Disrupted in schizophrenia 1 modulates medial prefrontal cortex pyramidal neuron activity through cAMP regulation of transient receptor potential C and small-conductance K+ channels

Exploration on the potential efficacy and mechanism of methyl salicylate glycosides in the treatment of schizophrenia based on bioinformatics, molecular docking and dynamics simulation

The etiological and therapeutic complexities of schizophrenia (SCZ) persist, prompting exploration of anti-inflammatory therapy as a potential treatment approach. Methyl salicylate glycosides (MSGs), possessing a structural parent nucleus akin to aspirin, are being investigated for their therapeutic potential in schizophrenia. Utilizing bioinformation mining, network pharmacology, molecular docking and dynamics simulation, the potential value and mechanism of MSGs (including MSTG-A, MSTG-B, and Gaultherin) in the treatment of SCZ, as well as the underlying pathogenesis of the disorder, were examined. 581 differentially expressed genes related to SCZ were identified in patients and healthy individuals, with 349 up-regulated genes and 232 down-regulated genes. 29 core targets were characterized by protein-protein interaction (PPI) network, with the top 10 core targets being BDNF, VEGFA, PVALB, KCNA1, GRIN2A, ATP2B2, KCNA2, APOE, PPARGC1A and SCN1A. The pathogenesis of SCZ primarily involves cAMP signaling, neurodegenerative diseases and other pathways, as well as regulation of ion transmembrane transport. Molecular docking analysis revealed that the three candidates exhibited binding activity with certain targets with binding affinities ranging from -4.7 to -109.2 kcal/mol. MSTG-A, MSTG-B and Gaultherin show promise for use in the treatment of SCZ, potentially through their ability to modulate the expression of multiple genes involved in synaptic structure and function, ion transport, energy metabolism. Molecular dynamics simulation revealed good binding abilities between MSTG-A, MSTG-B, Gaultherin and ATP2B2. It suggests new avenues for further investigation in this area.

Guanfacine inhibits interictal epileptiform events and sodium currents in prefrontal cortex pyramidal neurons

BACKGROUND

Guanfacine (an alpha-2A receptor agonist) is a commonly used drug with recognized efficacy in the treatment of attention deficit hyperactivity disorder (ADHD). This study aimed to assess the effects of guanfacine on short-lasting (interictal) epileptiform discharges in cortical neurons. Moreover, we assessed the effects of guanfacine on voltage-gated sodium currents.

METHODS

We conducted patch-clamp recordings in prefrontal cortex pyramidal neurons obtained from young rats. Interictal epileptiform events were evoked in cortical slices in a zero magnesium proepileptic extracellular solution with an elevated concentration of potassium ions.

RESULTS

Interictal epileptiform discharges were spontaneous depolarisations, which triggered action potentials. Guanfacine (10 and 100 µM) inhibited the frequency of epileptiform discharges. The effect of guanfacine on interictal events persisted in the presence of alpha-2 adrenergic receptor antagonist idazoxan. The tested drug inhibited neuronal excitability. Tonic NMDA currents were not influenced by guanfacine. Recordings from dispersed neurons showed that the tested drug (10 and 100 µM) inhibited persistent and fast inactivating voltage-gated sodium currents.

CONCLUSIONS

This study shows that guanfacine inhibits interictal discharges in cortical neurons independently of alpha-2A adrenergic receptors. This effect may be mediated by voltage-gated sodium currents. Inhibition of interictal activity by guanfacine may be of clinical importance because interictal events often occur in patients with ADHD and may contribute to symptoms of this disease.

Exploring the key factors of schizophrenia relapse by integrating LC-MS/1H NMR metabolomics and weighted correlation network analysis

BACKGROUND

Lack of comprehending key factors of schizophrenia relapse has impeded its effective treatment, indicating that the mechanism clarification and available intervention of schizophrenia relapse required further amelioration.

METHOD

Based on the integration of LC-MS and ¹H NMR metabolomics, a weighted correlation network was established to screen pivotal factors of accelerating schizophrenia relapse. Then, the cluster most correlated with schizophrenia relapse was explored, and the biological function of cluster was investigated. Next, the key biomarker related to schizophrenia relapse was obtained through multiple algorithms. Moreover, the Lilikoi algorithm and correlation analysis were implemented to reveal the association between key biomarker and schizophrenia relapse.

