Molecular fingerprints in the hippocampus of alcohol seeking during withdrawal

Alcohol use disorder (AUD) is characterized by pathological motivation to consume alcohol and cognitive inflexibility, leading to excessive alcohol seeking and use. Due to limited understanding of the molecular basis of the disease, there are few pharmacological interventions available to combat AUD. In this study, we aimed to investigate the molecular correlates of impaired extinction of alcohol seeking during alcohol withdrawal using a mouse model of AUD implemented in the automated IntelliCage social system. This model enabled us to distinguish between animals exhibiting AUD-prone and AUD-resistant phenotypes, based on the presence of ≥ 2 or < 2 criteria of AUD, respectively. We utilized new generation RNA sequencing to identify genes that were differentially expressed in the hippocampus and amygdala of mice meeting ≥ 2 or < 2 criteria, as these brain regions are implicated in alcohol motivation, seeking, consumption and the cognitive inflexibility characteristic of AUD. To complement the sequencing studies, we conducted ex vivo electrophysiology experiments. Our findings revealed significant dysregulation of the hippocampal genes associated with the actin cytoskeleton and synaptic function, including actin binding molecule cofilin, during alcohol withdrawal in mice meeting ≥ 2 criteria compared to those meeting < 2 criteria. Moreover, this dysregulation was accompanied by impaired synaptic transmission in the molecular layer of the hippocampal dentate gyrus (ML-DG). Additionally, we demonstrated that overexpression of cofilin in the polymorphic layer of the hippocampal dentate gyrus (PoDG) inhibited ML-DG synapses, increased motivation to seek alcohol, impaired extinction of alcohol seeking and increased correlation between AUD behaviors, resembling the phenotype observed in mice meeting ≥ 2 criteria. Overall, our study uncovers a novel mechanism linking increased hippocampal cofilin expression with the AUD phenotype.

Molecular fingerprints in the hippocampus of alcohol seeking during withdrawal

Alcohol use disorder (AUD) is characterized by excessive alcohol seeking and use. Here, we investigated the molecular correlates of impaired extinction of alcohol seeking using a multidimentional mouse model of AUD. We distinguished AUD-prone and AUD-resistant mice, based on the presence of ≥ 2 or < 2 criteria of AUD and utilized RNA sequencing to identify genes that were differentially expressed in the hippocampus and amygdala of mice meeting ≥ 2 or < 2 criteria, as these brain regions are implicated in alcohol motivation, seeking, consumption and the cognitive inflexibility characteristic of AUD. Our findings revealed dysregulation of the genes associated with the actin cytoskeleton, including actin binding molecule cofilin, and impaired synaptic transmission in the hippocampi of mice meeting ≥ 2 criteria. Overexpression of cofilin in the polymorphic layer of the dentate gyrus (PoDG) inhibited ML-DG synapses, increased motivation to seek alcohol and impaired extinction of alcohol seeking, resembling the phenotype observed in mice meeting ≥ 2 criteria. Overall, our study uncovers a novel mechanism linking increased hippocampal cofilin expression with the AUD phenotype.

Phosphorylation of PSD-95 at serine 73 in dCA1 is required for extinction of contextual fear

The updating of contextual memories is essential for survival in a changing environment. Accumulating data indicate that the dorsal CA1 area (dCA1) contributes to this process. However, the cellular and molecular mechanisms of contextual fear memory updating remain poorly understood. Postsynaptic density protein 95 (PSD-95) regulates the structure and function of glutamatergic synapses. Here, using dCA1-targeted genetic manipulations in vivo, combined with ex vivo 3D electron microscopy and electrophysiology, we identify a novel, synaptic mechanism that is induced during attenuation of contextual fear memories and involves phosphorylation of PSD-95 at Serine 73 in dCA1. Our data provide the proof that PSD-95-dependent synaptic plasticity in dCA1 is required for updating of contextual fear memory.

