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Based on recent genome-wide association studies, it is theorized that altered regulation of autophagy contributes to the pathophysiology of schizophrenia and bipolar disorder. As activity of autophagy-regulatory pathways is controlled by discrete phosphorylation sites on the relevant proteins, phospho-protein profiling is one of the few approaches available for enabling a quantitative assessment of autophagic activity in the brain. Despite this, a comprehensive phospho-protein assessment in the brains of schizophrenia and bipolar disorder subjects is currently lacking. Using this direction, our broad screening identifies an increase in AMP-activated protein kinase (AMPK)-mediated phospho-activation of the pro-autophagy protein beclin-1 solely in the prefrontal cortex of female, but not male, schizophrenia subjects. Using a reverse translational approach, we surprisingly find that this increase in beclin-1 activity facilitates synapse formation and enhances cognition. These findings are interpreted in the context of human studies demonstrating that female schizophrenia subjects have a lower susceptibility to cognitive dysfunction than males., Competing Interests: Declaration of interests The authors declare no competing interests., (Copyright © 2024 The Author(s). Published by Elsevier Inc. All rights reserved.)

Dendritic spines are protrusions on dendrites forming the postsynaptic aspect of excitatory connections within the brain. Spine morphology is associated with synaptic functional strength and the spatial regulation of protein nanodomains within dendritic spines is an important determinant of spine structure and function. Here, we present a protocol to resolve the nanoscale localization of proteins within dendritic spines using structured illumination microscopy. We describe steps for the structural analysis of dendritic spine parameters, protein localization analysis, and data processing. For complete details on the use and execution of this protocol, please refer to Bjornson et al. 1 ., Competing Interests: Declaration of interests The authors declare no competing interests., (Copyright © 2023 The Author(s). Published by Elsevier Inc. All rights reserved.)

Long-and middle-wavelength cone photoreceptors, which are responsible for our visual acuity and color vision, comprise ~95% of our total cone population and are concentrated in the fovea of our retina. Previously, we characterized the disease mechanisms of the L/M-cone opsin missense mutations N94K, W177R, P307L, R330Q and G338E, all of which are associated with congenital blue cone monochromacy (BCM) or color-vision deficiency. Here, we used a similar viral vector-based gene delivery approach in M-opsin knockout mice to investigate the pathogenic consequences of the BCM or color-vision deficient associated L-cone opsin (OPN1LW) mutants K82E, P187S, and M273K. We investigated their subcellular localization, the pathogenic effects on cone structure, function, and cone viability. K82E mutants were detected predominately in cone outer segments, and its expression partially restored expression and correct localization of cone PDE6α' and cone transducin γ. As a result, K82E also demonstrated the ability to mediate cone light responses. In contrast, expression of P187S was minimally detected by either western blot or by immunohistochemistry, probably due to efficient degradation of the mutant protein. M273K cone opsin appeared to be misfolded as it was primarily localized to the cone inner segment and endoplasmic reticulum. Additionally, M273K did not restore the expression of cone PDE6α' and cone transducin γ in dorsal cone OS, presumably by its inability to bind 11- cis retinal. Consistent with the observed expression pattern, P187S and M273K cone opsin mutants were unable to mediate light responses. Moreover, expression of K82E, P187S, and M273K mutants reduced cone viability. Due to the distinct expression patterns and phenotypic differences of these mutants observed in vivo , we suggest that the pathobiological mechanisms of these mutants are distinct., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. The author(s) declared that they were an editorial board member of Frontiers, at the time of submission. This had no impact on the peer review process and the final decision., (Copyright © 2024 Sechrest, Barbera, Ma, Dyka, Ahn, Brothers, Cahill, Hall, Baehr and Deng.)

Abstract: We compared mpox vaccination access between urban and rural residents who received ≥1 JYNNEOS dose using immunization data in Idaho and New Mexico. Rural residents traveled 5 times farther and 3 times longer than urban residents to receive mpox vaccination. Increasing mpox vaccine availability to health care facilities might increase uptake., Competing Interests: Conflict of Interest and Sources of Funding: None of the listed authors have any conflicts of interest to report or funding to declare regarding this manuscript or its findings., (Copyright © 2023 American Sexually Transmitted Diseases Association. All rights reserved.)

During the COVID-19 pandemic, public health authorities have encouraged the use of face masks to minimize transmission within the community. To assess mask wear during a COVID-19 surge and guide public health response efforts, including public messaging on mask recommendations, we compared observed mask use in the largest city in each of Idaho's 2 most populous counties, both without a current mask mandate. We recorded mask usage by every third person exiting stores of 5 retail chains in Boise and Nampa during November 8-December 5, 2021. Observations were conducted during three time periods (morning, afternoon, and evening) on weekday and weekend days. A multivariable model with city, retail chain, and city-chain interaction was used to assess mask wear differences by city for each chain. Of 3021 observed persons, 22.0% wore masks. In Boise, 31.3% (430/1376) of observed persons wore masks; in Nampa, 14.3% (236/1645) wore masks. Among all persons wearing masks, > 94% wore masks correctly; cloth and surgical masks were most common. By retail chain, observed individuals at Boise locations were 2.3-5.7 times as likely to wear masks than persons at respective Nampa locations. This study provided a rapid, nonconfrontational assessment of public use of mitigation measures in 2 Idaho cities during a COVID-19 surge., (© 2023. This is a U.S. Government work and not under copyright protection in the US; foreign copyright protection may apply.)

An arginine to cysteine substitution at amino acid position 203 (C203R) is the most common missense mutation in human cone opsin. Linked to color blindness and blue cone monochromacy (BCM), C203 is involved in a crucial disulfide bond required for proper folding. It has previously been postulated that expression of mutant C203R cone opsin exerts a toxic effect on cone photoreceptors, similar to some well-characterized missense mutations in rhodopsin that lead to protein misfolding. In this study, we generated and characterized a BCM mouse model carrying the equivalent C203R mutation (Opn1mwC198R Opn1sw-/-) to investigate the disease mechanism and develop a gene therapy approach for this disorder. Untreated Opn1mwC198R Opn1sw-/- cones phenocopied affected cones in human patients with the equivalent mutation, exhibiting shortened or absent cone outer segments and loss of function. We determined that gene augmentation targeting cones specifically yielded robust rescue of cone function and structure when Opn1mwC198R Opn1sw-/- mice were treated at early ages. Importantly, treated cones displayed elaborated outer segments and replenished expression of crucial cone phototransduction proteins. Interestingly, we were unable to detect OPN1MWC198R mutant opsin at any age. We believe this is the first proof-of-concept study exploring the efficacy of gene therapy in BCM associated with a C203R mutation.

The effects of repeated stress on cognitive impairment are thought to be mediated, at least in part, by reductions in the stability of dendritic spines in brain regions critical for proper learning and memory, including the hippocampus. Small GTPases are particularly potent regulators of dendritic spine formation, stability, and morphology in hippocampal neurons. Through the use of small GTPase protein profiling in mice, we identify increased levels of synaptic Rap1 in the hippocampal CA3 region in response to escalating, intermittent stress. We then demonstrate that increased Rap1 in the CA3 is sufficient in and of itself to produce stress-relevant dendritic spine and cognitive phenotypes. Further, using super-resolution imaging, we investigate how the pattern of Rap1 trafficking to synapses likely underlies its effects on the stability of select dendritic spine subtypes. These findings illuminate the involvement of aberrant Rap1 regulation in the hippocampus in contributing to the psychobiological effects of stress., Competing Interests: The authors declare no competing interests., (© 2023 The Author(s).)

