Search

Interconnectivity between neocortical areas is critical for sensory integration and sensorimotor transformations

Delineating the basic cellular components of cortical inhibitory circuits remains a fundamental issue in order to understand their specific contributions to microcircuit function. It is still unclear how current classifications of cortical interneuron subtypes relate to biological processes such as their developmental specification. Here we identified the developmental trajectory of neurogliaform cells (NGCs), the main effectors of a powerful inhibitory motif recruited by long-range connections. Using in vivo genetic lineage-tracing in mice, we report that NGCs originate from a specific pool of 5-HT3AR-expressing Hmx3+ cells located in the preoptic area (POA). Hmx3-derived 5-HT3AR+ cortical interneurons (INs) expressed the transcription factors PROX1, NR2F2, the marker reelin but not VIP and exhibited the molecular, morphological and electrophysiological profile of NGCs. Overall, these results indicate that NGCs are a distinct class of INs with a unique developmental trajectory and open the possibility to study their specific functional contribution to cortical inhibitory microcircuit motifs., eLife digest Our brain contains over a 100 billion nerve cells or neurons, and each of them is thought to connect to over 1,000 other neurons. Together, these cells form a complex network to convey information from our surroundings or transmit messages to designated destinations. This circuitry forms the basis of our unique cognitive abilities. In the cerebral cortex – the largest region of the brain – two main types of neurons can be found: projection neurons, which transfer information to other regions in the brain, and interneurons, which connect locally to different neurons and harmonize this information by inhibiting specific messages. The over 20 different types of known interneurons come in different shapes and properties and are thought to play a key role in powerful computations such as learning and memory. Since interneurons are hard to track, it is still unclear when and how they start to form and mature as the brain of an embryo develops. For example, one type of interneurons called the neurogliaform cells, have a very distinct shape and properties. But, until now, the origin of this cell type had been unknown. To find out how neurogliaform cells develop, Niquille, Limoni, Markopoulos et al. used a specific gene called Hmx3 to track these cells over time. With this strategy, the shapes and properties of the cells could be analyzed. The results showed that neurogliaform cells originate from a region outside of the cerebral cortex called the preoptic area, and later travel over long distances to reach their final location. The cells reach the cortex a few days after their birth and take several weeks to mature. These results suggest that the traits of a specific type of neuron is determined very early in life. By labeling this unique subset of interneurons, researchers will now be able to identify the specific molecular mechanisms that help the neurogliaform cells to develop. Furthermore, it will provide a new strategy to fully understand what role these cells play in processing information and guiding behavior.

IMPORTANCE Lithium is a first-line mood stabilizer for the treatment of bipolar affective disorder (BPAD). However, the efficacy of lithium varies widely, with a nonresponse rate of up to 30%. Biological response markers are lacking. Genetic factors are thought to mediate treatment response to lithium, and there is a previously reported genetic overlap between BPAD and schizophrenia (SCZ). OBJECTIVES To test whether a polygenic score for SCZ is associated with treatment response to lithium in BPAD and to explore the potential molecular underpinnings of this association. DESIGN, SETTING, AND PARTICIPANTS A total of 2586 patients with BPAD who had undergone lithium treatment were genotyped and assessed for long-term response to treatment between 2008 and 2013.Weighted SCZ polygenic scores were computed at different P value thresholds using summary statistics from an international multicenter genome-wide association study (GWAS) of 36 989 individuals with SCZ and genotype data from patients with BPAD from the Consortium on Lithium Genetics. For functional exploration, a cross-trait meta-GWAS and pathway analysis was performed, combining GWAS summary statistics on SCZ and response to treatment with lithium. Data analysis was performed from September 2016 to February 2017. MAIN OUTCOMES AND MEASURES Treatment response to lithiumwas defined on both the categorical and continuous scales using the Retrospective Criteria of Long-Term Treatment Response in Research Subjects with Bipolar Disorder score. The effect measures include odds ratios and the proportion of variance explained. RESULTS Of the 2586 patients in the study (mean [SD] age, 47.2 [13.9] years), 1478 were women and 1108 were men. The polygenic score for SCZ was inversely associated with lithium treatment response in the categorical outcome, at a threshold P < 5 ? 10-2. Patients with BPAD who had a low polygenic load for SCZ responded better to lithium, with odds ratios for lithium response ranging from 3.46 (95%CI, 1.42-8.41) at the first decile to 2.03 (95%CI, 0.86-4.81) at the ninth decile, compared with the patients in the 10th decile of SCZ risk. In the cross-trait meta-GWAS, 15 genetic loci that may have overlapping effects on lithium treatment response and susceptibility to SCZ were identified. Functional pathway and network analysis of these loci point to the HLA antigen complex and inflammatory cytokines. CONCLUSIONS AND RELEVANCE This study provides evidence for a negative association between high genetic loading for SCZ and poor response to lithium in patients with BPAD. These results suggest the potential for translational research aimed at personalized prescribing of lithium.

BACKGROUND: Serotonin 3A receptor (5-HT3A R) is associated at the genetic and epigenetic levels with a variety of psychiatric disorders and interacts with early-life stress such as childhood maltreatment. We studied the impact of childhood maltreatment on the methylation status of the 5-HT3A R and its association with clinical severity outcomes in relation with a functional genetic polymorphism. METHODS: Clinical severity indexes of 346 bipolar, borderline personality, and adult attention deficit hyperactivity disorders patients were tested for association with the DNA methylation status of eight 5-HT3A R gene CpGs. Relationship between the functional variant rs1062613 (C > T) and methylation status on severity of the disorders were also assessed. RESULTS: Childhood maltreatment was associated with higher severity of the disease (higher number of mood episodes, history of suicide attempts, hospitalization, and younger age at onset) across disorders and within each individual disorder. This effect was mediated by two 5-HT3A R CpGs. Compared to T allele carriers, CC carriers had higher methylation status at one CpG located 1 bp upstream of this variant. CONCLUSIONS: This study shows that epigenetic modification of the 5-HT3A R is involved in the mechanism underlying the relationship between maltreatment in childhood and the severity of several psychiatric disorders in adulthood. Language: en

Early life adversity plays a critical role in the emergence of borderline personality disorder (BPD) and this could occur through epigenetic programming. In this perspective, we aimed to determine whether childhood maltreatment could durably modify epigenetic processes by the means of a whole-genome methylation scan of BPD subjects. Using the Illumina Infinium® HumanMethylation450 BeadChip, global methylation status of DNA extracted from peripheral blood leucocytes was correlated to the severity of childhood maltreatment in 96 BPD subjects suffering from a high level of child adversity and 93 subjects suffering from major depressive disorder (MDD) and reporting a low rate of child maltreatment. Several CpGs within or near the following genes (IL17RA, miR124-3, KCNQ2, EFNB1, OCA2, MFAP2, RPH3AL, WDR60, CST9L, EP400, A2ML1, NT5DC2, FAM163A and SPSB2) were found to be differently methylated, either in BPD compared with MDD or in relation to the severity of childhood maltreatment. A highly relevant biological result was observed for cg04927004 close to miR124-3 that was significantly associated with BPD and severity of childhood maltreatment. miR124-3 codes for a microRNA (miRNA) targeting several genes previously found to be associated with BPD such as NR3C1. Our results highlight the potentially important role played by miRNAs in the etiology of neuropsychiatric disorders such as BPD and the usefulness of using methylome-wide association studies to uncover such candidate genes. Moreover, they offer new understanding of the impact of maltreatments on biological processes leading to diseases and may ultimately result in the identification of relevant biomarkers.

