Rare variants in the neurotrophin signaling pathway implicated in schizophrenia risk

Morphogenetic theory of mental and cognitive disorders: the role of neurotrophic and guidance molecules

Mental illness and cognitive disorders represent a serious problem for the modern society. Many studies indicate that mental disorders are polygenic and that impaired brain development may lay the ground for their manifestation. Neural tissue development is a complex and multistage process that involves a large number of distant and contact molecules. In this review, we have considered the key steps of brain morphogenesis, and the major molecule families involved in these process. The review provides many indications of the important contribution of the brain development process and correct functioning of certain genes to human mental health. To our knowledge, this comprehensive review is one of the first in this field. We suppose that this review may be useful to novice researchers and clinicians wishing to navigate the field.

Mechanism of electroconvulsive therapy in schizophrenia: a bioinformatics analysis study of RNA-seq data

OBJECTIVE

The molecular mechanism of electroconvulsive therapy (ECT) for schizophrenia remains unclear. The aim of this study was to uncover the underlying biological mechanisms of ECT in the treatment of schizophrenia using a transcriptional dataset.

METHODS

The peripheral blood mRNA sequencing data of eight patients (before and after ECT) and eight healthy controls were analyzed by integrated co-expression network analysis and the differentially expressed genes were analyzed by cluster analysis. Gene set overlap analysis was performed using the hypergeometric distribution of phypfunction in R. Associations of these gene sets with psychiatric disorders were explored. Tissue-specific enrichment analysis, gene ontology enrichment analysis, and protein-protein interaction enrichment analysis were used for gene set organization localization and pathway analysis.

RESULTS

We found the genes of the green-yellow module were significantly associated with the effect of ECT treatment and the common gene variants of schizophrenia ( P  = 0.0061; family-wise error correction). The genes of the green-yellow module are mainly enriched in brain tissue and mainly involved in the pathways of neurotrophin, mitogen-activated protein kinase and long-term potentiation.

CONCLUSION

Genes associated with the efficacy of ECT were predominantly enriched in neurotrophin, mitogen-activated protein kinase and long-term potentiation signaling pathways.

Kidins220 sets the threshold for survival of neural stem cells and progenitors to sustain adult neurogenesis

In the adult mammalian brain, neural stem cells (NSCs) located in highly restricted niches sustain the generation of new neurons that integrate into existing circuits. A reduction in adult neurogenesis is linked to ageing and neurodegeneration, whereas dysregulation of proliferation and survival of NSCs have been hypothesized to be at the origin of glioma. Thus, unravelling the molecular underpinnings of the regulated activation that NSCs must undergo to proliferate and generate new progeny is of considerable relevance. Current research has identified cues promoting or restraining NSCs activation. Yet, whether NSCs depend on external signals to survive or if intrinsic factors establish a threshold for sustaining their viability remains elusive, even if this knowledge could involve potential for devising novel therapeutic strategies. Kidins220 (Kinase D-interacting substrate of 220 kDa) is an essential effector of crucial pathways for neuronal survival and differentiation. It is dramatically altered in cancer and in neurological and neurodegenerative disorders, emerging as a regulatory molecule with important functions in human disease. Herein, we discover severe neurogenic deficits and hippocampal-based spatial memory defects accompanied by increased neuroblast death and high loss of newly formed neurons in Kidins220 deficient mice. Mechanistically, we demonstrate that Kidins220-dependent activation of AKT in response to EGF restraints GSK3 activity preventing NSCs apoptosis. We also show that NSCs with Kidins220 can survive with lower concentrations of EGF than the ones lacking this molecule. Hence, Kidins220 levels set a molecular threshold for survival in response to mitogens, allowing adult NSCs growth and expansion. Our study identifies Kidins220 as a key player for sensing the availability of growth factors to sustain adult neurogenesis, uncovering a molecular link that may help paving the way towards neurorepair.

Update on genetics of attention deficit/hyperactivity disorder: current status 2023

PURPOSE OF REVIEW

Attention deficit/hyperactivity disorder (ADHD) shows consistently high heritability in genetic research. In this review article, we give an overview of the analysis of common and rare variants and some insight into current genetic methodology and their link to clinical practice.