RESULT

Results showed that 458 different forms of metabolites were identified for structuring the weighted correlation network. The module-trait correlation indicated that the turquoise module was the most highly correlated with schizophrenia relapse. Further, network analysis revealed that, in turquoise module, cluster 1 composed of 139 metabolites (involved in lipid metabolism and energy metabolism) was the most important subnetwork relevant to schizophrenia relapse. Finally, phenylalanylphenylalanine was recommended as the key biomarker related to schizophrenia relapse. Moreover, the correlation analysis indicated that phenylalanylphenylalanine might affect the progression of schizophrenia by intervening in energy metabolism.

CONCLUSION

In summary, critical factors of schizophrenia relapse have been revealed in our research, expounding the schizophrenia progression more systemically, which could shed some light on improving the intervention of schizophrenia relapse.

Single-cell RNA-seq and its Applications in the Study of Psychiatric Disorders

Neuroscience is currently one of the most challenging research fields owing to the enormous complexity of the mammalian nervous system. We are yet to understand precise transcriptional programs that govern cell fate during neurodevelopment, resolve the connectome of the mammalian brain, and determine the etiology of various neurodegenerative and psychiatric disorders. Technological advances in the past decade, notably single-cell RNA sequencing, have enabled huge progress in our understanding of such features. Our current knowledge of the transcriptome is largely derived from bulk RNA sequencing, which reveals only the average gene expression of millions of cells, potentially missing out on minor transcriptome differences between cells detectable only at single-cell resolution. Since 2009, several single-cell RNA sequencing techniques have emerged that enable the accurate classification of neuronal and glial cell subtypes beyond classical molecular markers and electrophysiological features and allow the identification of previously unknown cell types. Furthermore, it enables the interrogation of molecular and disease-relevant mechanisms and offers further possibilities for the discovery of new drug targets and disease biomarkers. This review intends to familiarize the reader with the main single-cell RNA sequencing techniques developed throughout the past decade and discusses their application in the fields of brain cell taxonomy, neurodevelopment, and psychiatric disorders.

Physiology and Therapeutic Potential of SK, H, and M Medium AfterHyperPolarization Ion Channels

SK, HCN, and M channels are medium afterhyperpolarization (mAHP)-mediating ion channels. The three channels co-express in various brain regions, and their collective action strongly influences cellular excitability. However, significant diversity exists in the expression of channel isoforms in distinct brain regions and various subcellular compartments, which contributes to an equally diverse set of specific neuronal functions. The current review emphasizes the collective behavior of the three classes of mAHP channels and discusses how these channels function together although they play specialized roles. We discuss the biophysical properties of these channels, signaling pathways that influence the activity of the three mAHP channels, various chemical modulators that alter channel activity and their therapeutic potential in treating various neurological anomalies. Additionally, we discuss the role of mAHP channels in the pathophysiology of various neurological diseases and how their modulation can alleviate some of the symptoms.

Noradrenergic Suppression of Persistent Firing in Hippocampal CA1 Pyramidal Cells through cAMP-PKA Pathway

Persistent firing is believed to be a cellular correlate of working memory. While the effects of noradrenaline (NA) on working memory have widely been described, its effect on the cellular mechanisms of persistent firing remains largely unknown. Using in vitro intracellular recordings, we demonstrate that persistent firing is supported by individual neurons in hippocampal CA1 pyramidal cells through cholinergic receptor activation, but is dramatically attenuated by NA. In contrast to the classical theory that recurrent synaptic excitation supports persistent firing, suppression of persistent firing by NA was independent of synaptic transmission, indicating that the mechanism is intrinsic to individual cells. In agreement with detrimental effects of cAMP on working memory, we demonstrate that the suppressive effect of NA was through cAMP-PKA pathway. In addition, activation of β1 and/or β3 adrenergic receptors, which increases cAMP levels, suppressed persistent firing. These results are in line with working memory decline observed during high levels of NA and cAMP, which are implicated in high stress, aging, and schizophrenia.