ImportanceLithium is a first-line mood stabilizer for the maintenance treatment of Bipolar Disorder (BPD). However, the efficacy of lithium varies widely, with a non-response rate of up to 30%. Biological response markers and predictors are lacking.ObjectiveGenetic factors are thought to mediate lithium treatment response, and the previously reported genetic overlap between BPD and schizophrenia (SCZ) led us to test whether a polygenic score (PGS) for SCZ could predict lithium treatment response in BPD. Further, we explored the potential molecular underpinnings of this association.DesignWeighted SCZ PGSs were computed at ten p-value thresholds (PT) using summary statistics from a genome-wide association study (GWAS) of 36,989 SCZ cases, and genotype data for BPD patients from the Consortium on Lithium Genetics (ConLi+Gen). For functional exploration, we performed a cross-trait meta-GWAS and pathway analysis, combining GWAS summary statistics on SCZ and lithium treatment response.SettingInternational multicenter GWAS.ParticipantsPatients with BPD who had undergone lithium treatment were genotyped and retrospectively assessed for long-term treatment response (n=2,586).Main outcome measuresClinical treatment response to lithium was defined on both the categorical and continuous scales using the ALDA score. The effect measures include odds ratios (ORs) and the proportion of variance explained (R2), and a significant association was determined at pResultsThe PGS for SCZ was inversely associated with lithium treatment response in the categorical outcome (p=8×10−5), at PT−2. Patients with BPD who had low polygenic load for SCZ responded better to lithium, with ORs for lithium response ranging from 3.46 [95%CI: 1.42-8.41 at 1stdecile] to 2.03 [95%CI: 0.86-4.81 at the 9th decile], compared to the patients in the 10thdecile of SCZ risk. In the cross-trait meta-GWAS, 15 genetic loci that may have overlapping effects on lithium treatment response and susceptibility to SCZ were identified. Functional pathway and network analysis of these loci point to the HLA complex and inflammatory cytokines (TNFα, IL-4, IFNγ) as molecular contributors to lithium treatment response in BPD.Conclusions and RelevanceThe study provides, for the first-time, evidence for a negative association between high genetic loading for SCZ and poor response to lithium in patients with BPD. These results suggest the potential for translational research aimed at personalized prescribing of lithium.Key PointsQuestionDoes a polygenic score for Schizophrenia (SCZ) predict response to lithium in patients with Bipolar Disorder (BPD)? What are the molecular drivers of the association between SCZ and lithium treatment response?FindingsWe found an inverse association between genetic loading for SCZ risk variants and response to lithium in patients with BPD. Genetic variants in the HLA region on chromosome 6, the antigen presentation pathway and markers of inflammation (TNFα, IL-4, IFNγ) point to molecular underpinnings of lithium treatment response in BPD.MeaningIn patients with BPD, an assessment of a polygenic load for SCZ risk variants may assist in conjunction with clinical data to predict whether they would respond to lithium treatment.

The neuron-specific K-Cl cotransporter, KCC2, is highly expressed in the vicinity of excitatory synapses in pyramidal neurons, and recent in vitro data suggest that this protein plays a role in the development of dendritic spines. The in vivo relevance of these observations is, however, unknown. Using in utero electroporation combined with post hoc iontophoretic injection of Lucifer Yellow, we show that premature expression of KCC2 induces a highly significant and permanent increase in dendritic spine density of layer 2/3 pyramidal neurons in the somatosensory cortex. Whole-cell recordings revealed that this increased spine density is correlated with an enhanced spontaneous excitatory activity in KCC2-transfected neurons. Precocious expression of the N-terminal deleted form of KCC2, which lacks the chloride transporter function, also increased spine density. In contrast, no effect on spine density was observed following in utero electroporation of a point mutant of KCC2 (KCC2-C568A) where both the cotransporter function and the interaction with the cytoskeleton are disrupted. Transfection of the C-terminal domain of KCC2, a region involved in the interaction with the dendritic cytoskeleton, also increased spine density. Collectively, these results demonstrate a role for KCC2 in excitatory synaptogenesis in vivo through a mechanism that is independent of its ion transport function.

Strategies to enhance the capacity of grafted stem/progenitors cells to generate multipotential, proliferative and migrating pools of cells in the postnatal brain could be crucial for structural repair after brain damage. We investigated whether the over-expression of basic fibroblast growth factor 2 (FGF-2) in neural progenitor cells (NPCs) could provide a robust source of migrating NPCs for tissue repair in the rat cerebral cortex. Using live imaging we provide direct evidence that FGF-2 over-expression significantly enhances the migratory capacity of grafted NPCs in complex 3D structures, such as cortical slices. Furthermore, we show that the migratory as well as proliferative properties of FGF-2 over-expressing NPCs are maintained after in vivo transplantation. Importantly, after transplantation into a neonatal ischaemic cortex, FGF-2 over-expressing NPCs efficiently invade the injured cortex and generate an increased pool of immature neurons available for brain repair. Differentiation of progenitor cells into immature neurons was correlated with a gradual down-regulation of the FGF-2 transgene. These results reveal an important role for FGF-2 in regulating NPCs functions when interacting with the host tissue and offer a potential strategy to generate a robust source of migrating and immature progenitors for repairing a neonatal ischaemic cortex.

The cingulate and retrosplenial regions are major components of the dorsomedial (dm) limbic cortex and have been implicated in a range of cognitive functions such as emotion, attention, and spatial memory. While the structure and connectivity of these cortices are well characterized, little is known about their development. Notably, the timing and mode of migration that govern the appropriate positioning of late-born neurons remain unknown. Here, we analyzed migratory events during the early postnatal period from ventricular/subventricular zone (VZ/SVZ) to the cerebral cortex by transducing neuronal precursors in the VZ/SVZ of newborn rats/mice with Tomato/green fluorescent protein-encoding lentivectors. We have identified a pool of postmitotic pyramidal precursors in the dm part of the neonatal VZ/SVZ that migrate into the medial limbic cortex during the first postnatal week. Time-lapse imaging demonstrates that these cells migrate on radial glial fibers by locomotion and display morphological and behavioral changes as they travel through the white matter and enter into the cortical gray matter. In the granular retrosplenial cortex, these cells give rise to a Satb2+ pyramidal subtype and develop dendritic bundles in layer I. Our observations provide the first insight into the patterns and dynamics of cell migration into the medial limbic cortex.

Background Alterations in early steps of cortical circuit assembly are thought to play a critical role in vulnerability to schizophrenia (SZ), but the pathogenic impact of SZ-risk mutations on corticogenesis remains to be determined. DiGeorge syndrome critical region 2 (DGCR2) is located in the 22q11.2 locus, whose deletion is a major risk factor for SZ. Moreover, exome sequencing of individuals with idiopathic SZ identified a rare missense mutation in DGCR2, further suggesting that DGCR2 is involved in SZ. Methods Here we investigated the function of Dgcr2 and the pathogenic impact of the SZ-risk DGCR2 mutation in mouse corticogenesis using in utero electroporation targeted to projection neurons. Results Dgcr2 knockdown impaired radial locomotion and final translocation of projection neurons, leading to persistent laminar positioning alterations. The DGCR2 missense SZ-risk mutation had a pathogenic impact on projection neuron laminar allocation by reducing protein expression. Mechanistically, we identified Dgcr2 as a novel member of the Reelin complex, regulating the phosphorylation of Reelin-dependent substrates and the expression of Reelin-dependent transcriptional targets. Conclusions Overall, this study provides biological evidence that the SZ-risk gene DGCR2 regulates critical steps of early corticogenesis possibly through a Reelin-dependent mechanism. Additionally, we found that the SZ-risk mutation in DGCR2 has a pathogenic impact on cortical formation by reducing protein expression level, suggesting a functional role for DGCR2 haploinsufficiency in the 22q11.2 deletion syndrome.

