Deletion of CPEB3 enhances hippocampus-dependent memory via increasing expressions of PSD95 and NMDA receptors

Early-Life Exposure to 4-Hydroxy-4'-Isopropoxydiphenylsulfone Induces Behavioral Deficits Associated with Autism Spectrum Disorders in Mice

Exposure to bisphenol A (BPA) during gestation and lactation is considered to be a potential risk factor for autism spectrum disorder (ASD) in both humans and animals. As a novel alternative to BPA, 4-hydroxy-4'-isopropoxydiphenylsulfone (BPSIP) is frequently detected in breast milk and placental barrier systems, suggesting potential transmission from the mother to offspring and increased risk of exposure. Gestation and lactation are critical periods for central nervous system development, which are vulnerable to certain environmental pollutants. Herein, we investigated the behavioral impacts and neurobiological effects of early-life exposure to BPSIP (0.02, 0.1, and 0.5 mg/kg body weight/day) in mice offspring. Behavioral studies indicated that BPSIP exposure induced ASD-like behaviors, including elevated anxiety-related behavior and decreased spatial memory, in both male and female pups. A distinct pattern of reduced social novelty was observed only in female offspring, accompanied by significant alterations in antioxidant levels. Transcriptome analysis demonstrated that differentially expressed genes (DEGs) were mainly enriched in pathways related to behaviors and neurodevelopment, which were consistent with the observed phenotype. Besides, a decrease in the protein levels of complex IV (COX IV) across all tested populations suggests a profound impact on mitochondrial function, potentially leading to abnormal energy metabolism in individuals with autism. Additionally, changes in synaptic proteins, evidenced by alterations in synapsin 1 (SYN1) and postsynaptic density protein-95 (PSD95) levels in the cerebellum and hippocampus, support the notion of synaptic involvement. These findings suggest that BPSIP may induce sex-specific neurotoxic effects that involve oxidative stress, energy generation, and synaptic plasticity.

CPEB2-activated axonal translation of VGLUT2 mRNA promotes glutamatergic transmission and presynaptic plasticity

BACKGROUND

Local translation at synapses is important for rapidly remodeling the synaptic proteome to sustain long-term plasticity and memory. While the regulatory mechanisms underlying memory-associated local translation have been widely elucidated in the postsynaptic/dendritic region, there is no direct evidence for which RNA-binding protein (RBP) in axons controls target-specific mRNA translation to promote long-term potentiation (LTP) and memory. We previously reported that translation controlled by cytoplasmic polyadenylation element binding protein 2 (CPEB2) is important for postsynaptic plasticity and memory. Here, we investigated whether CPEB2 regulates axonal translation to support presynaptic plasticity.

METHODS

Behavioral and electrophysiological assessments were conducted in mice with pan neuron/glia- or glutamatergic neuron-specific knockout of CPEB2. Hippocampal Schaffer collateral (SC)-CA1 and temporoammonic (TA)-CA1 pathways were electro-recorded to monitor synaptic transmission and LTP evoked by 4 trains of high-frequency stimulation. RNA immunoprecipitation, coupled with bioinformatics analysis, were used to unveil CPEB2-binding axonal RNA candidates associated with learning, which were further validated by Western blotting and luciferase reporter assays. Adeno-associated viruses expressing Cre recombinase were stereotaxically delivered to the pre- or post-synaptic region of the TA circuit to ablate Cpeb2 for further electrophysiological investigation. Biochemically isolated synaptosomes and axotomized neurons cultured on a microfluidic platform were applied to measure axonal protein synthesis and FM4-64FX-loaded synaptic vesicles.

RESULTS

Electrophysiological analysis of hippocampal CA1 neurons detected abnormal excitability and vesicle release probability in CPEB2-depleted SC and TA afferents, so we cross-compared the CPEB2-immunoprecipitated transcriptome with a learning-induced axonal translatome in the adult cortex to identify axonal targets possibly regulated by CPEB2. We validated that Slc17a6, encoding vesicular glutamate transporter 2 (VGLUT2), is translationally upregulated by CPEB2. Conditional knockout of CPEB2 in VGLUT2-expressing glutamatergic neurons impaired consolidation of hippocampus-dependent memory in mice. Presynaptic-specific ablation of Cpeb2 in VGLUT2-dominated TA afferents was sufficient to attenuate protein synthesis-dependent LTP. Moreover, blocking activity-induced axonal Slc17a6 translation by CPEB2 deficiency or cycloheximide diminished the releasable pool of VGLUT2-containing synaptic vesicles.

CONCLUSIONS

We identified 272 CPEB2-binding transcripts with altered axonal translation post-learning and established a causal link between CPEB2-driven axonal synthesis of VGLUT2 and presynaptic translation-dependent LTP. These findings extend our understanding of memory-related translational control mechanisms in the presynaptic compartment.

Mrj is a chaperone of the Hsp40 family that regulates Orb2 oligomerization and long-term memory in Drosophila

Orb2 the Drosophila homolog of cytoplasmic polyadenylation element binding (CPEB) protein forms prion-like oligomers. These oligomers consist of Orb2A and Orb2B isoforms and their formation is dependent on the oligomerization of the Orb2A isoform. Drosophila with a mutation diminishing Orb2A's prion-like oligomerization forms long-term memory but fails to maintain it over time. Since this prion-like oligomerization of Orb2A plays a crucial role in the maintenance of memory, here, we aim to find what regulates this oligomerization. In an immunoprecipitation-based screen, we identify interactors of Orb2A in the Hsp40 and Hsp70 families of proteins. Among these, we find an Hsp40 family protein Mrj as a regulator of the conversion of Orb2A to its prion-like form. Mrj interacts with Hsp70 proteins and acts as a chaperone by interfering with the aggregation of pathogenic Huntingtin. Unlike its mammalian homolog, we find Drosophila Mrj is neither an essential gene nor causes any gross neurodevelopmental defect. We observe a loss of Mrj results in a reduction in Orb2 oligomers. Further, Mrj knockout exhibits a deficit in long-term memory and our observations suggest Mrj is needed in mushroom body neurons for the regulation of long-term memory. Our work implicates a chaperone Mrj in mechanisms of memory regulation through controlling the oligomerization of Orb2A and its association with the translating ribosomes.

Prenatal diesel exhaust exposure alters hippocampal synaptic plasticity in offspring

Diesel exhaust particles (DEPs) are major air pollutants emitted from automobile engines. Prenatal exposure to DEPs has been linked to neurodevelopmental and neurodegenerative diseases associated with aging. However, the specific mechanism by DEPs impair the hippocampal synaptic plasticity in the offspring remains unclear. Pregnant C57BL/6 mice were administered DEPs solution via the tail vein every other day for a total of 10 injections, then the male offsprings were studied to assess learning and memory by the Morris water maze. Additionally, protein expression in the hippocampus, including CPEB3, NMDAR (NR1, NR2A, NR2B), PKA, SYP, PSD95, and p-CREB was analyzed using Western blotting and immunohistochemistry. The alterations in the histomorphology of the hippocampus were observed in male offspring on postnatal day 7 following prenatal exposure to DEPs. Furthermore, 8-week-old male offspring exposed to DEPs during prenatal development exhibited impairments in the Morris water maze test, indicating deficits in learning and memory. Mechanistically, the findings from our study indicate that exposure to DEPs during pregnancy may alter the expression of CPEB3, SYP, PSD95, NMDAR (NR1, NR2A, and NR2B), PKA, and p-CREB in the hippocampus of both immature and mature male offspring. The results offer evidence for the role of the NMDAR/PKA/CREB and CPEB3 signaling pathway in mediating the learning and memory toxicity of DEPs in male offspring mice. The alterations in signaling pathways may contribute to the observed damage to synaptic structure and transmission function plasticity caused by DEPs. The findings hold potential for informing future safety assessments of DEPs.

Improved CaP Nanoparticles for Nucleic Acid and Protein Delivery to Neural Primary Cultures and Stem Cells

Efficiently delivering exogenous materials into primary neurons and neural stem cells (NSCs) has long been a challenge in neurobiology. Existing methods have struggled with complex protocols, unreliable reproducibility, high immunogenicity, and cytotoxicity, causing a huge conundrum and hindering in-depth analyses. Here, we establish a cutting-edge method for transfecting primary neurons and NSCs, named teleofection, by a two-step process to enhance the formation of biocompatible calcium phosphate (CaP) nanoparticles. Teleofection enables both nucleic acid and protein transfection into primary neurons and NSCs, eliminating the need for specialized skills and equipment. It can easily fine-tune transfection efficiency by adjusting the incubation time and nanoparticle quantity, catering to various experimental requirements. Teleofection's versatility allows for the delivery of different cargos into the same cell culture, whether simultaneously or sequentially. This flexibility proves invaluable for long-term studies, enabling the monitoring of neural development and synapse plasticity. Moreover, teleofection ensures the consistent and robust expression of delivered genes, facilitating molecular and biochemical investigations. Teleofection represents a significant advancement in neurobiology, which has promise to transcend the limitations of current gene delivery methods. It offers a user-friendly, cost-effective, and reproducible approach for researchers, potentially revolutionizing our understanding of brain function and development.