SK2 channel regulation of neuronal excitability, synaptic transmission, and brain rhythmic activity in health and diseases

Small conductance calcium-activated potassium channels (SKs) are solely activated by intracellular Ca2+ and their activation leads to potassium efflux, thereby repolarizing/hyperpolarizing membrane potential. Thus, these channels play a critical role in synaptic transmission, and consequently in information transmission along the neuronal circuits expressing them. SKs are widely but not homogeneously distributed in the central nervous system (CNS). Activation of SKs requires submicromolar cytoplasmic Ca2+ concentrations, which are reached following either Ca2+ release from intracellular Ca2+ stores or influx through Ca2+ permeable membrane channels. Both Ca2+ sensitivity and synaptic levels of SKs are regulated by protein kinases and phosphatases, and degradation pathways. SKs in turn control the activity of multiple Ca2+ channels. They are therefore critically involved in coordinating diverse Ca2+ signaling pathways and controlling Ca2+ signal amplitude and duration. This review highlights recent advances in our understanding of the regulation of SK2 channels and of their roles in normal brain functions, including synaptic plasticity, learning and memory, and rhythmic activities. It will also discuss how alterations in their expression and regulation might contribute to various brain disorders such as Angelman Syndrome, Alzheimer's disease and Parkinson's disease.

Autophagic Network Analysis of the Dual Effect of Sevoflurane on Neurons Associated with GABARAPL1 and 2

Background

Sevoflurane is commonly used as a general anesthetic in neonates to aged patients. Preconditioning or postconditioning with sevoflurane protects neurons from excitotoxic injury. Conversely, sevoflurane exposure induces neurotoxicity during early or late life. However, little is known about the underlying mechanism of the dual effect of sevoflurane on neurons. Autophagy is believed to control neuronal homeostasis. We hypothesized that autophagy determined the dual effect of sevoflurane on neurons.

Methods

DTome was used to identify the direct protein target (DPT) of sevoflurane. The STRING database was employed to investigate the proteins associated with the DPTs. Protein-protein interaction was assessed using Cytoscape. WebGestalt was used to analyze gene set enrichment. The linkage between candidate genes and autophagy was identified using GeneCards.

Results

This study found that 23 essential DPTs of sevoflurane interacted with 77 proteins from the STRING database. GABARAPL1 and 2, both of which are DPT- and autophagy-associated proteins, were significantly expressed in the brain and enriched in GABAergic synapses.

Conclusions

Taken together, our findings showed that the network of sevoflurane-DPT-GABARAPL1 and 2 is related to the dual effect of sevoflurane on neurons.

Therapeutic potential of pharmacological agents targeting TRP channels in CNS disorders

Central nervous system (CNS) disorders like Alzheimer's disease (AD), Parkinson disease (PD), stroke, epilepsy, depression, and bipolar disorder have a high impact on both medical and social problems due to the surge in their prevalence. All of these neuronal disorders share some common etiologies including disruption of Ca²⁺ homeostasis and accumulation of misfolded proteins. These misfolded proteins further disrupt the intracellular Ca²⁺ homeostasis by disrupting the activity of several ion channels including transient receptor potential (TRP) channels. TRP channel families include non-selective Ca²⁺ permeable channels, which act as cellular sensors activated by various physio-chemical stimuli, exogenous, and endogenous ligands responsible for maintaining the intracellular Ca²⁺ homeostasis. TRP channels are abundantly expressed in the neuronal cells and disturbance in their activity leads to various neuronal diseases. Under the pathological conditions when the activity of TRP channels is perturbed, there is a disruption of the neuronal homeostasis through increased inflammatory response, generation of reactive oxygen species, and mitochondrial dysfunction. Therefore, there is a potential of pharmacological interventions targeting TRP channels in CNS disorders. This review focuses on the role of TRP channels in neurological diseases; also, we have highlighted the current insights into the pharmacological modulators targeting TRP channels.

