The synapsins: beyond the regulation of neurotransmitter release

Lipopolysaccharides from Porphyromonas gingivalis indirectly induce neuronal GSK3β-dependent synaptic defects and cause cognitive decline in a low-amyloid-β-concentration environment in Alzheimer's disease

BackgroundLipopolysaccharides from Porphyromonas gingivalis (P.gLPS) are involved in the pathology of Alzheimer's disease (AD). However, the effect of P.gLPS on synaptic defects remains unclear.ObjectiveIn this study, we tested our hypothesis that P.gLPS induces synaptic defects in a low-amyloid-beta (Aβ)-concentration environment.MethodsMG6 microglia or N2a neurons was treated with P.gLPS (0.1 μg/mL), soluble Aβ42 (0.1 μM) or AL (combined P.gLPS and soluble Aβ42 at 0.1 μM).ResultsIn cultured MG6 microglia, increased the mRNA expression of TNF-α, IL-1β and IL-6 and the TNF-α release in parallel with increased NF-κB activation. In cultured N2a neurons, treatment with Aβ42, P.gLPS, and AL did not affect the mRNA expression of synapsin1 (SYN1) or post-synaptic density protein-95 (PSD-95). However, the treatment with conditioned medium from AL-exposed MG6 microglia (AL-MCM) significantly reduced the mRNA and protein expression of SYN1, PSD-95, and nuclear translocation of repressor element-1 silencing transcription factor (REST) but significantly increased the mRNA expression of TNF receptor type I (at 48 h) and glycogen synthase kinase (GSK)3β (at 24 h). TWS119 pretreatment (5 μM), a GSK3β specific inhibitor, significantly reversed the AL-MCM-induced reduction in the mRNA expression of SYN1 and PSD-95 and nuclear translocation of REST in cultured N2a neurons. In APPNL-F/NL-F mice, the immunofluorescence intensity of SYN1 and PSD-95 in cortical neurons was positively correlated with the index of the memory test but negatively correlated with that of TNF-α-positive microglia.ConclusionsThese observations demonstrate that P.gLPS induces neuronal GSK3β-dependent synaptic defects in a low-Aβ concentration environment via microglial activation.

Neural Stem Cells Transplanted into Rhesus Monkey Cortical Traumatic Brain Injury Can Survive and Differentiate into Neurons

Cortical traumatic brain injury (TBI) is a major cause of cognitive impairment accompanied by motor and behavioral deficits, and there is no effective treatment strategy in the clinic. Cell transplantation is a promising therapeutic strategy, and it is necessary to verify the survival and differentiation of cells after transplantation in large animal models like rhesus monkeys. In this study, we transplanted neural stem cells (NSCs) and simultaneously injected basic fibroblast growth factor/epidermal growth factor (bFGF/EGF) into the cortex (visual and sensory cortices) of rhesus monkeys with superficial TBI. The results showed that the transplanted NSCs did not enter the cerebrospinal fluid (CSF) and were confined to the transplantation site for at least one year. The transplanted NSCs differentiated into mature neurons that formed synaptic connections with host neurons, but glial scar formation between the graft and the host tissue did not occur. This study is the first to explore the repairing effect of transplanting NSCs into the superficial cerebral cortex of rhesus monkeys after TBI, and the results show the ability of NSCs to survive long-term and differentiate into neurons, demonstrating the potential of NSC transplantation for cortical TBI.

Activation of mTORC1 Signaling Cascade in Hippocampus and Medial Prefrontal Cortex Is Required for Antidepressant Actions of Vortioxetine in Mice

BACKGROUND

Although thought of as a multimodal-acting antidepressant targeting the serotonin system, more molecules are being shown to participate in the antidepressant mechanism of vortioxetine. A previous report has shown that vortioxetine administration enhanced the expression of rapamycin complex 1 (mTORC1) in neurons. It has been well demonstrated that mTORC1 participates in not only the pathogenesis of depression but also the pharmacological mechanisms of many antidepressants. Therefore, we speculate that the antidepressant mechanism of vortioxetine may require mTORC1.

METHODS

Two mouse models of depression (chronic social defeat stress and chronic unpredictable mild stress) and western blotting were first used together to examine whether vortioxetine administration produced reversal effects against the chronic stress-induced downregulation in the whole mTORC1 signaling cascade in both the hippocampus and medial prefrontal cortex (mPFC). Then, LY294002, U0126, and rapamycin were used together to explore whether the antidepressant effects of vortioxetine in mouse models of depression were attenuated by pharmacological blockade of the mTORC1 system. Furthermore, lentiviral-mTORC1-short hairpin RNA-enhanced green fluorescence protein (LV-mTORC1-shRNA-EGFP) was adopted to examine if genetic blockade of mTORC1 also abolished the antidepressant actions of vortioxetine in mice.

RESULTS

Vortioxetine administration produced significant reversal effects against the chronic stress-induced downregulation in the whole mTORC1 signaling cascade in both the hippocampus and mPFC. Both pharmacological and genetic blockade of the mTORC1 system notably attenuated the antidepressant effects of vortioxetine in mice.

CONCLUSIONS

Activation of the mTORC1 system in the hippocampus and mPFC is required for the antidepressant actions of vortioxetine in mice.

Lead-Induced Motor Dysfunction Is Associated with Oxidative Stress, Proteome Modulation, and Neurodegeneration in Motor Cortex of Rats

Lead (Pb) is a toxic metal with great neurotoxic potential. The aim of this study was to investigate the effects of a long-term Pb intoxication on the global proteomic profile, oxidative biochemistry and neuronal density in motor cortex of adult rats, and the possible outcomes related to motor functions. For this, Wistar rats received for 55 days a dose of 50 mg/Kg of Pb acetate by intragastric gavage. Then, the motor abilities were evaluated by open field and inclined plane tests. To investigate the possible oxidative biochemistry modulation, the levels of pro-oxidant parameters as lipid peroxidation and nitrites were evaluated. The global proteomic profile was evaluated by ultraefficiency liquid chromatography system coupled with mass spectrometry (UPLC/MS) followed by bioinformatic analysis. Moreover, it was evaluated the mature neuron density by anti-NeuN immunostaining. The statistical analysis was performed through Student's t-test, considering p < 0.05. We observed oxidative stress triggering by the increase in malonaldehyde and nitrite levels in motor cortex. In the proteomic analysis, the motor cortex presented alterations in proteins associated with neural functioning, morphological organization, and neurodegenerative features. In addition, it was observed a decrease in the number of mature neurons. These findings, associated with previous evidences observed in spinal cord, cerebellum, and hippocampus under the same Pb administration protocol, corroborate with the motor deficits in the rats towards Pb. Thus, we conclude that the long-term administration to Pb in young Wistar rats triggers impairments at several organizational levels, such as biochemical and morphological, which resulted in poor motor performance.

The Neurotrophic-Like Effect of Carvacrol: Perspective for Axonal and Synaptic Regeneration

Carvacrol (CARV) is a phytochemical widely used as flavoring, preservative, and fragrance in food and cosmetic industries. CARV is able to cross the blood-brain barrier (BBB) and has demonstrated protective potential against neurodegenerative diseases by several mechanisms, including antioxidant, anti-inflammatory, anticholinesterase, and antiapoptotic effects. However, it is not known whether CARV is able to modulate axonal and synaptic plasticity, crucial events in cognition, memory, and learning. Abnormalities in axonal and synaptic plasticity, low levels of neurotrophins, and bioenergetic failure have been associated with the pathogenesis of neurodegenerative diseases, including Parkinson's (PD) and Alzheimer's diseases (ADs). Small lipophilic molecules with neurotrophic activity might be able to restore the axonal and synaptic networks that are lost in neurodegenerative processes. Therefore, this study investigated the neurotrophic potential of CARV in PC12 cell-based neuronal model. Carvacrol induced neurite outgrowth by activating the NGF high-affinity trkA receptor and the downstream PI3K-AKT and MAPK-ERK pathways, without depending on NGF. In addition, CARV increased the expression of proteins involved in neuronal plasticity (β-tubulin III, F-actin, 200-kDa neurofilament, GAP-43 and synapsin-I) and improved bioenergetics (AMPKα, p-AMPKα, and ATP). Our study showed, for the first time, a promising neurotrophic mechanism of CARV that could be beneficial in neurodegenerative and neurological diseases.