Treatment of carbapenemase-producing carbapenem-resistant Pseudomonas aeruginosa (CP-CRPA) infections is challenging because of antibiotic resistance. CP-CRPA infections are highly transmissible in health care settings because they can spread from person to person and from environmental sources such as sink drains and toilets. During September 2021-January 2022, an Idaho hospital (hospital A) isolated CP-CRPA from sputum of two patients who stayed in the same intensive care unit (ICU) room (room X), 4 months apart. Both isolates had active-on-imipenem metallo-beta-lactamase (IMP) carbapenemase gene type 84 (bla IMP-84 ) and were characterized as multilocus sequence type 235 (ST235). A health care-associated infections team from the Idaho Division of Public Health visited hospital A during March 21-22, 2022, to discuss the cluster investigation with hospital A staff members and to collect environmental samples. CP-CRPA ST235 with bla IMP-84 was isolated from swab samples of one sink in room X, suggesting it was the likely environmental source of transmission. Recommended prevention and control measures included application of drain biofilm disinfectant, screening of future patients who stay in room X (e.g., the next 10 occupants) upon reopening, and continuing submission of carbapenem-resistant P. aeruginosa (CRPA) isolates to public health laboratories. Repeat environmental sampling did not detect any CRPA. As of December 2022, no additional CP-CRPA isolates had been reported by hospital A. Collaboration between health care facilities and public health agencies, including testing of CRPA isolates for carbapenemase genes and implementation of sink hygiene interventions, was critical in the identification of and response to this CP-CRPA cluster in a health care setting., Competing Interests: All authors have completed and submitted the International Committee of Medical Journal Editors form for disclosure of potential conflicts of interest. No potential conflicts of interest were disclosed.

Objectives. To examine the potential impact of contact tracing to identify contacts and prevent mpox transmission among gay, bisexual, and other men who have sex with men (MSM) as the outbreak expanded. Methods. We assessed contact tracing outcomes from 10 US jurisdictions before and after access to the mpox vaccine was expanded from postexposure prophylaxis for persons with known exposure to include persons at high risk for acquisition (May 17-June 30, 2022, and July 1-31, 2022, respectively). Results. Overall, 1986 mpox cases were reported in MSM from included jurisdictions (240 before expanded vaccine access; 1746 after expanded vaccine access). Most MSM with mpox were interviewed (95.0% before vaccine expansion and 97.0% after vaccine expansion); the proportion who named at least 1 contact decreased during the 2 time periods (74.6% to 38.9%). Conclusions. During the period when mpox cases among MSM increased and vaccine access expanded, contact tracing became less efficient at identifying exposed contacts. Public Health Implications. Contact tracing was more effective at identifying persons exposed to mpox in MSM sexual and social networks when case numbers were low, and it could be used to facilitate vaccine access. ( Am J Public Health . 2023;113(7):815-818. https://doi.org/10.2105/AJPH.2023.307301).

Background: Asthma, type 2 diabetes (T2D), and anthropometric measures are correlated complex traits that all have a major genetic component. Objective: To investigate the overlap in genetic variants associated with these complex traits. Methods: Using United Kingdom Biobank data, we performed univariate association analysis, fine-mapping, and mediation analysis to identify and dissect shared genomic regions associated with asthma, T2D, height, weight, body mass index (BMI), and waist circumference (WC). Results: We found several genome-wide significant variants in and around the JAZF1 gene that are associated with asthma, T2D, or height with two of these variants shared by the three phenotypes. We also observed an association in this region with WC when adjusted for BMI. However, there was no association with WC when it was not adjusted for BMI or weight. Additionally, only suggestive associations between variants in this region and BMI were observed. Fine-mapping analyses suggested that within JAZF1 there are non-overlapping regions harboring causal susceptibility variants for asthma, T2D, and height. Mediation analyses supported the conclusion that these are independent associations. Conclusion: Our findings indicate that variants in the JAZF1 are associated with asthma, T2D, and height, but the associated causal variant(s) are different for each of the three phenotypes., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 DeWan, Cahill, Cornejo-Sanchez, Li, Dong, Fabiha, Sun, Wang and Leal.)

West Nile viral infection causes severe neuroinvasive disease in less than 1% of infected humans. There are no targeted therapeutics for this serious and potentially fatal disease, and to date no vaccine has been approved for humans. With climate change expected to result in rising incidence of West Nile and other related vector-borne viral infections, there is an increasing need to identify those at risk for serious disease and potential leads for therapeutic and vaccine development. Genetic variation, particularly in genes whose products are either directly or indirectly connected to immune response to infections, is a critical avenue of investigation to identify those at higher risk of clinically apparent West Nile infection. Given the small percent of infections that progress to severe disease and the relatively low numbers of reported infections, it is challenging to conduct well-powered studies to identify genetic factors associated with more severe outcomes. In this chapter, we outline several approaches with the objective to take full advantage of all available data in order to identify genetic factors which lead to increased risk of severe West Nile neuroinvasive disease. These methods are generalizable to other conditions with limited cohort size and rare outcomes., (© 2023. The Author(s), under exclusive license to Springer Science+Business Media, LLC, part of Springer Nature.)

Mounting epidemiologic and scientific evidence indicates that many psychiatric disorders originate from a complex interplay between genetics and early life experiences, particularly in the womb. Despite decades of research, our understanding of the precise prenatal and perinatal experiences that increase susceptibility to neurodevelopmental disorders remains incomplete. Sleep apnea (SA) is increasingly common during pregnancy and is characterized by recurrent partial or complete cessations in breathing during sleep. SA causes pathological drops in blood oxygen levels (intermittent hypoxia, IH), often hundreds of times each night. Although SA is known to cause adverse pregnancy and neonatal outcomes, the long-term consequences of maternal SA during pregnancy on brain-based behavioral outcomes and associated neuronal functioning in the offspring remain unknown. We developed a rat model of maternal SA during pregnancy by exposing dams to IH, a hallmark feature of SA, during gestational days 10 to 21 and investigated the consequences on the offspring's forebrain synaptic structure, synaptic function, and behavioral phenotypes across multiples stages of development. Our findings represent a rare example of prenatal factors causing sexually dimorphic behavioral phenotypes associated with excessive (rather than reduced) synapse numbers and implicate hyperactivity of the mammalian target of rapamycin (mTOR) pathway in contributing to the behavioral aberrations. These findings have implications for neuropsychiatric disorders typified by superfluous synapse maintenance that are believed to result, at least in part, from largely unknown insults to the maternal environment., Competing Interests: The authors have declared that no competing interests exist.