Inhibition of Cpeb3 ribozyme elevates CPEB3 protein expression and polyadenylation of its target mRNAs and enhances object location memory

A self-cleaving ribozyme that maps to an intron of the cytoplasmic polyadenylation element-binding protein 3 (Cpeb3) gene is thought to play a role in human episodic memory, but the underlying mechanisms mediating this effect are not known. We tested the activity of the murine sequence and found that the ribozyme's self-scission half-life matches the time it takes an RNA polymerase to reach the immediate downstream exon, suggesting that the ribozyme-dependent intron cleavage is tuned to co-transcriptional splicing of the Cpeb3 mRNA. Our studies also reveal that the murine ribozyme modulates maturation of its harboring mRNA in both cultured cortical neurons and the hippocampus: inhibition of the ribozyme using an antisense oligonucleotide leads to increased CPEB3 protein expression, which enhances polyadenylation and translation of localized plasticity-related target mRNAs, and subsequently strengthens hippocampal-dependent long-term memory. These findings reveal a previously unknown role for self-cleaving ribozyme activity in regulating experience-induced co-transcriptional and local translational processes required for learning and memory.

Dynamic subtype- and context-specific subcellular RNA regulation in growth cones of developing neurons of the cerebral cortex

Molecular mechanisms that cells employ to compartmentalize function via localization of function-specific RNA and translation are only partially elucidated. We investigate long-range projection neurons of the cerebral cortex as highly polarized exemplars to elucidate dynamic regulation of RNA localization, stability, and translation within growth cones (GCs), leading tips of growing axons. Comparison of GC-localized transcriptomes between two distinct subtypes of projection neurons- interhemispheric-callosal and corticothalamic- across developmental stages identifies both distinct and shared subcellular machinery, and intriguingly highlights enrichment of genes associated with neurodevelopmental and neuropsychiatric disorders. Developmental context-specific components of GC-localized transcriptomes identify known and novel potential regulators of distinct phases of circuit formation: long-distance growth, target area innervation, and synapse formation. Further, we investigate mechanisms by which transcripts are enriched and dynamically regulated in GCs, and identify GC-enriched motifs in 3' untranslated regions. As one example, we identify cytoplasmic adenylation element binding protein 4 (CPEB4), an RNA binding protein regulating localization and translation of mRNAs encoding molecular machinery important for axonal branching and complexity. We also identify RNA binding motif single stranded interacting protein 1 (RBMS1) as a dynamically expressed regulator of RNA stabilization that enables successful callosal circuit formation. Subtly aberrant associative and integrative cortical circuitry can profoundly affect cortical function, often causing neurodevelopmental and neuropsychiatric disorders. Elucidation of context-specific subcellular RNA regulation for GC- and soma-localized molecular controls over precise circuit development, maintenance, and function offers generalizable insights for other polarized cells, and might contribute substantially to understanding neurodevelopmental and behavioral-cognitive disorders and toward targeted therapeutics.

MicroRNA-92a-CPEB3 axis protects neurons against inflammatory neurodegeneration

Neuroinflammation causes neuronal injury in multiple sclerosis (MS) and other neurological diseases. MicroRNAs (miRNAs) are important modulators of neuronal stress responses, but knowledge about their contribution to neuronal protection or damage during inflammation is limited. Here, we constructed a regulatory miRNA-mRNA network of inflamed motor neurons by leveraging cell type-specific miRNA and mRNA sequencing of mice undergoing experimental autoimmune encephalomyelitis (EAE). We found robust induction of miR-92a in inflamed spinal cord neurons and identified cytoplasmic polyadenylation element-binding protein 3 (Cpeb3) as a key target of miR-92a-mediated posttranscriptional silencing. We detected CPEB3 repression in inflamed neurons in murine EAE and human MS. Moreover, both miR-92a delivery and Cpeb3 deletion protected neuronal cultures against excitotoxicity. Supporting a detrimental effect of Cpeb3 in vivo, neuron-specific deletion in conditional Cpeb3 knockout animals led to reduced inflammation-induced clinical disability in EAE. Together, we identified a neuroprotective miR-92a-Cpeb3 axis in neuroinflammation that might serve as potential treatment target to limit inflammation-induced neuronal damage.

Neuralized1-Mediated CPEB3 Ubiquitination in the Spinal Dorsal Horn Contributes to the Pathogenesis of Neuropathic Pain in Rats

Compelling evidence has shown that Neuralized1 (Neurl1) facilitates hippocampal-dependent memory storage by modulating cytoplasmic polyadenylation element-binding protein 3 (CPEB3)-dependent protein synthesis. In the current study, we investigated the role of Neurl1 in the pathogenesis of neuropathic pain and the underlying mechanisms. The neuropathic pain was evaluated by lumbar 5 spinal nerve ligation (SNL) in rats. Immunofluorescence staining, Western blotting, qRT-PCR, and coimmunoprecipitation (Co-IP) were performed to investigate the underlying mechanisms. Our results showed that SNL led to an increase of Neurl1 in the spinal dorsal horn. Spinal microinjection of AAV-EGFP-Neurl1 shRNA alleviated mechanical allodynia; decreased the level of CPEB3 ubiquitination; inhibited the production of GluA1, GluA2, and PSD95; and reduced GluA1-containing AMPA receptors in the membrane of the dorsal horn following SNL. Knockdown of spinal CPEB3 decreased the production of GluA1, GluA2, and PSD95 in the dorsal horn and attenuated abnormal pain after SNL. Overexpression of Neurl1 in the dorsal horn resulted in pain-related hypersensitivity in naïve rats; raised the level of CPEB3 ubiquitination; increased the production of GluA1, GluA2, and PSD95; and augmented GluA1-containing AMPA receptors in the membrane in the dorsal horn. Moreover, spinal Neurl1 overexpression-induced mechanical allodynia in naïve rats was partially reversed by repeated intrathecal injections of CPEB3 siRNA. Collectively, our results suggest that SNL-induced upregulation of Neurl1 through CPEB3 ubiquitination-dependent production of GluA1, GluA2, and PSD95 in the dorsal horn contributes to the pathogenesis of neuropathic pain in rats. Targeting spinal Neurl1 might be a promising therapeutic strategy for the treatment of neuropathic pain.

CPEB and translational control by cytoplasmic polyadenylation: impact on synaptic plasticity, learning, and memory

The late 1990s were banner years in molecular neuroscience; seminal studies demonstrated that local protein synthesis, at or near synapses, was necessary for synaptic plasticity, the underlying cellular basis of learning and memory [1, 2]. The newly made proteins were proposed to "tag" the stimulated synapse, distinguishing it from naive synapses, thereby forming a cellular memory [3]. Subsequent studies demonstrated that the transport of mRNAs from soma to dendrite was linked with translational unmasking at synapses upon synaptic stimulation. It soon became apparent that one prevalent mechanism governing these events is cytoplasmic polyadenylation, and that among the proteins that control this process, CPEB, plays a central role in synaptic plasticity, and learning and memory. In vertebrates, CPEB is a family of four proteins, all of which regulate translation in the brain, that have partially overlapping functions, but also have unique characteristics and RNA binding properties that make them control different aspects of higher cognitive function. Biochemical analysis of the vertebrate CPEBs demonstrate them to respond to different signaling pathways whose output leads to specific cellular responses. In addition, the different CPEBs, when their functions go awry, result in pathophysiological phenotypes resembling specific human neurological disorders. In this essay, we review key aspects of the vertebrate CPEB proteins and cytoplasmic polyadenylation within the context of brain function.

Inhibition of CPEB3 ribozyme elevates CPEB3 protein expression and polyadenylation of its target mRNAs, and enhances object location memory

A self-cleaving ribozyme that maps to an intron of the cytoplasmic polyadenylation element binding protein 3 (CPEB3) gene is thought to play a role in human episodic memory, but the underlying mechanisms mediating this effect are not known. We tested the activity of the murine sequence and found that the ribozyme's self-scission half-life matches the time it takes an RNA polymerase to reach the immediate downstream exon, suggesting that the ribozyme-dependent intron cleavage is tuned to co-transcriptional splicing of the CPEB3 mRNA. Our studies also reveal that the murine ribozyme modulates maturation of its harboring mRNA in both cultured cortical neurons and the hippocampus: inhibition of the ribozyme using an antisense oligonucleotide leads to increased CPEB3 protein expression, which enhances polyadenylation and translation of localized plasticity-related target mRNAs, and subsequently strengthens hippocampal-dependent long-term memory. These findings reveal a previously unknown role for self-cleaving ribozyme activity in regulating experience-induced co-transcriptional and local translational processes required for learning and memory.