Organophosphorus flame retardants are developmental neurotoxicants in a rat primary brainsphere in vitro model

Due to regulatory bans and voluntary substitutions, halogenated polybrominated diphenyl ether (PBDE) flame retardants (FR) are increasingly substituted by mainly organophosphorus FR (OPFR). Leveraging a 3D rat primary neural organotypic in vitro model (rat brainsphere), we compare developmental neurotoxic effects of BDE-47-the most abundant PBDE congener-with four OPFR (isopropylated phenyl phosphate-IPP, triphenyl phosphate-TPHP, isodecyl diphenyl phosphate-IDDP, and tricresyl phosphate (also known as trimethyl phenyl phosphate)-TMPP). Employing mass spectroscopy-based metabolomics and transcriptomics, we observe at similar human-relevant non-cytotoxic concentrations (0.1-5 µM) stronger developmental neurotoxic effects by OPFR. This includes toxicity to neurons in the low µM range; all FR decrease the neurotransmitters glutamate and GABA (except BDE-47 and TPHP). Furthermore, n-acetyl aspartate (NAA), considered a neurologic diagnostic molecule, was decreased by all OPFR. At similar concentrations, the FR currently in use decreased plasma membrane dopamine active transporter expression, while BDE-47 did not. Several findings suggest astrogliosis induced by the OPFR, but not BDE-47. At the 5 µM concentrations, the OPFR more than BDE-47 interfered with myelination. An increase of cytokine gene and receptor expressions suggests that exposure to OPFR may induce an inflammatory response. Pathway/category overrepresentation shows disruption in 1) transmission of action potentials, cell-cell signaling, synaptic transmission, receptor signaling, (2) immune response, inflammation, defense response, (3) cell cycle and (4) lipids metabolism and transportation. Taken together, this appears to be a case of regretful substitution with substances not less developmentally neurotoxic in a primary rat 3D model.

Development of optically controlled "living electrodes" with long-projecting axon tracts for a synaptic brain-machine interface

For implantable neural interfaces, functional/clinical outcomes are challenged by limitations in specificity and stability of inorganic microelectrodes. A biological intermediary between microelectrical devices and the brain may improve specificity and longevity through (i) natural synaptic integration with deep neural circuitry, (ii) accessibility on the brain surface, and (iii) optogenetic manipulation for targeted, light-based readout/control. Accordingly, we have developed implantable "living electrodes," living cortical neurons, and axonal tracts protected within soft hydrogel cylinders, for optobiological monitoring/modulation of brain activity. Here, we demonstrate fabrication, rapid axonal outgrowth, reproducible cytoarchitecture, and simultaneous optical stimulation and recording of these tissue engineered constructs in vitro. We also present their transplantation, survival, integration, and optical recording in rat cortex as an in vivo proof of concept for this neural interface paradigm. The creation and characterization of these functional, optically controllable living electrodes are critical steps in developing a new class of optobiological tools for neural interfacing.

IGF-1 treatment causes unique transcriptional response in neurons from individuals with idiopathic autism

BACKGROUND

Research evidence accumulated in the past years in both rodent and human models for autism spectrum disorders (ASD) have established insulin-like growth factor 1 (IGF-1) as one of the most promising ASD therapeutic interventions to date. ASD is phenotypically and etiologically heterogeneous, making it challenging to uncover the underlying genetic and cellular pathophysiology of the condition; and to efficiently design drugs with widespread clinical benefits. While IGF-1 effects have been comprehensively studied in the literature, how IGF-1 activity may lead to therapeutic recovery in the ASD context is still largely unknown.

METHODS

In this study, we used a previously characterized neuronal population derived from induced pluripotent stem cells (iPSC) from neurotypical controls and idiopathic ASD individuals to study the transcriptional signature of acutely and chronically IGF-1-treated cells.

RESULTS

We present a comprehensive list of differentially regulated genes and molecular interactions resulting from IGF-1 exposure in developing neurons from controls and ASD individuals. Our results indicate that IGF-1 treatment has a different impact on neurons from ASD patients compared to controls. Response to IGF-1 treatment in neurons derived from ASD patients was heterogeneous and correlated with IGF-1 receptor expression, indicating that IGF-1 response may have responder and non-responder distinctions across cohorts of ASD patients. Our results suggest that caution should be used when predicting the effect of IGF-1 treatment on ASD patients using neurotypical controls. Instead, IGF-1 response should be studied in the context of ASD patients' neural cells.

LIMITATIONS

The limitation of our study is that our cohort of eight sporadic ASD individuals is comorbid with macrocephaly in childhood. Future studies will address weather downstream transcriptional response of IGF-1 is comparable in non-macrocephalic ASD cohorts.

CONCLUSIONS

The results presented in this study provide an important resource for researchers in the ASD field and underscore the necessity of using ASD patient lines to explore ASD neuronal-specific responses to drugs such as IGF-1. This study further helps to identify candidate pathways and targets for effective clinical intervention and may help to inform clinical trials in the future.

Ascorbic acid presents rapid behavioral and hippocampal synaptic plasticity effects

Growing evidence has suggested that ascorbic acid may exhibit rapid anxiolytic and antidepressant-like effects. In this study the effects of a single administration of ascorbic acid (1 mg/kg, p.o.), ketamine (1 mg/kg, i.p., a fast-acting antidepressant) and fluoxetine (10 mg/kg, p.o., conventional antidepressant) were investigated on: a) behavioral performance in the novelty suppressed feeding (NSF) test; b) hippocampal synaptic protein immunocontent; c) dendritic spine density and morphology in the dorsal and ventral dentate gyrus (DG) of the hippocampus and d) hippocampal dendritic arborization. Ascorbic acid or ketamine, but not fluoxetine, decreased the latency to feed in the NSF test in mice. This effect was accompanied by increased p70S6K (Thr³⁸⁹) phosphorylation 1 h after ascorbic acid or ketamine treatment, although only ascorbic acid increased synapsin I immunocontent. Ketamine administration increased the dendritic spine density in the dorsal DG, but none of the treatments affected the maturation of dendritic spines in this region. In addition, both ascorbic acid and ketamine increased the dendritic spine density in the ventral DG, particularly the mature spines. Sholl analysis demonstrated no effect of any treatment on hippocampal dendritic arborization. Altogether, the results provide evidence that the behavioral and synaptic responses observed following ascorbic acid administration might occur via the upregulation of synaptic proteins, dendritic spine density, and maturation in the ventral DG, similar to ketamine. These findings contribute to understand the cellular targets implicated in its antidepressant/anxiolytic behavioral responses and support the notion that ascorbic acid may share with ketamine the ability to increase synaptic function.

Distribution of Pheromone Biosynthesis-Activating Neuropeptide in the Central Nervous System of Plutella xylostella (Lepidoptera: Plutellidae)

Insect neuropeptides in the pyrokinin/pheromone biosynthesis-activating neuropeptide (PBAN) family are actively involved in many essential endocrinal functions and serve as potential targets in the search for novel insect control agents. Here, we dissect the nervous system of larval, pupal, and adult Plutella xylostella (L.) (Lepidoptera: Plutellidae) and describe the ganglion morphology and localization of PBAN during different insect developmental stages. Our results show that the central nervous system (CNS) of this species consists of four types of ganglia: cerebral ganglia (brain), subesophageal ganglion (SEG), thoracic ganglia, and abdominal ganglia. A two-lobed brain is connected to the reniform SEG with a nerve cord in larvae and prepupae, whereas in the late pupae and adults, the brain and SEG are fused, forming a brain-SEG complex. The larvae and prepupae have eight abdominal ganglia each, whereas the late pupae and adults each have four abdominal ganglia. Furthermore, all life stages of P. xylostella had similar patterns of PBAN immunoreactivity in the CNS, and the accumulation of PBAN was similar during all life stages except in adult males. PBAN immunoreactive signals were observed in the brain and SEG, and fluorescence signals originating in the SEG extended the entire length of the ventral nerve cord, ending in the terminal abdominal ganglia. Our results provide morphological data that inform the development and evolution of the CNS. In addition, they indicate that the nervous system contains PBAN, which could be used to control P. xylostella populations.