The neural molecular and biochemical response to stress is a distinct physiological process, and multiple lines of evidence indicate that the prefrontal cortex (PFC) is particularly sensitive to, and afflicted by, exposure to stress. Largely through this PFC dysfunction, stress has a characterized role in facilitating cognitive impairment, which is often dissociable from its effects on non-cognitive behaviors. The Rap1 small GTPase pathway has emerged as a commonly disrupted intracellular target in neuropsychiatric conditions, whether it be via alterations in Rap1 expression or through alterations in the expression of direct and specific upstream Rap1 activators and inhibitors. Here we demonstrate that escalating, intermittent stress increases Rap1 in mouse PFC synapses, results in cognitive impairments, and reduces the preponderance of mature dendritic spines in PFC neurons. Using viral-mediated gene transfer, we reveal that the hyper-induction of Rap1 in the PFC is sufficient to drive stress-relevant cognitive and synaptic phenotypes. These findings point to Rap1 as a critical mediator of stress-driven neuronal and behavioral pathology and highlight a previously unrecognized involvement for Rap1 in novelty-driven PFC engagement., (© 2020. The Author(s), under exclusive licence to Springer Nature Limited.)

The Akt family of kinases exerts many of its cellular effects via the activation of the mammalian target of rapamycin (mTOR) kinase through a series of intermediary proteins. Multiple lines of evidence have identified Akt-family kinases as candidate schizophrenia and bipolar disorder genes. Although dysfunction of the prefrontal cortex (PFC) is a key feature of both schizophrenia and bipolar disorder, no studies have comprehensively assessed potential alterations in Akt-mTOR pathway activity in the PFC of either disorder. Here, we examined the activity and expression profile of key proteins in the Akt-mTOR pathway in bipolar disorder and schizophrenia homogenates from two different PFC subregions. Our findings identify reduced Akt-mTOR PFC signaling in a subset of bipolar disorder subjects. Using a reverse-translational approach, we demonstrated that Akt hypofunction in the PFC is sufficient to give rise to key cognitive phenotypes that are paralleled by alterations in synaptic connectivity and function., Competing Interests: Declaration of interests The authors declare no competing interests., (Copyright © 2021 Elsevier Inc. All rights reserved.)

Background: The identification of gene-gene and gene-environment interactions in genome-wide association studies is challenging due to the unknown nature of the interactions and the overwhelmingly large number of possible combinations. Parametric regression models are suitable to look for prespecified interactions. Nonparametric models such as tree ensemble models, with the ability to detect any unspecified interaction, have previously been difficult to interpret. However, with the development of methods for model explainability, it is now possible to interpret tree ensemble models efficiently and with a strong theoretical basis., Results: We propose a tree ensemble- and SHAP-based method for identifying as well as interpreting potential gene-gene and gene-environment interactions on large-scale biobank data. A set of independent cross-validation runs are used to implicitly investigate the whole genome. We apply and evaluate the method using data from the UK Biobank with obesity as the phenotype. The results are in line with previous research on obesity as we identify top SNPs previously associated with obesity. We further demonstrate how to interpret and visualize interaction candidates., Conclusions: The new method identifies interaction candidates otherwise not detected with parametric regression models. However, further research is needed to evaluate the uncertainties of these candidates. The method can be applied to large-scale biobanks with high-dimensional data.

West Nile virus (WNV) is a mosquito-borne virus which causes symptomatic disease in a minority of infected humans. To identify novel genetic variants associated with severe disease, we utilized data from an existing case-control study of WNV and included population controls for an expanded analysis. We conducted imputation and gene-gene interaction analysis in the largest and most comprehensive genetic study conducted to date for West Nile neuroinvasive disease (WNND). Within the imputed West Nile virus dataset (severe cases n = 381 and asymptomatic/mild controls = 441), we found novel loci within the MCF.2 Cell Line Derived Transforming Sequence Like ( MCF2L ) gene (rs9549655 and rs2297192) through the individual loci analyses, although none reached statistical significance. Incorporating population controls from the Wisconsin Longitudinal Study on Aging (n = 9012) did not identify additional novel variants, a possible reflection of the cohort's inclusion of individuals who could develop mild or severe WNV disease upon infection. Many of the top gene-gene interaction results were intergenic, with currently undefined biological roles, highlighting the need for further investigation into these regions and other identified gene targets in severe WNND. Further studies including larger sample sizes and more diverse populations reflective of those at risk are needed to fully understand the genetic architecture of severe WNDD and provide guidance on viable targets for therapeutic and vaccine development.

The genus Flavivirus contains many mosquito-borne human pathogens of global epidemiological importance such as dengue virus, West Nile virus, and Zika virus, which has recently emerged at epidemic levels. Infections with these viruses result in divergent clinical outcomes ranging from asymptomatic to fatal. Myriad factors influence infection severity including exposure, immune status and pathogen/host genetics. Furthermore, pre-existing infection may skew immune pathways or divert immune resources. We profiled immune cells from dengue virus-infected individuals by multiparameter mass cytometry (CyTOF) to define functional status. Elevations in IFNβ were noted in acute patients across the majority of cell types and were statistically elevated in 31 of 36 cell subsets. We quantified response to in vitro (re)infection with dengue or Zika viruses and detected a striking pattern of upregulation of responses to Zika infection by innate cell types which was not noted in response to dengue virus. Significance was discovered by statistical analysis as well as a neural network-based clustering approach which identified unusual cell subsets overlooked by conventional manual gating. Of public health importance, patient cells showed significant enrichment of innate cell responses to Zika virus indicating an intact and robust anti-Zika response despite the concurrent dengue infection., Competing Interests: The authors have declared that no competing interests exist.

While research has identified alterations in dorsolateral prefrontal cortical function as a key factor to the etiology of bipolar disorder, few studies have uncovered robust changes in protein signal transduction pathways in this disorder. Given the direct relevance of protein-based expressional alterations to cellular functions and because many of the key regulatory mechanisms for the disease pathogenesis likely include alterations in protein activity rather than changes in expression alone, the identification of alterations in discrete signal transduction pathways in bipolar disorder would have broad implications for understanding the disease pathophysiology. As prior microarray data point to a previously unrecognized involvement of the RhoA network in bipolar disorder, here we investigate the protein expression and activity of key components of a RhoA signal transduction pathway in dorsolateral prefrontal cortical homogenates from subjects with bipolar disorder. The results of this investigation implicate overactivation of prefrontal cortical RhoA signaling in specific subtypes of bipolar disorder. The specificity of these findings is demonstrated by a lack of comparable changes in schizophrenia; however, our findings do identify convergence between both disorders at the level of activity-mediated actin cytoskeletal regulation. These findings have implications for understanding the altered cortical synaptic connectivity of bipolar disorder., (© The Author(s) 2019. Published by Oxford University Press. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

The effects of chronic adolescent fluoxetine (FLX, Prozac®) exposure on adult cognition are largely unknown. We used a serial multiple choice (SMC) task to characterize the effects of adolescent FLX exposure on rat serial pattern learning in adulthood. Male rats were exposed to either 1.0, 2.0, or 4.0 mg/kg/day FLX for five consecutive days each week for five weeks during adolescence, followed by a 35-day drug-free period. As adults, the rats were trained in a task that required them to learn a highly structured sequential pattern of responses in an octagonal chamber for water reinforcement. In a transfer phase, the terminal element of the pattern was replaced by a violation element that was inconsistent with previously learned pattern structure. Results indicated that adolescent FLX exposure caused differential learning deficits for different types of elements in the serial pattern. Adolescent exposure to 1.0 or 4.0 mg/kg/day FLX, but not 2.0 mg/kg/day FLX, impaired chunk-boundary element learning, which is known to be mediated by stimulus-response (S-R) learning. All three doses of FLX impaired violation element learning, which is known to be mediated by multiple-cue learning. FLX did not impair within-chunk element learning, which is known to be mediated by rule-learning mechanisms. The results indicate that adolescent FLX exposure produced multiple cognitive impairments that were detectable in adulthood long after drug exposure ended., (Copyright © 2019 Elsevier Inc. All rights reserved.)