Cytoplasmic Polyadenylation Is an Ancestral Hallmark of Early Development in Animals

Differential regulation of gene expression has produced the astonishing diversity of life on Earth. Understanding the origin and evolution of mechanistic innovations for control of gene expression is therefore integral to evolutionary and developmental biology. Cytoplasmic polyadenylation is the biochemical extension of polyadenosine at the 3'-end of cytoplasmic mRNAs. This process regulates the translation of specific maternal transcripts and is mediated by the Cytoplasmic Polyadenylation Element-Binding Protein family (CPEBs). Genes that code for CPEBs are amongst a very few that are present in animals but missing in nonanimal lineages. Whether cytoplasmic polyadenylation is present in non-bilaterian animals (i.e., sponges, ctenophores, placozoans, and cnidarians) remains unknown. We have conducted phylogenetic analyses of CPEBs, and our results show that CPEB1 and CPEB2 subfamilies originated in the animal stem lineage. Our assessment of expression in the sea anemone, Nematostella vectensis (Cnidaria), and the comb jelly, Mnemiopsis leidyi (Ctenophora), demonstrates that maternal expression of CPEB1 and the catalytic subunit of the cytoplasmic polyadenylation machinery (GLD2) is an ancient feature that is conserved across animals. Furthermore, our measurements of poly(A)-tail elongation reveal that key targets of cytoplasmic polyadenylation are shared between vertebrates, cnidarians, and ctenophores, indicating that this mechanism orchestrates a regulatory network that is conserved throughout animal evolution. We postulate that cytoplasmic polyadenylation through CPEBs was a fundamental innovation that contributed to animal evolution from unicellular life.

Increased level of RAB39B leads to neuronal dysfunction and behavioural changes in mice

Duplications of the Xq28 region are a common cause of X-linked intellectual disability (XLID). The RAB39B gene locates in Xq28 and has been implicated in disease pathogenesis. However, whether increased dosage of RAB39B leads to cognitive impairment and synaptic dysfunction remains elusive. Herein, we overexpressed RAB39B in mouse brain by injecting AAVs into bilateral ventricles of neonatal animals. We found that at 2 months of age, neuronal overexpression of RAB39B impaired the recognition memory and the short-term working memory in mice and resulted in certain autism-like behaviours, including social novelty defect and repetitive grooming behaviour in female mice. Moreover, overexpression of RAB39B decreased dendritic arborization of primary neurons in vitro and reduced synaptic transmission in female mice. Neuronal overexpression of RAB39B also altered autophagy without affecting levels and PSD distribution of synaptic proteins. Our results demonstrate that overexpression of RAB39B compromises normal neuronal development, thereby resulting in dysfunctional synaptic transmission and certain intellectual disability and behavioural abnormalities in mice. These findings identify a molecular mechanism underlying XLID with increased copy numbers of Xq28 and provide potential strategies for disease intervention.

CPEB3 low-complexity motif regulates local protein synthesis via protein-protein interactions in neuronal ribonucleoprotein granules

Biomolecular condensates, membraneless organelles found throughout the cell, play critical roles in many aspects of cellular function. Ribonucleoprotein granules (RNPs) are a type of biomolecular condensate necessary for local protein synthesis and are involved in synaptic plasticity and long-term memory. Most of the proteins in RNPs possess low-complexity motifs (LCM), allowing for increased promiscuity of protein-protein interactions. Here, we describe the importance of protein-protein interactions mediated by the LCM of RNA-binding protein cytoplasmic polyadenylation element binding protein 3 (CPEB3). CPEB3 is necessary for long-term synaptic plasticity and memory persistence, but the mechanisms involved are still not completely elucidated. We now present key mechanisms involved in its regulation of synaptic plasticity. We find that CPEB3-LCM plays a role in appropriate local protein synthesis of messenger ribonucleic acid (mRNA) targets, through crucial protein-protein interactions that drive localization to neuronal Decapping protein 1 (DCP1)-bodies. Translation-promoting CPEB3 and translation-inhibiting CPEB1 are packaged into neuronal RNP granules immediately after chemical long-term potentiation is induced, but only translation-promoting CPEB3 is repackaged to these organelles at later time points. This localization to neuronal RNP granules is critical for functional influence on translation as well as overall local protein synthesis (measured as α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) insertion into the membrane and localization to the synapse). We therefore conclude that protein-protein interaction between the LCM of CPEB3 plays a critical role in local protein synthesis by utilizing neuronal RNP granules.

Targeting the overexpressed mitochondrial protein VDAC1 in a mouse model of Alzheimer's disease protects against mitochondrial dysfunction and mitigates brain pathology

BACKGROUND

Alzheimer's disease (AD) exhibits mitochondrial dysfunctions associated with dysregulated metabolism, brain inflammation, synaptic loss, and neuronal cell death. As a key protein serving as the mitochondrial gatekeeper, the voltage-dependent anion channel-1 (VDAC1) that controls metabolism and Ca²⁺ homeostasis is positioned at a convergence point for various cell survival and death signals. Here, we targeted VDAC1 with VBIT-4, a newly developed inhibitor of VDAC1 that prevents its pro-apoptotic activity, and mitochondria dysfunction.

METHODS

To address the multiple pathways involved in AD, neuronal cultures and a 5 × FAD mouse model of AD were treated with VBIT-4. We addressed multiple topics related to the disease and its molecular mechanisms using immunoblotting, immunofluorescence, q-RT-PCR, 3-D structural analysis and several behavioral tests.

RESULTS

In neuronal cultures, amyloid-beta (Aβ)-induced VDAC1 and p53 overexpression and apoptotic cell death were prevented by VBIT-4. Using an AD-like 5 × FAD mouse model, we showed that VDAC1 was overexpressed in neurons surrounding Aβ plaques, but not in astrocytes and microglia, and this was associated with neuronal cell death. VBIT-4 prevented the associated pathophysiological changes including neuronal cell death, neuroinflammation, and neuro-metabolic dysfunctions. VBIT-4 also switched astrocytes and microglia from being pro-inflammatory/neurotoxic to neuroprotective phenotype. Moreover, VBIT-4 prevented cognitive decline in the 5 × FAD mice as evaluated using several behavioral assessments of cognitive function. Interestingly, VBIT-4 protected against AD pathology, with no significant change in phosphorylated Tau and only a slight decrease in Aβ-plaque load.

CONCLUSIONS

The study suggests that mitochondrial dysfunction with its gatekeeper VDAC1 is a promising target for AD therapeutic intervention, and VBIT-4 is a promising drug candidate for AD treatment.

RNA-binding protein signaling in adult neurogenesis

The process of neurogenesis in the brain, including cell proliferation, differentiation, survival, and maturation, results in the formation of new functional neurons. During embryonic development, neurogenesis is crucial to produce neurons to establish the nervous system, but the process persists in certain brain regions during adulthood. In adult neurogenesis, the production of new neurons in the hippocampus is accomplished via the division of neural stem cells. Neurogenesis is regulated by multiple factors, including gene expression at a temporal scale and post-transcriptional modifications. RNA-binding Proteins (RBPs) are known as proteins that bind to either double- or single-stranded RNA in cells and form ribonucleoprotein complexes. The involvement of RBPs in neurogenesis is crucial for modulating gene expression changes and posttranscriptional processes. Since neurogenesis affects learning and memory, RBPs are closely associated with cognitive functions and emotions. However, the pathways of each RBP in adult neurogenesis remain elusive and not clear. In this review, we specifically summarize the involvement of several RBPs in adult neurogenesis, including CPEB3, FXR2, FMRP, HuR, HuD, Lin28, Msi1, Sam68, Stau1, Smaug2, and SOX2. To understand the role of these RBPs in neurogenesis, including cell proliferation, differentiation, survival, and maturation as well as posttranscriptional gene expression, we discussed the protein family, structure, expression, functional domain, and region of action. Therefore, this narrative review aims to provide a comprehensive overview of the RBPs, their function, and their role in the process of adult neurogenesis as well as to identify possible research directions on RBPs and neurogenesis.

Comparative analyses of vertebrate CPEB proteins define two subfamilies with coordinated yet distinct functions in post-transcriptional gene regulation

Background

Vertebrate CPEB proteins bind mRNAs at cytoplasmic polyadenylation elements (CPEs) in their 3′ UTRs, leading to cytoplasmic changes in their poly(A) tail lengths; this can promote translational repression or activation of the mRNA. However, neither the regulation nor the mechanisms of action of the CPEB family per se have been systematically addressed to date.

Results

Based on a comparative analysis of the four vertebrate CPEBs, we determine their differential regulation by phosphorylation, the composition and properties of their supramolecular assemblies, and their target mRNAs. We show that all four CPEBs are able to recruit the CCR4-NOT deadenylation complex to repress the translation. However, their regulation, mechanism of action, and target mRNAs define two subfamilies. Thus, CPEB1 forms ribonucleoprotein complexes that are remodeled upon a single phosphorylation event and are associated with mRNAs containing canonical CPEs. CPEB2–4 are regulated by multiple proline-directed phosphorylations that control their liquid–liquid phase separation. CPEB2–4 mRNA targets include CPEB1-bound transcripts, with canonical CPEs, but also a specific subset of mRNAs with non-canonical CPEs.

Conclusions

Altogether, these results show how, globally, the CPEB family of proteins is able to integrate cellular cues to generate a fine-tuned adaptive response in gene expression regulation through the coordinated actions of all four members.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13059-022-02759-y.

