Polycomb repressive complex 2 is critical for mouse cortical glutamatergic neuron development.

The Polycomb Repressive Complex 2 (PRC2) regulates corticogenesis, yet the consequences of mutations to this epigenetic modifier in the mature brain are poorly defined. Importantly, PRC2 core genes are haploinsufficient and causative of several human neurodevelopmental disorders. To address the role of PRC2 in mature cortical structure and function, we conditionally deleted the PRC2 gene Eed from the developing mouse dorsal telencephalon. Adult homozygotes displayed smaller forebrain structures. Single-nucleus transcriptomics revealed that glutamatergic neurons were particularly affected, exhibiting dysregulated gene expression profiles, accompanied by aberrations in neuronal morphology and connectivity. Remarkably, homozygous mice performed well on challenging cognitive tasks. In contrast, while heterozygous mice did not exhibit clear anatomical or behavioral differences, they displayed dysregulation of neuronal genes and altered neuronal morphology that was strikingly different from homozygous phenotypes. Collectively, these data reveal how alterations to PRC2 function shape the mature brain and reveal a dose-specific role for PRC2 in determining glutamatergic neuron identity.

Serum sulfate level and Slc13a1 mRNA expression remain unaltered in a mouse model of moderate vitamin D deficiency.

Sulfate is essential for healthy foetal growth and neurodevelopment. The SLC13A1 sulfate transporter is primarily expressed in the kidney where it mediates sulfate reabsorption and maintains circulating sulfate levels. To meet foetal demands, maternal sulfate levels increase by twofold in pregnancy via upregulated SLC13A1 expression. Previous studies found hyposulfataemia and reduced renal Slc13a1 mRNA expression in rodent models with either severe vitamin D deficiency or perturbed vitamin D signalling. Here we investigated a mouse model of moderate vitamin D deficiency. However, serum sulfate level and renal Slc13a1 mRNA expression was not decreased by a moderate reduction in circulating vitamin D level. We confirmed that the mouse Slc13a1 5'-flanking region was upregulated by 1,25(OH)2D3 using luciferase assays in a cultured renal OK cell line. These results support the presence of a functional VDRE in the mouse Slc13a1 but suggests that moderate vitamin D deficiency does not impact on sulfate homeostasis. As sulfate biology is highly conserved between rodents and humans, we proposed that human SLC13A1 would be under similar transcriptional regulation by 1,25(OH)2D3. Using an online prediction tool we identified a putative VDRE in the SLC13A1 5'-flanking region but unlike the mouse Slc13a1 sequence, the human sequence did not confer a significant response to 1,25(OH)2D3 in vitro. Overall, this study suggests that moderate vitamin D deficiency may not alter sulfate homeostasis. This needs to be confirmed in humans, particularly during pregnancy when vitamin D and sulfate levels need to be maintained at high levels for healthy maternal and child outcomes.

Vitamin D and schizophrenia: 20 years on.

Many epidemiological studies have highlighted the link between vitamin D deficiency and schizophrenia. In particular, two prominent studies report an association between neonatal vitamin D deficiency and an increased risk of schizophrenia. In parallel, much has been learnt about the role of vitamin D in the developing central nervous system over the last two decades. Studies in rodent models of developmental vitamin D (DVD)-deficiency describe how brain development is altered leading to a range of neurobiological and behavioral phenotypes of interest to schizophrenia. While glutamate and gamma aminobutyric acid (GABA) systems have been little investigated in these models, alterations in developing dopamine systems are frequently reported. There have been far more studies reporting patients with schizophrenia have an increased risk of vitamin D deficiency compared to well controls. Here we have conducted a systematic review and meta-analysis that basically confirms this association and extends this to first-episode psychosis. However, patients with schizophrenia also have poorer general health, poorer diets, are frequently less active and also have an increased risk of other medical conditions, all factors which reduce circulating vitamin D levels. Therefore, we would urge caution in any causal interpretation of this association. We also summarize the inconsistent results from existing vitamin D supplementation trials in patients with schizophrenia. In respect to animal models of adult vitamin D deficiency, such exposures produce subtle neurochemical alterations and effects on cognition but do not appear to produce behavioral phenotypes of relevance to schizophrenia. We conclude, the hypothesis that vitamin D deficiency during early life may increase the risk of schizophrenia remains plausible and warrants ongoing research.