Systemic Blockade of the CB1 Receptor Augments Hippocampal Gene Expression Involved in Synaptic Plasticity but Perturbs Hippocampus-Dependent Learning Task

Chronic and acute agonism as well as acute antagonism of CB₁ receptors reveal modulation of learning and memory during stable performance of a delayed-nonmatch-to-sample (DNMS) memory task. However, it remains unclear how chronic blockade of the CB₁ receptor alters acquisition of the behavioral task. We examined the effects of chronic rimonabant exposure during DNMS task acquisition to determine if blockade of the CB₁ receptor with the antagonist rimonabant enhanced acquisition of operant task. Long-Evans rats, trained in the DNMS task before imposition of the trial delay, were surgically implanted with osmotic mini pumps to administer rimonabant (1.0 mg/kg/day) or vehicle (dimethyl sulfoxide/Tween-80/Saline). Following surgical recovery, DNMS training was resumed with the imposition of gradually longer delays (1-30 sec). The number of days required to achieve stable performance with either increasing length of delay or reversal of task contingency was compared between vehicle and rimonabant-treated rats. Following the completion of DNMS training, animals were euthanized, and both hippocampi were harvested for gene expression assay analysis. Rimonabant treatment animals required more time to achieve stable DNMS performance than vehicle-treated controls. Quantitative real-time polymerase chain reaction analysis revealed that the expressions of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor subunit, brain-derived neurotrophic factor, and synapsin 1 (Syn1) were significantly increased. These results are consistent with rimonabant increasing mRNAs for proteins associated with hippocampal synapse remodeling, but that those alterations did not necessarily accelerate the acquisition of an operant behavioral task that required learning new contingencies.

Synaptic loss in schizophrenia: a meta-analysis and systematic review of synaptic protein and mRNA measures

Although synaptic loss is thought to be core to the pathophysiology of schizophrenia, the nature, consistency and magnitude of synaptic protein and mRNA changes has not been systematically appraised. Our objective was thus to systematically review and meta-analyse findings. The entire PubMed database was searched for studies from inception date to the 1st of July 2017. We selected case-control postmortem studies in schizophrenia quantifying synaptic protein or mRNA levels in brain tissue. The difference in protein and mRNA levels between cases and controls was extracted and meta-analysis conducted. Among the results, we found a significant reduction in synaptophysin in schizophrenia in the hippocampus (effect size: -0.65, p < 0.01), frontal (effect size: -0.36, p = 0.04), and cingulate cortices (effect size: -0.54, p = 0.02), but no significant changes for synaptophysin in occipital and temporal cortices, and no changes for SNAP-25, PSD-95, VAMP, and syntaxin in frontal cortex. There were insufficient studies for meta-analysis of complexins, synapsins, rab3A and synaptotagmin and mRNA measures. Findings are summarised for these, which generally show reductions in SNAP-25, PSD-95, synapsin and rab3A protein levels in the hippocampus but inconsistency in other regions. Our findings of moderate-large reductions in synaptophysin in hippocampus and frontal cortical regions, and a tendency for reductions in other pre- and postsynaptic proteins in the hippocampus are consistent with models that implicate synaptic loss in schizophrenia. However, they also identify potential differences between regions and proteins, suggesting synaptic loss is not uniform in nature or extent.

Glycans and glycosaminoglycans in neurobiology: key regulators of neuronal cell function and fate

The aim of the present study was to examine the roles of l-fucose and the glycosaminoglycans (GAGs) keratan sulfate (KS) and chondroitin sulfate/dermatan sulfate (CS/DS) with selected functional molecules in neural tissues. Cell surface glycans and GAGs have evolved over millions of years to become cellular mediators which regulate fundamental aspects of cellular survival. The glycocalyx, which surrounds all cells, actuates responses to growth factors, cytokines and morphogens at the cellular boundary, silencing or activating downstream signaling pathways and gene expression. In this review, we have focused on interactions mediated by l-fucose, KS and CS/DS in the central and peripheral nervous systems. Fucose makes critical contributions in the area of molecular recognition and information transfer in the blood group substances, cytotoxic immunoglobulins, cell fate-mediated Notch-1 interactions, regulation of selectin-mediated neutrophil extravasation in innate immunity and CD-34-mediated new blood vessel development, and the targeting of neuroprogenitor cells to damaged neural tissue. Fucosylated glycoproteins regulate delivery of synaptic neurotransmitters and neural function. Neural KS proteoglycans (PGs) were examined in terms of cellular regulation and their interactive properties with neuroregulatory molecules. The paradoxical properties of CS/DS isomers decorating matrix and transmembrane PGs and the positive and negative regulatory cues they provide to neurons are also discussed.

The Role of Synapsins in Neurological Disorders

Synapsins serve as flagships among the presynaptic proteins due to their abundance on synaptic vesicles and contribution to synaptic communication. Several studies have emphasized the importance of this multi-gene family of neuron-specific phosphoproteins in maintaining brain physiology. In the recent times, increasing evidence has established the relevance of alterations in synapsins as a major determinant in many neurological disorders. Here, we give a comprehensive description of the diverse roles of the synapsin family and the underlying molecular mechanisms that contribute to several neurological disorders. These physiologically important roles of synapsins associated with neurological disorders are just beginning to be understood. A detailed understanding of the diversified expression of synapsins may serve to strategize novel therapeutic approaches for these debilitating neurological disorders.

A novel non genomic glucocorticoid signaling mediated by a membrane palmitoylated glucocorticoid receptor cross talks with GnRH in gonadotrope cells

Glucocorticoid hormones (GC) are the main stress mediators associated with reproductive disorders. GC exert their effects through activation of the glucocorticoid receptor (GR) principally acting as a transcription factor. Beside well-established GR-mediated genomic actions, several lines of evidence suggest a role for rapid membrane-initiated GC signaling in gonadotrope cells triggered by a membrane-associated GR. Herein, we demonstrate the existence of a specific membrane-initiated GC signaling in LβT2 gonadotrope cells involving two related phosphoproteins: Ca²⁺/Calmodulin-dependent protein kinase II (CaMKII) and synapsin-I. Within 5 min, LβT2 cells treated with stress range of 10⁻⁷ M Corticosterone or a membrane impermeable-GC, BSA-conjugated corticosterone, exhibited a 2-fold increase in levels of phospho-CaMKII and phospho-synapsin-I. Biochemical approaches revealed that this rapid signaling is promoted by a palmitoylated GR. Importantly, GC significantly alter GnRH-induced CaMKII phosphorylation, consistent with a novel cross-talk between the GnRH receptor and GC. This negative effect of GC on GnRH signaling was further observed on LH release by mouse pituitary explants. Altogether, our work provides new findings in GC field by bringing novel understanding on how GR integrates plasma membrane, allowing GC membrane-initiated signaling that differs in presence of GnRH to disrupt GnRH-dependent signaling and LH secretion.

Rare Synaptogenesis-Impairing Mutations in SLITRK5 Are Associated with Obsessive Compulsive Disorder

Obsessive compulsive disorder (OCD) is substantially heritable, but few molecular genetic risk factors have been identified. Knockout mice lacking SLIT and NTRK-Like Family, Member 5 (SLITRK5) display OCD-like phenotypes including serotonin reuptake inhibitor-sensitive pathologic grooming, and corticostriatal dysfunction. Thus, mutations that impair SLITRK5 function may contribute to the genetic risk for OCD. We re-sequenced the protein-coding sequence of the human SLITRK5 gene (SLITRK5) in three hundred and seventy seven OCD subjects and compared rare non-synonymous mutations (RNMs) in that sample with similar mutations in the 1000 Genomes database. We also performed in silico assessments and in vitro functional synaptogenesis assays on the Slitrk5 mutations identified. We identified four RNM's among these OCD subjects. There were no significant differences in the prevalence or in silico effects of rare non-synonymous mutations in the OCD sample versus controls. Direct functional testing of recombinant SLITRK5 proteins found that all mutations identified in OCD subjects impaired synaptogenic activity whereas none of the pseudo-matched mutations identified in 1000 Genomes controls had significant effects on SLITRK5 function (Fisher's exact test P = 0.028). These results demonstrate that rare functional mutations in SLITRK5 contribute to the genetic risk for OCD in human populations. They also highlight the importance of biological characterization of allelic effects in understanding genotype-phenotype relationships as there were no statistical differences in overall prevalence or bioinformatically predicted effects of OCD case versus control mutations. Finally, these results converge with others to highlight the role of aberrant synaptic function in corticostriatal neurons in the pathophysiology of OCD.