Addictive behaviors, including relapse, are thought to depend in part on long-lasting drug-induced adaptations in dendritic spine signaling and morphology in the nucleus accumbens (NAc). While the influence of activity-dependent actin remodeling in these phenomena has been studied extensively, the role of microtubules and associated proteins remains poorly understood. We report that pharmacological inhibition of microtubule polymerization in the NAc inhibited locomotor sensitization to cocaine and contextual reward learning. We then investigated the roles of microtubule end-binding protein 3 (EB3) and SRC kinase in the neuronal and behavioral responses to volitionally administered cocaine. In synaptoneurosomal fractions from the NAc of self-administering male rats, the phosphorylation of SRC at an activating site was induced after 1 d of withdrawal, while EB3 levels were increased only after 30 d of withdrawal. Blocking SRC phosphorylation during early withdrawal by virally overexpressing SRCIN1, a negative regulator of SRC activity known to interact with EB3, abolished the incubation of cocaine craving in both male and female rats. Conversely, mimicking the EB3 increase observed after prolonged withdrawal increased the motivation to consume cocaine in male rats. In mice, the overexpression of either EB3 or SRCIN1 increased dendritic spine density and altered the spine morphology of NAc medium spiny neurons. Finally, a cocaine challenge after prolonged withdrawal recapitulated most of the synaptic protein expression profiles observed at early withdrawal. These findings suggest that microtubule-associated signaling proteins such as EB3 cooperate with actin remodeling pathways, notably SRC kinase activity, to establish and maintain long-lasting cellular and behavioral alterations following cocaine self-administration. SIGNIFICANCE STATEMENT Drug-induced morphological restructuring of dendritic spines of nucleus accumbens neurons is thought to be one of the cellular substrates of long-lasting drug-associated memories. The molecular basis of these persistent changes has remained incompletely understood. Here we implicate for the first time microtubule function in this process, together with key players such as microtubule-bound protein EB3 and synaptic SRC phosphorylation. We propose that microtubule and actin remodeling cooperate during withdrawal to maintain the plastic structural changes initially established by cocaine self-administration. This work opens new translational avenues for further characterization of microtubule-associated regulatory molecules as putative drug targets to tackle relapse to drug taking., (Copyright © 2019 the authors.)

Sleep disordered breathing (SDB) affects 3-5% of the pediatric population, including neonates who are highly susceptible due to an underdeveloped ventilatory control system, and REM-dominated sleep. Although pediatric SDB is associated with poor cognitive outcomes, very little research has focused on models of pediatric SDB, particularly in neonates. In adults and neonates, intermittent hypoxia (IH), a hallmark of SDB, recapitulates multiple physiological aspects of severe SDB, including neuronal apoptosis, sex-specific cognitive deficits, and neuroinflammation. Microglia, resident CNS immune cells, are important mediators of neurodevelopment and neuroinflammation, but to date, no studies have examined the molecular properties of microglia in the context of neonatal IH. Here, we tested the hypothesis that neonatal IH will enhance microglial inflammation and sex-specifically lead to long-term changes in working memory. To test this hypothesis, we exposed post-natal day (P1) neonates with dams to an established adult model of pathological IH consisting of 2 min cycles of 10.5% O 2 followed by 21% O 2 , 8 h/day for 8 days. We then challenged the offspring with bacterial lipopolysaccharide (LPS) at P9 or at 6-8 weeks of age and immunomagnetically isolated microglia for gene expression analyses and RNA-sequencing. We also characterized neonatal CNS myeloid cell populations by flow cytometry analyses. Lastly, we examined working memory performance using a Y-maze in the young adults. Contrary to our hypothesis, we found that neonatal IH acutely augmented basal levels of microglial anti-inflammatory cytokines, attenuated microglial responses to LPS, and sex-specifically altered CNS myeloid populations. We identified multiple sex differences in basal neonatal microglial expression of genes related to chemotaxis, cognition, and aging. Lastly, we found that basal, but not LPS-induced, anti-inflammatory cytokines were augmented sex-specifically in the young adults, and that there was a significant interaction between sex and IH on basal working memory. Our results support the idea that neonates may be able to adapt to IH exposures that are pathological in adults. Further, they suggest that male and female microglial responses to IH are sex-specific, and that these sex differences in basal microglial gene expression may contribute to sexual dimorphisms in vulnerability to IH-induced cognitive disruption.

Synapse degeneration and dendritic spine dysgenesis are believed to be crucial early steps in Alzheimer's disease (AD), and correlate with cognitive deficits in AD patients. Soluble amyloid beta (Aβ)-derived oligomers, also termed Aβ-derived diffusible ligands (ADDLs), accumulate in the brain of AD patients and play a crucial role in AD pathogenesis. ADDLs bind to mature hippocampal neurons, induce structural changes in dendritic spines and contribute to neuronal death. However, mechanisms underlying structural and toxic effects are not fully understood. Here, we report that ADDLs bind to cultured mature cortical pyramidal neurons and induce spine dysgenesis. ADDL treatment induced the rapid depletion of kalirin-7, a brain-specific guanine-nucleotide exchange factor for the small GTPase Rac1, from spines. Kalirin-7 is a key regulator of dendritic spine morphogenesis and maintenance in forebrain pyramidal neurons and here we show that overexpression of kalirin-7 prevents ADDL-induced spine degeneration. Taken together, our results suggest that kalirin-7 may play a role in the early events leading to synapse degeneration, and its pharmacological activation may prevent or delay synapse pathology in AD., (© 2018 Federation of European Neuroscience Societies and John Wiley & Sons Ltd.)

Serial pattern learning is a model paradigm for studying parallel-processing in complex learning in rats. The current experiment extends the paradigm to the study of sequential memory by examining forgetting curves for the component element types that make up a serial pattern. Adult male and female rats were trained in a serial multiple choice (SMC) task in which rats learned a serial pattern of nose-poke responses in a circular array of 8 receptacles mounted on the walls of an octagonal operant chamber. The pattern was 123-234-345-456-567-678-781-818, where digits represent the clockwise positions of successive correct receptacles. Previous work has shown that chunk-boundary elements (the first element of each 3-element chunk), within-chunk elements (the second and third elements in all but the last chunk), and the violation element (the last element of the pattern) are learned via different cognitive mechanisms. After each rat was trained to an 85% correct performance criterion on the violation element, we then assessed serial pattern retention at 24-h, 2-week, and 4-week retention intervals. For chunk-boundary and within-chunk elements, forgetting was observed only at the 4-week retention interval. Sex differences were observed; females performed better than males on within-chunk elements at 24-h and 4-week retention intervals. For the violation element, significant forgetting was observed earlier at the 2-week retention interval as well as at the 4-week retention interval. Thus, pattern elements that were learned slower were forgotten faster. The experiment provides a proof of concept for evaluating forgetting curves separately for the multiple memory systems rats appear to employ concurrently in this paradigm, a method that may prove useful in characterizing the impact of relevant neurobiological manipulations on forgetting in multiple sequential memory systems., (Copyright © 2018 Elsevier Inc. All rights reserved.)