Otizm Spektrum Bozukluğu Olan Hastalarda Öğrenme ve Hafıza Bozukluklarının NEURL1 ve RGS14 Genleri ile İlişkisi

Aim: We aimed to evaluate the relationship between learning-memory difficulties and NEURL1 and RGS14 genes in patients with autism spectrum disorders (ASD). Method: Forty children with ASD (20 ASD, 20 high functioning autism (HFA)) and 20 healthy controls were enrolled in this study. NEURL1 and RGS14 gene expressions in the blood samples of volunteers were assessed by quantitative Real-Time PCR (qRT-PCR). The clinical and demographical findings in patients were determined and examined relation with the gene expressions. Results: According to our findings, NEURL1 gene expression was decreased in both patient groups compared to the control (p0.05). A statistically significant correlation was found between learning and memory difficulties and RGS14 gene expression in HFA patients (p = 0.045). There was a positive correlation between between NEURL1 and RGS14 gene expressions of ASD patients (p=0.032, r=0,59). Conclusion: According to this study, NEURL1 gene may be proposed as a candidate gene for ASD. Nonetheless, we recommend that both genes be studied with more patients and preferably with brain tissues. These genes were evaluated for the first time in a clinical study on autism, and we believe that they will contribute to the literature in this respect.

The amyloid state of proteins: A boon or bane?

Proteins and their aggregation is significant field of research due to their association with various conformational maladies including well-known neurodegenerative diseases like Alzheimer's (AD), Parkinson's (PD), and Huntington's (HD) diseases. Amyloids despite being given negative role for decades are also believed to play a functional role in bacteria to humans. In this review, we discuss both facets of amyloid. We have shed light on AD, which is one of the most common age-related neurodegenerative disease caused by accumulation of Aβ fibrils as extracellular senile plagues. We also discuss PD caused by the aggregation and deposition of α-synuclein in form of Lewy bodies and neurites. Other amyloid-associated diseases such as HD and amyotrophic lateral sclerosis (ALS) are also discussed. We have also reviewed functional amyloids that have various biological roles in both prokaryotes and eukaryotes that includes formation of biofilm and cell attachment in bacteria to hormone storage in humans, We discuss in detail the role of Curli fibrils' in biofilm formation, chaplins in cell attachment to peptide hormones, and Pre-Melansomal Protein (PMEL) roles. The disease-related and functional amyloids are compared with regard to their structural integrity, variation in regulation, and speed of forming aggregates and elucidate how amyloids have turned from foe to friend.

CPEB3 deficiency in mice affect ovarian follicle development and causes premature ovarian insufficiency

Premature ovarian insufficiency (POI) is a heterogeneous and multifactorial disorder. In recent years, there has been an increasing interest in research on the pathogenesis and treatment of POI, owing to the implementation of the second-child policy in China. Cytoplasmic polyadenylation element-binding protein 3 (CPEB3) is an RNA-binding protein that can bind to specific RNA sequences. CPEB3 can bind to and affect the expression, cellular location, and stability of target RNAs. Cpeb3 is highly expressed in the ovary; however, its functions remain unknown. In this study, Cpeb3-mutant mice were used to characterize the physiological functions of CPEB3. Cpeb3-mutant female mice manifested signs of gradual loss of ovarian follicles, ovarian follicle development arrest, increased follicle atresia, and subfertility with a phenotype analogous to POI in women. Further analysis showed that granulosa cell proliferation was inhibited and apoptosis was markedly increased in Cpeb3-mutant ovaries. In addition, the expression of Gdf9, a potential target of CPEB3, was decreased in Cpeb3-mutant ovaries and oocytes. Altogether, these results reveal that CPEB3 is essential for ovarian follicle development and female fertility as it regulates the expression of Gdf9 in oocytes, disruption of which leads to impaired ovarian follicle development and POI.

Role of Different Doses of Ketamine in Postoperative Neurocognitive Function in Aged Mice Undergoing Partial Hepatectomy by Regulating the Bmal1/NMDA/NF-Κb Axis

BACKGROUND

The current study set out to probe the function of different doses of ketamine in postoperative neurocognitive disorder (PND) in aged mice undergoing partial hepatectomy (PH) with the involvement of the brain and muscle aryl hydrocarbon receptor nuclear translocator-like protein 1 (Bmal1)/n-methyl-D-aspartate (NMDA)/nuclear factor-kappa B (NF-κB) axis.

METHODS

First, aged mice were intraperitoneally injected with different doses of ketamine prior to surgery, followed by hepatic lobectomy. Afterward, mice cognitive function was assessed. In addition, Bmal1 mRNA expression patterns were quantified, while NMDA 2B receptor, NF-κB p65, synapsin 1, and postsynaptic density 95 (PSD95) levels were determined; the release of inflammatory factors was detected, and ionized calcium-binding adapter molecule-1 expression was measured to quantify microglia activation. In addition, Bmal1-knockout (Bmal1-KO) mice were intraperitoneally injected with a subanesthetic dose of ketamine to verify the mechanism of Bmal1 in regulating the NMDA 2B subunit (NR2B)/NF-κB axis to affect PH in aged patients.

RESULTS

After PH, hippocampal-dependent memory was impaired, and synapsin 1 and PSD95 levels were downregulated. On the other hand, PH diminished Bmal1 expression but elevated NR2B and NF-κB p65 levels and anesthetic doses of ketamine further regulated the Bmal1/NMDA/NF-κB axis. In Bmal1-KO mice, the NMDA/NF-κB axis was activated, the release of inflammatory cytokines was promoted, and hippocampus-dependent memory was impaired, which were reversed by a subanesthetic dose of ketamine.

CONCLUSION

Altogether, findings obtained in our study indicated that a subanesthetic dose of ketamine activated Bmal1, downregulated the NMDA/NF-κB axis, and reduced inflammation and microglia activation to alleviate PND in aged mice undergoing PH.

Human Cytomegalovirus Immediate Early Protein 2 Protein Causes Cognitive Disorder by Damaging Synaptic Plasticity in Human Cytomegalovirus-UL122-Tg Mice

Human cytomegalovirus (HCMV) infection is very common in the human population all around the world. Although the majority of HCMV infections are asymptomatic, they can cause neurologic deficits. Previous studies have shown that immediate early protein 2 (IE2, also known as UL122) of HCMV is related with the cognitive disorder mechanism. Due to species isolation, a HCMV-infected animal model could not be established which meant a study into the long-term effects of IE2 on neural development could not be carried out. By establishing HCMV-UL122-Tg mice (UL122 mice), we explored the cognitive behavior and complexity of neuron changes in this transgenic UL122 mice that could consistently express IE2 protein at different ages (confirmed in both 6- and 12-month-old UL122 mice). In the Morris water maze, cognitive impairment was more pronounced in 12-month-old UL122 mice than in 6-month-old ones. At the same time, a decrease of the density of dendritic spines and branches in the hippocampal neurons of 12-month-old mice was observed. Moreover, long-term potentiation was showed to be impaired in 12-month-old UL122 mice. The expressions of several synaptic plasticity-regulated molecules were reduced in 12-month-old UL122 mice, including scaffold proteins postsynaptic density protein 95 (PSD95) and microtubule-associated protein 2 (MAP2). Binding the expression of IE2 was increased in 12-month-old mice compared with 6-month-old mice, and results of statistical analysis suggested that the cognitive damage was not caused by natural animal aging, which might exclude the effect of natural aging on cognitive impairment. All these results suggested that IE2 acted as a pathogenic regulator in damaging synaptic plasticity by downregulating the expression of plasticity-related proteins (PRPs), and this damage increased with aging.

CPEB3-dowregulated Nr3c1 mRNA translation confers resilience to developing posttraumatic stress disorder-like behavior in fear-conditioned mice

Susceptibility or resilience to posttraumatic stress disorder (PTSD) depends on one's ability to appropriately adjust synaptic plasticity for coping with the traumatic experience. Activity-regulated mRNA translation synthesizes plasticity-related proteins to support long-term synaptic changes and memory. Hence, cytoplasmic polyadenylation element-binding protein 3-knockout (CPEB3-KO) mice, showing dysregulated translation-associated synaptic rigidity, may be susceptible to PTSD-like behavior. Here, using a context-dependent auditory fear conditioning and extinction paradigm, we found that CPEB3-KO mice exhibited traumatic intensity-dependent PTSD-like fear memory. A genome-wide screen of CPEB3-bound transcripts revealed that Nr3c1, encoding glucocorticoid receptor (GR), was translationally suppressed by CPEB3. Thus, CPEB3-KO neurons with elevated GR expression exhibited increased corticosterone-induced calcium influx and decreased mRNA and protein levels of brain-derived neurotrophic factor (Bdnf). Moreover, the reduced expression of BDNF was associated with increased GR level during fear extinction in CPEB3-KO hippocampi. Intracerebroventricular delivery of BDNF before extinction training mitigated spontaneous fear intrusion in CPEB3-KO mice during extinction recall. Analysis of two GEO datasets revealed decreased transcriptomic expression of CPEB3 but not NR3C1 in peripheral blood mononuclear cells of humans with PTSD. Collectively, this study reveals that CPEB3, as a potential PTSD-risk gene, downregulates Nr3c1 translation to maintain proper GR-BDNF signaling for fear extinction.