Cortical GABAergic interneurons constitute a highly diverse population of inhibitory neurons that are key regulators of cortical microcircuit function. An important and heterogeneous group of cortical interneurons specifically expresses the serotonin receptor 3A (5-HT3AR) but how this diversity emerges during development is poorly understood. Here we use single-cell transcriptomics to identify gene expression patterns operating in Htr3a-GFP+ interneurons during early steps of cortical circuit assembly. We identify three main molecular types of Htr3a-GFP+ interneurons, each displaying distinct developmental dynamics of gene expression. The transcription factor Meis2 is specifically enriched in a type of Htr3a-GFP+ interneurons largely confined to the cortical white matter. These MEIS2-expressing interneurons appear to originate from a restricted region located at the embryonic pallial–subpallial boundary. Overall, this study identifies MEIS2 as a subclass-specific marker for 5-HT3AR-containing interstitial interneurons and demonstrates that the transcriptional and anatomical parcellation of cortical interneurons is developmentally coupled.

Objectives Many adults with attention-deficit/hyperactivity disorder (ADHD) report sleeping difficulties. The relationship between sleep and ADHD is poorly understood, and shows discrepancies between subjective and objective measures. In order to determine the specificity of sleep-associated symptoms in ADHD, subjective sleep assessments among ADHD adult patients were compared with control subjects and with individuals suffering from borderline personality disorder (BPD). Methods 129 outpatients with ADHD, 70 with BPD (including 17 patients with BPD and ADHD comorbidity), and 65 control participants were assessed for sleep quality, insomnia, and sleepiness, using the Pittsburgh Sleep Quality Index (PSQI), the Insomnia Severity Index (ISI), and the Epworth Sleepiness Scale (ESS). Results ADHD- and BPD-sufferers achieved higher insomnia and lower sleep quality scores than control subjects. Clinical groups did not differ in terms of sleep quality, although insomnia was more severe among BPD patients. Depression scores explained most of sleep symptoms, but even when controlling for depression, ADHD sufferers showed higher sleep latency. Inattentive symptoms were associated with somnolence, while hyperactive/impulsive symptoms were associated with insomnia and lower sleep efficiency. Conclusion Sleep-related symptoms associated with ADHD were partly explained by non-specific factors, especially depression symptoms. In a dimensional perspective, hyperactive and inattentive symptoms were associated with specific sleep symptoms.

Attention-deficit hyperactivity disorder (ADHD) is a highly heritable neurodevelopmental disorder. Besides genetic factors, several environmental factors occurring either before the emergence of the disorder (prenatally or perinatally), or when the disorder is already diagnosed, or close to its emergence, such as childhood maltreatment have been shown to play a major role in ADHD. Epigenetics has attempted to link these environmental factors to the disorder and its persistence in adulthood. Findings of epigenetic studies have implicated genes encoding: proteins involved in neurotransmission, namely dopamine receptor4 ( DRD4 ), serotonin transporter ( SLC6A4 ), serotonin receptor 3A ( 5-HT3AR ); proteins involved in the epigenetic machinery like histone deacetylase1 ( HDAC1 ) and methyl-CpG binding protein2 ( MeCP2 ); and proteins involved in brain development, namely vasoactive intestinal peptide receptor 2 ( VIPR2 ). Nevertheless the number of studies is limited and replications as well as new studies are still needed to better define the underlying neurobiological mechanisms of ADHD.

The aim of this study was to examine the relationship of maternal interpersonal violence-related posttraumatic stress disorder (IPV-PTSD), associated neural activity in response to mother-child relational stimuli, and child psychopathology indicators at child ages 12-42 months and one year later. The study tested the hypothesis that decreased maternal neural activity in regions that subserve emotion regulation would be associated with child symptoms associated with emotional dysregulation at both time points. Functional magnetic resonance imaging of 42 mothers with or without violence-exposure and associated IPV-PTSD were assessed. Their child's life-events and symptoms/behaviors indicative of high-risk subsequent PTSD diagnosis on a maternal-report questionnaire were measured one year later. Maternal IPV-PTSD severity was significantly associated with decreased ventromedial prefrontal cortex (vmPFC) activation in response to mother-child relational stimuli. Maternal IPV-PTSD severity and decreased vmPFC activation were then significantly associated with a child attachment disturbance at 12-42 months and symptoms/behaviors one year later, that were correlated with emotional dysregulation and risk for child PTSD. Maternal IPV-PTSD and child exposure to IPV were both predictive of child PTSD symptoms with maternal IPV-PTSD likely mediating the effects of child IPV exposure on child PTSD symptoms. These findings suggest that maternal IPV-PTSD severity and associated decreased vmPFC activity in response to mother-child relational stimuli are predictors of child psychopathology by age 12-42 months and one-year later. Significant findings in this paper may well be useful in understanding how maternal top-down cortico-limbic dysregulation promotes intergenerational transmission of IPV and related psychopathology and, thus should be targeted in treatment.

Neocortical microcircuits are built during development and require the coordinated assembly of excitatory glutamatergic projection neurons (PNs) into functional networks. Neuronal migration is an essential step in this process. In addition to cell-intrinsic mechanisms, external cues including neurotransmitters regulate cortical neuron migration, suggesting that early activity could influence this process. Here, we aimed to investigate the role of cell-intrinsic activity in migrating PNs in vivo using a designer receptor exclusively activated by a designer drug (DREADD) chemogenetic approach. In utero electroporation was used to specifically express the human M3 muscarinic cholinergic Gq-coupled receptor (hM3Dq) in PNs and calcium activity, migratory dynamics, gene expression, and laminar positioning of PNs were assessed following embryonic DREADD activation. We found that transient embryonic DREADD activation induced premature branching and transcriptional changes in migrating PNs leading to a persistent laminar mispositioning of superficial layer PNs into deep cortical layers without affecting expression of layer-specific molecular identity markers. In addition, live imaging approaches indicated that embryonic DREADD activation increased calcium transients in migrating PNs and altered their migratory dynamics by increasing their pausing time. Taken together, these results support the idea that increased cell-intrinsic activity during migration acts as a stop signal for migrating cortical PNs.

Stimulation of endogenous neurogenesis and recruitment of neural progenitors from the subventricular zone (SVZ) neurogenic site may represent a useful strategy to improve regeneration in the ischemic cortex. Here, we tested whether transgenic overexpression of extracellular matrix metalloproteinase inducer (EMMPRIN), the regulator of matrix metalloproteinases (MMPs) expression, in endogenous neural progenitor cells (NPCs) in the subventricular zone (SVZ) could increase migration towards ischemic injury. For this purpose, we applied a lentivector-mediated gene transfer system. We found that EMMPRIN-transduced progenitors exhibited enhanced MMP-2 activity in vitro and showed improved motility in 3D collagen gel as well as in cortical slices. Using a rat model of neonatal ischemia, we showed that EMMPRIN overexpressing SVZ cells invade the injured cortical tissue more efficiently than controls. Our results suggest that EMMPRIN overexpression could be suitable approach to improve capacities of endogenous or transplanted progenitors to invade the injured cortex.

Women who have experienced interpersonal violence (IPV) are at a higher risk to develop posttraumatic stress disorder (PTSD), with dysregulation of the hypothalamic-pituitary-adrenal (HPA) axis and impaired social behavior. Previously, we had reported impaired maternal sensitivity and increased difficulty in identifying emotions (i.e. alexithymia) among IPV-PTSD mothers. One of the aims of the present study was to examine maternal IPV-PTSD salivary cortisol levels diurnally and reactive to their child’s distress in relation to maternal alexithymia. Given that mother-child interaction during infancy and early childhood has important long-term consequences on the stress response system, toddlers’ cortisol levels were assessed during the day and in response to a laboratory stressor. Mothers collected their own and their 12-48 month-old toddlers’ salivary samples at home three times: 30 min after waking up, between 2-3 pm and at bedtime. Moreover, mother-child dyads articipated in a 120-min laboratory session, consisting of 3 phases: baseline, stress situation (involving mother-child separation and exposure to novelty) and a 60-min regulation phase. Compared to non-PTSD controls, IPV-PTSD mothers -but not their toddlers-, had lower morning cortisol and higher bedtime cortisol levels. As expected, IPV-PTSD mothers and their children showed blunted cortisol reactivity to the laboratory stressor. Maternal cortisol levels were negatively correlated to difficulty in identifying emotions. Our data highlights PTSDIPV-related alterations in the HPA system and its relevance to maternal behavior. Toddlers of IPV-PTSD mothers also showed an altered pattern of cortisol reactivity to stress that potentially may predispose them to later psychological disorders.