RECENT FINDINGS

The heritability of about 80% is also high in comparison to other psychiatric diseases. However, recent studies estimate the proportion of heritability based on single nucleotide variants at 22%. The hidden heritability is an ongoing question in ADHD genetics. Common variants derived from mega genome-wide association analyses (GWAS) and subsequent meta-analyses usually display small effect sizes and explain only a small fraction of phenotypic variance. Rare variants, on the contrary, not only display large effect sizes but also rather explain, due to their rareness, a small fraction on phenotypic variance. Applying polygenic risk score (PRS) analysis is an improved approach of combining effect sizes of many common variants with clinically relevant measures in ADHD.

SUMMARY

We provide a concise overview on how genetic analysis, with a focus on GWAS and PRS, can help explain different behavioural phenotypes in ADHD and how they can be used for diagnosis and therapy prediction. Increased sample sizes of GWAS, meta-analyses and use of PRS is increasingly informative and sets the course for a new era in genetics of ADHD.

ARMS/Kidins220 regulates nociception by controlling brain-derived neurotrophic factor secretion

ABSTRACT

Pain is an alarm mechanism to prevent body damage in response to noxious stimuli. The nerve growth factor (NGF)/TrkA axis plays an essential role as pain mediator, and several clinical trials using antibodies against NGF have yielded promising results, but side effects have precluded their clinical approval. A better understanding of the mechanism of NGF/TrkA-mediated nociception is needed. Here, we find that ARMS/Kidins220, a scaffold protein for Trk receptors, is a modulator of nociception. Male mice, with ARMS/Kidins220 reduction exclusively in TrkA-expressing cells, displayed hyperalgesia to heat, inflammatory, and capsaicin stimuli, but not to cold or mechanical stimuli. Simultaneous deletion of brain-derived neurotrophic factor (BDNF) reversed the effects of ARMS/Kidins220 knock down alone. Mechanistically, ARMS/Kidins220 levels are reduced in vitro and in vivo in response to capsaicin through calpains, and this reduction leads to enhanced regulated BDNF secretion from dorsal root ganglion. Altogether, these data indicate that ARMS/Kidins220 protein levels have a role as a pain modulator in the NGF/TrkA axis regulating BDNF secretion.

ARMS-NF-κB signaling regulates intracellular ROS to induce autophagy-associated cell death upon oxidative stress

Ankyrin repeat-rich membrane spanning (ARMS) plays roles in neural development, neuropathies, and tumor formation. Such pleiotropic function of ARMS is often attributed to diverse ARMS-interacting molecules in different cell context. However, it might be achieved by ARMS' effect on global biological mediator like reactive oxygen species (ROS). We established ARMS-knockdown in melanoma cells (siARMS) and in Drosophila eyes (GMR>dARMS ^RNAi ) and challenged them with H₂O₂. Decreased ARMS in both systems compromises nuclear translocation of NF-κB and induces ROS, which in turn augments autophagy flux and confers susceptibility to H₂O₂-triggered autophagic cell death. Resuming NF-κB activity or reducing ROS by antioxidants in siARMS cells and GMR>dARMS ^RNAi fly decreases intracellular peroxides level concurrent with reduced autophagy and attenuated cell death. Conversely, blocking NF-κB activity in wild-type flies/melanoma enhances ROS and induces autophagy with cell death. We thus uncover intracellular ROS modulated by ARMS-NFκB signaling primes autophagy for autophagic cell death upon oxidative stress.

A sister's search for the seeds of psychosis

Dr. Dolores Malaspina sought a better way to understand the origins of psychosis than a schizophrenogenic mother, as her family had been informed upon her sisters illness. She moved her attention from environmental biology and zoology, to medical science and assembled knowledge on the multilevel components purported to underpin severe mental illness. Her studies cross levels to consider connections among exposures and genetic etiologies, intrinsic homeostatic mechanisms, stimuli perception and clinical illness features. Original contributions include associating later paternal age with increasing risk for schizophrenia in offspring and proposing that de novo mutations with shorter cell cycles explained the association, showing increased resting hippocampal blood flow in psychosis and that it was associated with inflammation, and that autonomic nervous system dysfunction was related to hippocampal inflammation, plausibly reflecting vascular abnormalities. She has been a professor of psychiatry in medical schools at Columbia University, New York University and at Mount Sinai in New York, USA.