Neurons Differentiated from Transplanted Stem Cells Respond Functionally to Acoustic Stimuli in the Awake Monkey Brain

Here, we examine whether neurons differentiated from transplanted stem cells can integrate into the host neural network and function in awake animals, a goal of transplanted stem cell therapy in the brain. We have developed a technique in which a small "hole" is created in the inferior colliculus (IC) of rhesus monkeys, then stem cells are transplanted in situ to allow for investigation of their integration into the auditory neural network. We found that some transplanted cells differentiated into mature neurons and formed synaptic input/output connections with the host neurons. In addition, c-Fos expression increased significantly in the cells after acoustic stimulation, and multichannel recordings indicated IC specific tuning activities in response to auditory stimulation. These results suggest that the transplanted cells have the potential to functionally integrate into the host neural network.

A single dose of vortioxetine, but not ketamine or fluoxetine, increases plasticity-related gene expression in the rat frontal cortex

Ketamine is a non-competitive N-methyl-D-aspartate (NMDA) receptor antagonist that has been shown to induce a rapid antidepressant effect in treatment-resistant patients. Vortioxetine is a multimodal-acting antidepressant that exert its therapeutic activity through serotonin (5-hydroxytryptamine; 5-HT) reuptake inhibition and modulation of several 5-HT receptors. In clinical trials, vortioxetine improves depression symptoms and cognitive dysfunction. Neuroplasticity as well as serotonergic and glutamatergic signaling attain significant roles in depression pathophysiology and antidepressant responses. Here, we investigate the effects of ketamine and vortioxetine on gene expression related to serotonergic and glutamatergic neurotransmission as well as neuroplasticity and compare them to those of the selective serotonin reuptake inhibitor fluoxetine. Rats were injected with fluoxetine (10mg/kg), ketamine (15mg/kg), or vortioxetine (10mg/kg) at 2, 8, 12, or 27h prior to harvesting of the frontal cortex and hippocampus. mRNA levels were measured by real-time quantitative polymerase chain reaction (qPCR). The main finding was that vortioxetine enhanced plasticity-related gene expression (Mtor, Mglur1, Pkcα, Homer3, Spinophilin, and Synapsin3) in the frontal cortex at 8h after a single dose. Ingenuity pathway analysis of this subset of data identified a biological network that was engaged by vortioxetine and is plausibly associated with neuroplasticity. Transcript levels had returned to baseline levels 12h after injection. Only minor effects on gene expression were found for ketamine or fluoxetine. In conclusion, acute vortioxetine, but not fluoxetine or ketamine, transiently increased plasticity-related gene expression in the frontal cortex. These effects may be ascribed to the direct 5-HT receptor activities of vortioxetine.

Ganglioside GQ1b induces dopamine release through the activation of Pyk2

Growing evidence indicates that GQ1b, one of the gangliosides members, contributes to synaptic transmission and synapse formation. Previous studies have shown that GQ1b could enhance depolarization induced neurotransmitter release, while the role of GQ1b in asynchronous release is still largely unknown. Here in our result, we found low concentration of GQ1b, but not GT1b or GD1b (which were generated from GQ1b by plasma membrane-associated sialidases), evoked asynchronous dopamine (DA) release from both clonal rat pheochromocytoma PC12 cells and rat striatal slices significantly. The release peaked at 2 min after GQ1b exposure, and lasted for more than 6 min. This effect was caused by the enhancement of intracellular Ca(2+) and the activation of Pyk2. Inhibition of Pyk2 by PF-431396 (a dual inhibitor of Pyk2 and FAK) or Pyk2 siRNA abolished DA release induced by GQ1b. Moreover, Pyk2 Y402, but not other tyrosine site, was phosphorylated at the peaking time. The mutant of Pyk2 Y402 (Pyk2-Y402F) was built to confirm the essential role of Y402 activation. Further studies revealed that activated Pyk2 stimulated ERK1/2 and p-38, while only the ERK1/2 activation was indispensable for GQ1b induced DA release, which interacted with Synapsin I directly and led to its phosphorylation, then depolymerization of F-actin, thus contributed to DA release. In conclusion, low concentration of GQ1b is able to enhance asynchronous DA release through Pyk2/ERK/Synapsin I/actin pathway. Our findings provide new insights into the role of GQ1b in neuronal communication, and implicate the potential application of GQ1b in neurological disorders.

De novo assembly and characterization of tissue-specific transcriptome in the endangered golden mahseer, Tor putitora

The golden mahseer (Tor putitora) graces most of the Himalayan Rivers of India and neighboring South Asian countries. Despite its several importance as a research model, as food, and in sport fishing, knowledge on transcriptome database is nil. Therefore, it was targeted to develop reference transcriptome databases of the species using next-generation sequencing. In the present study, 100,540,130 high-quality paired-end reads were obtained from six cDNA libraries of spleen, liver, gill, kidney, muscle, and brain with 28.4 GB data using Illumina paired-end sequencing technology. Tissue-specific transcriptomes as well as complete transcriptome assembly were analyzed for concise representation of the study. In brief, the de novo assembly of individual tissue resulted in an average of 31,829 (18,512–46,348) contigs per sample, while combined transcriptome comprised 77,907 unique transcript fragments (unigenes) assembled from reads of six tissues. Approximately 75,407 (96.8%) unigenes could be annotated according to their homology matches in the nr, SwisseProt, GO, or KEGG databases. Comparative analysis showed that 84% of the unigenes have significant similarity to zebra fish RefSeq proteins. Tissue-specific-dominated genes were also identified to hypothesize their localization and expression in individual tissue. In addition, 2485 simple sequence repeats (SSRs) were detected from 77,907 transcripts in the combined transcriptome of the golden mahseer. This study has generated organ-specific transcriptome profiles, which will be helpful to understand the local adaptation, genome evolution, and also future functional studies on immune system of the golden mahseer.

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Organ specific and concatenated transcriptome of 6 organs of golden mahseer was generated using illumina sequencing.

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A total of 100,540,130 high-quality paired-ends reads with 28.4 GB data that assembled into 77,907 contigs were obtained.

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Contigs were annotated using GO and KEGG pathway and organ-specific few genes were identified.

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Thirty four usable SSR markers were extracted from 2485 identified.

Fluoxetine regulates mTOR signalling in a region-dependent manner in depression-like mice

Previous studies have demonstrated that the mammalian target of rapamycin (mTOR) signaling pathway has an important role in ketamine-induced, rapid antidepressant effects despite the acute administration of fluoxetine not affecting mTOR phosphorylation in the brain. However, the effects of long-term fluoxetine treatment on mTOR modulation have not been assessed to date. In the present study, we examined whether fluoxetine, a type of commonly used antidepressant agent, alters mTOR signaling following chronic administration in different brain regions, including the frontal cortex, hippocampus, amygdala and hypothalamus. We also investigated whether fluoxetine enhanced synaptic protein levels in these regions via the activation of the mTOR signaling pathway and its downstream regulators, p70S6K and 4E-BP-1. The results indicated that chronic fluoxetine treatment attenuated the chronic, unpredictable, mild stress (CUMS)-induced mTOR phosphorylation reduction in the hippocampus and amygdala of mice but not in the frontal cortex or the hypothalamus. Moreover, the CUMS-decreased PSD-95 and synapsin I levels were reversed by fluoxetine, and these effects were blocked by rapamycin only in the hippocampus. In conclusion, our findings suggest that chronic treatment with fluoxetine can induce synaptic protein expression by activating the mTOR signaling pathway in a region-dependent manner and mainly in the hippocampus.