We used functional magnetic resonance imaging (fMRI) to examine affective control longitudinally in a group of patients with bipolar disorder (BD). Participants comprised 12 BD patients who underwent repeated fMRI scans in euthymic (n=11), depressed (n=9), or hypomanic (n=9) states, and were compared with 12 age-matched healthy controls. During fMRI, participants performed an emotional face-word interference task with either low or high attentional demands. Relative to healthy controls, patients showed decreased activation of the cognitive control network normally associated with conflict processing, more severely during hypomania than during depression, but regardless of level of task demand in both cases. During euthymia, a decreased response to conflict was observed only during the high load condition. Additionally, unlike healthy participants, patients exhibited deactivation in several key areas in response to emotion-conflict trials - including the rostral anterior cingulate cortex during euthymia, the hippocampus during depression, and the posterior cingulate cortex during hypomania. Our results indicate that the ability of BD patients to recruit control networks when processing affective conflict, and the abnormal suppression of activity in distinct components of the default mode network, may depend on their current clinical state and attentional demand.

Objectives: Thought disorders such as rumination or flight of ideas are frequent in patients with mood disorders, and not systematically linked to mood state. These symptoms point to anomalies in cognitive processes mediating the generation and control of thoughts; for example, associative thinking and inhibition. However, their neural substrates are not known. Method: To obtain an ecological measure of neural processes underlying the generation and suppression of spontaneous thoughts, we designed a free word association task during fMRI allowing us to explore verbal associative patterns in patients with mood disorders and matched controls. Participants were presented with emotionally negative, positive or neutral words, and asked to produce two words either related or unrelated to these stimuli. Results: Relative to controls, patients produced a reverse pattern of answer typicality for the related vs unrelated conditions. Controls activated larger semantic and executive control networks, as well as basal ganglia, precuneus and middle frontal gyrus. Unlike controls, patients activated fusiform gyrus, parahippocampal gyrus and medial prefrontal cortex for emotional stimuli. Conclusions: Mood disorder patients are impaired in automated associative processes, but prone to produce more unique/personal associations through activation of memory and self-related areas.

Background: Racing thoughts, crowded thoughts and flight of ideas are frequent symptoms in mood disorders, but the underlying subjective experience of overactivation of thought processes remains poorly documented. Methods: Qualitative analysis of audiotaped interviews explored subjective experience of thought overactivation in patients with mood disorders (sample 1, n = 45). Quantitative analysis considered the properties of a newly developed rating scale in sample 1, in an additional sample of patients with mood disorders (sample 2, n = 37) and in healthy subjects (sample 3, n = 38). Results: Qualitative analysis of individual interviews revealed that 5 conceptual categories characterized thought overactivation: sequential thought flow, overstimulation, competition for resource allocation, unexpected/unexplained onset, and association with mood and emotions. A principal component analysis of the initial 16-item rating scale indicated that a single component explained 55.9% of the variance, with major and exclusive contributions from 9 items, which were retained in the final 9-item Subjective Thought Overactivation Questionnaire (STOQ; Cronbach's α = 0.95). Total score correlated significantly with activation, depression and perceived conflict subscales of the Internal State Scale (ISS; rs = 0.57-0.66, p < 0.001). It was associated with decreased well-being (ISS; rs = -0.48, p = 0.001) and increased state anxiety (State-Trait Anxiety Inventory; rs = 0.60, p < 0.001). The STOQ score was significantly higher in patients than in healthy subjects. It allowed distinguishing between ISS mood states, with the highest median score in mixed states. Limitations: Sample size, representativeness, possible bias in qualitative analysis, and quality of expert consensus. Conclusions: Qualitative analysis of clinical interviews, together with a new short rating scale, contributed to a documentation of subjective thought overactivation, an important but often undetected feature in mood disorders.

The corpus callosum (CC) plays a crucial role in interhemispheric communication. It has been shown that CC formation relies on the guidepost cells located in the midline region that include glutamatergic and GABAergic neurons as well as glial cells. However, the origin of these guidepost GABAergic neurons and their precise function in callosal axon pathfinding remain to be investigated. Here, we show that two distinct GABAergic neuronal subpopulations converge toward the midline prior to the arrival of callosal axons. Using in vivo and ex vivo fate mapping we show that CC GABAergic neurons originate in the caudal and medial ganglionic eminences (CGE and MGE) but not in the lateral ganglionic eminence (LGE). Time lapse imaging on organotypic slices and in vivo analyses further revealed that CC GABAergic neurons contribute to the normal navigation of callosal axons. The use of Nkx2.1 knockout (KO) mice confirmed a role of these neurons in the maintenance of proper behavior of callosal axons while growing through the CC. Indeed, using in vitro transplantation assays, we demonstrated that both MGE- and CGE-derived GABAergic neurons exert an attractive activity on callosal axons. Furthermore, by combining a sensitive RT-PCR technique with in situ hybridization, we demonstrate that CC neurons express multiple short and long range guidance cues. This study strongly suggests that MGE- and CGE-derived interneurons may guide CC axons by multiple guidance mechanisms and signaling pathways.

Lithium is considered to be the prototypical mood stabilizer. Naturalistic studies indicate that about one third of bipolar patients show a good or very good clinical response to lithium therapy. However, based on clinical evaluation, it remains difficult to reliably predict which patients are more likely to benefit from lithium therapy. In the era of personalized medicine, pharmacogenetics offers the hope that genetic markers could provide reliable predictors of individual responses to lithium therapy. As reviewed in this chapter, pharmacogenetic studies performed over the past two decades have unfortunately failed to produce predictive markers for lithium response that are meaningful for clinical practice. Lack of progress may be due to a variety of factors, including small sample sizes, clinical heterogeneity and variable definitions of lithium response versus non-response phenotypes. To circumvent these difficulties, large-scale international collaborative consortia are emerging, thus opening the possibility of performing genome-wide association studies on well-defined lithium-response phenotypes.

Objectif Les plaintes concernant le sommeil sont tres frequentes chez les patients adultes avec TDA-H. Cependant leur origine est mal comprise et il existe une discordance entre les plaintes subjectives et les anomalies objectives. Ainsi, il n’est pas clair si les anomalies du sommeil sont specifiques au diagnostic TDA-H ou s’ils sont lies au statut de population clinique. Methodes 129 patients adultes avec TDA-H, 70 patients avec trouble de la personnalite borderline (TPB) (dont 17 avec comorbidite TDA-H) et 65 sujets controle ont evalue leur qualite du sommeil (PSQI), leur degre d’insomnie (ISI) et leur somnolence diurne (ESS). Resultats Les patients TPB avaient une alteration du sommeil et un retentissement diurne plus marques que les patients TDA-H, qui eux-memes etaient plus alteres que les controles. L’analyse multivariee a montre que le facteur explicatif principal des plaintes subjectives sur le sommeil etait l’intensite des symptomes depressifs. Les patients avec TDAH-H avaient une latence plus importante et une efficacite moindre meme en ajustant sur le score de depression. Les symptomes inattentifs etaient associes avec le degre de somnolence et les symptomes hyperactifs associes avec l’insomnie et une moindre efficacite. Conclusion Les plaintes concernant le sommeil chez les adultes avec TDA-H semblent en partie expliquees par des facteurs non specifiques. Certaines anomalies du sommeil sont plus caracteristiques des troubles de l’attention, dans une perspective dimensionnelle, et peuvent etre mises en lien avec les difficultes de regulation de la vigilance dans le TDA-H.