The nucleus accumbens (NAc) is a critical brain reward region that mediates the rewarding effects of drugs of abuse, including those of morphine and other opiates. Drugs of abuse induce widespread alterations in gene transcription and dendritic spine morphology in medium spiny neurons (MSNs) of the NAc that ultimately influence NAc excitability and hence reward-related behavioral responses. Growing evidence indicates that within the NAc small GTPases are common intracellular targets of drugs of abuse where these molecules regulate drug-mediated transcriptional and spine morphogenic effects. The RhoA small GTPase is among the most well-characterized members of the Ras superfamily of small GTPases, and recent work highlights an important role for hippocampal RhoA in morphine-facilitated reward behavior. Despite this, it remains unclear how RhoA pathway signaling in the NAc is affected by withdrawal from morphine. To investigate this question, using subcellular fractionation and subsequent protein profiling we examined the expression of key components of the RhoA pathway in NAc nuclear, cytoplasmic, and synaptosomal compartments during multiple withdrawal periods from repeated morphine administration. Furthermore, using in vivo viral-mediated gene transfer, we determined the consequences of revealed RhoA pathway alterations on NAc MSN dendritic spine morphology. Our findings reveal an important role for RhoA signaling cascades in mediating the effects of long-term morphine withdrawal on NAc MSN dendritic spine elimination., Open Practices: Open Science: This manuscript was awarded with the Open Materials Badge. For more information see: https://cos.io/our-services/open-science-badges/., (© 2018 International Society for Neurochemistry.)

Background: Lasting changes in gene expression in brain reward regions, including nucleus accumbens (NAc), contribute to persistent functional changes in the addicted brain. We and others have demonstrated that altered expression of several candidate transcription factors in NAc regulates drug responses. A recent large-scale genome-wide study from our group predicted transcription factor E2F3 (E2F3) as a prominent upstream regulator of cocaine-induced changes in gene expression and alternative splicing., Methods: We studied expression of two E2F3 isoforms-E2F3a and E2F3b-in mouse NAc after repeated cocaine administration and assayed the effects of overexpression or depletion of E2f3 isoforms in NAc on cocaine behavioral responses. We then performed RNA sequencing to investigate the effect of E2f3a overexpression in this region on gene expression and alternative splicing and performed quantitative chromatin immunoprecipitation at downstream targets in NAc following E2f3a overexpression or repeated cocaine exposure. Sample sizes varied between experiments and are noted in the text., Results: We showed that E2f3a, but not E2f3b, overexpression or knockdown in mouse NAc regulates cocaine-induced locomotor and place conditioning behavior. Furthermore, we demonstrated that E2f3a overexpression substantially recapitulates genome-wide transcriptional profiles and alternative splicing induced by cocaine. We further validated direct binding of E2F3a at key target genes following cocaine exposure., Conclusions: This study establishes E2F3a as a novel transcriptional regulator of cocaine action in NAc. The findings reveal a crucial role for E2F3a in the regulation of cocaine-elicited behavioral states. Moreover, the importance of this role is bolstered by the extensive recapitulation of cocaine's transcriptional effects in NAc by overexpression of E2f3a., (Copyright © 2017 Society of Biological Psychiatry. Published by Elsevier Inc. All rights reserved.)

Elucidating mechanisms by which physical exercise promotes resilience, the brain's ability to cope with prolonged stress exposure while maintaining normal psychological functioning, is a major research challenge given the high prevalence of stress-related mental disorders, including major depressive disorder. Chronic voluntary wheel running (VWR), a rodent model that mimics aspects of human physical exercise, induces the transcription factor ΔFosB in the nucleus accumbens (NAc), a key reward-related brain area. ΔFosB expression in NAc modulates stress susceptibility. Here, we explored whether VWR induction of NAc ΔFosB promotes resilience to chronic social defeat stress (CSDS). Male young-adult C57BL/6J mice were single housed for up to 21 d with or without running wheels and then subjected to 10 d of CSDS. Stress-exposed sedentary mice developed a depressive-like state, characterized by anhedonia and social avoidance, whereas stress-exposed mice that had been wheel running showed resilience. Functional inhibition of NAc ΔFosB during VWR, by viral-mediated overexpression of a transcriptionally inactive JunD mutant, reinstated susceptibility to CSDS. Within the NAc, VWR induction of ΔFosB was CREB-dependent, associated with altered dendritic morphology, and medium spiny neuron (MSN) subtype specific in the NAc core and shell subregions. Finally, when mice performed VWR following the onset of CSDS-induced social avoidance, VWR normalized such behavior. These data indicate that VWR promoted resilience to CSDS, and suggest that sustained induction of ΔFosB in the NAc underlies, at least in part, the stress resilience mediated by VWR. These findings provide a potential framework for the development of treatments for stress-associated mental illnesses based on physical exercise.

Background: Dengue and West Nile viruses are highly cross-reactive and have numerous parallels in geography, potential vector host (Aedes family of mosquitoes), and initial symptoms of infection. While the vast majority (> 80%) of both dengue and West Nile virus infections result in asymptomatic infections, a minority of individuals experience symptomatic infection and an even smaller proportion develop severe disease. The mechanisms by which these infections lead to severe disease in a subset of infected individuals is incompletely understood, but individual host differences including genetic factors and immune responses have been proposed. We sought to identify genetic risk factors that are associated with more severe disease outcomes for both viruses in order to shed light on possible shared mechanisms of resistance and potential therapeutic interventions., Methods: We applied a search strategy using four major databases (Medline, PubMed, Embase, and Global Health) to find all known genetic associations identified to date with dengue or West Nile virus disease. Here we present a review of our findings and a meta-analysis of genetic variants identified., Results: We found genetic variations that are significantly associated with infections of these viruses. In particular we found variation within the OAS1 (meta-OR = 0.83, 95% CI: 0.69-1.00) and CCR5 (meta-OR = 1.29, 95% CI: 1.08-1.53) genes is significantly associated with West Nile virus disease, while variation within MICB (meta-OR = 2.35, 95% CI: 1.68-3.29), PLCE1 (meta-OR = 0.55, 95% CI: 0.42-0.71), MBL2 (meta-OR = 1.54, 95% CI: 1.02-2.31), and IFN-γ (meta-OR = 2.48, 95% CI: 1.30-4.71), is associated with dengue disease., Conclusions: Despite substantial heterogeneity in populations studied, genes examined, and methodology, significant associations with genetic variants were found across studies within both diseases. These gene associations suggest a key role for immune mechanisms in susceptibility to severe disease. Further research is needed to elucidate the role of these genes in disease pathogenesis and may reveal additional genetic factors associated with disease severity.