Transcriptome Analysis Identifies Multifaceted Regulatory Mechanisms Dictating a Genetic Switch from Neuronal Network Establishment to Maintenance During Postnatal Prefrontal Cortex Development

The prefrontal cortex (PFC) is one of the latest brain regions to mature, which allows the acquisition of complex cognitive abilities through experience. To unravel the underlying gene expression changes during postnatal development, we performed RNA-sequencing (RNA-seq) in the rat medial PFC (mPFC) at five developmental time points from infancy to adulthood, and analyzed the differential expression of protein-coding genes, long intergenic noncoding RNAs (lincRNAs), and alternative exons. We showed that most expression changes occur in infancy, and that the number of differentially expressed genes reduces toward adulthood. We observed 137 differentially expressed lincRNAs and 796 genes showing alternative exon usage during postnatal development. Importantly, we detected a genetic switch from neuronal network establishment in infancy to maintenance of neural networks in adulthood based on gene expression dynamics, involving changes in protein-coding and lincRNA gene expression as well as alternative exon usage. Our gene expression datasets provide insights into the multifaceted transcriptional regulation of the developing PFC. They can be used to study the basic developmental processes of the mPFC and to understand the mechanisms of neurodevelopmental and neuropsychiatric disorders. Our study provides an important contribution to the ongoing efforts to complete the "brain map", and to the understanding of PFC development.

HERV-W env regulates calcium influx via activating TRPC3 channel together with depressing DISC1 in human neuroblastoma cells

The activation and involvement of human endogenous retroviruses W family envelope gene (HERV-W env, also called ERVWE1) have been reported in several neuropsychiatric disorders, including schizophrenia, as well as in multiple sclerosis (MS). Dysregulation of intracellular calcium content is also involved in the pathogenesis of these diseases. Our previous studies showed that HERV-W env overexpression results in activation of small conductance Ca²⁺-activated K⁺ channel protein 3 (SK3), a potential risk factor for schizophrenia. In the present study, we aimed to elucidate the relationship between HERV-W env and calcium signaling in schizophrenia. Our results showed that HERV-W env could induce Ca²⁺ influx in two human neuroblastoma cell lines and upregulate the expression and activation of TRPC3 in cells. The abnormal increase in intracellular Ca²⁺ concentration was inhibited by addition of the TRPC3 channel blocker pyr3, demonstrating that the Ca²⁺ influx induced by HERV-W env was TRPC3-dependent. Further experiments showed that HERV-W env overexpression downregulated DISC1, while knockdown of DISC1 promoted activation of TRPC3 without affecting TRPC3 expression. In conclusion, HERV-W env induced Ca²⁺ influx in human neuroblastoma cells by activating the TRPC3 channel through directly regulating its expression or downregulating DISC1, which could also increase TRPC3 activation without affecting TRPC3 expression. These findings provide new insights into how HERV-W env affects neuronal activity and contributes to the pathogenesis of schizophrenia.

Plasma cytokines in minimally treated schizophrenia

In schizophrenia, plasma cytokines abnormalities offer vital support for immunopathogenetic basis. However, most of the previous studies on plasma cytokines are confounded by examination of antipsychotic-treated schizophrenia patients. In this study, we examined a large sample of antipsychotic-naïve/free schizophrenia patients (N = 75) in comparison with healthy controls (N = 102). Plasma cytokines (Interleukins ([IL] 2, 4, 6, 10, 17), Tumor necrosis factor [TNF] and Interferon gamma [IFN-g]) were assessed using cytometric bead array assay. Schizophrenia patients showed significantly greater levels of IL-6 and lower levels of IL-17 as well as IFN-g in comparison to healthy controls. However, after taking censoring into account and adjusting for potential confounders (sex, age, BMI and smoking), only IL-6 was found to be elevated in patients. Cytokine profile showed differential and pathogenetically relevant correlation with clinical symptoms. Together, these observations offer further support to immunological component in schizophrenia pathogenesis.