Emotion dysregulation and interpersonal hardships constitute core features of borderline personality disorder (BPD). Research has established the link between these core dysregulations and fluctuations in the capacity to appreciate the mental states that underlie behavior (mentalizing, operationalized as reflective functioning (RF)). As emotion dysregulation and interpersonal hardships also characterize adults with attention deficit hyperactivity disorder (ADHD), this study sought to examine the potential RF impairments affecting this population. 101 adults with ADHD, 108 with BPD and 236 controls were assessed using the RF questionnaire (RFQ), evaluating how individuals employ information about mental states to better understand their own and others' behaviors. The RFQ comprises two dimensions, certainty (RF_c) and uncertainty (RF_u) about mental states. RF scores helped distinguish ADHD from controls, but also from BPD (F = 48.1(2/441); p < 0.0001 for RF_c and F = 92.5(2/441); p < 0.0001 for RF_u). The ADHD group showed intermediary RF scores compared to the controls (b = -0.70; p < 0.0001 and b = 0.89; p < 0.0001 for RF_c and RF_u) and BPD group (b = 0.44; p = 0.001 and b = -0.56; p = 0.001 for RF_c and RF_u). Lower RF scores correlated with poor anger control and high levels of impulsivity. Higher severity of ADHD (more attentional and hyperactive/impulsive symptoms) was correlated with RF impairments. In conclusion, RF may constitute an important process underlying attentional, hyperactive/impulsive as well as emotional symptoms in ADHD; it should therefore be considered in the assessment of these patients.

Cortical GABAergic interneurons constitute a highly diverse population of inhibitory neurons that are key regulators of cortical microcircuit function. An important and heterogeneous group of cortical interneurons specifically expresses the serotonin receptor 3A (5-HT3AR) but how this diversity emerges during development is poorly understood. Here we use single-cell transcriptomics to identify gene expression patterns operating in Htr3a-GFP+ interneurons during early steps of cortical circuit assembly. We identify three main molecular types of Htr3a-GFP+ interneurons, each displaying distinct developmental dynamics of gene expression. The transcription factor Meis2 is specifically enriched in a type of Htr3a-GFP+ interneurons largely confined to the cortical white matter. These MEIS2-expressing interneurons appear to originate from a restricted region located at the embryonic pallial–subpallial boundary. Overall, this study identifies MEIS2 as a subclass-specific marker for 5-HT3AR-containing interstitial interneurons and demonstrates that the transcriptional and anatomical parcellation of cortical interneurons is developmentally coupled., Cortical GABAergic interneurons are highly diverse in their gene expression, electrophysiological properties, and connectivity. Here the authors reveal three distinct subtypes of Htr3a-GFP+ interneurons using the single-cell RNA-seq approach, and identify MEIS2 as a marker for one such subtype.

Bipolar disorder (BD) is a genetically complex mental illness characterized by severe oscillations of mood and behavior. Genome-wide association studies (GWAS) have identified several risk loci that together account for a small portion of the heritability. To identify additional risk loci, we performed a two-stage meta-analysis of >9 million genetic variants in 9,784 bipolar disorder patients and 30,471 controls, the largest GWAS of BD to date. In this study, to increase power we used ~2,000 lithium-treated cases with a long-term diagnosis of BD from the Consortium on Lithium Genetics, excess controls, and analytic methods optimized for markers on the X-chromosome. In addition to four known loci, results revealed genome-wide significant associations at two novel loci: an intergenic region on 9p21.3 (rs12553324, p = 5.87×10−9; odds ratio = 1.12) and markers within ERBB2 (rs2517959, p = 4.53×10−9; odds ratio = 1.13). No significant X-chromosome associations were detected and X-linked markers explained very little BD heritability. The results add to a growing list of common autosomal variants involved in BD and illustrate the power of comparing well-characterized cases to an excess of controls in GWAS.

BACKGROUND: Lithium is a first-line treatment in bipolar disorder, but individual response is variable. Previous studies have suggested that lithium response is a heritable trait. However, no genetic markers of treatment response have been reproducibly identified.METHODS: Here, we report the results of a genome-wide association study of lithium response in 2563 patients collected by 22 participating sites from the International Consortium on Lithium Genetics (ConLiGen). Data from common single nucleotide polymorphisms (SNPs) were tested for association with categorical and continuous ratings of lithium response. Lithium response was measured using a well established scale (Alda scale). Genotyped SNPs were used to generate data at more than 6 million sites, using standard genomic imputation methods. Traits were regressed against genotype dosage. Results were combined across two batches by meta-analysis.FINDINGS: A single locus of four linked SNPs on chromosome 21 met genome-wide significance criteria for association with lithium response (rs79663003, p=1·37 × 10(-8); rs78015114, p=1·31 × 10(-8); rs74795342, p=3·31 × 10(-9); and rs75222709, p=3·50 × 10(-9)). In an independent, prospective study of 73 patients treated with lithium monotherapy for a period of up to 2 years, carriers of the response-associated alleles had a significantly lower rate of relapse than carriers of the alternate alleles (p=0·03268, hazard ratio 3·8, 95% CI 1·1-13·0).INTERPRETATION: The response-associated region contains two genes for long, non-coding RNAs (lncRNAs), AL157359.3 and AL157359.4. LncRNAs are increasingly appreciated as important regulators of gene expression, particularly in the CNS. Confirmed biomarkers of lithium response would constitute an important step forward in the clinical management of bipolar disorder. Further studies are needed to establish the biological context and potential clinical utility of these findings.FUNDING: Deutsche Forschungsgemeinschaft, National Institute of Mental Health Intramural Research Program.

Emotional dysregulation in subjects with attention deficit and hyperactivity disorder (ADHD) is a topic of growing interest among clinicians and researchers. The present study aims at investigating components of emotional dysregulation in adults ADHD compared to subjects suffering from bipolar disorder (BD).A total of 150 adults ADHD, 335 adults BD subjects and 48 controls were assessed using the Affective Lability Scale (ALS) and the Affect Intensity Measure (AIM), measuring respectively emotion lability and emotion responsiveness.ADHD and BD subjects scored significantly higher on the ALS compared to controls (p=0.0001). BD subjects scored above ADHD ones (3.07 (SD=0.66) vs. 2.30 (SD=0.68); p0.0001). The average total scores achieved on the AIM were significantly different for the three groups (p=0.0001) with significantly higher scores for ADHD subjects compared to BD ones (3.74 (SD=0.59) vs. 3.56 (SD=0.69); p0.0001).Suspected cases of ADHD in the BD and control groups were derived from the Wender Utah Rating Scale (WURS). This study is a retrospective one.Our study thus highlights the importance of emotional dysregulation in adults suffering from ADHD, showing that they display higher emotional intensity than bipolar disorder subjects and controls. Although the current diagnostic criteria of ADHD do not contain an emotional dimension, a better recognition of the significance of emotional responsiveness in ADHD patients can improve the care afforded to these patients, beyond the inattentive and hyperactive/impulsive components.

Bipolar disorder (BD) is a genetically complex mental illness characterized by severe oscillations of mood and behaviour. Genome-wide association studies (GWAS) have identified several risk loci that together account for a small portion of the heritability. To identify additional risk loci, we performed a two-stage meta-analysis of >9 million genetic variants in 9,784 bipolar disorder patients and 30,471 controls, the largest GWAS of BD to date. In this study, to increase power we used ∼2,000 lithium-treated cases with a long-term diagnosis of BD from the Consortium on Lithium Genetics, excess controls, and analytic methods optimized for markers on the X-chromosome. In addition to four known loci, results revealed genome-wide significant associations at two novel loci: an intergenic region on 9p21.3 (rs12553324, P = 5.87 × 10 (-) (9); odds ratio (OR) = 1.12) and markers within ERBB2 (rs2517959, P = 4.53 × 10 (-) (9); OR = 1.13). No significant X-chromosome associations were detected and X-linked markers explained very little BD heritability. The results add to a growing list of common autosomal variants involved in BD and illustrate the power of comparing well-characterized cases to an excess of controls in GWAS.