The role of CPEB family proteins in the nervous system function in the norm and pathology

Posttranscriptional gene regulation includes mRNA transport, localization, translation, and regulation of mRNA stability. CPEB (cytoplasmic polyadenylation element binding) family proteins bind to specific sites within the 3′-untranslated region and mediate poly- and deadenylation of transcripts, activating or repressing protein synthesis. As part of ribonucleoprotein complexes, the CPEB proteins participate in mRNA transport and localization to different sub-cellular compartments. The CPEB proteins are evolutionarily conserved and have similar functions in vertebrates and invertebrates. In the nervous system, the CPEB proteins are involved in cell division, neural development, learning, and memory. Here we consider the functional features of these proteins in the nervous system of phylogenetically distant organisms: Drosophila, a well-studied model, and mammals. Disruption of the CPEB proteins functioning is associated with various pathologies, such as autism spectrum disorder and brain cancer. At the same time, CPEB gene regulation can provide for a recovery of the brain function in patients with fragile X syndrome and Huntington's disease, making the CPEB genes promising targets for gene therapy.

Long non-coding RNA MIR22HG inhibits glioma progression by downregulating microRNA-9/CPEB3

Glioma is one of the most common and aggressive malignant intracranial tumors worldwide. Recently, non-coding RNAs have been found to play critical roles in the development of glioma. However, the exact mechanisms have not been fully elucidated. In the present study, reverse transcription-quantitative PCR was used to determine the expression level of the long non-coding RNA MIR22HG and microRNA (miR)-9, while western blot analysis was used to detect the protein expression level of CPEB3. The potential binding sites were predicted using the StarBase v2.0 online tool and the hypothesis was verified using a luciferase reporter assay. A Cell Counting Kit-8 assay was used to assess cell viability, while wound healing and Matrigel assays were used to determine the migration and invasion ability of glioma cancer cells. The results showed that MIR22HG expression level was decreased but miR-9 expression level was elevated in glioma tissues and cell lines. Furthermore, MIR22HG was found to sponge miR-9, while CPEB3 was the direct target of miR-9 in the glioma cell line. Functionally, MIR22HG regulated the proliferation, invasion and migration of the glioma cell line by targeting miR-9. CPEB3 may be involved in the progression of the glioma cell line. Taken together, these findings confirmed that MIR22HG suppressed glioma development by inhibiting the miR-9/CPEB3 axis and provides a novel therapeutic strategy for glioma treatment.

CPEB3 regulates neuron-specific alternative splicing and involves neurogenesis gene expression

In the mammalian brain, alternative pre-mRNA splicing is a fundamental mechanism that modifies neuronal function dynamically where secretion of different splice variants regulates neurogenesis, development, pathfinding, maintenance, migration, and synaptogenesis. Sequence-specific RNA-Binding Protein CPEB3 has distinctive isoform-distinct biochemical interactions and neuronal development assembly roles. Nonetheless, the mechanisms moderating splice isoform options remain unclear. To establish the modulatory trend of CPEB3, we cloned and excessively expressed CPEB3 in HT22 cells. We used RNA-seq to analyze CPEB3-regulated alternative splicing on control and CPEB3-overexpressing cells. Consequently, we used iRIP-seq to identify CPEB-binding targets. We additionally validated CPEB3-modulated genes using RT-qPCR. CPEB3 overexpression had insignificant effects on gene expression in HT22 cells. Notably, CPEB3 partially modulated differential gene splicing enhanced in the modulation of neural development, neuron cycle, neurotrophin, synapse, and specific development pathway, implying an alternative splicing regulatory mechanism associated with neurogenesis. Moreover, qRT-PCR verified the CPEB3-modulated transcription of neurogenesis genes LCN2 and NAV2, synaptogenesis gene CYLD, as well as neural development gene JADE1. Herein, we established that CPEB3 is a critical modulator of alternative splicing in neurogenesis, which remarkably enhances the current understanding of the CPEB3 mediated alternative pre-mRNA splicing.

Loss of TREM2 Confers Resilience to Synaptic and Cognitive Impairment in Aged Mice

Triggering receptor expressed on myeloid cells 2 (TREM2), a receptor exclusively expressed by microglia in the brain, modulates microglial immune homeostasis. Human genetic studies have shown that the loss-of-function mutations in TREM2 signaling are strongly associated with an elevated risk of age-related neurodegenerative diseases including Alzheimer's disease (AD). Numerous studies have investigated the impact of TREM2 deficiency in the pathogenic process of AD. However, the role of TREM2 in shaping neuronal and cognitive function during normal aging is underexplored. In the present study, we employed behavioral, electrophysiological, and biochemical approaches to assess cognitive and synaptic function in male and female young and aged TREM2-deficient (Trem2-/-) mice compared with age-matched, sex-matched, and genetic background-matched wild-type (WT) C57BL/6J controls. Young Trem2-/- mice exhibited normal cognitive function and synaptic plasticity but had increased dendritic spine density compared with young WT. Unexpectedly, aged Trem2-/- mice showed superior cognitive performance compared with aged WT controls. Consistent with the behavioral data, aged Trem2-/- mice displayed significantly enhanced hippocampal long-term potentiation (LTP) and increased dendritic spine density and synaptic markers compared with aged WT mice. Taken together, these findings suggest that loss of TREM2 affects the neuronal structure and confers resilience to age-related synaptic and cognitive impairment during non-pathogenic aging.SIGNIFICANCE STATEMENT Microglia are innate immune cells of the brain that orchestrates neurodevelopment, synaptic function, and immune response to environmental stimuli. Microglial triggering receptor expressed on myeloid cells 2 (TREM2) signaling plays pivotal roles in regulating these functions and loss of TREM2 signaling leads to increased risk of developing age-related neurologic disorders. However, the neurologic role of TREM2 in normal aging is poorly understood. The results of the present study unveil the positive impacts of TREM2 deficiency on cognitive and synaptic function during aging and suggest that TREM2 may exert detrimental effects on neuronal function. The possibility of age-related negative impacts from TREM2 is critically important since TREM2 has emerged as a major therapeutic target for Alzheimer's dementia.

Role of CPEB3 protein in learning and memory: new insights from synaptic plasticity

The cytoplasmic polyadenylation element-binding (CPEB) protein family have demonstrated a crucial role for establishing synaptic plasticity and memory in model organisms. In this review, we outline evidence for CPEB3 as a crucial regulator of learning and memory, citing evidence from behavioral, electrophysiological and morphological studies. Subsequently, the regulatory role of CPEB3 is addressed in the context of the plasticity-related proteins, including AMPA and NMDA receptor subunits, actin, and the synaptic scaffolding protein PSD95. Finally, we delve into some of the more well-studied molecular mechanisms that guide the functionality of this dynamic regulator both during synaptic stimulation and in its basal state, including a variety of upstream regulators, post-translational modifications, and important structural domains that confer the unique properties of CPEB3. Collectively, this review offers a comprehensive view of the regulatory layers that allow a pathway for CPEB3’s maintenance of translational control that guides the necessary protein changes required for the establishment and maintenance of lasting synaptic plasticity and ultimately, long term learning and memory.

Emotional Stress Induces Structural Plasticity in Bergmann Glial Cells via an AC5-CPEB3-GluA1 Pathway

Stress alters brain function by modifying the structure and function of neurons and astrocytes. The fine processes of astrocytes are critical for the clearance of neurotransmitters during synaptic transmission. Thus, experience-dependent remodeling of glial processes is anticipated to alter the output of neural circuits. However, the molecular mechanisms that underlie glial structural plasticity are not known. Here we show that a single exposure of male and female mice to an acute stress produced a long-lasting retraction of the lateral processes of cerebellar Bergmann glial cells. These cells express the GluA1 subunit of AMPA-type glutamate receptors, and GluA1 knockdown is known to shorten the length of glial processes. We found that stress reduced the level of GluA1 protein and AMPA receptor-mediated currents in Bergmann glial cells, and these effects were absent in mice devoid of CPEB3, a protein that binds to GluA1 mRNA and regulates GluA1 protein synthesis. Administration of a β-adrenergic receptor blocker attenuated the reduction in GluA1, and deletion of adenylate cyclase 5 prevented GluA1 suppression. Therefore, stress suppresses GluA1 protein synthesis via an adrenergic/adenylyl cyclase/CPEB3 pathway, and reduces the length of astrocyte lateral processes. Our results identify a novel mechanism for GluA1 subunit plasticity in non-neuronal cells and suggest a previously unappreciated role for AMPA receptors in stress-induced astrocytic remodeling.SIGNIFICANCE STATEMENT Astrocytes play important roles in synaptic transmission by extending fine processes around synapses. In this study, we showed that a single exposure to an acute stress triggered a retraction of lateral/fine processes in mouse cerebellar astrocytes. These astrocytes express GluA1, a glutamate receptor subunit known to lengthen astrocyte processes. We showed that astrocytic structural changes are associated with a reduction of GluA1 protein levels. This requires activation of β-adrenergic receptors and is triggered by noradrenaline released during stress. We identified adenylyl cyclase 5, an enzyme that elevates cAMP levels, as a downstream effector and found that lowering GluA1 levels depends on CPEB3 proteins that bind to GluA1 mRNA. Therefore, stress regulates GluA1 protein synthesis via an adrenergic/adenylyl cyclase/CPEB3 pathway in astrocytes and remodels their fine processes.