Classification for psychiatric disorders including schizophrenia, bipolar disorder, and major depressive disorder using machine learning

Schizophrenia (SCZ), bipolar disorder (BP), and major depressive disorder (MDD) are the most common psychiatric disorders. Because there were lots of overlaps among these disorders from genetic epidemiology and molecular genetics, it is hard to realize the diagnoses of these psychiatric disorders. Currently, plenty of studies have been conducted for contributing to the diagnoses of these diseases. However, constructing a classification model with superior performance for differentiating SCZ, BP, and MDD samples is still a great challenge. In this study, the transcriptomic data was applied for discovering key genes and constructing a classification model. In this dataset, there were 268 samples including four groups (67 SCZ patients, 40 BP patients, 57 MDD patients, and 104 healthy controls), which were applied for constructing a classification model. First, 269 probes of differentially expressed genes (DEGs) among four sample groups were identified by the feature selection method. Second, these DEGs were validated by the literature review including disease relevance with the psychiatric disorders of these DEGs, the hub genes in the PPI (protein–protein interaction) network, and GO (gene ontology) terms and pathways. Third, a classification model was constructed using the identified DEGs by machine learning method to classify different groups. The ROC (receiver operator characteristic) curve and AUC (area under the curve) value were used to assess the classification capacity of the model. In summary, this classification model might provide clues for the diagnoses of these psychiatric disorders.

Kidins220 deficiency causes ventriculomegaly via SNX27-retromer-dependent AQP4 degradation

Several psychiatric, neurologic and neurodegenerative disorders present increased brain ventricles volume, being hydrocephalus the disease with the major manifestation of ventriculomegaly caused by the accumulation of high amounts of cerebrospinal fluid (CSF). The molecules and pathomechanisms underlying cerebral ventricular enlargement are widely unknown. Kinase D interacting substrate of 220 kDa (KIDINS220) gene has been recently associated with schizophrenia and with a novel syndrome characterized by spastic paraplegia, intellectual disability, nystagmus and obesity (SINO syndrome), diseases frequently occurring with ventriculomegaly. Here we show that Kidins220, a transmembrane protein effector of various key neuronal signalling pathways, is a critical regulator of CSF homeostasis. We observe that both KIDINS220 and the water channel aquaporin-4 (AQP4) are markedly downregulated at the ventricular ependymal lining of idiopathic normal pressure hydrocephalus (iNPH) patients. We also find that Kidins220 deficient mice develop ventriculomegaly accompanied by water dyshomeostasis and loss of AQP4 in the brain ventricular ependymal layer and astrocytes. Kidins220 is a known cargo of the SNX27-retromer, a complex that redirects endocytosed plasma membrane proteins (cargos) back to the cell surface, thus avoiding their targeting to lysosomes for degradation. Mechanistically, we show that AQP4 is a novel cargo of the SNX27-retromer and that Kidins220 deficiency promotes a striking and unexpected downregulation of the SNX27-retromer that results in AQP4 lysosomal degradation. Accordingly, SNX27 silencing decreases AQP4 levels in wild-type astrocytes whereas SNX27 overexpression restores AQP4 content in Kidins220 deficient astrocytes. Together our data suggest that the KIDINS220-SNX27-retromer-AQP4 pathway is involved in human ventriculomegaly and open novel therapeutic perspectives.