A nutrient combination designed to enhance synapse formation and function improves outcome in experimental spinal cord injury

Spinal cord injury leads to major neurological impairment for which there is currently no effective treatment. Recent clinical trials have demonstrated the efficacy of Fortasyn® Connect in Alzheimer's disease. Fortasyn® Connect is a specific multi-nutrient combination containing DHA, EPA, choline, uridine monophosphate, phospholipids, and various vitamins. We examined the effect of Fortasyn® Connect in a rat compression model of spinal cord injury. For 4 or 9 weeks following the injury, rats were fed either a control diet or a diet enriched with low, medium, or high doses of Fortasyn® Connect. The medium-dose Fortasyn® Connect-enriched diet showed significant efficacy in locomotor recovery after 9 weeks of supplementation, along with protection of spinal cord tissue (increased neuronal and oligodendrocyte survival, decreased microglial activation, and preserved axonal integrity). Rats fed the high-dose Fortasyn® Connect-enriched diet for 4 weeks showed a much greater enhancement of locomotor recovery, with a faster onset, than rats fed the medium dose. Bladder function recovered quicker in these rats than in rats fed the control diet. Their spinal cord tissues showed a smaller lesion, reduced neuronal and oligodendrocyte loss, decreased neuroinflammatory response, reduced astrocytosis and levels of inhibitory chondroitin sulphate proteoglycans, and better preservation of serotonergic axons than those of rats fed the control diet. These results suggest that this multi-nutrient preparation has a marked therapeutic potential in spinal cord injury, and raise the possibility that this original approach could be used to support spinal cord injured patients.

Hoxb8 intersection defines a role for Lmx1b in excitatory dorsal horn neuron development, spinofugal connectivity, and nociception

Spinal cord neurons respond to peripheral noxious stimuli and relay this information to higher brain centers, but the molecules controlling the assembly of such pathways are poorly known. In this study, we use the intersection of Lmx1b and Hoxb8::Cre expression in the spinal cord to genetically define nociceptive circuits. Specifically, we show that Lmx1b, previously shown to be expressed in glutamatergic dorsal horn neurons and critical for dorsal horn development, is expressed in nociceptive dorsal horn neurons and that its deletion results in the specific loss of excitatory dorsal horn neurons by apoptosis, without any effect on inhibitory neuron numbers. To assess the behavioral consequences of Lmx1b deletion in the spinal cord, we used the brain-sparing driver Hoxb8::Cre. We show that such a deletion of Lmxb1 leads to a robust reduction in sensitivity to mechanical and thermal noxious stimulation. Furthermore, such conditional mutant mice show a loss of a subpopulation of glutamatergic dorsal horn neurons, abnormal sensory afferent innervations, and reduced spinofugal innervation of the parabrachial nucleus and the periaqueductal gray, important nociceptive structures. Together, our results demonstrate an important role for the intersection of Lmx1b and Hoxb8::cre expression in the development of nociceptive dorsal horn circuits critical for mechanical and thermal pain processing.

Calcium current homeostasis and synaptic deficits in hippocampal neurons from Kelch-like 1 knockout mice

Kelch-like 1 (KLHL1) is a neuronal actin-binding protein that modulates voltage-gated Ca_V2.1 (P/Q-type) and Ca_V3.2 (α_1H T-type) calcium channels; KLHL1 knockdown experiments (KD) cause down-regulation of both channel types and altered synaptic properties in cultured rat hippocampal neurons (Perissinotti et al., 2014). Here, we studied the effect of ablation of KLHL1 on calcium channel function and synaptic properties in cultured hippocampal neurons from KLHL1 knockout (KO) mice. Western blot data showed the P/Q-type channel α_1A subunit was less abundant in KO hippocampus compared to wildtype (WT); and P/Q-type calcium currents were smaller in KO neurons than WT during early days in vitro, although this decrease was compensated for at late stages by increases in L-type calcium current. In contrast, T-type currents did not change in culture. However, biophysical properties and western blot analysis revealed a differential contribution of T-type channel isoforms in the KO, with Ca_V3.2 α_1H subunit being down-regulated and Ca_V3.1 α_1G up-regulated. Synapsin I levels were also reduced in the KO hippocampus and cultured neurons displayed a concomitant reduction in synapsin I puncta and decreased miniature excitatory postsynaptic current (mEPSC) frequency. In summary, genetic ablation of the calcium channel modulator resulted in compensatory mechanisms to maintain calcium current homeostasis in hippocampal KO neurons; however, synaptic alterations resulted in a reduction of excitatory synapse number, causing an imbalance of the excitatory-inhibitory synaptic input ratio favoring inhibition.

Temporal lobe proteins implicated in synaptic failure exhibit differential expression and deamidation in vascular dementia

Progressive synaptic failure precedes the loss of neurons and decline in cognitive function in neurodegenerative disorders, but the specific proteins and posttranslational modifications that promote synaptic failure in vascular dementia (VaD) remain largely unknown. We therefore used an isobaric tag for relative and absolute proteomic quantitation (iTRAQ) to profile the synapse-associated proteome of post-mortem human cortex from vascular dementia patients and age-matched controls. Brain tissue from VaD patients exhibited significant down-regulation of critical synaptic proteins including clathrin (0.29; p < 1.0⋅10(-3)) and GDI1 (0.51; p = 3.0⋅10(-3)), whereas SNAP25 (1.6; p = 5.5⋅10(-3)), bassoon (1.4; p = 1.3⋅10(-3)), excitatory amino acid transporter 2 (2.6; p = 9.2⋅10(-3)) and Ca(2+)/calmodulin dependent kinase II (1.6; p = 3.0⋅10(-2)) were substantially up-regulated. Our analyses further revealed divergent patterns of protein modification in the dementia patient samples, including a specific deamidation of synapsin1 predicted to compromise protein structure. Our results reveal potential molecular targets for intervention in synaptic failure and prevention of cognitive decline in VaD.

The procognitive and synaptogenic effects of angiotensin IV-derived peptides are dependent on activation of the hepatocyte growth factor/c-met system

A subset of angiotensin IV (AngIV)-related molecules are known to possess procognitive/antidementia properties and have been considered as templates for potential therapeutics. However, this potential has not been realized because of two factors: 1) a lack of blood-brain barrier-penetrant analogs, and 2) the absence of a validated mechanism of action. The pharmacokinetic barrier has recently been overcome with the synthesis of the orally active, blood-brain barrier-permeable analog N-hexanoic-tyrosine-isoleucine-(6) aminohexanoic amide (dihexa). Therefore, the goal of this study was to elucidate the mechanism that underlies dihexa's procognitive activity. Here, we demonstrate that dihexa binds with high affinity to hepatocyte growth factor (HGF) and both dihexa and its parent compound Norleucine 1-AngIV (Nle(1)-AngIV) induce c-Met phosphorylation in the presence of subthreshold concentrations of HGF and augment HGF-dependent cell scattering. Further, dihexa and Nle(1)-AngIV induce hippocampal spinogenesis and synaptogenesis similar to HGF itself. These actions were inhibited by an HGF antagonist and a short hairpin RNA directed at c-Met. Most importantly, the procognitive/antidementia capacity of orally delivered dihexa was blocked by an HGF antagonist delivered intracerebroventricularly as measured using the Morris water maze task of spatial learning.

Protein kinase A mediates adenosine A2a receptor modulation of neurotransmitter release via synapsin I phosphorylation in cultured cells from medulla oblongata

Synaptic transmission is an essential process for neuron physiology. Such process is enabled in part due to modulation of neurotransmitter release. Adenosine is a synaptic modulator of neurotransmitter release in the Central Nervous System, including neurons of medulla oblongata, where several nuclei are involved with neurovegetative reflexes. Adenosine modulates different neurotransmitter systems in medulla oblongata, specially glutamate and noradrenaline in the nucleus tractussolitarii, which are involved in hypotensive responses. However, the intracellular mechanisms involved in this modulation remain unknown. The adenosine A2a receptor modulates neurotransmitter release by activating two cAMP protein effectors, the protein kinase A and the exchange protein activated by cAMP. Therefore, an in vitro approach (cultured cells) was carried out to evaluate modulation of neurotransmission by adenosine A2a receptor and the signaling intracellular pathway involved. Results show that the adenosine A2a receptor agonist, CGS 21680, increases neurotransmitter release, in particular, glutamate and noradrenaline and such response is mediated by protein kinase A activation, which in turn increased synapsin I phosphorylation. This suggests a mechanism of A2aR modulation of neurotransmitter release in cultured cells from medulla oblongata of Wistar rats and suggest that protein kinase A mediates this modulation of neurotransmitter release via synapsin I phosphorylation.