The wild species genome ancestry of domestic chickens

BACKGROUND

Hybridisation and introgression play key roles in the evolutionary history of animal species. They are commonly observed within several orders in wild birds. The domestic chicken Gallus gallus domesticus is the most common livestock species. More than 65 billion chickens are raised annually to produce meat and 80 million metric tons of egg for global human consumption by the commercial sector. Unravelling the origin of its genetic diversity has major application for sustainable breeding improvement programmes.

RESULTS

In this study, we report genome-wide analyses for signatures of introgression between indigenous domestic village chicken and the four wild Gallus species. We first assess the genome-wide phylogeny and divergence time across the genus Gallus. Genome-wide sequence divergence analysis supports a sister relationship between the Grey junglefowl G. sonneratii and Ceylon junglefowl G. lafayettii. Both species form a clade that is sister to the Red junglefowl G. gallus, with the Green junglefowl G. varius the most ancient lineage within the genus. We reveal extensive bidirectional introgression between the Grey junglefowl and the domestic chicken and to a much lesser extent with the Ceylon junglefowl. We identify a single case of Green junglefowl introgression. These introgressed regions include genes with biological functions related to development and immune system.

CONCLUSIONS

Our study shows that while the Red junglefowl is the main ancestral species, introgressive hybridisation episodes have impacted the genome and contributed to the diversity of the domestic chicken, although likely at different levels across its geographic range.

RPS23RG1 Is Required for Synaptic Integrity and Rescues Alzheimer's Disease-Associated Cognitive Deficits

BACKGROUND

Although synaptic impairment is a prerequisite to cognitive deficiencies in Alzheimer's disease (AD), mechanisms underlying the dysregulation of essential synaptic scaffolding components and their integrity remain elusive. RPS23RG1 is a newly identified protein implicated in AD. However, the physiological function of RPS23RG1 has yet to be determined.

METHODS

We investigated the role of RPS23RG1 in maintaining synaptic structure and function in cell cultures and in Rps23rg1 knockout mice and determined whether targeting RPS23RG1-mediated pathways has therapeutic potential in APP/PS1 AD model mice.

RESULTS

Deletion of the Rps23rg1 gene resulted in severe memory deficits and impairment of postsynaptic structure and function, with marked reductions in postsynaptic densities-93 and -95 (PSD-93 and PSD-95) levels. RPS23RG1 interacted with PSD-93/PSD-95 through its intracellular domain, consequently sequestering PSD-93/PSD-95 from murine double minute 2-mediated ubiquitination and degradation, thereby maintaining synaptic function. Restoration of PSD-93/PS-D95 levels reversed synaptic and memory deficits in Rps23rg1 knockout mice. We further observed attenuated RPS23RG1 expression in human AD, which positively correlated with PSD-93/PSD-95 levels. Importantly, an RPS23RG1-derived peptide comprising a unique PSD-93/PSD-95 interaction motif rescued synaptic and cognitive defects in Rps23rg1 knockout and AD mouse models.

CONCLUSIONS

Our results reveal a role for RPS23RG1 in maintaining synaptic integrity and function and provide a new mechanism for synaptic dysfunction in AD pathogenesis. This demonstrates that RPS23RG1-mediated pathways show good therapeutic potential in AD intervention.

CPEB4-Dependent Neonate-Born Granule Cells Are Required for Olfactory Discrimination

The rodent olfactory bulb (OB) contains two distinct populations of postnatally born interneurons, mainly granule cells (GCs), to support local circuits throughout life. During the early postnatal period (i.e., 2 weeks after birth), GCs are mostly produced locally from progenitor cells in the OB with a proportion of them deriving from proliferating cells in the rostral migratory stream (RMS). Afterward, the replenishment of GCs involves differentiated neuroblasts from the subventricular zone (SVZ) in a process known as adult neurogenesis. Although numerous studies have addressed the role of SVZ-born GCs in olfactory behaviors, the function of GCs produced early postnatally in the OB remains elusive. Our previous study demonstrated that the translational regulator, cytoplasmic polyadenylation element-binding protein 4 (CPEB4), is a survival factor exclusively for neonate-born but not SVZ/adult-derived GCs, so CPEB4-knockout (KO) mice provide unique leverage to study early postnatal-born GC-regulated olfactory functions. CPEB4-KO mice with hypoplastic OBs showed normal olfactory sensitivity and short-term memory, but impaired ability to spontaneously discriminate two odors. Such olfactory dysfunction was recapitulated in specific ablation of Cpeb4 gene in inhibitory interneurons but not in excitatory projection neurons or SVZ-derived interneurons. The continuous supply of GCs from adult neurogenesis eventually restored the OB size but not the discrimination function in 6-month-old KO mice. Hence, in the early postnatal OB, whose function cannot be replaced by adult-born GCs, construct critical circuits for odor discrimination.

CPEB2-dependent translation of long 3'-UTR Ucp1 mRNA promotes thermogenesis in brown adipose tissue

Expression of mitochondrial proton transporter uncoupling protein 1 (UCP1) in brown adipose tissue (BAT) is essential for mammalian thermogenesis. While human UCP1 mRNA exists in a long form only, alternative polyadenylation creates two different isoforms in mice with 10% of UCP1 mRNA found in the long form (Ucp1L) and ~90% in the short form (Ucp1S). We generated a mouse model expressing only Ucp1S and found that it showed impaired thermogenesis due to a 60% drop in UCP1 protein levels, suggesting that Ucp1L is more efficiently translated than Ucp1S. In addition, we found that β3 adrenergic receptor signaling promoted the translation of mouse Ucp1L and human Ucp1 in a manner dependent on cytoplasmic polyadenylation element binding protein 2 (CPEB2). CPEB2-knockout mice showed reduced UCP1 levels and impaired thermogenesis in BAT, which was rescued by ectopic expression of CPEB2. Hence, long 3'-UTR Ucp1 mRNA translation activated by CPEB2 is likely conserved and important in humans to produce UCP1 for thermogenesis.

Hippocampal β2‑microglobulin mediates sepsis‑induced cognitive impairment

Acute brain dysfunction is a frequent complication in sepsis patients and is associated with long‑term neurocognitive consequences and increased mortality, yet the underlying mechanism remains unclear. Emerging evidence has suggested that β2‑microglobulin [a component of major histocompatibility complex (MHC) class I molecules] is involved in cognitive dysfunction in various neurological diseases. Therefore, the present study tested the hypothesis that β2‑microglobulin in the brain also mediates sepsis‑induced cognitive impairment. In the present study, wild‑type and antigen processing 1 (Tap1)‑deficient mice (Tap1‑/‑) were subjected to cecal ligation and puncture (CLP). Survival rate, cognitive function, and biochemical analysis were performed at the indicated time points. The data revealed that CLP induced anxiety‑like behavior and impaired hippocampal‑dependent contextual memory in wild‑type mice, which was accompanied by hippocampal microglial activation, increased level of interleukin‑1β, and decreased concentrations of brain derived neurotrophic factor and postsynaptic density protein 95. Notably, it was demonstrated that Tap1‑/‑ mice with reduced cell surface expression of MHC I protected mice from anxiety‑like behavior and impaired hippocampal‑dependent contextual memory and reversed most of these biochemical parameters following sepsis development. In summary, the results of the present study suggest that β2‑microglobulin negatively regulates cognitive impairment in an animal model of sepsis induced by CLP.

JIP1-Mediated JNK Activation Negatively Regulates Synaptic Plasticity and Spatial Memory

The c-Jun N-terminal kinase (JNK) signal transduction pathway is implicated in learning and memory. Here, we examined the role of JNK activation mediated by the JNK-interacting protein 1 (JIP1) scaffold protein. We compared male wild-type mice with a mouse model harboring a point mutation in the Jip1 gene that selectively blocks JIP1-mediated JNK activation. These male mutant mice exhibited increased NMDAR currents, increased NMDAR-mediated gene expression, and a lower threshold for induction of hippocampal long-term potentiation. The JIP1 mutant mice also displayed improved hippocampus-dependent spatial memory and enhanced associative fear conditioning. These results were confirmed using a second JIP1 mutant mouse model that suppresses JNK activity. Together, these observations establish that JIP1-mediated JNK activation contributes to the regulation of hippocampus-dependent, NMDAR-mediated synaptic plasticity and learning.SIGNIFICANCE STATEMENT The results of this study demonstrate that c-Jun N-terminal kinase (JNK) activation induced by the JNK-interacting protein 1 (JIP1) scaffold protein negatively regulates the threshold for induction of long-term synaptic plasticity through the NMDA-type glutamate receptor. This change in plasticity threshold influences learning. Indeed, mice with defects in JIP1-mediated JNK activation display enhanced memory in hippocampus-dependent tasks, such as contextual fear conditioning and Morris water maze, indicating that JIP1-JNK constrains spatial memory. This study identifies JIP1-mediated JNK activation as a novel molecular pathway that negatively regulates NMDAR-dependent synaptic plasticity and memory.