Autophosphorylation of αCaMKII regulates alcohol consumption by controlling sedative effects of alcohol and alcohol-induced loss of excitatory synapses

Calcium/calmodulin-dependent kinase II (CaMKII) is a key enzyme at the glutamatergic synapses. CAMK2A gene variants have been linked with alcohol use disorder (AUD) by an unknown mechanism. Here, we looked for the link between αCaMKII autophosphorylation and the AUD aetiology. Autophosphorylation-deficient heterozygous αCaMKII mutant mice (T286A^+/- ) were trained in the IntelliCages to test the role of αCaMKII activity in AUD-related behaviours. The glutamatergic synapses morphology in CeA was studied in the animals drinking alcohol using 3D electron microscopy. We found that T286A^+/- mutants consumed less alcohol and were more sensitive to sedating effects of alcohol, as compared to wild-type littermates (WT). After voluntary alcohol drinking, T286A^+/- mice had less excitatory synapses in the CeA, as compared to alcohol-naive animals. This change correlated with alcohol consumption was not reversed after alcohol withdrawal and not observed in WT mice. Our study suggests that αCaMKII autophosphorylation affects alcohol consumption by controlling sedative effects of alcohol and preventing synaptic loss in the individuals drinking alcohol. This finding advances our understanding of the molecular processes that regulate alcohol dependence.

Arc controls alcohol cue relapse by a central amygdala mechanism

Alcohol use disorder (AUD) is a chronic and fatal disease. The main impediment of the AUD therapy is a high probability of relapse to alcohol abuse even after prolonged abstinence. The molecular mechanisms of cue-induced relapse are not well established, despite the fact that they may offer new targets for the treatment of AUD. Using a comprehensive animal model of AUD, virally-mediated and amygdala-targeted genetic manipulations by CRISPR/Cas9 technology and ex vivo electrophysiology, we identify a mechanism that selectively controls cue-induced alcohol relapse and AUD symptom severity. This mechanism is based on activity-regulated cytoskeleton-associated protein (Arc)/ARG3.1-dependent plasticity of the amygdala synapses. In humans, we identified single nucleotide polymorphisms in the ARC gene and their methylation predicting not only amygdala size, but also frequency of alcohol use, even at the onset of regular consumption. Targeting Arc during alcohol cue exposure may thus be a selective new mechanism for relapse prevention.

Impaired synaptic transmission in dorsal dentate gyrus increases impulsive alcohol seeking

Both human and animal studies indicate that the dentate gyrus (DG) of the hippocampus is highly exploited by drug and alcohol abuse. Yet, it is poorly understood how DG dysfunction affects addiction-related behaviors. Here, we used an animal model of alcohol use disorder (AUD) in automated IntelliCages and performed local genetic manipulation to investigate how synaptic transmission in the dorsal DG (dDG) affects alcohol-related behaviors. We show that a cue light induces potentiation-like plasticity of dDG synapses in alcohol-naive mice. This process is impaired in mice trained to drink alcohol. Acamprosate (ACA), a drug that reduces alcohol relapse, rescues the impairment of dDG synaptic transmission in alcohol mice. A molecular manipulation that reduces dDG synaptic AMPAR and NMDAR levels increases impulsive alcohol seeking during cue relapse (CR) in alcohol mice but does not affect alcohol reward, motivation or craving. These findings suggest that hindered dDG synaptic transmission specifically underlies impulsive alcohol seeking induced by alcohol cues, a core symptom of AUD.

Disrupting interaction between miR-132 and Mmp9 3'UTR improves synaptic plasticity and memory in mice

As microRNAs have emerged to be important regulators of molecular events occurring at the synapses, the new questions about their regulatory effect on the behavior have araised. In the present study, we show for the first time that the dysregulated specific targeting of miR132 to Mmp9 mRNA in the mouse brain results in the increased level of Mmp9 protein, which affects synaptic plasticity and has an effect on memory formation. Our data points at the importance of complex and precise regulation of the Mmp9 level by miR132 in the brain.