Schizophrenia risk candidate EGR3 is a novel transcriptional regulator of RELN and regulates neurite outgrowth via the Reelin signal pathway in vitro

Schizophrenia is a severe psychiatric disorder with a strong hereditary component that affects approximately 1% of the world's population. The disease is most likely caused by the altered expression of a number of genes that function at the level of biological pathways or gene networks. Transcription factors (TF) are indispensable regulators of gene expression. EGR3 is a TF associated with schizophrenia. In the current study, DNA microarray and ingenuity pathway analyses (IPA) demonstrated that EGR3 regulates Reelin signaling pathway in SH-SY5Y cells. ChIP and luciferase reporter studies confirmed that EGR3 directly binds to the promoter region of RELN thereby activating RELN expression. The expression of both EGR3 and RELN was decreased during neuronal differentiation induced by retinoic acid (RA) in SH-SY5Y cells, and EGR3 over-expression reduced neurite outgrowth which could be partially reversed by the knockdown of RELN. The expression levels of EGR3 and RELN in peripheral blood of subjects with schizophrenia were found to be down-regulated (compared with healthy controls), and were positively correlated. Furthermore, data mining from public databases revealed that the expression levels of EGR3 and RELN were presented a positive correlation in post-mortem brain tissue of subjects with schizophrenia. Taken together, this study suggests that EGR3 is a novel TF of the RELN gene and regulates neurite outgrowth via the Reelin signaling pathway. Our findings contribute to the understanding of the regulatory role of EGR3 in the pathophysiology and molecular mechanisms of schizophrenia, and potentially to the development of new therapies and diagnostic biomarkers for the disorder.

Identification of the gene signature reflecting schizophrenia's etiology by constructing artificial intelligence-based method of enhanced reproducibility

Aims

As one of the most fundamental questions in modern science, “what causes schizophrenia (SZ)” remains a profound mystery due to the absence of objective gene markers. The reproducibility of the gene signatures identified by independent studies is found to be extremely low due to the incapability of available feature selection methods and the lack of measurement on validating signatures’ robustness. These irreproducible results have significantly limited our understanding of the etiology of SZ.

Methods

In this study, a new feature selection strategy was developed, and a comprehensive analysis was then conducted to ensure a reliable signature discovery. Particularly, the new strategy (a) combined multiple randomized sampling with consensus scoring and (b) assessed gene ranking consistency among different datasets, and a comprehensive analysis among nine independent studies was conducted.

Results

Based on a first‐ever evaluation of methods’ reproducibility that was cross‐validated by nine independent studies, the newly developed strategy was found to be superior to the traditional ones. As a result, 33 genes were consistently identified from multiple datasets by the new strategy as differentially expressed, which might facilitate our understanding of the mechanism underlying the etiology of SZ.

Conclusion

A new strategy capable of enhancing the reproducibility of feature selection in current SZ research was successfully constructed and validated. A group of candidate genes identified in this study should be considered as great potential for revealing the etiology of SZ.

Regulation of BDNF Release by ARMS/Kidins220 through Modulation of Synaptotagmin-IV Levels

BDNF is a growth factor with important roles in the nervous system in both physiological and pathological conditions, but the mechanisms controlling its secretion are not completely understood. Here, we show that ARMS/Kidins220 negatively regulates BDNF secretion in neurons from the CNS and PNS. Downregulation of the ARMS/Kidins220 protein in the adult mouse brain increases regulated BDNF secretion, leading to its accumulation in the striatum. Interestingly, two mouse models of Huntington's disease (HD) showed increased levels of ARMS/Kidins220 in the hippocampus and regulated BDNF secretion deficits. Importantly, reduction of ARMS/Kidins220 in hippocampal slices from HD mice reversed the impaired regulated BDNF release. Moreover, there are increased levels of ARMS/Kidins220 in the hippocampus and PFC of patients with HD. ARMS/Kidins220 regulates Synaptotagmin-IV levels, which has been previously observed to modulate BDNF secretion. These data indicate that ARMS/Kidins220 controls the regulated secretion of BDNF and might play a crucial role in the pathogenesis of HD.SIGNIFICANCE STATEMENT BDNF is an important growth factor that plays a fundamental role in the correct functioning of the CNS. The secretion of BDNF must be properly controlled to exert its functions, but the proteins regulating its release are not completely known. Using neuronal cultures and a new conditional mouse to modulate ARMS/Kidins220 protein, we report that ARMS/Kidins220 negatively regulates BDNF secretion. Moreover, ARMS/Kidins220 is overexpressed in two mouse models of Huntington's disease (HD), causing an impaired regulation of BDNF secretion. Furthermore, ARMS/Kidins220 levels are increased in brain samples from HD patients. Future studies should address whether ARMS/Kidins220 has any function on the pathophysiology of HD.