Altered brain protein expression profiles are associated with molecular neurological dysfunction in the PKU mouse model

Phenylketonuria (PKU), if not detected and treated in newborns, causes severe neurological dysfunction and cognitive and behavioral deficiencies. Despite the biochemical characterization of PKU, the molecular mechanisms underlying PKU-associated brain dysfunction remain poorly understood. The aim of this study was to gain insights into the pathogenesis of this neurological damage by analyzing protein expression profiles in brain tissue of Black and Tan BRachyury-PahEnu2 mice (a mouse model of PKU). We compared the cerebral protein expression of homozygous PKU mice with that of their heterozygous counterparts using two-dimensional difference gel electrophoresis analysis, and identified 21 differentially expressed proteins, four of which were over-expressed and 17 under-expressed. An in silico bioinformatic approach indicated that protein under-expression was related to neuronal differentiation and dendritic growth, and to such neurological disorders as progressive motor neuropathy and movement disorders. Moreover, functional annotation analyses showed that some identified proteins were involved in oxidative metabolism. To further investigate the proteins involved in the neurological damage, we validated two of the proteins that were most strikingly under-expressed, namely, Syn2 and Dpysl2, which are involved in synaptic function and neurotransmission. We found that Glu2/3 and NR1 receptor subunits were over-expressed in PKU mouse brain. Our results indicate that differential expression of these proteins may be associated with the processes underlying PKU brain dysfunction, namely, decreased synaptic plasticity and impaired neurotransmission.

Down-regulation of endogenous KLHL1 decreases voltage-gated calcium current density

The actin-binding protein Kelch-like 1 (KLHL1) can modulate voltage-gated calcium channels in vitro. KLHL1 interacts with actin and with the pore-forming subunits of Cav2.1 and CaV3.2 calcium channels, resulting in up-regulation of P/Q and T-type current density. Here we tested whether endogenous KLHL1 modulates voltage gated calcium currents in cultured hippocampal neurons by down-regulating the expression of KLHL1 via adenoviral delivery of shRNA targeted against KLHL1 (shKLHL1). Control adenoviruses did not affect any of the neuronal properties measured, yet down-regulation of KLHL1 resulted in HVA current densities ~68% smaller and LVA current densities 44% smaller than uninfected controls, with a concomitant reduction in α(1A) and α(1H) protein levels. Biophysical analysis and western blot experiments suggest Ca(V)3.1 and 3.3 currents are also present in shKLHL1-infected neurons. Synapsin I levels, miniature postsynaptic current frequency, and excitatory and inhibitory synapse number were reduced in KLHL1 knockdown. This study corroborates the physiological role of KLHL1 as a calcium channel modulator and demonstrates a novel, presynaptic role.

Maggot learning and Synapsin function

Drosophila larvae are focused on feeding and have few neurons. Within these bounds, however, there still are behavioural degrees of freedom. This review is devoted to what these elements of flexibility are, and how they come about. Regarding odour-food associative learning, the emerging working hypothesis is that when a mushroom body neuron is activated as a part of an odour-specific set of mushroom body neurons, and coincidently receives a reinforcement signal carried by aminergic neurons, the AC-cAMP-PKA cascade is triggered. One substrate of this cascade is Synapsin, and therefore this review features a general and comparative discussion of Synapsin function. Phosphorylation of Synapsin ensures an alteration of synaptic strength between this mushroom body neuron and its target neuron(s). If the trained odour is encountered again, the pattern of mushroom body neurons coding this odour is activated, such that their modified output now allows conditioned behaviour. However, such an activated memory trace does not automatically cause conditioned behaviour. Rather, in a process that remains off-line from behaviour, the larvae compare the value of the testing situation (based on gustatory input) with the value of the odour-activated memory trace (based on mushroom body output). The circuit towards appetitive conditioned behaviour is closed only if the memory trace suggests that tracking down the learned odour will lead to a place better than the current one. It is this expectation of a positive outcome that is the immediate cause of appetitive conditioned behaviour. Such conditioned search for reward corresponds to a view of aversive conditioned behaviour as conditioned escape from punishment, which is enabled only if there is something to escape from - much in the same way as we only search for things that are not there, and run for the emergency exit only when there is an emergency. One may now ask whether beyond 'value' additional information about reinforcement is contained in the memory trace, such as information about the kind and intensity of the reinforcer used. The Drosophila larva may allow us to develop satisfyingly detailed accounts of such mnemonic richness - if it exists.

Noninvasive strategies to promote functional recovery after stroke

Stroke is a common and disabling global health-care problem, which is the third most common cause of death and one of the main causes of acquired adult disability in many countries. Rehabilitation interventions are a major component of patient care. In the last few years, brain stimulation, mirror therapy, action observation, or mental practice with motor imagery has emerged as interesting options as add-on interventions to standard physical therapies. The neural bases for poststroke recovery rely on the concept of plasticity, namely, the ability of central nervous system cells to modify their structure and function in response to external stimuli. In this review, we will discuss recent noninvasive strategies employed to enhance functional recovery in stroke patients and we will provide an overview of neural plastic events associated with rehabilitation in preclinical models of stroke.

Synapsin II gene expression in the dorsolateral prefrontal cortex of brain specimens from patients with schizophrenia and bipolar disorder: effect of lifetime intake of antipsychotic drugs

Synapsins are neuronal phosphoproteins crucial to regulating the processes required for normal neurotransmitter release. Synapsin II, in particular, has been implied as a candidate gene for schizophrenia. This study investigated synapsin II mRNA expression, using Real Time RT-PCR, in coded dorsolateral prefrontal cortical samples provided by the Stanley Foundation Neuropathology Consortium. Synapsin IIa was decreased in patients with schizophrenia when compared to both healthy subjects and patients with bipolar disorder, whereas the synapsin IIb was only significantly reduced in patients with schizophrenia when compared to healthy subjects, but not patients with bipolar disorder. Furthermore, lifetime antipsychotic drug use was positively associated with synapsin IIa expression in patients with schizophrenia. Results suggest that impairment of synaptic transmission by synapsin II reduction may contribute to dysregulated convergent molecular mechanisms which result in aberrant neural circuits that characterize schizophrenia, while implicating involvement of synapsin II in therapeutic mechanisms of currently prescribed antipsychotic drugs.

Evaluation of metabolically stabilized angiotensin IV analogs as procognitive/antidementia agents

Angiotensin IV (AngIV: VYIHPF)-related peptides have long been recognized as procognitive agents with potential as antidementia therapeutics. Their development as useful therapeutics, however, has been limited by physiochemical properties that make them susceptible to metabolic degradation and impermeable to gut and blood-brain barriers. A previous study demonstrated that the core structural information required to impart the procognitive activity of the AngIV analog, norleucine(1)-angiotensin IV, resides in its three N-terminal amino acids, Nle-Tyr-Ile. The goal of this project was to chemically modify this tripeptide in such a way to enhance its metabolic stability and barrier permeability to produce a drug candidate with potential clinical utility. Initial results demonstrated that several N- and C-terminal modifications lead to dramatically improved stability while maintaining the capability to reverse scopolamine-induced deficits in Morris water maze performance and augment hippocampal synaptogenesis. Subsequent chemical modifications, which were designed to increase hydrophobicity and decrease hydrogen bonding, yielded an orally active, blood-barrier permeant, metabolically stabilized analog, N-hexanoic-Tyr-Ile-(6) aminohexanoic amide (dihexa), that exhibits excellent antidementia activity in the scopolamine and aged rat models and marked synaptogenic activity. These data suggest that dihexa may have therapeutic potential as a treatment of disorders, such as Alzheimer's disease, where augmented synaptic connectivity may be beneficial.