A meta-analytic approach to genes that are associated with impaired and elevated spatial memory performance

Spatial memory deficits are a common hallmark of psychiatric conditions, possibly due to a genetic predisposition. Thus, unravelling the relationship between genes and memory might suggest novel therapeutic targets and pathogenetic pathways. Genetic deletions are known to lead to memory deficits (post-deletion "forgetfulness" genes, PDF), or, in few instances to improve spatial memory (post-deletion "hypermnesic" genes, PDH). To assess this topic, we performed a meta-analytic approach on memory behavior in knock-out mice. We screened 300 studies from PubMed and retrieved 87 genes tested for possible effects on spatial memory. This database was crossed with the Allen Brain Atlas (brain distribution) and the Enrichr (gene function) databases. The results show that PDF genes have higher expression level in several ventral brain structures, particularly the encephalic trunk and in the hypothalamus. Moreover, part of these genes are implicated in synaptic functions. Conversely, the PDH genes are associated to G-protein coupled receptors downstream signalling. Some candidate drugs were also found to interfere with some of the PDH genes, further suggesting that this approach might help in identifying drugs to improve memory performance in psychiatric conditions.

The Cyanthin Diterpenoid and Sesterterpene Constituents of Hericium erinaceus Mycelium Ameliorate Alzheimer's Disease-Related Pathologies in APP/PS1 Transgenic Mice

Hericium erinaceus was used in traditional Chinese medicine for physiologically beneficial medicines. Recently, it has become a candidate in causing positive brain health-related activities. We previously reported that Hericium erinaceus mycelium ameliorates Alzheimer’s disease (AD)-related pathologies. To reveal the role of the cyanthin diterpenoid and sesterterpene constituents on this effects, erinacine A and S were isolated and their effects on attenuating AD-related pathology in APPswe/PS1dE9 transgenic mice were investigated. A 30 day short-term administration of erinacine A and S were performed to explore the effect of each erinacine on AD-related pathology including amyloid β production and degradation, plaque formation, plaque growth, glial activation and neurogenesis deterioration. Our results indicated the benefit effects of both erinacine A and S in cerebrum of APPswe/PS1dE9 mice, including: (1) attenuating cerebral plaque loading by inhibiting plaque growth; (2) diminishing the activation of glial cells; (3) raising the level of insulin degrading enzyme; and (4) promoting hippocampal neurogenesis. Moreover, erinacine A reduced the level of insoluble amyloid β and C-terminal fragment of amyloid precursor protein which was not mediated by erinacine S. We further performed a long term administration of erinacine A and found that erinacine A recovered the impairment in the tasks including burrowing, nesting, and Morris water maze. Our data pointed out that although both erinacine A and S reduce AD pathology via reducing amyloid deposition and promoting neurogenesis, erinacine A can also inhibit amyloid β production and is worth to be further developed for AD therapeutic use.

A Novel Short Isoform of Cytosolic PSD-95 Interactor (Cypin) Regulates Neuronal Development

The guanine deaminase cypin (cytosolic PSD-95 interactor) binds to PSD-95 (postsynaptic density protein 95) and regulates dendrite branching by promoting microtubule polymerization. Here, we identify a novel short isoform of cypin, termed cypinS, which is expressed in mouse and human, but not rat, tissues. Cypin and cypinS mRNA and protein levels peak at P7 and P14 in the mouse brain, suggesting a role for these isoforms during development. Interestingly, although cypinS lacks guanine deaminase activity, overexpression of cypinS increases dendrite branching. This increase occurs further away from soma than do increases resulting from overexpression of cypin. In contrast, overexpression of cypin, but not cypinS, decreases dendritic spine density and maturity. This suggests that changes to spines, but not to dendrites, may be dependent on guanine deaminase activity. Furthermore, overexpression of either cypin or cypinS increases miniature excitatory postsynaptic current (mEPSC) frequency, pointing to a presynaptic role for both isoforms. Interestingly, overexpression of cypinS results in a significantly greater increase in frequency than does overexpression of cypin. Thus, cypin and cypinS play distinct roles in neuronal development.

Learning induces the translin/trax RNase complex to express activin receptors for persistent memory

Long-lasting forms of synaptic plasticity and memory require de novo protein synthesis. Yet, how learning triggers this process to form memory is unclear. Translin/trax is a candidate to drive this learning-induced memory mechanism by suppressing microRNA-mediated translational silencing at activated synapses. We find that mice lacking translin/trax display defects in synaptic tagging, which requires protein synthesis at activated synapses, and long-term memory. Hippocampal samples harvested from these mice following learning show increases in several disease-related microRNAs targeting the activin A receptor type 1C (ACVR1C), a component of the transforming growth factor-β receptor superfamily. Furthermore, the absence of translin/trax abolishes synaptic upregulation of ACVR1C protein after learning. Finally, synaptic tagging and long-term memory deficits in mice lacking translin/trax are mimicked by ACVR1C inhibition. Thus, we define a new memory mechanism by which learning reverses microRNA-mediated silencing of the novel plasticity protein ACVR1C via translin/trax.

Loss of Protein Arginine Methyltransferase 8 Alters Synapse Composition and Function, Resulting in Behavioral Defects

Diverse molecular mechanisms regulate synaptic composition and function in the mammalian nervous system. The multifunctional protein arginine methyltransferase 8 (PRMT8) possesses both methyltransferase and phospholipase activities. Here we examine the role of this neuron-specific protein in hippocampal plasticity and cognitive function. PRMT8 protein localizes to synaptic sites, and conditional whole-brain Prmt8 deletion results in altered levels of multiple synaptic proteins in the hippocampus, using both male and female mice. Interestingly, these altered protein levels are due to post-transcriptional mechanisms as the corresponding mRNA levels are unaffected. Strikingly, electrophysiological recordings from hippocampal slices of mice lacking PRMT8 reveal multiple defects in excitatory synaptic function and plasticity. Furthermore, behavioral analyses show that PRMT8 conditional knock-out mice exhibit impaired hippocampal-dependent fear learning. Together, these findings establish PRMT8 as an important component of the molecular machinery required for hippocampal neuronal function.SIGNIFICANCE STATEMENT Numerous molecular processes are critically required for normal brain function. Here we use mice lacking protein arginine methyltransferase 8 (PRMT8) in the brain to examine how loss of this protein affects the structure and function of neurons in the hippocampus. We find that PRMT8 localizes to the sites of communication between neurons. Hippocampal neurons from mice lacking PRMT8 have no detectable structural differences compared with controls; however, multiple aspects of their function are altered. Consistently, we find that mice lacking PRMT8 also exhibit reduced hippocampus-dependent memory. Together, our findings establish important roles for PRMT8 in regulating neuron function and cognition in the mammalian brain.

Phosphoproteomic Analysis Reveals a Novel Mechanism of CaMKIIα Regulation Inversely Induced by Cocaine Memory Extinction versus Reconsolidation

Successful addiction treatment depends on maintaining long-term abstinence, making relapse prevention an essential therapeutic goal. However, exposure to environmental cues associated with drug use often thwarts abstinence efforts by triggering drug using memories that drive craving and relapse. We sought to develop a dual approach for weakening cocaine memories through phosphoproteomic identification of targets regulated in opposite directions by memory extinction compared with reconsolidation in male Sprague-Dawley rats that had been trained to self-administer cocaine paired with an audiovisual cue. We discovered a novel, inversely regulated, memory-dependent phosphorylation event on calcium-calmodulin-dependent kinase II α (CaMKIIα) at serine (S)331. Correspondingly, extinction-associated S331 phosphorylation inhibited CaMKIIα activity. Intra-basolateral amygdala inhibition of CaMKII promoted memory extinction and disrupted reconsolidation, leading to a reduction in subsequent cue-induced reinstatement. CaMKII inhibition had no effect if the memory was neither retrieved nor extinguished. Therefore, inhibition of CaMKII represents a novel mechanism for memory-based addiction treatment that leverages both extinction enhancement and reconsolidation disruption to reduce relapse-like behavior.

SIGNIFICANCE STATEMENT

Preventing relapse to drug use is an important goal for the successful treatment of addictive disorders. Relapse-prevention therapies attempt to interfere with drug-associated memories, but are often hindered by unintentional memory strengthening. In this study, we identify phosphorylation events that are bidirectionally regulated by the reconsolidation versus extinction of a cocaine-associated memory, including a novel site on CaMKIIα. Additionally, using a rodent model of addiction, we show that CaMKII inhibition in the amygdala can reduce relapse-like behavior. Together, our data supports the existence of mechanisms that can be used to enhance current strategies for addiction treatment.

Genetic dissection of the planarian reproductive system through characterization of Schmidtea mediterranea CPEB homologs

Cytoplasmic polyadenylation is a mechanism of mRNA regulation prevalent in metazoan germ cells; it is largely dependent on Cytoplasmic Polyadenylation Element Binding proteins (CPEBs). Two CPEB homologs were identified in the planarian Schmidtea mediterranea. Smed-CPEB1 is expressed in ovaries and yolk glands of sexually mature planarians, and required for oocyte and yolk gland development. In contrast, Smed-CPEB2 is expressed in the testes and the central nervous system; its function is required for spermatogenesis as well as non-autonomously for development of ovaries and accessory reproductive organs. Transcriptome analysis of CPEB knockdown animals uncovered a comprehensive collection of molecular markers for reproductive structures in S. mediterranea, including ovaries, testes, yolk glands, and the copulatory apparatus. Analysis by RNA interference revealed contributions for a dozen of these genes during oogenesis, spermatogenesis, or capsule formation. We also present evidence suggesting that Smed-CPEB2 promotes translation of Neuropeptide Y-8, a prohormone required for planarian sexual maturation. These findings provide mechanistic insight into potentially conserved processes of germ cell development, as well as events involved in capsule deposition by flatworms.