Humans are able to categorize face properties with impressively short latencies. Nevertheless, the latency at which gaze recognition occurs is still a matter of debate. Through spatio-temporal analysis of high-density event-related potentials (ERP), we investigated the brain activity underlying the ability to spontaneously and quickly process gaze. We presented neutral faces with direct and averted gaze in a matching picture paradigm, where subjects had to detect repetition of identical faces and gaze was implicitly manipulated. The results indicate that faces with averted gaze were better discriminated than faces with direct gaze, and evoked stronger P100 amplitudes localized to the right fusiform gyrus. In contrast, direct gaze induced stronger activation in the orbital frontal gyrus at this latency. Later in time, at the beginning of the N170 component, direct gaze induced changes in scalp topography with a stronger activation in the right medial temporal gyrus. The location of these differential activations of direct vs. averted gaze further support the view that faces with averted gaze are perceived as less rewarding than faces with direct gaze. We additionally found differential ERP responses between repeated and novel faces as early as 50ms, thereby replicating earlier studies of very fast detection of mnestic aspects of stimuli. Together, these results suggest an early dissociation between implicit gaze detection and explicit identity processing.

Monoamines such as serotonin and dopamine have been shown to regulate cortical interneuron migration but very little is known regarding noradrenaline. Similarly to other monoamines, noradrenaline is detected during embryonic cortical development and adrenergic receptors are expressed in transient embryonic zones of the pallium that contain migrating neurons. Evidence of a functional role for the adrenergic system in interneuron migration is lacking. In this study we first investigated the expression pattern of adrenergic receptors in mouse cortical interneuron subtypes preferentially derived from the caudal ganglionic eminences, and found that they expressed different subtypes of adrenergic receptors. To directly monitor the effects of adrenergic receptor stimulation on interneuron migration we used time-lapse recordings in cortical slices and observed that alpha2 adrenergic receptors (adra2) receptor activation inhibits the migration of cortical interneurons in a concentration-dependent and reversible manner. Furthermore, we observed that following adra2 activation the directionality of migrating interneurons was significantly modified, suggesting that adra2 stimulation could modulate their responsiveness to guidance cues. Finally the distribution of cortical interneurons was altered in vivo in adra2a/2c-knockout mice. These results support the general hypothesis that adrenergic dysregulation occurring during embryonic development alters cellular processes involved in the formation of cortical circuits.

The migration of cortical γ-aminobutyric acidergic interneurons has been extensively studied in rodent embryos, whereas few studies have documented their postnatal migration. Combining in vivo analysis together with time-lapse imaging on cortical slices, we explored the origin and migration of cortical interneurons during the first weeks of postnatal life. Strikingly, we observed that a large pool of GAD65-GFP-positive cells accumulate in the dorsal white matter region during the first postnatal week. Part of these cells divides and expresses the transcription factor paired box 6 indicating the presence of local transient amplifying precursors. The vast majority of these cells are immature interneurons expressing the neuronal marker doublecortin and partly the calcium-binding protein calretinin. Time-lapse imaging reveals that GAD65-GFP-positive neurons migrate from the white matter pool into the overlying anterior cingulate cortex (aCC). Some interneurons in the postnatal aCC express the same immature neuronal markers suggesting ongoing migration of calretinin-positive interneurons. Finally, bromodeoxyuridine incorporation experiments confirm that a small fraction of interneurons located in the aCC are generated during the early postnatal period. These results altogether reveal that at postnatal ages, the dorsal white matter contains a pool of interneuron precursors that divide and migrate into the aCC.

Thought processing and mood regulation are closely linked, but existing classifications of mood disorders fail to recognize the complex interplay between these two clinical dimensions. Furthermore, existing classifications fail to account for the possibility that depression might be associated with an increased frequency of self-referential thoughts that could in some circumstances be related to creativity processes. Based on recent evidence from clinical phenomenology, experimental psychology and affective neuroscience, we propose a novel comprehensive theoretical framework that incorporates thought processing and emotional valence. This new taxonomy provides insights into the clinical understanding of the spectrum of mood disorders and accounts for the possibility of increased creativity in altered mood states.

It is known that increased circulating glucocorticoids in the wake of excessive, chronic, repetitive stress increases anxiety and impairs Brain-Derived Neurotrophic Factor (BDNF) signaling. Recent studies of BDNF gene methylation in relation to maternal care have linked high BDNF methylation levels in the blood of adults to lower quality of received maternal care measured via self-report. Yet the specific mechanisms by which these phenomena occur remain to be established. The present study examines the link between methylation of the BDNF gene promoter region and patterns of neural activity that are associated with maternal response to stressful versus non-stressful child stimuli within a sample that includes mothers with interpersonal violence-related PTSD (IPV-PTSD). 46 mothers underwent fMRI. The contrast of neural activity when watching children—including their own— was then correlated to BDNF methylation. Consistent with the existing literature, the present study found that maternal BDNF methylation was associated with higher levels of maternal anxiety and greater childhood exposure to domestic violence. fMRI results showed a positive correlation of BDNF methylation with maternal brain activity in the anterior cingulate (ACC), and ventromedial prefrontal cortex (vmPFC), regions generally credited with a regulatory function toward brain areas that are generating emotions. Furthermore we found a negative correlation of BDNF methylation with the activity of the right hippocampus. Since our stimuli focus on stressful parenting conditions, these data suggest that the correlation between vmPFC/ACC activity and BDNF methylation may be linked to mothers who are at a disadvantage with respect to emotion regulation when facing stressful parenting situations. Overall, this study provides evidence that epigenetic signatures of stress-related genes can be linked to functional brain regions regulating parenting stress, thus advancing our understanding of mothers at risk for stress-related psychopathology.

Background Recent observations demonstrate that anesthetics rapidly impair synaptogenesis during neuronal circuitry development. Whether these effects are lasting and depend on the developmental stage at which these drugs are administered remains, however, to be explored. Methods Wistar rats received propofol anesthesia at defined developmental stages during early postnatal life. The acute and long-term effects of these treatments on neuronal cytoarchitecture were evaluated by Neurolucida and confocal microscopy analysis after iontophoretic injections of Lucifer Yellow into layer 5 pyramidal neurons in the medial prefrontal cortex. Quantitative electron microscopy was applied to investigate synapse density. Results Layer 5 pyramidal neurons of the medial prefrontal cortex displayed intense dendritic growth and spinogenesis during the first postnatal month. Exposure of rat pups to propofol at postnatal days 5 and 10 significantly decreased dendritic spine density, whereas this drug induced a significant increase in spine density when administered at postnatal days 15, 20, or 30. Quantitative electron microscopy revealed that the propofol-induced increase in spine density was accompanied by a significant increase in the number of synapses. Importantly, the propofol-induced modifications in dendritic spine densities persisted up to postnatal day 90. Conclusion These new results demonstrate that propofol anesthesia can rapidly induce significant changes in dendritic spine density and that these effects are developmental stage-dependent, persist into adulthood, and are accompanied by alterations in synapse number. These data suggest that anesthesia in the early postnatal period might permanently impair circuit assembly in the developing brain.