REST is a novel prognostic factor and therapeutic target for medulloblastoma

Medulloblastoma is a malignant pediatric brain tumor. Current treatment following patient stratification into standard and high-risk groups using clinical features has improved survival. However, a subset of patients with standard risk features have unanticipated aggressive disease, underscoring the need for a better understanding of tumor biology and the development of novel treatments. Poor differentiation, a hallmark of medulloblastomas is associated with elevated expression levels of the repressor of neuronal differentiation called repressor element 1-silencing transcription factor (REST). Here, we assessed whether elevated REST expression levels had prognostic significance and whether its pharmacologic manipulation would promote neurogenesis and block tumor cell growth. REST levels in patient tumors were measured by immunohistochemistry and stratified into negative, low/moderate- (+/++/+++), and high-REST (+++++) groups. Kaplan-Meier curves revealed that patients with high-REST tumors had worse overall and event-free survival compared with patients with REST-negative or REST-low tumors. Because histone deacetylases (HDAC) are required for REST-dependent repression of neurogenesis, we evaluated a panel of HDAC inhibitors (HDACI) for their effects on growth and differentiation of established and primary REST-positive cell lines. MS-275, trichostatin-A (TSA), valproic acid (VPA), and suberoylanilide hydroxamic acid (SAHA) upregulated expression of the REST-target neuronal differentiation gene, Syn1, suggesting a potential effect of these HDACIs on REST function. Interestingly, VPA and TSA substantially increased histone acetylation at the REST promoter and activated its transcription, whereas SAHA unexpectedly promoted its proteasomal degradation. A REST-dependent decrease in cell growth was also observed following SAHA treatment. Thus, our studies suggest that HDACIs may have therapeutic potential for patients with REST-positive tumors. This warrants further investigation.

Absence of Ca2+-stimulated adenylyl cyclases leads to reduced synaptic plasticity and impaired experience-dependent fear memory

Ca(2+)-stimulated adenylyl cyclase (AC) 1 and 8 are two genes that have been shown to play critical roles in fear memory. AC1 and AC8 couple neuronal activity and intracellular Ca(2+) increases to the production of cyclic adenosine monophosphate and are localized synaptically, suggesting that Ca(2+)-stimulated ACs may modulate synaptic plasticity. Here, we first established that Ca(2+)-stimulated ACs modulate protein markers of synaptic activity at baseline and after learning. Primary hippocampal cell cultures showed that AC1/AC8 double-knockout (DKO) mice have reduced SV2, a synaptic vesicle protein, abundance along their dendritic processes, and this reduction can be rescued through lentivirus delivery of AC8 to the DKO cells. Additionally, phospho-synapsin, a protein implicated in the regulation of neurotransmitter release at the synapse, is decreased in vivo 1 h after conditioned fear (CF) training in DKO mice. Importantly, additional experiments showed that long-term potentiation deficits present in DKO mice are rescued by acutely replacing AC8 in the forebrain, further supporting the idea that Ca(2+)-stimulated AC activity is a crucial modulator of synaptic plasticity. Previous studies have demonstrated that memory is continually modulated by gene-environment interactions. The last set of experiments evaluated the effects of knocking out AC1 and AC8 genes on experience-dependent changes in CF memory. We showed that the strength of CF memory in wild-type mice is determined by previous environment, minimal or enriched, whereas memory in DKO mice is unaffected. Thus, overall these results show that AC1 and AC8 modulate markers of synaptic activity and help integrate environmental information to modulate fear memory.

Behavioral effects of non-viral mediated RNA interference of synapsin II in the medial prefrontal cortex of the rat

Synapsin II is a synaptic vesicle-associated phosphoprotein that has been implicated in the pathophysiology of schizophrenia. Researchers have demonstrated reductions in synapsin II mRNA and protein in post-mortem prefrontal cortex and hippocampus samples from patients with schizophrenia. Synapsin II protein expression has been shown to be regulated by dopamine D(1) and D(2) receptor activation. Furthermore, behavioral testing of the synapsin II knockout mouse has revealed a schizophrenic-like behavioral phenotype in this mutant strain, suggesting a relationship between dysregulated and/or reduced synapsin II and schizophrenia. However, it remains unknown the specific regions of the brain of which perturbations in synapsin II play a role in the pathophysiology of this disease. The aim of this project was to evaluate animals with a selective knock-down of synapsin II in the medial prefrontal cortex through the use of siRNA technology. Two weeks after continuous infusion of synapsin II siRNAs, animals were examined for the presence of a schizophrenic-like behavioral phenotype. Our results reveal that rats with selective reductions in medial prefrontal cortical synapsin II demonstrate deficits in sensorimotor gating (prepulse inhibition), hyperlocomotion, and reduced social behavior. These results implicate a role for decreased medial prefrontal cortical synapsin II levels in the pathophysiology of schizophrenia and the mechanisms of aberrant prefrontal cortical circuitry, and suggest that increasing synapsin II levels in the medial prefrontal cortex may potentially serve as a novel therapeutic target for this devastating disorder.

Transcriptome sequencing revealed significant alteration of cortical promoter usage and splicing in schizophrenia

Background

While hybridization based analysis of the cortical transcriptome has provided important insight into the neuropathology of schizophrenia, it represents a restricted view of disease-associated gene activity based on predetermined probes. By contrast, sequencing technology can provide un-biased analysis of transcription at nucleotide resolution. Here we use this approach to investigate schizophrenia-associated cortical gene expression.

Methodology/Principal Findings

The data was generated from 76 bp reads of RNA-Seq, aligned to the reference genome and assembled into transcripts for quantification of exons, splice variants and alternative promoters in postmortem superior temporal gyrus (STG/BA22) from 9 male subjects with schizophrenia and 9 matched non-psychiatric controls. Differentially expressed genes were then subjected to further sequence and functional group analysis. The output, amounting to more than 38 Gb of sequence, revealed significant alteration of gene expression including many previously shown to be associated with schizophrenia. Gene ontology enrichment analysis followed by functional map construction identified three functional clusters highly relevant to schizophrenia including neurotransmission related functions, synaptic vesicle trafficking, and neural development. Significantly, more than 2000 genes displayed schizophrenia-associated alternative promoter usage and more than 1000 genes showed differential splicing (FDR<0.05). Both types of transcriptional isoforms were exemplified by reads aligned to the neurodevelopmentally significant doublecortin-like kinase 1 (DCLK1) gene.

Conclusions

This study provided the first deep and un-biased analysis of schizophrenia-associated transcriptional diversity within the STG, and revealed variants with important implications for the complex pathophysiology of schizophrenia.

Emergent functional properties of neuronal networks with controlled topology

The interplay between anatomical connectivity and dynamics in neural networks plays a key role in the functional properties of the brain and in the associated connectivity changes induced by neural diseases. However, a detailed experimental investigation of this interplay at both cellular and population scales in the living brain is limited by accessibility. Alternatively, to investigate the basic operational principles with morphological, electrophysiological and computational methods, the activity emerging from large in vitro networks of primary neurons organized with imposed topologies can be studied. Here, we validated the use of a new bio-printing approach, which effectively maintains the topology of hippocampal cultures in vitro and investigated, by patch-clamp and MEA electrophysiology, the emerging functional properties of these grid-confined networks. In spite of differences in the organization of physical connectivity, our bio-patterned grid networks retained the key properties of synaptic transmission, short-term plasticity and overall network activity with respect to random networks. Interestingly, the imposed grid topology resulted in a reinforcement of functional connections along orthogonal directions, shorter connectivity links and a greatly increased spiking probability in response to focal stimulation. These results clearly demonstrate that reliable functional studies can nowadays be performed on large neuronal networks in the presence of sustained changes in the physical network connectivity.