The nucleus accumbens (NAc) is a primary brain reward region composed predominantly of medium spiny neurons (MSNs). In response to early withdrawal from repeated cocaine administration, de novo dendritic spine formation occurs in NAc MSNs. Much evidence indicates that this new spine formation facilitates the rewarding properties of cocaine. Early withdrawal from repeated cocaine also produces dramatic alterations in the transcriptome of NAc MSNs, but how such alterations influence cocaine's effects on dendritic spine formation remain unclear. Studies in non-neuronal cells indicate that actin cytoskeletal regulatory pathways in nuclei have a direct role in the regulation of gene transcription in part by controlling the access of co-activators to their transcription factor partners. In particular, actin state dictates the interaction between the serum response factor (SRF) transcription factor and one of its principal co-activators, MAL. Here we show that cocaine induces alterations in nuclear F-actin signaling pathways in the NAc with associated changes in the nuclear subcellular localization of SRF and MAL. Using in vivo optogenetics, the brain region-specific inputs to the NAc that mediate these nuclear changes are investigated. Finally, we demonstrate that regulated SRF expression, in turn, is critical for the effects of cocaine on dendritic spine formation and for cocaine-mediated behavioral sensitization. Collectively, these findings reveal a mechanism by which nuclear-based changes influence the structure of NAc MSNs in response to cocaine.

Most people exposed to stress do not develop depression. Animal models have shown that stress resilience is an active state that requires broad transcriptional adaptations, but how this homeostatic process is regulated remains poorly understood. In this study, we analyze upstream regulators of genes differentially expressed after chronic social defeat stress. We identify estrogen receptor α (ERα) as the top regulator of pro-resilient transcriptional changes in the nucleus accumbens (NAc), a key brain reward region implicated in depression. In accordance with these findings, nuclear ERα protein levels are altered by stress in male and female mice. Further, overexpression of ERα in the NAc promotes stress resilience in both sexes. Subsequent RNA-sequencing reveals that ERα overexpression in NAc reproduces the transcriptional signature of resilience in male, but not female, mice. These results indicate that NAc ERα is an important regulator of pro-resilient transcriptional changes, but with sex-specific downstream targets.

West Nile virus (WNV) infection is mainly asymptomatic but can be severe in elderly persons. As part of studies on immunity and aging in Connecticut, USA, we detected WNV seroconversion in 8.5% of nonimmunosuppressed and 16.8% of immunosuppressed persons. Age was not a significant seroconversion factor. Our findings suggest that immune factors affect seroconversion.

Wiskott-Aldrich syndrome protein (WASP) family verprolin homologous protein 1 (WAVE1) regulates actin-related protein 2/3 (Arp2/3) complex-mediated actin polymerization. Our previous studies have found WAVE1 to be inhibited by Cdk5-mediated phosphorylation in brain and to play a role in the regulation of dendritic spine morphology. Here we report that mice in which WAVE1 was knocked out (KO) in neurons expressing the D1 dopamine receptor (D1-KO), but not mice where WAVE1 was knocked out in neurons expressing the D2 dopamine receptor (D2-KO), exhibited a significant decrease in place preference associated with cocaine. In contrast to wild-type (WT) and WAVE1 D2-KO mice, cocaine-induced sensitized locomotor behavior was not maintained in WAVE1 D1-KO mice. After chronic cocaine administration and following withdrawal, an acute cocaine challenge induced WAVE1 activation in striatum, which was assessed by dephosphorylation. The cocaine-induced WAVE1 dephosphorylation was attenuated by coadministration of either a D1 dopamine receptor or NMDA glutamate receptor antagonist. Upon an acute challenge of cocaine following chronic cocaine exposure and withdrawal, we also observed in WT, but not in WAVE1 D1-KO mice, a decrease in dendritic spine density and a decrease in the frequency of excitatory postsynaptic AMPA receptor currents in medium spiny projection neurons expressing the D1 dopamine receptor (D1-MSNs) in the nucleus accumbens. These results suggest that WAVE1 is involved selectively in D1-MSNs in cocaine-evoked neuronal activity-mediated feedback regulation of glutamatergic synapses., Competing Interests: The authors declare no conflict of interest.

Although both males and females become addicted to cocaine, females transition to addiction faster and experience greater difficulties remaining abstinent. We demonstrate an oestrous cycle-dependent mechanism controlling increased cocaine reward in females. During oestrus, ventral tegmental area (VTA) dopamine neuron activity is enhanced and drives post translational modifications at the dopamine transporter (DAT) to increase the ability of cocaine to inhibit its function, an effect mediated by estradiol. Female mice conditioned to associate cocaine with contextual cues during oestrus have enhanced mesolimbic responses to these cues in the absence of drug. Using chemogenetic approaches, we increase VTA activity to mechanistically link oestrous cycle-dependent enhancement of VTA firing to enhanced cocaine affinity at DAT and subsequent reward processing. These data have implications for sexual dimorphism in addiction vulnerability and define a mechanism by which cellular activity results in protein alterations that contribute to dysfunctional learning and reward processing.

Repeated cocaine exposure regulates transcriptional regulation within the nucleus accumbens (NAc), and epigenetic mechanisms-such as histone acetylation and methylation on Lys residues-have been linked to these lasting actions of cocaine. In contrast to Lys methylation, the role of histone Arg (R) methylation remains underexplored in addiction models. Here we show that protein-R-methyltransferase-6 (PRMT6) and its associated histone mark, asymmetric dimethylation of R2 on histone H3 (H3R2me2a), are decreased in the NAc of mice and rats after repeated cocaine exposure, including self-administration, and in the NAc of cocaine-addicted humans. Such PRMT6 down-regulation occurs selectively in NAc medium spiny neurons (MSNs) expressing dopamine D2 receptors (D2-MSNs), with opposite regulation occurring in D1-MSNs, and serves to protect against cocaine-induced addictive-like behavioral abnormalities. Using ChIP-seq, we identified Src kinase signaling inhibitor 1 (Srcin1; also referred to as p140Cap) as a key gene target for reduced H3R2me2a binding, and found that consequent Srcin1 induction in the NAc decreases Src signaling, cocaine reward, and the motivation to self-administer cocaine. Taken together, these findings suggest that suppression of Src signaling in NAc D2-MSNs, via PRMT6 and H3R2me2a down-regulation, functions as a homeostatic brake to restrain cocaine action, and provide novel candidates for the development of treatments for cocaine addiction., Competing Interests: The authors declare no conflict of interest.

Dendritic spines are the sites of most excitatory synapses in the CNS, and opposing alterations in the synaptic structure of medium spiny neurons (MSNs) of the nucleus accumbens (NAc), a primary brain reward region, are seen at early versus late time points after cocaine administration. Here we investigate the time-dependent molecular and biochemical processes that regulate this bidirectional synaptic structural plasticity of NAc MSNs and associated changes in cocaine reward in response to chronic cocaine exposure. Our findings reveal key roles for the bidirectional synaptic expression of the Rap1b small GTPase and an associated local synaptic protein translation network in this process. The transcriptional mechanisms and pathway-specific inputs to NAc that regulate Rap1b expression are also characterized. Collectively, these findings provide a precise mechanism by which nuclear to synaptic interactions induce "metaplasticity" in NAc MSNs, and we reveal the specific effects of this plasticity on reward behavior in a brain circuit-specific manner., (Copyright © 2016 Elsevier Inc. All rights reserved.)