Abnormal Behavior and Cortical Connectivity Deficits in Mice Lacking Usp9x.

Genetic association studies have identified many factors associated with neurodevelopmental disorders such as autism spectrum disorder (ASD). However, the way these genes shape neuroanatomical structure and connectivity is poorly understood. Recent research has focused on proteins that act as points of convergence for multiple factors, as these may provide greater insight into understanding the biology of neurodevelopmental disorders. USP9X, a deubiquitylating enzyme that regulates the stability of many ASD-related proteins, is one such point of convergence. Loss of function variants in human USP9X lead to brain malformations, which manifest as a neurodevelopmental syndrome that frequently includes ASD, but the underlying structural and connectomic abnormalities giving rise to patient symptoms is unknown. Here, we analyzed forebrain-specific Usp9x knockout mice (Usp9x-/y) to address this knowledge gap. Usp9x-/y mice displayed abnormal communication and social interaction behaviors. Moreover, the absence of Usp9x culminated in reductions to the size of multiple brain regions. Diffusion tensor magnetic resonance imaging revealed deficits in all three major forebrain commissures, as well as long-range hypoconnectivity between cortical and subcortical regions. These data identify USP9X as a key regulator of brain formation and function, and provide insights into the neurodevelopmental syndrome arising as a consequence of USP9X mutations in patients.

Neurogenic differentiation by hippocampal neural stem and progenitor cells is biased by NFIX expression.

Our understanding of the transcriptional programme underpinning adult hippocampal neurogenesis is incomplete. In mice, under basal conditions, adult hippocampal neural stem cells (AH-NSCs) generate neurons and astrocytes, but not oligodendrocytes. The factors limiting oligodendrocyte production, however, remain unclear. Here, we reveal that the transcription factor NFIX plays a key role in this process. NFIX is expressed by AH-NSCs, and its expression is sharply upregulated in adult hippocampal neuroblasts. Conditional ablation of Nfix from AH-NSCs, coupled with lineage tracing, transcriptomic sequencing and behavioural studies collectively reveal that NFIX is cell-autonomously required for neuroblast maturation and survival. Moreover, a small number of AH-NSCs also develop into oligodendrocytes following Nfix deletion. Remarkably, when Nfix is deleted specifically from intermediate progenitor cells and neuroblasts using a Dcx-creERT2 driver, these cells also display elevated signatures of oligodendrocyte gene expression. Together, these results demonstrate the central role played by NFIX in neuroblasts within the adult hippocampal stem cell neurogenic niche in promoting the maturation and survival of these cells, while concomitantly repressing oligodendrocyte gene expression signatures.

NFIX-Mediated Inhibition of Neuroblast Branching Regulates Migration Within the Adult Mouse Ventricular-Subventricular Zone.

Understanding the migration of newborn neurons within the brain presents a major challenge in contemporary biology. Neuronal migration is widespread within the developing brain but is also important within the adult brain. For instance, stem cells within the ventricular-subventricular zone (V-SVZ) and the subgranular zone of dentate gyrus of the adult rodent brain produce neuroblasts that migrate to the olfactory bulb and granule cell layer of the dentate gyrus, respectively, where they regulate key brain functions including innate olfactory responses, learning, and memory. Critically, our understanding of the factors mediating neuroblast migration remains limited. The transcription factor nuclear factor I X (NFIX) has previously been implicated in embryonic cortical development. Here, we employed conditional ablation of Nfix from the adult mouse brain and demonstrated that the removal of this gene from either neural stem and progenitor cells, or neuroblasts, within the V-SVZ culminated in neuroblast migration defects. Mechanistically, we identified aberrant neuroblast branching, due in part to increased expression of the guanylyl cyclase natriuretic peptide receptor 2 (Npr2), as a factor contributing to abnormal migration in Nfix-deficient adult mice. Collectively, these data provide new insights into how neuroblast migration is regulated at a transcriptional level within the adult brain.

Vitamin D deficiency is associated with reduced hippocampal volume and disrupted structural connectivity in patients with mild cognitive impairment.