Analysis of 182 cerebral palsy transcriptomes points to dysregulation of trophic signalling pathways and overlap with autism

Cerebral palsy (CP) is the most common motor disability of childhood. It is characterised by permanent, non-progressive but not unchanging problems with movement, posture and motor function, with a highly heterogeneous clinical spectrum and frequent neurodevelopmental comorbidities. The aetiology of CP is poorly understood, despite recent reports of a genetic contribution in some cases. Here we demonstrate transcriptional dysregulation of trophic signalling pathways in patient-derived cell lines from an unselected cohort of 182 CP-affected individuals using both differential expression analysis and weighted gene co-expression network analysis (WGCNA). We also show that genes differentially expressed in CP, as well as network modules significantly correlated with CP status, are enriched for genes associated with ASD. Combining transcriptome and whole exome sequencing (WES) data for this CP cohort likely resolves an additional 5% of cases separated to the 14% we have previously reported as resolved by WES. Collectively, these results support a convergent molecular abnormality in CP and ASD.

Rare missense coding variants in oxytocin receptor (OXTR) in schizophrenia cases are associated with early trauma exposure, cognition and emotional processing

BACKGROUND

Oxytocin is a peptide hormone that influences the integration of social cognition with behavior and affect regulation. Oxytocin also prominently directs the transition of neuronal GABA neurotransmission from excitatory to inhibitory after birth. The oxytocin receptor (OXTR) is linked to schizophrenia, a heterogeneous syndrome. Relationships of OXTR polymorphisms with specific clinical features could aid in evaluating any role of oxytocin in the pathogenesis of schizophrenia.

METHOD

Schizophrenia cases with rare missense coding OXTR single nucleotide variants (SNVs) were identified from a well-characterized sample of cases and controls who were assessed for symptoms, cognition and early life trauma.

RESULTS

Five of 48 cases showed rare OXTR variants. Compared to the other cases they had less severe negative symptoms (deficits in emotional expression and motivation) and less severe general psychopathology scores (depression and anxiety). They demonstrated lower nonverbal (performance) than verbal intelligence due to deficient perceptual organization and slow processing speed. They also reported greater early trauma exposure (physical and sexual abuse and emotional trauma).

CONCLUSION

Cases carrying rare OXTR SNVs had less negative and affective symptoms than other cases, but similar psychotic symptoms, along with specific cognitive deficits. The clinical characterization of these cases occurred in association with environmental exposure to early trauma, especially sexual abuse, which may have influenced the expression of schizophrenia in subjects harboring specific SNVs in the OXTR.

Functions of the multi-interacting protein KIDINS220/ARMS in cancer and other pathologies

Development of an organ and subsequently the whole system from an embryo is a highly integrated process. Although there is evidence that different systems are interconnected during developmental stages, the molecular understanding of this relationship is either not known or only to a limited extent. Nervous system development, amongst all, is maybe the most crucial and complex process. It relies on the correct distribution of specific neuronal growth factors and hormones to the specific receptors. Among the plethora of proteins that are involved in downstream signalling of neuronal growth factors, we find the kinase-D interacting substrate of 220 kDa (KIDINS220), also known as ankyrin-rich repeat membrane spanning (ARMS) protein. KIDINS220 has been shown to play a substantial role in the nervous system and vascular system development as well as in neuronal survival and differentiation. It serves as a downstream regulator for many important neuronal and vascular growth factors such as vascular endothelial growth factor (VEGF), the neurotrophin family, glutamate receptors and ephrin receptors. Moreover, activation and differentiation of B- and T-cells, as well as tumour cell proliferation has also shown to be related to KIDINS220. This review comprehensively summarises the existing research data on this protein, with a particular interest in its role in cancer and in other pathologies.