Mefloquine continues to be a key drug used for malaria chemoprophylaxis and treatment, despite reports of adverse events like depression and anxiety. It is unknown how mefloquine acts within the central nervous system to cause depression and anxiety or why some individuals are more vulnerable. We show that intraperitoneal injection of mefloquine in mice, when coupled to subthreshold social defeat stress, is sufficient to produce depression-like social avoidance behavior. Direct infusion of mefloquine into the nucleus accumbens (NAc), a key brain reward region, increased stress-induced social avoidance and anxiety behavior. In contrast, infusion into the ventral hippocampus had no effect. Whole cell recordings from NAc medium spiny neurons indicated that mefloquine application increases the frequency of spontaneous excitatory postsynaptic currents, a synaptic adaptation that we have previously shown to be associated with increased susceptibility to social defeat stress. Together, these data demonstrate a role for the NAc in mefloquine-induced depression and anxiety-like behaviors., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Improved treatment for major depressive disorder (MDD) remains elusive because of the limited understanding of its underlying biological mechanisms. It is likely that stress-induced maladaptive transcriptional regulation in limbic neural circuits contributes to the development of MDD, possibly through epigenetic factors that regulate chromatin structure. We establish that persistent upregulation of the ACF (ATP-utilizing chromatin assembly and remodeling factor) ATP-dependent chromatin-remodeling complex, occurring in the nucleus accumbens of stress-susceptible mice and depressed humans, is necessary for stress-induced depressive-like behaviors. We found that altered ACF binding after chronic stress was correlated with altered nucleosome positioning, particularly around the transcription start sites of affected genes. These alterations in ACF binding and nucleosome positioning were associated with repressed expression of genes implicated in susceptibility to stress. Together, our findings identify the ACF chromatin-remodeling complex as a critical component in the development of susceptibility to depression and in regulating stress-related behaviors.

Ten-eleven translocation (TET) enzymes mediate the conversion of 5-methylcytosine (5mC) to 5-hydroxymethylcytosine (5hmC), which is enriched in brain, and its ultimate DNA demethylation. However, the influence of TET and 5hmC on gene transcription in brain remains elusive. We found that ten-eleven translocation protein 1 (TET1) was downregulated in mouse nucleus accumbens (NAc), a key brain reward structure, by repeated cocaine administration, which enhanced behavioral responses to cocaine. We then identified 5hmC induction in putative enhancers and coding regions of genes that have pivotal roles in drug addiction. Such induction of 5hmC, which occurred similarly following TET1 knockdown alone, correlated with increased expression of these genes as well as with their alternative splicing in response to cocaine administration. In addition, 5hmC alterations at certain loci persisted for at least 1 month after cocaine exposure. Together, these reveal a previously unknown epigenetic mechanism of cocaine action and provide new insight into how 5hmC regulates transcription in brain in vivo.

Brain-derived neurotrophic factor (BDNF) has a crucial role in modulating neural and behavioral plasticity to drugs of abuse. We found a persistent downregulation of exon-specific Bdnf expression in the ventral tegmental area (VTA) in response to chronic opiate exposure, which was mediated by specific epigenetic modifications at the corresponding Bdnf gene promoters. Exposure to chronic morphine increased stalling of RNA polymerase II at these Bdnf promoters in VTA and altered permissive and repressive histone modifications and occupancy of their regulatory proteins at the specific promoters. Furthermore, we found that morphine suppressed binding of phospho-CREB (cAMP response element binding protein) to Bdnf promoters in VTA, which resulted from enrichment of trimethylated H3K27 at the promoters, and that decreased NURR1 (nuclear receptor related-1) expression also contributed to Bdnf repression and associated behavioral plasticity to morphine. Our findings suggest previously unknown epigenetic mechanisms of morphine-induced molecular and behavioral neuroadaptations.

Dendritic spine pathology is a key feature of several neuropsychiatric disorders. The Rac1 guanine nucleotide exchange factor kalirin-7 is critical for spine morphogenesis on cortical pyramidal neurons. Here we identify a rare coding variant in the KALRN gene region that encodes the catalytic domain, in a schizophrenia patient and his sibling with major depressive disorder. The D1338N substitution significantly diminished the protein's ability to catalyse the activation of Rac1. Contrary to wild-type kalirin-7, kalirin-7-D1338N failed to increase spine size and density. Both subjects carrying the polymorphism displayed reduced cortical volume in the superior temporal sulcus (STS), a region implicated in schizophrenia. Consistent with this, mice with reduced kalirin expression showed reduced neuropil volume in the rodent homologue of the STS. These data suggest that single amino acid changes in proteins involved in dendritic spine function can have significant effects on the structure and function of the cerebral cortex.

Background: Increasing evidence supports a role for altered gene expression in mediating the lasting effects of cocaine on the brain, and recent work has demonstrated the involvement of chromatin modifications in these alterations. However, all such studies to date have been restricted by their reliance on microarray technologies that have intrinsic limitations., Results: We use next generation sequencing methods, RNA-seq and ChIP-seq for RNA polymerase II and several histone methylation marks, to obtain a more complete view of cocaine-induced changes in gene expression and associated adaptations in numerous modes of chromatin regulation in the mouse nucleus accumbens, a key brain reward region. We demonstrate an unexpectedly large number of pre-mRNA splicing alterations in response to repeated cocaine treatment. In addition, we identify combinations of chromatin changes, or signatures, that correlate with cocaine-dependent regulation of gene expression, including those involving pre-mRNA alternative splicing. Through bioinformatic prediction and biological validation, we identify one particular splicing factor, A2BP1(Rbfox1/Fox-1), which is enriched at genes that display certain chromatin signatures and contributes to drug-induced behavioral abnormalities. Together, this delineation of the cocaine-induced epigenome in the nucleus accumbens reveals several novel modes of regulation by which cocaine alters the brain., Conclusions: We establish combinatorial chromatin and transcriptional profiles in mouse nucleus accumbens after repeated cocaine treatment. These results serve as an important resource for the field and provide a template for the analysis of other systems to reveal new transcriptional and epigenetic mechanisms of neuronal regulation.

Decreased medial prefrontal cortex (mPFC) neuronal activity is associated with social defeat-induced depression- and anxiety-like behaviors in mice. However, the molecular mechanisms underlying the decreased mPFC activity and its prodepressant role remain unknown. We show here that induction of the transcription factor ΔFosB in mPFC, specifically in the prelimbic (PrL) area, mediates susceptibility to stress. ΔFosB induction in PrL occurred selectively in susceptible mice after chronic social defeat stress, and overexpression of ΔFosB in this region, but not in the nearby infralimbic (IL) area, enhanced stress susceptibility. ΔFosB produced these effects partly through induction of the cholecystokinin (CCK)-B receptor: CCKB blockade in mPFC induces a resilient phenotype, whereas CCK administration into mPFC mimics the anxiogenic- and depressant-like effects of social stress. We previously found that optogenetic stimulation of mPFC neurons in susceptible mice reverses several behavioral abnormalities seen after chronic social defeat stress. Therefore, we hypothesized that optogenetic stimulation of cortical projections would rescue the pathological effects of CCK in mPFC. After CCK infusion in mPFC, we optogenetically stimulated mPFC projections to basolateral amygdala or nucleus accumbens, two subcortical structures involved in mood regulation. Stimulation of corticoamygdala projections blocked the anxiogenic effect of CCK, although no effect was observed on other symptoms of social defeat. Conversely, stimulation of corticoaccumbens projections reversed CCK-induced social avoidance and sucrose preference deficits but not anxiogenic-like effects. Together, these results indicate that social stress-induced behavioral deficits are mediated partly by molecular adaptations in mPFC involving ΔFosB and CCK through cortical projections to distinct subcortical targets.