Vitamin D deficiency may exacerbate adverse neurocognitive outcomes in the progression of diseases such as Parkinson's, Alzheimer's, and other dementias. Mild cognitive impairment (MCI) is prodromal for these neurocognitive disorders and neuroimaging studies suggest that, in the elderly, this cognitive impairment is associated with a reduction in hippocampal volume and white matter structural integrity. To test whether vitamin D is associated with neuroanatomical correlates of MCI, we analyzed an existing structural and diffusion MRI dataset of elderly patients with MCI. Based on serum 25-OHD levels, patients were categorized into serum 25-OHD deficient (<12 ng/mL, n = 27) or not-deficient (>12 ng/mL, n = 29). Freesurfer 6.0 was used to parcellate the whole brain into 164 structures and segment the hippocampal subfields. Whole-brain structural connectomes were generated using probabilistic tractography with MRtrix. The network-based statistic (NBS) was used to identify subnetworks of connections that significantly differed between the groups. We found a significant reduction in total hippocampal volume in the serum 25-OHD deficient group especially in the CA1, molecular layer, dentate gyrus, and fimbria. We observed a connection deficit in 13 regions with the right hippocampus at the center of the disrupted network. Our results demonstrate that low vitamin D is associated with reduced volumes of hippocampal subfields and connection deficits in elderly people with MCI, which may exacerbate neurocognitive outcomes. Longitudinal studies are now required to determine if vitamin D can serve as a biomarker for Alzheimer's disease and if intervention can prevent the progression from MCI to major cognitive disorders.

Transcriptional regulation of intermediate progenitor cell generation during hippocampal development.

During forebrain development, radial glia generate neurons through the production of intermediate progenitor cells (IPCs). The production of IPCs is a central tenet underlying the generation of the appropriate number of cortical neurons, but the transcriptional logic underpinning this process remains poorly defined. Here, we examined IPC production using mice lacking the transcription factor nuclear factor I/X (Nfix). We show that Nfix deficiency delays IPC production and prolongs the neurogenic window, resulting in an increased number of neurons in the postnatal forebrain. Loss of additional Nfi alleles (Nfib) resulted in a severe delay in IPC generation while, conversely, overexpression of NFIX led to precocious IPC generation. Mechanistically, analyses of microarray and ChIP-seq datasets, coupled with the investigation of spindle orientation during radial glial cell division, revealed that NFIX promotes the generation of IPCs via the transcriptional upregulation of inscuteable (Insc). These data thereby provide novel insights into the mechanisms controlling the timely transition of radial glia into IPCs during forebrain development.

Cyclooctatetraene: A Bioactive Cubane Paradigm Complement.

Cubane was recently validated as a phenyl ring (bio)isostere, but highly strained caged carbocyclic systems lack π character, which is often critical for mediating key biological interactions. This electronic property restriction associated with cubane has been addressed herein with cyclooctatetraene (COT), using known pharmaceutical and agrochemical compounds as templates. COT either outperformed or matched cubane in multiple cases suggesting that versatile complementarity exists between the two systems for enhanced bioactive molecule discovery.

Functional and molecular changes in the nucleus accumbens of MK-801-sensitized rats.

Behavioural sensitization is a putative mechanism in the pathophysiology of drug addiction and neuropsychiatric disorders such as schizophrenia. In rodents, drug-induced behavioural sensitization has been described for several different drug classes. The N-methyl-D-aspartate receptor antagonist MK-801 can inhibit sensitization to other drugs of abuse. However, MK-801 also produces behavioural sensitization to its own hyperlocomotor inducing effects, suggesting that MK-801 sensitization has a distinctive mechanism of action. The aim of this study was to carry out a functional and molecular analysis of the nucleus accumbens (NAc) of adult male Sprague-Dawley rats sensitized to MK-801 (seven daily injections of 0.25 mg/kg, 5 days of withdrawal and subsequent 0.25 mg/kg challenge), or following acute MK-801 (0.25 mg/kg), or naive rats as controls. Locomotor activity was the primary measure of sensitization. Ex-vivo slice electrophysiology showed a decrease in the excitatory synaptic strength in the NAc of rats sensitized to MK-801 compared with acute MK-801 treatment or naive controls. An LC-MS/MS SWATH proteomics approach showed that proteins altered by MK-801 sensitization were predominantly related to functions including calcium and glutamate signalling, and mitochondrial dysfunction. These results shed some light on neural changes in the NAc after sensitization to MK-801. This model could prove useful for studying the role of N-methyl-D-aspartate receptors in the pathophysiology of drug addiction and schizophrenia.