Do TRPC channels support working memory? Comparing modulations of TRPC channels and working memory through G-protein coupled receptors and neuromodulators

Working memory is a crucial ability we use in daily life. However, the cellular mechanisms supporting working memory still remain largely unclear. A key component of working memory is persistent neural firing which is believed to serve short-term (hundreds of milliseconds up to tens of seconds) maintenance of necessary information. In this review, we will focus on the role of transient receptor potential canonical (TRPC) channels as a mechanism underlying persistent firing. Many years of in vitro work have been suggesting a crucial role of TRPC channels in working memory and temporal association tasks. If TRPC channels are indeed a central mechanism for working memory, manipulations which impair or facilitate working memory should have a similar effect on TRPC channel modulation. However, modulations of working memory and TRPC channels were never systematically compared, and it remains unanswered whether TRPC channels indeed contribute to working memory in vivo or not. In this article, we review the effects of G-protein coupled receptors (GPCR) and neuromodulators, including acetylcholine, noradrenalin, serotonin and dopamine, on working memory and TRPC channels. Based on comparisons, we argue that GPCR and downstream signaling pathways that activate TRPC, generally support working memory, while those that suppress TRPC channels impair it. However, depending on the channel types, areas, and systems tested, this is not the case in all studies. Further work to clarify involvement of specific TRPC channels in working memory tasks and how they are affected by neuromodulators is still necessary in the future.

mGluR2/3 mechanisms in primate dorsolateral prefrontal cortex: evidence for both presynaptic and postsynaptic actions

Cognitive deficits in psychiatric and age-related disorders generally involve dysfunction of the dorsolateral prefrontal cortex (dlPFC), but there are few treatments for these debilitating symptoms. Group II metabotropic glutamate receptors (mGluR2/3), which couple to Gi/Go, have been a focus of therapeutics based on rodent research, where mGluR2/3 have been shown to reduce axonal glutamate release and increase glial glutamate uptake. However, this strategy has had mixed results in patients, and understanding mGluR2/3 mechanisms in primates will help guide therapeutic interventions. The current study examined mGluR2/3 localization and actions in the primate dlPFC layer III circuits underlying working memory, where the persistent firing of 'Delay cells' is mediated by N-methyl-d-aspartate receptors and weakened by cAMP-PKA-potassium channel signaling in dendritic spines. Immunoelectron microscopy identified postsynaptic mGluR2/3 in the spines, in addition to the traditional presynaptic and astrocytic locations. In vivo iontophoretic application of the mGluR2/3 agonists (2R, 4R)-APDC or LY379268 onto dlPFC Delay cells produced an inverted-U effect on working memory representation, with enhanced neuronal firing following low doses of mGluR2/3 agonists. The enhancing effects were reversed by an mGluR2/3 antagonist or by activating cAMP signaling, consistent with mGluR2/3 inhibiting postsynaptic cAMP signaling in spines. Systemic administration of these agonists to monkeys performing a working memory task also produced an inverted-U dose-response, where low doses improved performance but higher doses, similar to clinical trials, had mixed effects. Our data suggest that low doses of mGluR2/3 stimulation may have therapeutic effects through unexpected postsynaptic actions in dlPFC, strengthening synaptic connections and improving cognitive function.

Small conductance Ca2+-activated K+ channels in the plasma membrane, mitochondria and the ER: Pharmacology and implications in neuronal diseases

Ca²⁺-activated K⁺ (K_Ca) channels regulate after-hyperpolarization in many types of neurons in the central and peripheral nervous system. Small conductance Ca²⁺-activated K⁺ (K_Ca2/SK) channels, a subfamily of K_Ca channels, are widely expressed in the nervous system, and in the cardiovascular system. Voltage-independent SK channels are activated by alterations in intracellular Ca²⁺ ([Ca²⁺]_i) which facilitates the opening of these channels through binding of Ca²⁺ to calmodulin that is constitutively bound to the SK2 C-terminus. In neurons, SK channels regulate synaptic plasticity and [Ca²⁺]_i homeostasis, and a number of recent studies elaborated on the emerging neuroprotective potential of SK channel activation in conditions of excitotoxicity and cerebral ischemia, as well as endoplasmic reticulum (ER) stress and oxidative cell death. Recently, SK channels were discovered in the inner mitochondrial membrane and in the membrane of the endoplasmic reticulum which sheds new light on the underlying molecular mechanisms and pathways involved in SK channel-mediated protective effects. In this review, we will discuss the protective properties of pharmacological SK channel modulation with particular emphasis on intracellularly located SK channels as potential therapeutic targets in paradigms of neuronal dysfunction.