Inhibition of exocytosis or endocytosis blocks activity-dependent redistribution of synapsin

The synaptic vesicle cycle encompasses the pre-synaptic events that drive neurotransmission. Influx of calcium leads to the fusion of synaptic vesicles with the plasma membrane and the release of neurotransmitter, closely followed by endocytosis. Vacated release sites are repopulated with vesicles which are then primed for release. When activity is intense, reserve vesicles may be mobilized to counteract an eventual decline in transmission. Recently, interplay between endocytosis and repopulation of the readily releasable pool of vesicles has been identified. In this study, we show that exo-endocytosis is necessary to enable detachment of synapsin from reserve pool vesicles during synaptic activity. We report that blockage of exocytosis in cultured mouse hippocampal neurons, either by tetanus toxin or by the deletion of munc13, inhibits the activity-dependent redistribution of synapsin from the pre-synaptic terminal into the axon. Likewise, perturbation of endocytosis with dynasore or by a dynamin dominant-negative mutant fully prevents synapsin redistribution. Such inhibition of synapsin redistribution occurred despite the efficient phosphorylation of synapsin at its protein kinase A/CaMKI site, indicating that disengagement of synapsin from the vesicles requires exocytosis and endocytosis in addition to phosphorylation. Our results therefore reveal hitherto unidentified feedback within the synaptic vesicle cycle involving the synapsin-managed reserve pool.

Facilitation of hippocampal synaptogenesis and spatial memory by C-terminal truncated Nle1-angiotensin IV analogs

Angiotensin IV (AngIV; Val(1)-Tyr(2)-Ile(3)-His(4)-Pro(5)-Phe(6))-related peptides have emerged as potential antidementia agents. However, their development as practical therapeutic agents has been impeded by a combination of metabolic instability, poor blood-brain barrier permeability, and an incomplete understanding of their mechanism of action. This study establishes the core structure contained within norleucine(1)-angiotensin IV (Nle(1)-AngIV) that is required for its procognitive activity. Results indicated that Nle(1)-AngIV-derived peptides as small as tetra- and tripeptides are capable of reversing scopolamine-induced deficits in Morris water maze performance. This identification of the active core structure contained within Nle(1)-AngIV represents an initial step in the development of AngIV-based procognitive drugs. The second objective of the study was to clarify the general mechanism of action of these peptides by assessing their ability to affect changes in dendritic spines. A correlation was observed between a peptide's procognitive activity and its capacity to increase spine numbers and enlarge spine head size. These data suggest that the procognitive activity of these molecules is attributable to their ability to augment synaptic connectivity.

Medial prefrontal cortical synapsin II knock-down induces behavioral abnormalities in the rat: examining synapsin II in the pathophysiology of schizophrenia

Synapsin II is a synaptic vesicle-associated phosphoprotein that has been implicated in the pathophysiology of schizophrenia. Studies have demonstrated reductions in synapsin II mRNA and protein in medial prefrontal cortical post-mortem samples from patients with schizophrenia, genetic associations between synapsin II and schizophrenia, and synapsin II protein regulation by dopamine receptor activation. Collectively, this research indicates a relationship between synapsin II dysregulation and schizophrenia; however, it remains unknown whether perturbations in synapsin II play a role in the pathophysiology of this disease. The aim of this project was to evaluate animals with selective knock-down of synapsin II in the medial prefrontal cortex. After continuous infusion of synapsin II antisense sequences, animals were examined for the presence of schizophrenic-like behavioral phenotypes and assessed on the response to clinically relevant antipsychotic drugs. Our results indicate that rats with selective reductions in medial prefrontal cortical synapsin II demonstrate deficits in sensorimotor gating (prepulse inhibition), reduced social behavior, and hyperlocomotion, which are corrected by the atypical antipsychotic drug olanzapine. Additionally, synapsin II knock-down disrupts serial search efficiency. These behavioral changes are accompanied by reductions in vesicular neurotransmitter transporter protein concentrations for glutamate (VGLUT1 and VGLUT2) and GABA (VGAT), without affecting dopamine (VMAT2). These results implicate a causal role for decreased synapsin II in the medial prefrontal cortex in the pathophysiology of schizophrenia and the mechanisms of aberrant prefrontal cortical circuitry, and suggest that synapsin II may potentially serve as a novel therapeutic target for this disorder.

Chronic stress and antidepressant agomelatine induce region-specific changes in synapsin I expression in the rat brain

The antidepressant agomelatine acts as a melatonergic receptor (MT(1)/MT(2)) agonist and 5-HT(2C) receptor antagonist. Agomelatine has demonstrated efficacy in treating depression, but its neurobiological effects merit further investigation. Preclinical studies reported that agomelatine enhances adult hippocampal neurogenesis and increases expression of several neuroplasticity-associated molecules. Recently, we showed that agomelatine normalizes hippocampal neuronal activity and promotes neurogenesis in the stress-compromised brain. To characterize further the effects of this antidepressant in the stressed brain, here we investigated whether it induces changes in the expression of synapsin I (SynI), a regulator of synaptic transmission and plasticity. Adult male rats were subjected to daily footshock stress and agomelatine treatment for 3 weeks. Their brains were subsequently stained for total and phosphorylated SynI. Chronic footshock and agomelatine induced region-specific changes in SynI expression. Whereas chronic stress increased total SynI expression in all layers of the medial prefrontal cortex, agomelatine treatment abolished some of these effects. Furthermore, chronic agomelatine administration decreased total SynI expression in the hippocampal subregions of both stressed and nonstressed rats. Importantly, chronic stress decreased the fraction of phosphorylated SynI in all layers of the medial prefrontal cortex as well as selectively in the outer and middle molecular layers of the hippocampal dentate gyrus. These stress effects were at least partially abolished by agomelatine. Altogether, our data show that chronic stress and agomelatine treatment induce region-specific changes in SynI expression and its phosphorylation. Moreover, agomelatine partially counteracts the stress effects on SynI, suggesting a modulation of synaptic function by this antidepressant.

The enhancement of stress-related memory by glucocorticoids depends on synapsin-Ia/Ib

The activation of glucocorticoid receptors (GR) by glucocorticoids increases stress-related memory through the activation of the MAPK signaling pathway and the downstream transcription factor Egr-1. Here, using converging in vitro and in vivo approaches, respectively, GR-expressing cell lines, culture of hippocampal neurons, and GR genetically modified mice (GR(NesCre)), we identified synapsin-Ia/Ib as one of the effectors of the glucocorticoid signaling cascade. Stress and glucocorticoid-induced activation of the GR modulate synapsin-Ia/Ib through two complementary mechanisms. First, glucocorticoids driving Egr-1 expression increase the expression of synapsin-Ia/Ib, and second, glucocorticoids driving MAPK activation increase its phosphorylation. Finally, we showed that blocking fucosylation of synapsin-Ia/Ib in the hippocampus inhibits its expression and prevents the glucocorticoid-mediated increase in stress-related memory. In conclusion, our data provide a complete molecular pathway (GR/Egr-1/MAPK/Syn-Ia/Ib) through which stress and glucocorticoids enhance the memory of stress-related events and highlight the function of synapsin-Ia/Ib as molecular effector of the behavioral effects of stress.

Differentiation and neural integration of hippocampal neuronal progenitors: signaling pathways sequentially involved

In the context of their potential implication in regenerative strategies, we characterized cell mechanisms underlying the fate of embryonic rat hippocampal H19-7 progenitors in culture upon induction of their differentiation, and tested their capacities to integrate into a neuronal network in vitro. Without addition of growth factors, nearly 100% of cells expressed various neuronal markers, with a progressive rise of the expression of Synapsin I and II, suggesting that cells developed as mature neurons with synaptogenic capacities. Fully differentiated neurons were identified as glutamatergic and expressed the receptor-associated protein PSD-95. Quantification of ATP showed that 60% of cells died within 24 h after differentiation. Cell death was shown to imply Erk1/2-dependent intrinsic mitochondrial apoptosis signaling pathway, with activation of caspase-9 and -3, finally leading to single-strand DNA. Surviving neurons displayed high levels of Akt, phospho-Akt, and antiapoptotic proteins such as Bcl-2 and Bcl-XL, with decreased caspase activation. In the absence of trophic support, the proapoptotic death-associated protein (DAP) kinase was dramatically stimulated by 24 h postdifferentiation, along with increased levels of p38 and phospho-p38, and caspase reactivation. These findings show that different signaling pathways are sequentially triggered by differentiation, and highlight that ultimate cell death would involve p38 and DAP kinase activation. This was supported by the improvement of cell survival at 24-h postdifferentiation when cells were treated by PD169316, a specific inhibitor of p38. Finally, when seeded on rat hippocampal primary cultured neurons, a significant number of differentiated H19-7 cells were able to survive and to develop cell-cell communication.