Inhibition of Matrix Metalloproteinase 9 Activity Promotes Synaptogenesis in the Hippocampus

Information coding in the hippocampus relies on the interplay between various neuronal ensembles. We discovered that the application of a cholinergic agonist, carbachol (Cch), which triggers oscillatory activity in the gamma range, induces the activity of matrix metalloproteinase 9 (MMP-9)—an enzyme necessary for the maintenance of synaptic plasticity. Using electrophysiological recordings in hippocampal organotypic slices, we show that Cch potentiates the frequency of miniature inhibitory and excitatory postsynaptic currents (mIPSCs and mEPSCs, respectively) in CA1 neurons and this effect is MMP-9 dependent. Interestingly, though MMP-9 inhibition prevents the potentiation of inhibitory events, it further boosts the frequency of excitatory mEPSCs. Such enhancement of the frequency of excitatory events is a result of increased synaptogenesis onto CA1 neurons. Thus, the function of MMP-9 in cholinergically induced plasticity in the hippocampus is to maintain the fine-tuned balance between the excitatory and the inhibitory synaptic transmission.

PSD-95 Serine 73 phosphorylation is not required for induction of NMDA-LTD

PSD-95 is a major scaffolding protein of the post-synaptic density (PSD) of a glutamatergic synapse. PSD-95, via interactions with stargazin, anchors AMPA receptors at the synapse and regulates AMPAR currents. The expression of PSD-95 is regulated during synaptic plasticity. It is, however, unknown whether this regulation is required for induction of functional plasticity of glutamatergic synapses. Here, we show that NMDA-induced long-term depression of synaptic transmission (NMDA-LTD) is accompanied by downregulation of PSD-95 protein levels. Using pharmacologic and molecular manipulations, we further demonstrate that the NMDA-induced downregulation of PSD-95 depends on the activation of CaMKII and CaMKII-driven phosphorylation of PSD-95 serine 73. Surprisingly, neither CaMKII activity nor CaMKII-dependent phosphorylation of PSD-95 serine 73 are required for the expression of NMDA-LTD. These results support the hypothesis that synaptic plasticity of AMPARs may occur without dynamic regulation of PSD-95 protein levels.

The energetic brain - A review from students to students

The past 20 years have resulted in unprecedented progress in understanding brain energy metabolism and its role in health and disease. In this review, which was initiated at the 14th International Society for Neurochemistry Advanced School, we address the basic concepts of brain energy metabolism and approach the question of why the brain has high energy expenditure. Our review illustrates that the vertebrate brain has a high need for energy because of the high number of neurons and the need to maintain a delicate interplay between energy metabolism, neurotransmission, and plasticity. Disturbances to the energetic balance, to mitochondria quality control or to glia-neuron metabolic interaction may lead to brain circuit malfunction or even severe disorders of the CNS. We cover neuronal energy consumption in neural transmission and basic ('housekeeping') cellular processes. Additionally, we describe the most common (glucose) and alternative sources of energy namely glutamate, lactate, ketone bodies, and medium chain fatty acids. We discuss the multifaceted role of non-neuronal cells in the transport of energy substrates from circulation (pericytes and astrocytes) and in the supply (astrocytes and microglia) and usage of different energy fuels. Finally, we address pathological consequences of disrupted energy homeostasis in the CNS.

The malleable brain: plasticity of neural circuits and behavior - a review from students to students

One of the most intriguing features of the brain is its ability to be malleable, allowing it to adapt continually to changes in the environment. Specific neuronal activity patterns drive long-lasting increases or decreases in the strength of synaptic connections, referred to as long-term potentiation and long-term depression, respectively. Such phenomena have been described in a variety of model organisms, which are used to study molecular, structural, and functional aspects of synaptic plasticity. This review originated from the first International Society for Neurochemistry (ISN) and Journal of Neurochemistry (JNC) Flagship School held in Alpbach, Austria (Sep 2016), and will use its curriculum and discussions as a framework to review some of the current knowledge in the field of synaptic plasticity. First, we describe the role of plasticity during development and the persistent changes of neural circuitry occurring when sensory input is altered during critical developmental stages. We then outline the signaling cascades resulting in the synthesis of new plasticity-related proteins, which ultimately enable sustained changes in synaptic strength. Going beyond the traditional understanding of synaptic plasticity conceptualized by long-term potentiation and long-term depression, we discuss system-wide modifications and recently unveiled homeostatic mechanisms, such as synaptic scaling. Finally, we describe the neural circuits and synaptic plasticity mechanisms driving associative memory and motor learning. Evidence summarized in this review provides a current view of synaptic plasticity in its various forms, offers new insights into the underlying mechanisms and behavioral relevance, and provides directions for future research in the field of synaptic plasticity. Read the Editorial Highlight for this article on page 788. Cover Image for this issue: doi: 10.1111/jnc.13815.

