genes of iron metabolism may be important in the AMD risk. In the present study, we analyzed the association between AMD and the -576G>A polymorphism of the transferrin gene or the 1892C>T polymorphism of the transferrin receptor 2 (TFR2) gene in 278 patients with AMD and 105 controls. The former polymorphism is located in the promoter region of the transferrin gene and may affect the level of its transcription, while the latter is a synonymous mutation in the exon 16, which may affect the efficiency of translation of TFR2 mRNA. Transferrin and TFR2 are important in iron homeostasis. The A allele of the -576A>G polymorphism was significantly associated with the increased risk of AMD in tobacco smokers, whereas the 1892C>T polymorphism did not influence the risk of AMD related to smoking. Moreover, each polymorphism does not influence the risk of AMD associated with age, sex or the family history of the disease. In conclusion, the A allele of the -576A>G polymorphism of the transferrin gene may increase the risk of AMD in smokers.

Linking oligodendrocyte and myelin dysfunction to neurocircuitry abnormalities in schizophrenia

Multiple lines of evidence in schizophrenia, from brain imaging, studies in postmortem brains, and genetic association studies, have implicated oligodendrocyte and myelin dysfunction in this disease. Recent studies suggest that oligodendrocyte and myelin dysfunction leads to changes in synaptic formation and function, which could lead to cognitive dysfunction, a core symptom of schizophrenia. Furthermore, there is accumulating data linking oligodendrocyte and myelin dysfunction with dopamine and glutamate abnormalities, both of which are found in schizophrenia. These findings implicate oligodendrocyte and myelin dysfunction as a primary change in schizophrenia, not only as secondary consequences of the illness or treatment. Strategies targeting oligodendrocyte and myelin abnormalities could therefore provide therapeutic opportunities for patients suffering from schizophrenia.

Glial cells in schizophrenia: pathophysiological significance and possible consequences for therapy

In the last 10 years, structural, molecular and functional changes in glial cells have become a major focus of interest in the search for the neurobiological foundations of schizophrenia. While neuronal degeneration, as seen in typical degenerative brain diseases, cannot be found in post-mortem brains of psychotic disorders called 'schizophrenia', many studies show abnormalities in the connecting elements between the nerve cell bodies (synapses, dendrites and axons) and in all three types of glial cells. There is accumulating evidence of reduced numbers of oligodendrocytes and altered gene expression of myelin/oligodendrocyte-related genes that might explain white matter abnormalities and disturbed inter- and intra-hemispheric connectivity, which have frequently been described in schizophrenia. Earlier reports of increased astrocyte densities as a sign of gliosis could not be confirmed by later studies; however, the expression of several astrocyte-related genes is abnormal. Since astrocytes play a key role in the synaptic metabolism of glutamate and monamines, astrocyte dysfunction may well be related to the current transmitter theories of schizophrenia. Results in increased densities of microglial cells, which act as the main cells for immune defence in the brain, are more controversial. There are, however, higher microglial cell numbers in psychotic patients dying from suicide, and several studies reported altered expression of microglia-related surface markers in schizophrenia, suggesting that immunological/inflammatory factors may be relevant for the pathophysiology of psychosis. Searches for future therapeutic options should aim at compensating disturbed functions of oligodendrocytes, astrocytes and microglial cells, by which at least some aspects of the pathophysiology of the very inhomogeneous clinical syndrome of schizophrenia might be explained.