Background Recent experimental observations suggest that, in addition to induce neuroapoptosis, anesthetics can also interfere with synaptogenesis during brain development. The aim of this study was to pursue this issue by evaluating the exposure time-dependent effects of volatile anesthetics on neuronal cytoarchitecture in 16-day-old rats, a developmental stage characterized by intense synaptogenesis in the cerebral cortex. Methods Whistar rats underwent isoflurane (1.5%), sevoflurane (2.5%), or desflurane (7%) anesthesia for 30, 60, and 120 min at postnatal day 16, and the effect of these treatments on neuronal cytoarchitecture was evaluated 6 h after the initiation of anesthesia. Cell death was assessed using Fluoro-Jade B staining and terminal deoxynucleotidyl transferase deoxyuridine triphosphate nick-end labeling assay. Ionotophoretic injections into layer 5 pyramidal neurons in the medial prefrontal cortex allowed visualization of dendritic arbor. Tracing of dendritic tree was carried out using the Neurolucida station (Microbrightfield, Williston, VT), whereas dendritic spines were analyzed using confocal microscopy. Results Up to a 2-h-long exposure, none of the volatile drugs induced neuronal cell death or significant changes in gross dendritic arbor pattern of layer 5 pyramidal neurons in pups at postnatal day 16. In contrast, these drugs significantly increased dendritic spine density on dendritic shafts of these cells. Importantly, considerable differences were found between these three volatile agents in terms of exposure time-dependent effects on dendritic spine density. Conclusion These new results suggest that volatile anesthetics, with different potencies and without inducing cell death, could rapidly interfere with physiologic patterns of synaptogenesis and thus might impair appropriate circuit assembly in the developing cerebral cortex.

Adult hippocampal. neurogenesis, a once unorthodox concept, has changed into one of the most rapidly growing fields in neuroscience. The present report results from the ECNP targeted expert meeting in 2007 during which cellular plasticity changes were addressed in the adult brain, focusing on neurogenesis and apoptosis in hippocampus and frontal cortex. We discuss recent studies investigating factors that regulate neurogenesis with special emphasis on effects of stress, sleep disruption, exercise and inflammation, a group of seemingly unrelated factors that share at least two unifying properties, namely that they all regulate adult hippocampal neurogenesis and have all been implicated in the pathophysiology of mood disorders. We conclude that although neurogenesis has been implicated in cognitive function and is stimulated by antidepressant drugs, its functional impact and contribution to the etiology of depression remains unclear. A lasting reduction in neurogenesis following severe or chronic stress exposure, either in adult or early life, may represent impaired hippocampal plasticity and can contribute to the cognitive symptoms of depression, but is, by itself, unlikely to produce the full mood disorder. Normalization of reductions in neurogenesis appears at least partly, implicated in antidepressant action. (C) 2009 Elsevier B.V. and ECNP. All rights reserved.

The discovery that a common polymorphism (5-HTTLPR, short variant) in the human serotonin transporter gene (SLC6A4) can influence personality traits and increase the risk for depression in adulthood has led to the hypothesis that a relative increase in the extracellular levels of serotonin (5-HT) during development could be critical for the establishment of brain circuits. Consistent with this idea, a large body of data demonstrate that 5-HT is a strong neurodevelopmental signal that can modulate a wide variety of cellular processes. In humans, serotonergic fibers appear in the developing cortex as early as the 10th gestational week, a period of intense neuronal migration. In this study we hypothesized that an excess of 5-HT could affect embryonic cortical interneuron migration. Using time-lapse videometry to monitor the migration of interneurons in embryonic mouse cortical slices, we discovered that the application of 5-HT decreased interneuron migration in a reversible and dose-dependent manner. We next found that 5-HT6 receptors were expressed in cortical interneurons and that 5-HT6 receptor activation decreased interneuron migration, whereas 5-HT6 receptor blockade prevented the migratory effects induced by 5-HT. Finally, we observed that interneurons were abnormally distributed in the cerebral cortex of serotonin transporter gene (Slc6a4) knockout mice that have high levels of extracellular 5-HT. These results shed new light on the neurodevelopmental alterations caused by an excess of 5-HT during the embryonic period and contribute to a better understanding of the cellular processes that could be modulated by genetically controlled differences in human 5-HT homeostasis.

Background An increasing number of clinical observations suggest adverse neurologic outcome after methylene blue (MB) infusion in the setting of parathyroid surgery. Hence, the aim of the current study was to investigate the potentially neurotoxic effects of MB using a combination of in vivo and in vitro experimental approaches. Methods Isoflurane-anesthetized adult rats were used to evaluate the impact of a single bolus intravascular administration of MB on systemic hemodynamic responses and on the minimum alveolar concentration (MAC) of isoflurane using the tail clamp test. In vivo, MB-induced cell death was evaluated 24 h after MB administration using Fluoro-Jade B staining and activated caspase-3 immunohistochemistry. In vitro, neurotoxic effects of MB were examined in hippocampal slice cultures by measuring excitatory field potentials as well as propidium iodide incorporation after MB exposure. The impact of MB on dendritic arbor was evaluated in differentiated single cell neuronal cultures. Results Bolus injections of MB significantly reduced isoflurane MAC and initiated widespread neuronal apoptosis. Electrophysiologic recordings in hippocampal slices revealed a rapid suppression of evoked excitatory field potentials by MB, and this was associated with a dose-dependent effect of this drug on cell death. Dose-response experiments in single cell neuronal cultures revealed that a 2-h-long exposure to MB at non-cell-death-inducing concentrations could still induce significant retraction of dendritic arbor. Conclusions These results suggest that MB exerts neurotoxic effects on the central nervous system and raise questions regarding the safety of using this drug at high doses during parathyroid gland surgery.

Objectives: To contribute to the definition of external and internal limits of mixed states and study the place of dysphoric symptoms in the psychopathology of mixed states. Methods: One hundred and sixty-five inpatients with major mood episodes were diagnosed as presenting with either pure depression, mixed depression (depression plus at least three manic symptoms), full mixed state (full depression and full mania), mixed mania (mania plus at least three depressive symptoms) or pure mania, using an adapted version of the Mini International Neuropsychiatric Interview (DSM-IV version). They were evaluated using a 33-item inventory of depressive, manic and mixed affective signs and symptoms. Results: Principal component analysis without rotation yielded three components that together explained 43.6% of the variance. The first component (24.3% of the variance) contrasted typical depressive symptoms with typical euphoric, manic symptoms. The second component, labeled ‘dysphoria’, (13.8%) had strong positive loadings for irritability, distressing sensitivity to light and noise, impulsivity and inner tension. The third component (5.5%) included symptoms of insomnia. Median scores for the first component significantly decreased from the pure depression group to the pure mania group. For the dysphoria component, scores were highest among patients with full mixed states and decreased towards both patients with pure depression and those with pure mania. Conclusions: Principal component analysis revealed that dysphoria represents an important dimension of mixed states.

Rett syndrome is a severe neurodevelopmental disorder affecting principally females and characterized by a normal postnatal development followed by stagnation and regression of acquired skills. We report a 4-year-old boy with a Rett syndrome phenotype and his unaffected mother both carrying a 44 bp truncating deletion mutation (c.1158del44 or p.388X) in the MECP2 gene. The presence of a skewed X inactivation in the mother provides a possible explanation for the absence of penetrance. The finding of a MECP2 mutation in an unaffected female complicates genetic counseling and further confirms that it is essential to look for mutations in the mothers of all patients with MECP2 mutations.