MMP-9 in translation: from molecule to brain physiology, pathology, and therapy

Matrix metalloproteinase-9 (MMP-9) is a member of the metzincin family of mostly extracellularly operating proteases. Despite the fact that all of these enzymes might be target promiscuous, with largely overlapping catalogs of potential substrates, MMP-9 has recently emerged as a major and apparently unique player in brain physiology and pathology. The specificity of MMP-9 may arise from its very local and time-restricted actions, even when released in the brain from cells of various types, including neurons, glia, and leukocytes. In fact, the quantity of MMP-9 is very low in the naive brain, but it is markedly activated at the levels of enzymatic activity, protein abundance, and gene expression following various physiological stimuli and pathological insults. Neuronal MMP-9 participates in synaptic plasticity by controlling the shape of dendritic spines and function of excitatory synapses, thus playing a pivotal role in learning, memory, and cortical plasticity. When improperly unleashed, MMP-9 contributes to a large variety of brain disorders, including epilepsy, schizophrenia, autism spectrum disorder, brain injury, stroke, neurodegeneration, pain, brain tumors, etc. The foremost mechanism of action of MMP-9 in brain disorders appears to be its involvement in immune/inflammation responses that are related to the enzyme's ability to process and activate various cytokines and chemokines, as well as its contribution to blood-brain barrier disruption, facilitating the extravasation of leukocytes into brain parenchyma. However, another emerging possibility (i.e., the control of MMP-9 over synaptic plasticity) should not be neglected. The translational potential of MMP-9 has already been recognized in both the diagnosis and treatment domains. The most striking translational aspect may be the discovery of MMP-9 up-regulation in a mouse model of Fragile X syndrome, quickly followed by human studies and promising clinical trials that have sought to inhibit MMP-9. With regard to diagnosis, suggestions have been made to use MMP-9 alone or combined with tissue inhibitor of matrix metalloproteinase-1 or brain-derived neurotrophic factor as disease biomarkers. MMP-9, through cleavage of specific target proteins, plays a major role in synaptic plasticity and neuroinflammation, and by those virtues contributes to brain physiology and a host of neurological and psychiatric disorders. This article is part of the 60th Anniversary special issue.

A ground state of PPARγ activity and expression is required for appropriate neural differentiation of hESCs

BACKGROUND

Several evidences indicate stimulation of peroxisome proliferator activated receptor γ (PPARg), promotes neuronal differentiation. This study was conducted to testify the prominence of PPARγ during neural differentiation of human embryonic stem cells (hESCs).

METHODS

PPARγ expression level was assessed during neural differentiation of hESCs. Meanwhile, the level of endogenous miRNAs, which could be engaged in regulation of PPARγ expression, was measured. Next, natural and synthetic components of PPARγ agonists and antagonist were implemented on neural progenitor formation during neural differentiation of hESCs.

RESULTS

Data showed an increasing wave of PPARγ expression level when human neural progenitors (NPs) were formed upon retinoic acid treatment. Interestingly, there was no significant difference in the amount of PPARγ proteins during the differentiation of hESCs that is inconsistent with what we observed for RNA level. Our results indicated that miRNAs are not involved in the regulation of PPARγ expression, while proteasome-mediated degradation may to some degree be involved in this process. Among numerous treatments, PPARγ inactivation during NPs formation significantly decreased expression of NP markers.

CONCLUSIONS

We conclude that a ground state of PPARγ activity is required for NP formation of hESCs during early neural differentiation. However, high expression and activity of PPARγ could not enhance the required neural differentiation, whereas the PPARγ inactivation could negatively influence NP formation from hESCs by antagonist.