A morphology independent approach for identifying dividing adult neural stem cells in the mouse hippocampus.

BACKGROUND: Type 1 adult hippocampal neural stem cells (AH-NSCs) continue to generate neurons throughout life, albeit at a very low rate. The relative quiescence of this population of cells has led to many studies investigating factors that may increase their division. Current methods of identifying dividing AH-NSCs in vivo require the identification and tracing of radial processes back to nuclei within the subgranular zone. However, caveats to this approach include the time-intensive nature of identifying AH-NSCs with such a process, as well as the fact that this approach ignores the relatively more active population of horizontally oriented AH-NSCs that also reside in the subgranular zone. RESULTS: Here we describe, and then verify using Hes5::GFP mice, that labeling for the cell cycle marker Ki67 and selection against the intermediate progenitor cell marker TBR2 (Ki67+ve ; TBR2-ve nuclei) is sufficient to identify dividing horizontally and radially oriented AH-NSCs in the adult mouse hippocampus. CONCLUSIONS: These findings provide a simple and accurate way to quantify dividing AH-NSCs in vivo using a morphology-independent approach that will facilitate studies into neurogenesis within the hippocampal stem cell niche of the adult brain. Developmental Dynamics 247:194-200, 2018. © 2017 Wiley Periodicals, Inc.

Associations of maternal and fetal vitamin D status with childhood body composition and cardiovascular risk factors.

Maternal vitamin D deficiency during pregnancy may have persistent adverse effects on childhood growth and development. We examined whether 25-hydroxyvitamin D (25(OH)D) concentrations during pregnancy and at cord blood were associated with childhood body composition and cardiovascular outcomes. This study was embedded in a population-based prospective cohort in Rotterdam, The Netherlands, among 4,903 mothers and their offspring. We measured 25(OH)D concentrations at a median gestational age of 20.4 weeks (95% range 18.5-23.4 weeks) and at birth (40.1 weeks [95% range 35.8-42.3 weeks]). 25(OH)D concentrations were categorized into severely deficient (<25.0 nmol/L); deficient (25.0 to 49.9 nmol/L); sufficient (50.0 to 74.9 nmol/L) and optimal (≥75.0 nmol/L). At 6 years, we measured childhood body mass index; fat and lean mass by Dual-energy X-ray Absorptiometry; blood pressure; and serum cholesterol, triglycerides, and insulin concentrations. Compared with children from mothers with optimal 25(OH)D concentrations (≥75.0 nmol/L), those of severely deficient vitamin D (<25.0 nmol/L) mothers had a 0.12 standard deviation score (SDS); (95% Confidence Interval (CI) [0.03, 0.21]) higher fat mass percentage and a 0.13 SDS (95% CI [-0.22, -0.04]) lower lean mass percentage. These associations remained after adjustment for current child vitamin D status. Maternal and cord blood 25(OH)D concentrations were not associated with cardiovascular risk factors in childhood. In conclusion, severe maternal 25(OH)D deficiency (<25.0 nmol/L) during pregnancy is associated with an adverse childhood body composition profile, but we did not observe evidence for an association with childhood cardiovascular risk factors. Further studies are needed to replicate our findings, to examine the underlying mechanisms, the causality of the associations, and the potential for public health interventions.

Short- and long-term effects of risperidone on catalepsy sensitisation and acquisition of conditioned avoidance response: Adolescent vs adult rats.

The effects of antipsychotic drugs (APDs) on the adolescent brain are poorly understood despite a dramatic increase in prescription of these drugs in adolescents over the past twenty years. Neuronal systems continue to be remodeled during adolescence. Therefore, when given in adolescence, antipsychotic drugs (APDs) have the potential to affect this remodeling. In this study we investigated the effects of chronic 22-day risperidone treatment (1.3mg/kg/day) in both adolescent and adult rats. We examined short- and long-term changes in behaviour (catalepsy, locomotion and conditioned avoidance response (CAR)), and dopaminergic and serotonergic neurochemistry in the striatum and the nucleus accumbens. Here, we report that, both during chronic treatment and after a lengthy drug-free interval, risperidone induced a sensitised cataleptic response regardless of the age of exposure. Selectively in adolescents, risperidone-induced catalepsy was inversely correlated with striatal dopamine turnover immediately after chronic treatment. After a drug-free interval, a significant proportion of rats with prior adolescent risperidone treatment also failed to acquire CAR to a defined criterion. Our data provide evidence that the same chronic risperidone treatment regimen can induce contrasting short- and long-term neural outcomes in the adolescent and adult brains.