The Effects of Prenatal Iron Deficiency and Risperidone Treatment on the Rat Frontal Cortex: A Proteomic Analysis

Prenatal iron deficiency (pID) has been described to increase the risk for neurodevelopmental disorders such as autism and schizophrenia; however, the precise molecular mechanisms are still unknown. Here, we utilized high-throughput MS to examine the proteomic effects of pID in adulthood on the rat frontal cortex area (FCA). In addition, the FCA proteome was examined in adulthood following risperidone treatment in adolescence to see if these effects could be prevented. We identified 1501 proteins of which 100 were significantly differentially expressed in the FCA at postnatal day 90. Pathway analysis of proteins affected by pID revealed changes in metabolic processes, including the tricyclic acid cycle, mitochondrial dysfunction, and P13K/Akt signaling. Interestingly, most of these protein changes were not present in the adult pID offspring who received risperidone in adolescence. Considering the link between pID and several neurodevelopmental disorders such as autism and schizophrenia these presented results bring new perspectives to understand the role of iron in metabolic pathways and provide novel biomarkers for future studies of pID.

Neurotrophin signalling: novel insights into mechanisms and pathophysiology

Neurotrophins, such as brain-derived neurotrophic factor (BDNF), are prominent regulators of neuronal survival, growth and differentiation during development. While trophic factors are viewed as well-understood but not innovative molecules, there are many lines of evidence indicating that BDNF plays an important role in the pathophysiology of many neurodegenerative disorders, depression, anxiety and other psychiatric disorders. In particular, lower levels of BDNF are associated with the aetiology of Alzheimer's and Huntington's diseases. A major challenge is to explain how neurotrophins are able to induce plasticity, improve learning and memory and prevent age-dependent cognitive decline through receptor signalling. This article will review the mechanism of action of neurotrophins and how BDNF/tropomyosin receptor kinase B (TrkB) receptor signaling can dictate trophic responses and change brain plasticity through activity-dependent stimulation. Alternative approaches for modulating BDNF/TrkB signalling to deliver relevant clinical outcomes in neurodegenerative and neuropsychiatric disorders will also be described.

Prefrontal neuronal integrity predicts symptoms and cognition in schizophrenia and is sensitive to genetic heterogeneity

Schizophrenia is a genetically complex syndrome with substantial inter-subject variability in multiple domains. Person-specific measures to resolve its heterogeneity could focus on the variability in prefrontal integrity, which this study indexed as relative rostralization within the anterior cingulate cortex (ACC). Twenty-two schizophrenia cases and 11 controls underwent rigorous diagnostic procedures, symptom assessments (PANSS, Deficit Syndrome Scale) and intelligence testing. All underwent multivoxel MRSI at 3T to measure concentrations of the neuronal-specific biomarker N-acetylaspartate (NAA) in all of the voxels of the ACC. The concentrations of NAA were separately calculated and then compared across the rostral and caudal subregions to generate a rostralization ratio, which was examined with respect to the study measures and to which cases carried a missense coding polymorphism in PTPRG, SCL39A13, TGM5, NTRK1 or ARMS/KIDINS220. Rostralization significantly differed between cases and controls (χ(2)=18.40, p<.0001). In cases, it predicted verbal intelligence (r=.469, p=.043) and trait negative symptoms (diminished emotional range (r=-.624, p=.010); curbed interests, r=-.558, p=.025). Rostralization was similar to controls for missense coding variants in TGM5 and was significantly greater than controls for the PTPRG variant carrier. This is the first study examining the utility of MRS metrics in describing pathological features at both group and person-specific levels. Rostralization predicted core illness features and differed based on which signaling genes were disrupted. While future studies in larger populations are needed, ACC rostralization appears to be a promising measure to reduce the heterogeneity of schizophrenia for genetic research and selecting cases for treatment studies.