Enhanced expression of FNDC5 in human embryonic stem cell-derived neural cells along with relevant embryonic neural tissues

Availability of human embryonic stem cells (hESCs) has enhanced the capability of basic and clinical research in the context of human neural differentiation. Derivation of neural progenitor (NP) cells from hESCs facilitates the process of human embryonic development through the generation of neuronal subtypes. We have recently indicated that fibronectin type III domain containing 5 protein (FNDC5) expression is required for appropriate neural differentiation of mouse embryonic stem cells (mESCs). Bioinformatics analyses have shown the presence of three isoforms for human FNDC5 mRNA. To differentiate which isoform of FNDC5 is involved in the process of human neural differentiation, we have used hESCs as an in vitro model for neural differentiation by retinoic acid (RA) induction. The hESC line, Royan H5, was differentiated into a neural lineage in defined adherent culture treated by RA and basic fibroblast growth factor (bFGF). We collected all cell types that included hESCs, rosette structures, and neural cells in an attempt to assess the expression of FNDC5 isoforms. There was a contiguous increase in all three FNDC5 isoforms during the neural differentiation process. Furthermore, the highest level of expression of the isoforms was significantly observed in neural cells compared to hESCs and the rosette structures known as neural precursor cells (NPCs). High expression levels of FNDC5 in human fetal brain and spinal cord tissues have suggested the involvement of this gene in neural tube development. Additional research is necessary to determine the major function of FDNC5 in this process.

C86Y: as a destructive homozygous mutation deteriorating Pex7p function causing rhizomelic chondrodysplasia punctata type I

Rhizomelic Chondrodysplasia Punctata (RCDP) type 1 is a peroxisomal biogenesis disorder with a genetic abnormality in PEX7 gene. In the present study, mutational analysis was performed on two Iranian RCDP patients with distinct clinical phonotype. Mutation detection was carried out by sequencing of RT-PCR product consisting the whole length of PEX7 cDNA. Sequence data revealed the same missense homozygous mutation of G to A at nucleotide 257 in exon3 of PEX7 coding sequence in both patients. Moreover, genomic analysis of the PEX7 gene confirmed the RT-PCR data. This mutation caused one amino acid residue substitution of Cys to Tyr at codon 86 located on WD1 repeat domain region of Pex7p, which severely affected the functionality of PEX7 protein. Back-transfection of vector encoding mutant Pex7p did not restore the normal peroxisomal function in RCDP patient's fibroblast cells dissimilar to the native type of PEX7.

Functional expression of potassium channels in cardiomyocytes derived from embryonic stem cells

Royan B(1) stem cell can be differentiated to specialized cell types including cardiomyocytes. This developmental change is accompanied with expression of various K(+) channel types. The aim of this study was to detect functional expression of K(+) currents from stem cell stage and one week and two weeks after differentiation into cardiomyocyte. Mouse stem cell derived cardiomyocytes (ES-cardiomyocytes) were isolated to single cell suspension for K(+) current recording using whole cell patch-clamp technique. The predominant depolarizing current in ES-cardiomyocytes was a tetraethylammonium (TEA) (10 mM) sensitive current which was partially blocked by nifedipine (1 μM) and attenuated by increasing concentration of EGTA (10 mM) in the pipette solution. Pharmacology and electrophysiological properties of this oscillatory sustained current very well matched with characteristics of Ca(2+) activated K(+) current. In addition there was another kind of sustained outward K(+) current which was resistance to TEA but was inhibited by 3,4-diaminopyridine. The characteristic features of this current indicate that this current was due to activation of delayed rectifier K(+) channels. RT-PCR study also confirmed expression of these two types of K(+) channels in ES-cardiomyocytes. Therefore, present study shows functional expression of two types of K(+) ionic current in ES-cardiomyocytes.