Associations of maternal and fetal 25-hydroxyvitamin D levels with childhood eczema: The Generation R Study.

BACKGROUND: Exposure to low levels of vitamin D in fetal life might affect the developing immune system, and subsequently the risk of childhood eczema. We examined whether 25-hydroxyvitamin D levels in mid-gestation and at birth were associated with the risk of eczema until the age of 4 years. METHODS: In a population-based prospective cohort study of 3019 mothers and their children, maternal blood samples in mid-gestation and umbilical cord blood samples at birth were used to determine 25-hydroxyvitamin D levels (severely deficient <25.0 nmol/l, deficient 25.0-49.9 nmol/l, sufficient 50.0-74.9 nmol/l, optimal ≥75.0 nmol/l). Eczema was prospectively assessed by annual questionnaires until the age of 4 years. Eczema patterns included never, early (age ≤1 year only), late (age >1 year only), and persistent eczema (age ≤ and >1 year). Data were assessed using the generalized estimating equations and multinomial regression models. RESULTS: Compared with the optimal 25-hydroxyvitamin D group, sufficient, deficient, and severely deficient groups of 25-hydroxyvitamin D level in mid-gestation were not associated with the risk of overall eczema (odds ratios [95% confidence interval]: 1.09 [0.82, 1.43], 1.04 [0.87, 1.25], and 0.94 [0.81, 1.10], p-values for trend >0.05), nor with eczema per year or eczema patterns in children up to the age of 4 years. Similarly, we observed no associations of 25-hydroxyvitamin D groups at birth with any eczema outcome. CONCLUSION: Our results suggest that levels of 25-hydroxyvitamin D in mid-gestation and at birth are not associated with the risk of overall eczema, eczema per year, or eczema patterns among children until the age of 4 years.

Vitamin D as a neurosteroid affecting the developing and adult brain.

Vitamin D deficiency is prevalent throughout the world, and growing evidence supports a requirement for optimal vitamin D levels for the healthy developing and adult brain. Vitamin D has important roles in proliferation and differentiation, calcium signaling within the brain, and neurotrophic and neuroprotective actions; it may also alter neurotransmission and synaptic plasticity. Recent experimental studies highlight the impact that vitamin D deficiency has on brain function in health and disease. In addition, results from recent animal studies suggest that vitamin D deficiency during adulthood may exacerbate underlying brain disorders and/or worsen recovery from brain stressors. An increasing number of epidemiological studies indicate that vitamin D deficiency is associated with a wide range of neuropsychiatric disorders and neurodegenerative diseases. Vitamin D supplementation is readily available and affordable, and this review highlights the need for further research.

Vitamin D, effects on brain development, adult brain function and the links between low levels of vitamin D and neuropsychiatric disease.

Increasingly vitamin D deficiency is being associated with a number of psychiatric conditions. In particular for disorders with a developmental basis, such as autistic spectrum disorder and schizophrenia the neurobiological plausibility of this association is strengthened by the preclinical data indicating vitamin D deficiency in early life affects neuronal differentiation, axonal connectivity, dopamine ontogeny and brain structure and function. More recently epidemiological associations have been made between low vitamin D and psychiatric disorders not typically associated with abnormalities in brain development such as depression and Alzheimer's disease. Once again the preclinical findings revealing that vitamin D can regulate catecholamine levels and protect against specific Alzheimer-like pathology increase the plausibility of this link. In this review we have attempted to integrate this clinical epidemiology with potential vitamin D-mediated basic mechanisms. Throughout the review we have highlighted areas where we think future research should focus.

Developmentally vitamin D-deficient rats show enhanced prepulse inhibition after acute Δ9-tetrahydrocannabinol.