Di-(2-ethylhexyl)phtalate (DEHP) is a plasticizer with endocrine disrupting properties found ubiquitously in the environment and altering reproduction in rodents. Here we investigated the impact of prenatal exposure to DEHP on spermatogenesis and DNA sperm methylation in two distinct, selected, and sequenced mice strains. FVB/N and C57BL/6J mice were orally exposed to 300 mg/kg/day of DEHP from gestation day 9 to 19. Prenatal DEHP exposure significantly decreased spermatogenesis in C57BL/6J (fold-change = 0.6, p-value = 8.7*10-4), but not in FVB/N (fold-change = 1, p-value = 0.9). The number of differentially methylated regions (DMRs) by DEHP-exposure across the entire genome showed increased hyper- and decreased hypo-methylation in C57BL/6J compared to FVB/N. At the promoter level, three important subsets of genes were massively affected. Promoters of vomeronasal and olfactory receptors coding genes globally followed the same trend, more pronounced in the C57BL/6J strain, of being hyper-methylated in DEHP related conditions. In contrast, a large set of micro-RNAs were hypo-methylated, with a trend more pronounced in the FVB/N strain. We additionally analyze both the presence of functional genetic variations within genes that were associated with the detected DMRs and that could be involved in spermatogenesis, and DMRs related with the DEHP exposure that affected both strains in an opposite manner. The major finding in this study indicates that prenatal exposure to DEHP can decrease spermatogenesis in a strain-dependent manner and affects sperm DNA methylation in promoters of large sets of genes putatively involved in both sperm chemotaxis and post-transcriptional regulatory mechanisms.

Subcellular target recognition in the CNS is the culmination of a multiple-step program including axon guidance, target recognition, and synaptogenesis. In cerebellum, basket cells (BCs) innervate the soma and axon initial segment (AIS) of Purkinje cells (PCs) to form the pinceau synapse, but the underlying mechanisms remain incompletely understood. Here, we demonstrate that neuropilin-1 (NRP1), a Semaphorin receptor expressed in BCs, controls both axonal guidance and subcellular target recognition. We show that loss of Semaphorin 3A function or specific deletion of NRP1 in BCs alters the stereotyped organization of BC axon and impairs pinceau synapse formation. Further, we identified NRP1 as a trans-synaptic binding partner of the cell adhesion molecule neurofascin-186 (NF186) expressed in the PC AIS during pinceau synapse formation. These findings identify a dual function of NRP1 in both axon guidance and subcellular target recognition in the construction of GABAergic circuitry.

5-HT6 receptor (5-HT6R) is a G protein-coupled receptor that has recently emerged as a new regulator of neural development. In addition to the canonical Gs adenylyl cyclase pathway, recent proteomics approaches reveal that 5-HT6R is able to engage key developmental signaling pathways controlling neuronal circuit formation, neuronal connectivity, and psychiatric-relevant behaviors. For example, at early stages of neuronal development, expression of 5-HT6R constitutively regulates the activity of the cyclin-dependent kinase (Cdk)5 and, through this mechanism, controls cellular processes involved in circuit formation, including neuronal migration and neurite outgrowth. In addition to the Cdk5 pathway, 5-HT6R modulates a variety of key developmental targets such as Fyn, Jab1, and mammalian target of rapamycin (mTOR). Engagement of developmental pathways through 5-HT6R pharmacological manipulation has led to interesting new therapeutic perspectives in the field of psychiatric-related disorders. Indeed, 5-HT6R blockade can rescue a pathological overactivation of the mTOR pathway induced by early life insults in rodents and normalizes the associated social and episodic memory deficits. Here, we review recent evidence supporting the notion that 5-HT6R is at the interface of key developmental signaling pathways and a novel actor in the orchestration of neural circuit formation.

Early-life deficiency of the serotonin transporter (SERT) gives rise to a wide range of psychiatric-relevant phenotypes; however, the molecular and cellular targets of serotonin dyregulation during neural circuit formation remain to be identified. Interestingly, migrating cortical interneurons (INs) derived from the caudal ganglionic eminence (CGE) have been shown to be more responsive to serotonin-mediated signalling compared with INs derived from the medial ganglionic eminence (MGE). Here we investigated the impact of early-life SERT deficiency on the migration and positioning of CGE-derived cortical INs in SERT-ko mice and in mice exposed to the SERT inhibitor fluoxetine during the late embryonic period. Using confocal time-lapse imaging and microarray-based expression analysis we found that genetic and pharmacological SERT deficiency significantly increased the migratory speed of CGE-derived INs and affected transcriptional programmes regulating neuronal migration. Postnatal studies revealed that SERT deficiency altered the cortical laminar distribution of subtypes of CGE-derived INs but not MGE-derived INs. More specifically, we found that the distribution of vasointestinal peptide (VIP)-expressing INs in layer 2/3 was abnormal in both genetic and pharmacological SERT-deficiency models. Collectively, these data indicate that early-life SERT deficiency has an impact on the migration and molecular programmes of CGE-derived INs, thus leading to specific alterations in the positioning of VIP-expressing INs. These data add to the growing evidence that early-life serotonin dysregulation affects cortical microcircuit formation and contributes to the emergence of psychiatric-relevant phenotypes.

Prior research has shown that mothers with Interpersonal Violence-related Posttraumatic Stress Disorder (IPV-PTSD) report greater difficulty in parenting their toddlers. Relative to their frequent early exposure to violence and maltreatment, these mothers display dysregulation of their hypothalamic pituitary adrenal axis (HPA-axis), characterized by hypocortisolism. Considering methylation of the promoter region of the glucocorticoid receptor gene NR3C1 as a marker for HPA-axis functioning, with less methylation likely being associated with less circulating cortisol, the present study tested the hypothesis that the degree of methylation of this gene would be negatively correlated with maternal IPV-PTSD severity and parenting stress, and positively correlated with medial prefrontal cortical (mPFC) activity in response to video-stimuli of stressful versus non-stressful mother-child interactions. Following a mental health assessment, 45 mothers and their children (ages 12-42 months) participated in a behavioral protocol involving free-play and laboratory stressors such as mother-child separation. Maternal DNA was extracted from saliva. Interactive behavior was rated on the CARE-Index. During subsequent fMRI scanning, mothers were shown films of free-play and separation drawn from this protocol. Maternal PTSD severity and parenting stress were negatively correlated with the mean percentage of methylation of NR3C1. Maternal mPFC activity in response to video-stimuli of mother-child separation versus play correlated positively to NR3C1 methylation, and negatively to maternal IPV-PTSD and parenting stress. Among interactive behavior variables, child cooperativeness in play was positively correlated with NR3C1 methylation. Thus, the present study is the first published report to our knowledge, suggesting convergence of behavioral, epigenetic, and neuroimaging data that form a psychobiological signature of parenting-risk in the context of early life stress and PTSD.

Some authors advocate a broadening of the narrow concept of mixed episodes in the direction of mania leading to the concept of mixed mania, and in the direction of depression leading to the concept of mixed depression. The latter has been little investigated so far. In the present article, we retrospectively compare 49 patients with pure depression with 51 patients with mixed depression in terms of socio-demographic and clinical variables in order to contribute to the validation of the distinction between mixed and pure depression. Supporting this distinction, we observed that mixed depressive patients more frequently had past histories of bipolar disorder and alcohol abuse and had longer durations of hospital stay. These last two points remain significant even when we control for the effect of the association with bipolarity.

Several psychiatric disorders have been associated with CpG methylation changes in CG rich promoters of the brain-derived neurotrophic factor (BDNF) mainly by extracting DNA from peripheral blood cells. Whether changes in peripheral DNA methylation can be used as a proxy for brain-specific alterations remains an open question. In this study we aimed to compare DNA methylation levels in BDNF promoter regions in human blood cells, muscle and brain regions using bisulfite-pyrosequencing. We found a significant correlation between the levels of BDNF promoter I methylation measured in quadriceps and vPFC tissues extracted from the same individuals (n = 98, Pearson, r = 0.48, p = 4.5 × 10−7). In the hippocampus, BDNF promoter I and IV methylation levels were strongly correlated (Pearson, n = 37, r = 0.74, p = 1.4 × 10−7). We found evidence for sex-dependent effect on BDNF promoter methylation levels in the various tissues and blood samples. Taken together, these data indicate a strong intra-individual correlation between peripheral and brain tissue. They also suggest that sex determines methylation patterns in BDNF promoter region across different types of tissue, including muscle, brain, and blood.