Impaired Cholinergic Excitation of Prefrontal Attention Circuitry in the TgCRND8 Model of Alzheimer's Disease

Attention deficits in Alzheimer's disease can exacerbate its other cognitive symptoms, yet relevant disruptions of key prefrontal circuitry are not well understood. Here, in the TgCRND8 mouse model of this neurological disorder, we demonstrate and characterize a disruption of cholinergic excitation in the major corticothalamic layer of the prefrontal cortex, in which modulation by acetylcholine is essential for optimal attentional function. Using electrophysiology with concurrent multiphoton imaging, we show that layer 6 pyramidal cells are unable to sustain cholinergic excitation to the same extent as their nontransgenic littermate controls, as a result of the excessive activation of calcium-activated hyperpolarizing conductances. We report that cholinergic excitation can be improved in TgCRND8 cortex by pharmacological blockade of SK channels, suggesting a novel target for the treatment of cognitive dysfunction in Alzheimer's disease.

SIGNIFICANCE STATEMENT

Alzheimer's disease is accompanied by attention deficits that exacerbate its other cognitive symptoms. In brain slices of a mouse model of this neurological disorder, we demonstrate, characterize, and rescue impaired cholinergic excitation of neurons essential for optimal attentional performance. In particular, we show that the excessive activation of a calcium-activated potassium conductance disrupts the acetylcholine excitation of prefrontal layer 6 pyramidal neurons and that its blockade normalizes responses. These findings point to a novel potential target for the treatment of cognitive dysfunction in Alzheimer's disease.

An interaction between NDE1 and high birth weight increases schizophrenia susceptibility

Pre- and perinatal environmental factors have been shown to increase schizophrenia risk particularly when combined with genetic liability. The investigation of specific gene environment interactions in the etiology of psychiatric disorders has gained momentum. We used multivariate GEE regression modeling to investigate the interaction between genes of the DISC1 pathway and birth weight, in relation to schizophrenia susceptibility in a Finnish schizophrenia family cohort. The study sample consisted of 457 subjects with both genotype and birth weight information. Gender and place of birth were adjusted for in the models. We found a significant interaction between birth weight and two NDE1 markers in relation to increased schizophrenia risk: a four SNP haplotype spanning NDE1 (b=1.26, SE=0.5, p=0.012) and one of its constituent SNPs rs4781678 (b=1.33, SE=0.51, p=0.010). Specifically, high birth weight (>4000g) was associated with increased schizophrenia risk among subjects homozygous for the previously identified risk alleles. The study was based on a family study sample with high genetic loading for schizophrenia and thus our findings cannot directly be generalized as representing the general population. Our results suggest that the functions mediated by NDE1 during the early stages of neurodevelopment are susceptible to the additional disruptive effects of pre- and perinatal environmental factors associated with high birth weight, augmenting schizophrenia susceptibility.

Stress weakens prefrontal networks: molecular insults to higher cognition

A variety of cognitive disorders are worsened by stress exposure and involve dysfunction of the newly evolved prefrontal cortex (PFC). Exposure to acute, uncontrollable stress increases catecholamine release in PFC, reducing neuronal firing and impairing cognitive abilities. High levels of noradrenergic α1-adrenoceptor and dopaminergic D1 receptor stimulation activate feedforward calcium-protein kinase C and cyclic AMP-protein kinase A signaling, which open potassium channels to weaken synaptic efficacy in spines. In contrast, high levels of catecholamines strengthen the primary sensory cortices, amygdala and striatum, rapidly flipping the brain from reflective to reflexive control of behavior. These mechanisms are exaggerated by chronic stress exposure, where architectural changes lead to persistent loss of PFC function. Understanding these mechanisms has led to the successful translation of prazosin and guanfacine for treating stress-related disorders. Dysregulation of stress signaling pathways by genetic insults likely contributes to PFC deficits in schizophrenia, while age-related insults initiate interacting vicious cycles that increase vulnerability to Alzheimer's degeneration.