Developmental vitamin D (DVD) deficiency has been proposed as a risk factor for schizophrenia. DVD-deficient rats show selective cognitive deficits and novelty-induced hyperlocomotion and enhanced locomotor responses from acute treatment with psychomimetic drugs, such as amphetamine and MK-801. Here we aimed to examine the effect of a drug from a different class of psychomimetic/psychoactive compounds, Δ9-tetrahydrocannabinol (THC), on tasks of relevance to the cognitive and positive symptoms of schizophrenia. The aim of this study was to investigate whether DVD deficiency modulates the behavioural effects of THC on tests of delay-dependent memory, sensorimotor gating and locomotion. Adult control and DVD-deficient rats were injected with THC (0, 0.3, 0.6, 1.25, 2.5 mg/kg) 15 min before a delay match to sample (DMTS) task using variable delays (0-24 s). A separate group of rats was injected with either 2.5 mg/kg THC or vehicle before tests of either prepulse inhibition (PPI) of the acoustic startle response or in the open field. Control and DVD-deficient rats showed a similar dose-dependent impairment in performance on the DMTS. The greatest impairment was observed at 2.5 mg/kg for all delays (0-24 s). DVD-deficient rats showed THC-induced enhancement of PPI, which was not observed in control rats. There was no effect of maternal diet on acoustic startle response or locomotor responses in the open field. This study reports the novel findings that DVD-deficient rats were more sensitive to the acute effects of THC on PPI. It appears that prenatal vitamin D deficiency has long-term effects on sensitivity to the behavioural effects of cannabinoids.

Perineuronal nets are associated with decision making under conditions of uncertainty in female but not male mice.

Biological sex influences decision-making processes in significant ways, differentiating the responses animals choose when faced with a range of stimuli. The neurobiological underpinnings that dictate sex differences in decision-making tasks remains an important open question, yet single-sex studies of males form most studies in behavioural neuroscience. Here we used female and male BALB/c mice on two spatial learning and memory tasks and examined the expression of perineuronal nets (PNNs) and parvalbumin interneurons (PV) in regions correlated with spatial memory. Mice underwent the aversive active place avoidance (APA) task or the appetitive trial-unique nonmatching-to-location (TUNL) touchscreen task. Mice in the APA cohort learnt to avoid the foot-shock and no differences were observed on key measures of the task nor in the number and intensity of PNNs and PV. On the delay but not separation manipulation in the TUNL task, females received more incorrect trials and less correct trials compared to males. Furthermore, females in this cohort exhibited higher intensity PNNs and PV cells in the agranular and granular retrosplenial cortex, compared to males. These data show that female and male mice perform similarly on spatial learning tasks. However, sex differences in neural circuitry may underly differences in making decisions under conditions of uncertainty on an appetitive task. These data emphasise the importance of using mice of both sexes in studies of decision-making neuroscience.

Antagonism of D2 receptors via raclopride ameliorates amphetamine-induced associative learning deficits in male mice.

Dopamine levels in the dorsomedial striatum (DMS) are highly dynamic and are thought to underly the encoding of action-outcome associations. Although it is known that amphetamine disrupts the learning that is required for goal-directed action, the role of D1 and D2 receptors in this process has not been established. In this study, we examined the role of D1 and D2 receptor antagonists on learning in response to amphetamine. We used the outcome-specific devaluation task to examine goal-directed action in male C57BL6/J mice treated systemically with either a D1 antagonist (SCH-23990; 0.01 mg/kg) or a D2 antagonist (raclopride; 0.5 mg/kg) and then administered amphetamine (1 mg/kg). The mice were injected repeatedly throughout the instrumental training phase of the task to assess the impact on the learning of action-outcomes, and the subsequent choice test assessing performance of goal-directed action was conducted drug free. Effects of chronic drug administration on locomotor behaviour was assessed before and after the choice test. Treatment during learning with either amphetamine, or the D1 or D2 antagonists, impaired the subsequent performance of goal-directed action. The amphetamine-induced impairment in goal-directed action was reversed in mice treated with raclopride, but not when treated with SCH-23990. By contrast, amphetamine-induced hyperactivity was reversed in mice treated with SCH-23990, but not in mice treated with raclopride. Taken together, these data support the role of a balance of dopamine receptor signalling after amphetamine treatment. While overall D1 receptor availability is necessary to promote learning, in a state of elevated dopamine, modifying D2 receptor function can ameliorate learning deficits.