Amplification of GC-rich Putative Mouse PeP Promoter using Betaine and DMSO in Ammonium Sulfate Polymerase Chain Reaction Buffer

BACKGROUND

Recently, we have shown that peroxisomal protein expression was induced upon retinoic acid treatment in mouse embryonic stem cells during the process of neurogenesis. Thus, characterization of the respective promoter could elucidate the molecular aspects of transcriptional regulation of this gene.

METHODS

Using the conventional software programs for promoter prediction, a putative promoter region was identified approximately 561 bp upstream of the peroxisomal protein coding sequence. In order to clone this region with a GC-content of 71.01%, a cocktail of ammonium sulfate buffer supplied with two additive components, betaine and dimethyl sulfoxide, and a high concentration of MgCl(2) was used.

RESULTS

The modulated polymerase chain reaction composition significantly improved the amplification of GC-rich DNA target sequences. Improved amplification of this region was due to reduction in the formation of secondary structures by the GC-rich region.

CONCLUSION

Therefore, this polymerase chain reaction composition could be generally used to facilitate the amplification of other GC-rich DNA sequences as verified by amplification of different GC rich regions.

Characterization and Functional Assessment of Mouse PPARγ1 Promoter

BACKGROUND

Peroxisome Proliferator Activated Receptor gamma (PPARγ), a member of nuclear receptor superfamily, comprises two isoforms in mouse. These two isoforms are encoded by different mRNAs, which are arisen by alternative promoter usage. There are two promoter regions upstream of PPARγ gene. A 3 kb fragment, containing several transcription factor binding sites, acts as PPARγ1 promoter region. Thus, expression pattern of PPARγ1 isoform is due to the potential transcription factors that could influence its promoter activity. PPARγ, Retinoid X Receptor (RXR) and Vitamin D Receptor (VDR), as nuclear receptors could influence PPARγ gene expression pattern during several differentiation processes. During neural differentiation, PPARγ1 isoform expression reaches to maximal level at neural precursor cell formation.

METHODS

A vast computational analysis was carried out to reveal the PPARγ1 promoter region. The putative promoter region was then subcloned upstream of an EGFP reporter gene. Then the functionality of PPARγ1 promoter was assessed in different cell lines.

RESULTS

Results indicated that Rosiglitazone increased PPARγ1 promoter regulated EGFP expression of neural precursor cells during Embryoid Body (EB) formation. Furthermore vitamin D reduced PPARγ1 promoter regulated EGFP expression of neural precursor cells during EB formation through binding to its receptor.

CONCLUSION

This study suggests that there are potential response elements for PPAR/RXR and VDR/RXR heterodimers in PPARγ1 isoform promoter. Also VDR/RXR heterodimers may decrease PPARγ expression through binding to its promoter.

Quantitative expression of phospholipase C zeta, as an index to assess fertilization potential of a semen sample

BACKGROUND

Failed fertilization post-ICSI has been mainly attributed to the sperm's inability to induce oocyte activation. Phospholipase C zeta (PLCζ) is considered to be one of the factors for the induction of oocyte activation. The aim of this study was to quantitatively assess the expression of PLCζ in globozoospermic men or those with previously low or failed fertilization in comparison with fertile men or those with high fertilization potential. In addition, the relationship between expression of PLCζ and that of other sperm markers was evaluated.

METHODS

Real-time PCR was carried out to evaluate relative expression of PLCζ mRNA. Chromatin maturity and acrosin activity were assessed by CMA3 staining and a colorimetric method.

RESULTS

The expression of PLCζ was significantly lower in globozoospermic men (P< 0.01, n= 8) or individuals with previously low or failed fertilization (P< 0.01, n= 36) in comparison to fertile men (n= 24). In addition, a significant difference was observed between globozoospermic (P< 0.01) and individuals with previously low or failed fertilization (P= 0.003) in comparison to high fertilization individuals (n= 17). Expression of PLCζ was not correlated with either chromatin maturity or acrosin activity. However, a significant correlation was observed between the percentage of fertilization and relative expression of PLCζ (r= 0.4, P< 0.01).

CONCLUSION

In this study, for the first time, we have shown that assessment of relative expression of PLCζ may provide a useful marker for the ability of sperm to induce oocyte activation after ICSI.