Neuroglial Transmission

Neuroglia, the "glue" that fills the space between neurons in the central nervous system, takes active part in nerve cell signaling. Neuroglial cells, astroglia, oligodendroglia, and microglia, are together about as numerous as neurons in the brain as a whole, and in the cerebral cortex grey matter, but the proportion varies widely among brain regions. Glial volume, however, is less than one-fifth of the tissue volume in grey matter. When stimulated by neurons or other cells, neuroglial cells release gliotransmitters by exocytosis, similar to neurotransmitter release from nerve endings, or by carrier-mediated transport or channel flux through the plasma membrane. Gliotransmitters include the common neurotransmitters glutamate and GABA, the nonstandard amino acid d-serine, the high-energy phosphate ATP, and l-lactate. The latter molecule is a "buffer" between glycolytic and oxidative metabolism as well as a signaling substance recently shown to act on specific lactate receptors in the brain. Complementing neurotransmission at a synapse, neuroglial transmission often implies diffusion of the transmitter over a longer distance and concurs with the concept of volume transmission. Transmission from glia modulates synaptic neurotransmission based on energetic and other local conditions in a volume of tissue surrounding the individual synapse. Neuroglial transmission appears to contribute significantly to brain functions such as memory, as well as to prevalent neuropathologies.

Molecular underpinnings of prefrontal cortex development in rodents provide insights into the etiology of neurodevelopmental disorders

The prefrontal cortex (PFC), seat of the highest-order cognitive functions, constitutes a conglomerate of highly specialized brain areas and has been implicated to have a role in the onset and installation of various neurodevelopmental disorders. The development of a properly functioning PFC is directed by transcription factors, guidance cues and other regulatory molecules and requires the intricate and temporal orchestration of a number of developmental processes. Disturbance or failure of any of these processes causing neurodevelopmental abnormalities within the PFC may contribute to several of the cognitive deficits seen in patients with neurodevelopmental disorders. In this review, we elaborate on the specific processes underlying prefrontal development, such as induction and patterning of the prefrontal area, proliferation, migration and axonal guidance of medial prefrontal progenitors, and their eventual efferent and afferent connections. We furthermore integrate for the first time the available knowledge from genome-wide studies that have revealed genes linked to neurodevelopmental disorders with experimental molecular evidence in rodents. The integrated data suggest that the pathogenic variants in the neurodevelopmental disorder-associated genes induce prefrontal cytoarchitectonical impairments. This enhances our understanding of the molecular mechanisms of prefrontal (mis)development underlying the four major neurodevelopmental disorders in humans, that is, intellectual disability, autism spectrum disorders, attention deficit hyperactivity disorder and schizophrenia, and may thus provide clues for the development of novel therapies.

Effects of a Balanced Translocation between Chromosomes 1 and 11 Disrupting the DISC1 Locus on White Matter Integrity

Objective

Individuals carrying rare, but biologically informative genetic variants provide a unique opportunity to model major mental illness and inform understanding of disease mechanisms. The rarity of such variations means that their study involves small group numbers, however they are amongst the strongest known genetic risk factors for major mental illness and are likely to have large neural effects. DISC1 (Disrupted in Schizophrenia 1) is a gene containing one such risk variant, identified in a single Scottish family through its disruption by a balanced translocation of chromosomes 1 and 11; t(1;11) (q42.1;q14.3).

Method

Within the original pedigree, we examined the effects of the t(1;11) translocation on white matter integrity, measured by fractional anisotropy (FA). This included family members with (n = 7) and without (n = 13) the translocation, along with a clinical control sample of patients with psychosis (n = 34), and a group of healthy controls (n = 33).

Results

We report decreased white matter integrity in five clusters in the genu of the corpus callosum, the right inferior fronto-occipital fasciculus, acoustic radiation and fornix. Analysis of the mixed psychosis group also demonstrated decreased white matter integrity in the above regions. FA values within the corpus callosum correlated significantly with positive psychotic symptom severity.

Conclusions

We demonstrate that the t(1;11) translocation is associated with reduced white matter integrity in frontal commissural and association fibre tracts. These findings overlap with those shown in affected patients with psychosis and in DISC1 animal models and highlight the value of rare but biologically informative mutations in modeling psychosis.