The biological functions of the neuregulin 1 (NRG1) and ERBB4 genes have received much recent attention due to several studies showing associations between these genes and schizophrenia. Moreover, reduced forebrain dendritic spine density is a consistent feature of schizophrenia. It is thus important to understand the mechanisms whereby NRG1 and erbB4 modulate spine morphogenesis. Here, we show that long-term incubation with NRG1 increases both spine size and density in cortical pyramidal neurons. NRG1 also enhances the content of α-amino-3-hydroxy-5-methylisoxazole-4-propionate receptors in spines. Knockdown of ERBB4 expression prevented the effects of NRG1 on spine size, but not on spine density. The effects of NRG1 and erbB4 on spines were mediated by the RacGEF kalirin, a well-characterized regulator of dendritic spines. Finally, we show that environmental enrichment, known to promote spine growth, robustly enhances the levels of erbB4 protein in the forebrain. These findings provide a mechanistic link between NRG1 signaling and spine morphogenesis, (2013 International Society for Neurochemistry)

It is well established that behavioral sensitization to cocaine is accompanied by increased spine density and AMPA receptor (AMPAR) transmission in the nucleus accumbens (NAc), but two major questions remain unanswered. Are these adaptations mechanistically coupled? And, given that they can be dissociated from locomotor sensitization, what is their functional significance? We tested the hypothesis that the guanine-nucleotide exchange factor Kalirin-7 (Kal-7) couples cocaine-induced AMPAR and spine upregulation and that these adaptations underlie sensitization of cocaine's incentive-motivational properties-the properties that make it "wanted." Rats received eight daily injections of saline or cocaine. On withdrawal day 14, we found that Kal-7 levels and activation of its downstream effectors Rac-1 and PAK were increased in the NAc of cocaine-sensitized rats. Furthermore, AMPAR surface expression and spine density were increased, as expected. To determine whether these changes require Kal-7, a lentiviral vector expressing Kal-7 shRNA was injected into the NAc core before cocaine exposure. Knocking down Kal-7 abolished the AMPAR and spine upregulation normally seen during cocaine withdrawal. Despite the absence of these adaptations, rats with reduced Kal-7 levels developed locomotor sensitization. However, incentive sensitization, which was assessed by how rapidly rats learned to self-administer a threshold dose of cocaine, was severely impaired. These results identify a signaling pathway coordinating AMPAR and spine upregulation during cocaine withdrawal, demonstrate that locomotor and incentive sensitization involve divergent mechanisms, and link enhanced excitatory transmission in the NAc to incentive sensitization.

Depression induces structural and functional synaptic plasticity in brain reward circuits, although the mechanisms promoting these changes and their relevance to behavioral outcomes are unknown. Transcriptional profiling of the nucleus accumbens (NAc) for Rho GTPase-related genes, which are known regulators of synaptic structure, revealed a sustained reduction in RAS-related C3 botulinum toxin substrate 1 (Rac1) expression after chronic social defeat stress. This was associated with a repressive chromatin state surrounding the proximal promoter of Rac1. Inhibition of class 1 histone deacetylases (HDACs) with MS-275 rescued both the decrease in Rac1 transcription after social defeat stress and depression-related behavior, such as social avoidance. We found a similar repressive chromatin state surrounding the RAC1 promoter in the NAc of subjects with depression, which corresponded with reduced RAC1 transcription. Viral-mediated reduction of Rac1 expression or inhibition of Rac1 activity in the NAc increases social defeat-induced social avoidance and anhedonia in mice. Chronic social defeat stress induces the formation of stubby excitatory spines through a Rac1-dependent mechanism involving the redistribution of synaptic cofilin, an actin-severing protein downstream of Rac1. Overexpression of constitutively active Rac1 in the NAc of mice after chronic social defeat stress reverses depression-related behaviors and prunes stubby spines. Taken together, our data identify epigenetic regulation of RAC1 in the NAc as a disease mechanism in depression and reveal a functional role for Rac1 in rodents in regulating stress-related behaviors.

The dendritic field of a neuron, which is determined by both dendritic architecture and synaptic strength, defines the synaptic input of a cell. Once established, a neuron's dendritic field is thought to remain relatively stable throughout a cell's lifetime. Perturbations in a dendritic structure or excitatory tone of a cell and thus its dendritic field are cellular alterations thought to be correlated with a number of psychiatric disorders. Although several proteins are known to regulate the development of dendritic arborization, much less is known about the mechanisms that maintain dendritic morphology and synaptic strength. In this study, we find that afadin, a component of N-cadherin·β-catenin·α-N-catenin adhesion complexes, is required for the maintenance of established dendritic arborization and synapse number. We further demonstrate that afadin directly interacts with AMPA receptors and that loss of this protein reduces the surface expression of GluA1- and GluA2-AMPA receptor subunits. Collectively, these data suggest that afadin is required for the maintenance of dendritic structure and excitatory tone.

Dendritic spines are the sites of most excitatory synapses in the central nervous system. Recent studies have shown that spines function independently of each other, and they are currently the smallest known processing units in the brain. Spines exist in an array of morphologies, and spine structure helps dictate synaptic function. Dendritic spines are rich in actin, and actin rearrangements are critical regulators of spine morphology and density. In this review, we discuss the importance of actin in regulating dendritic spine morphogenesis, and discuss the upstream signal transduction pathways that either foster or inhibit actin polymerization. The understanding of actin regulatory pathways is best conceptualized as a hierarchical network in which molecules function in discrete levels defined by their molecular distance to actin. To this end, we focus on several classes of molecules, including guanine nucleotide exchange factors, small GTPases, small GTPase effectors, and actin binding proteins. We discuss how individual proteins in these molecular classes impact spine morphogenesis, and reveal the biochemical interactions in these networks that are responsible for shaping actin polymerization. Finally, we discuss the importance of these actin regulatory pathways in neuropsychiatric disorders., (Copyright © 2012 Wiley Periodicals, Inc.)

Repeated cocaine administration increases the dendritic arborization of nucleus accumbens neurons, but the underlying signaling events remain unknown. Here we show that repeated exposure to cocaine negatively regulates the active form of Rac1, a small GTPase that controls actin remodeling in other systems. Further, we show, using viral-mediated gene transfer, that overexpression of a dominant negative mutant of Rac1 or local knockout of Rac1 is sufficient to increase the density of immature dendritic spines on nucleus accumbens neurons, whereas overexpression of a constitutively active Rac1 or light activation of a photoactivatable form of Rac1 blocks the ability of repeated cocaine exposure to produce this effect. Downregulation of Rac1 activity likewise promotes behavioral responses to cocaine exposure, with activation of Rac1 producing the opposite effect. These findings establish that Rac1 signaling mediates structural and behavioral plasticity in response to cocaine exposure.