Stepping Out of the Shade: Control of Neuronal Activity by the Scaffold Protein Kidins220/ARMS

The correct functioning of the nervous system depends on the exquisitely fine control of neuronal excitability and synaptic plasticity, which relies on an intricate network of protein-protein interactions and signaling that shapes neuronal homeostasis during development and in adulthood. In this complex scenario, Kinase D interacting substrate of 220 kDa/ankyrin repeat-rich membrane spanning (Kidins220/ARMS) acts as a multi-functional scaffold protein with preferential expression in the nervous system. Engaged in a plethora of interactions with membrane receptors, cytosolic signaling components and cytoskeletal proteins, Kidins220/ARMS is implicated in numerous cellular functions including neuronal survival, neurite outgrowth and maturation and neuronal activity, often in the context of neurotrophin (NT) signaling pathways. Recent studies have highlighted a number of cell- and context-specific roles for this protein in the control of synaptic transmission and neuronal excitability, which are at present far from being completely understood. In addition, some evidence has began to emerge, linking alterations of Kidins220 expression to the onset of various neurodegenerative diseases and neuropsychiatric disorders. In this review, we present a concise summary of our fragmentary knowledge of Kidins220/ARMS biological functions, focusing on the mechanism(s) by which it controls various aspects of neuronal activity. We have tried, where possible, to discuss the available evidence in the wider context of NT-mediated regulation, and to outline emerging roles of Kidins220/ARMS in human pathologies.

Phenotypically distinct subtypes of psychosis accompany novel or rare variants in four different signaling genes

BACKGROUND

Rare gene variants are important sources of schizophrenia vulnerability that likely interact with polygenic susceptibility loci. This study examined if novel or rare missense coding variants in any of four different signaling genes in sporadic schizophrenia cases were associated with clinical phenotypes in an exceptionally well-characterized sample.

METHOD

Structured interviews, cognition, symptoms and life course features were assessed in 48 ethnically-diverse cases with psychosis who underwent targeted exome sequencing of PTPRG (Protein Tyrosine Phosphatase, Receptor Type G), SLC39A13 (Solute Carrier Family 39 (Zinc Transporter) Member 13), TGM5 (transglutaminase 5) and ARMS/KIDINS220 (Ankyrin repeat-rich membrane spanning protein or Kinase D-Interacting Substrate of 220kDa). Cases harboring rare missense coding polymorphisms or novel mutations in one or more of these genes were compared to other cases not carrying any rare missense coding polymorphisms or novel mutations in these genes and healthy controls.

FINDINGS

Fifteen of 48 cases (31.25%) carried rare or novel missense coding variants in one or more of these genes. The subgroups significantly differed in important features, including specific working memory deficits for PTPRG (n=5); severe negative symptoms, global cognitive deficits and poor educational attainment, suggesting a developmental disorder, for SLC39A13 (n=4); slow processing speed, childhood attention deficit disorder and milder symptoms for TGM5 (n=4); and global cognitive deficits with good educational attainment suggesting neurodegeneration for ARMS/KIDINS220 (n=5). Case vignettes are included in the appendix.

INTERPRETATION

Genes prone to missense coding polymorphisms and/or mutations in sporadic cases may highlight influential genes for psychosis and illuminate heterogeneous pathways to schizophrenia. Ethnicity appears less important at the level of genetic variability. The sequence variations that potentially alter the function of specific genes or their signaling partners may contribute to particular subtypes of psychosis. This approach may be applicable to other complex disorders.

Early Life Stress Effects on Glucocorticoid-BDNF Interplay in the Hippocampus

Early life stress (ELS) is implicated in the etiology of multiple psychiatric disorders. Important biological effects of ELS are manifested in stress-susceptible regions of the hippocampus and are partially mediated by long-term effects on glucocorticoid (GC) and/or neurotrophin signaling pathways. GC-signaling mediates the regulation of stress response to maintain homeostasis, while neurotrophin signaling plays a key role in neuronal outgrowth and is crucial for axonal guidance and synaptic integrity. The neurotrophin and GC-signaling pathways co-exist throughout the central nervous system (CNS), particularly in the hippocampus, which has high expression levels of glucocorticoid-receptors (GR) and mineralocorticoid-receptors (MR) as well as brain-derived neurotrophic factor (BDNF) and its receptor, tropomyosin-related kinase receptor B (TrkB). This review addresses the effects of ELS paradigms on GC- and BDNF-dependent mechanisms and their crosstalk in the hippocampus, including potential implications for the pathogenesis of common stress-related disorders.