Translational Regulation in the Mammalian Oocyte

Fully grown oocytes arrest meiosis at prophase I and deposit maternal RNAs. A subset of maternal transcripts is stored in a dormant state in the oocyte, and the timely driven translation of specific mRNAs guides meiotic progression, the oocyte-embryo transition, and early embryo development. In the absence of transcription, the regulation of gene expression in oocytes is controlled almost exclusively at the level of transcriptome and proteome stabilization and at the level of protein synthesis.This chapter focuses on the recent findings on RNA distribution related to the temporal and spatial translational control of the meiotic cycle progression in mammalian oocytes. We discuss the most relevant mechanisms involved in the organization of the oocyte's maternal transcriptome storage and localization, and the regulation of translation, in correlation with the regulation of oocyte meiotic progression.

Deficiency of CPEB2-Confined Choline Acetyltransferase Expression in the Dorsal Motor Nucleus of Vagus Causes Hyperactivated Parasympathetic Signaling-Associated Bronchoconstriction

Cytoplasmic polyadenylation element binding protein 2 (CPEB2) is an RNA-binding protein and translational regulator. To understand the physiological function of CPEB2, we generated CPEB2 knock-out (KO) mice and found that most died within 3 d after birth. CPEB2 is highly expressed in the brainstem, which controls vital functions, such as breathing. Whole-body plethysmography revealed that KO neonates had aberrant respiration with frequent apnea. Nevertheless, the morphology and function of the respiratory rhythm generator and diaphragm neuromuscular junctions appeared normal. We found that upregulated translation of choline acetyltransferase in the CPEB2 KO dorsal motor nucleus of vagus resulted in hyperactivation of parasympathetic signaling-induced bronchoconstriction, as evidenced by increased pulmonary acetylcholine and phosphorylated myosin light chain 2 in bronchial smooth muscles. Specific deletion of CPEB2 in cholinergic neurons sufficiently caused increased apnea in neonatal pups and airway hyper-reactivity in adult mice. Moreover, inhalation of an anticholinergic bronchodilator reduced apnea episodes in global and cholinergic CPEB2-KO mice. Together, the elevated airway constriction induced by cholinergic transmission in KO neonates may account for the respiratory defect and mortality.

SIGNIFICANCE STATEMENT

This study first generated and characterized cpeb2 gene-deficient mice. CPEB2-knock-out (KO) mice are born alive but most die within 3 d after birth showing no overt defects in anatomy. We found that the KO neonates showed severe apnea and altered respiratory pattern. Such respiratory defects could be recapitulated in mice with pan-neuron-specific or cholinergic neuron-specific ablation of the cpeb2 gene. Further investigation revealed that cholinergic transmission in the KO dorsal motor nucleus of vagus was overactivated because KO mice lack CPEB2-suppressed translation of the rate-limiting enzyme in the production of acetylcholine (i.e., choline acetyltransferase). Consequently, increased parasympathetic signaling leads to hyperactivated bronchoconstriction and abnormal respiration in the KO neonates.

Loss of CPEB3 Upregulates MEGF10 to Impair Mosaic Development of ON Starburst Amacrine Cells

Cytoplasmic polyadenylation element binding protein 3 (CPEB3) regulates target RNA translation in neurons. Here, we examined CPEB3 distribution and function in the mouse retina. CPEB3 is expressed in retinal neurons, including those located in the inner nuclear layer (INL) and ganglion cell layer (GCL) but not in cone and rod photoreceptors in the outer nuclear layer (ONL). A previous study found CPEB3 expressed in cholinergic starburst amacrine cells (SACs). We first examined these cells and observed aberrant SAC mosaicism in CPEB3-knockout (KO) retinas. Retinal neurons showed orderly spatial arrangements. Many individual subtypes are organized non-randomly in patterns called mosaics. Despite CPEB3 being expressed in both populations of SACs, OFF SACs in the INL and ON SACs in the GCL, aberrant mosaic regularity was observed in only ON SACs of CPEB3-KO retinas. Molecular characterization revealed that translation of multiple epidermal growth factor 10 (Megf10) RNA is suppressed by CPEB3 during the first week of postnatal development, when MEGF10 is primarily expressed in SACs and mediates homotypic repulsive interactions to define intercellular spacing of SACs. Thus, elevated MEGF10 expression in the absence of the translational repressor CPEB3 may account for the defective spatial organization of ON SACs. Our findings uncover for the first time that translational control plays a role in shaping retinal mosaic arrangement.

RNA-binding profiles of Drosophila CPEB proteins Orb and Orb2

Localized protein translation is critical in many biological contexts, particularly in highly polarized cells, such as neurons, to regulate gene expression in a spatiotemporal manner. The cytoplasmic polyadenylation element-binding (CPEB) family of RNA-binding proteins has emerged as a key regulator of mRNA transport and local translation required for early embryonic development, synaptic plasticity, and long-term memory (LTM). Drosophila Orb and Orb2 are single members of the CPEB1 and CPEB2 subfamilies of the CPEB proteins, respectively. At present, the identity of the mRNA targets they regulate is not fully known, and the binding specificity of the CPEB2 subfamily is a matter of debate. Using transcriptome-wide UV cross-linking and immunoprecipitation, we define the mRNA-binding sites and targets of Drosophila CPEBs. Both Orb and Orb2 bind linear cytoplasmic polyadenylation element-like sequences in the 3' UTRs of largely overlapping target mRNAs, with Orb2 potentially having a broader specificity. Both proteins use their RNA-recognition motifs but not the Zinc-finger region for RNA binding. A subset of Orb2 targets is translationally regulated in cultured S2 cells and fly head extracts. Moreover, pan-neuronal RNAi knockdown of these targets suggests that a number of these targets are involved in LTM. Our results provide a comprehensive list of mRNA targets of the two CPEB proteins in Drosophila, thus providing insights into local protein synthesis involved in various biological processes, including LTM.

Conditional Knockout of Breast Carcinoma Amplified Sequence 2 (BCAS2) in Mouse Forebrain Causes Dendritic Malformation via β-catenin

Breast carcinoma amplified sequence 2 (BCAS2) is a core component of the hPrP19 complex that controls RNA splicing. Here, we performed an exon array assay and showed that β-catenin is a target of BCAS2 splicing regulation. The regulation of dendrite growth and morphology by β-catenin is well documented. Therefore, we generated conditional knockout (cKO) mice to eliminate the BCAS2 expression in the forebrain to investigate the role of BCAS2 in dendrite growth. BCAS2 cKO mice showed a microcephaly-like phenotype with a reduced volume in the dentate gyrus (DG) and low levels of learning and memory, as evaluated using Morris water maze analysis and passive avoidance, respectively. Golgi staining revealed shorter dendrites, less dendritic complexity and decreased spine density in the DG of BCAS2 cKO mice. Moreover, the cKO mice displayed a short dendrite length in newborn neurons labeled by DCX, a marker of immature neurons, and BrdU incorporation. To further examine the mechanism underlying BCAS2-mediated dendritic malformation, we overexpressed β-catenin in BCAS2-depleted primary neurons and found that the dendritic growth was restored. In summary, BCAS2 is an upstream regulator of β-catenin gene expression and plays a role in dendrite growth at least partly through β-catenin.

Impaired neurodevelopment by the low complexity domain of CPEB4 reveals a convergent pathway with neurodegeneration

CPEB4 is an RNA binding protein expressed in neuronal tissues including brain and spinal cord. CPEB4 has two domains: one that is structured for RNA binding and one that is unstructured and low complexity that has no known function. Unstructured low complexity domains (LCDs) in proteins are often found in RNA-binding proteins and have been implicated in motor neuron degenerative diseases such as amyotrophic lateral sclerosis, indicating that these regions mediate normal RNA processing as well as pathological events. While CPEB4 null knockout mice are normal, animals expressing only the CPEB4 LCD are neonatal lethal with impaired mobility that display defects in neuronal development such as reduced motor axon branching and abnormal neuromuscular junction formation. Although full-length CPEB4 is nearly exclusively cytoplasmic, the CPEB4 LCD forms nucleolar aggregates and CPEB4 LCD-expressing animals have altered ribosomal RNA biogenesis, ribosomal protein gene expression, and elevated levels of stress response genes such as the actin-bundling protein DRR1, which impedes neurite outgrowth. Some of these features share similarities with other LCD-related neurodegenerative disease. Most strikingly, DRR1 appears to be a common focus of several neurodevelopmental and neurodegenerative disorders. Our study reveals a possible molecular convergence between a neurodevelopmental defect and neurodegeneration mediated by LCDs.