Synapsin I Controls Synaptic Maturation of Long-Range Projections in the Lateral Amygdala in a Targeted Selective Fashion

Spatially Resolved Transcriptomic Signatures of Hippocampal Subregions and Arc-Expressing Ensembles in Active Place Avoidance Memory

The rodent hippocampus is a spatially organized neuronal network that supports the formation of spatial and episodic memories. We conducted bulk RNA sequencing and spatial transcriptomics experiments to measure gene expression changes in the dorsal hippocampus following the recall of active place avoidance (APA) memory. Through bulk RNA sequencing, we examined the gene expression changes following memory recall across the functionally distinct subregions of the dorsal hippocampus. We found that recall induced differentially expressed genes (DEGs) in the CA1 and CA3 hippocampal subregions were enriched with genes involved in synaptic transmission and synaptic plasticity, while DEGs in the dentate gyrus (DG) were enriched with genes involved in energy balance and ribosomal function. Through spatial transcriptomics, we examined gene expression changes following memory recall across an array of spots encompassing putative memory-associated neuronal ensembles marked by the expression of the IEGs Arc, Egr1, and c-Jun. Within samples from both trained and untrained mice, the subpopulations of spatial transcriptomic spots marked by these IEGs were transcriptomically and spatially distinct from one another. DEGs detected between Arc+ and Arc- spots exclusively in the trained mouse were enriched in several memory-related gene ontology terms, including "regulation of synaptic plasticity" and "memory." Our results suggest that APA memory recall is supported by regionalized transcriptomic profiles separating the CA1 and CA3 from the DG, transcriptionally and spatially distinct IEG expressing spatial transcriptomic spots, and biological processes related to synaptic plasticity as a defining the difference between Arc+ and Arc- spatial transcriptomic spots.

Effects and mechanisms of salidroside on the behavior of SPS-induced PTSD rats

Post-traumatic stress disorder (PTSD) is a complex mental disorder, closely associated with stress and traumatic events. Salidroside (Sal) has been reported to possess neuroprotective effects. However, the behavioral effects and mechanisms of Sal on PTSD remain unknown. In this study, we utilized a rat model of PTSD induced by single prolonged stress (SPS) and administered Sal intraperitoneally (25, 50, 75 mg/kg/d) for 14 days. We then examined the behavioral effects and underlying mechanisms of Sal on SPS-induced PTSD rats. Our findings demonstrated that Sal alleviated anxiety-like behavior and spatial learning and memory impairment in SPS-induced PTSD rats. Furthermore, Sal treatment preserved the histomorphology of the hippocampal region. It was observed that Sal protected against hippocampal neuronal apoptosis in PTSD rats by reducing the number of TUNEL-positive cells and modulating apoptosis-related proteins (Bcl-2 and Bax). Additionally, Sal inhibited the activation of the NF-κB/iNOS/COX-2 signaling pathway in the hippocampus of PTSD rats, thereby suppressing the release of inflammatory factors (TNF-α and IL-1β) and the activation of microglia. Notably, Sal increased the expression of synapse-associated proteins PSD95 and Synapsin I in the hippocampus, while also enhancing dendritic density in the region. In conclusion, our results demonstrated that Sal could attenuate SPS-induced PTSD-like behaviors by inhibiting hippocampal neuronal apoptosis, enhancing hippocampal synaptic plasticity, and reducing neuroinflammatory responses. These findings may provide a foundation for the potential clinical application of Sal in the treatment of PTSD.

A Maternal High-Fat Diet during Early Development Provokes Molecular Changes Related to Autism Spectrum Disorder in the Rat Offspring Brain

Autism spectrum disorder (ASD) is a disruptive neurodevelopmental disorder manifested by abnormal social interactions, communication, emotional circuits, and repetitive behaviors and is more often diagnosed in boys than in girls. It is postulated that ASD is caused by a complex interaction between genetic and environmental factors. Epigenetics provides a mechanistic link between exposure to an unbalanced maternal diet and persistent modifications in gene expression levels that can lead to phenotype changes in the offspring. To better understand the impact of the early development environment on the risk of ASD in offspring, we assessed the effect of maternal high-fat (HFD), high-carbohydrate, and mixed diets on molecular changes in adolescent and young adult offspring frontal cortex and hippocampus. Our results showed that maternal HFD significantly altered the expression of 48 ASD-related genes in the frontal cortex of male offspring. Moreover, exposure to maternal HFD led to sex- and age-dependent changes in the protein levels of ANKRD11, EIF4E, NF1, SETD1B, SHANK1 and TAOK2, as well as differences in DNA methylation levels in the frontal cortex and hippocampus of the offspring. Taken together, it was concluded that a maternal HFD during pregnancy and lactation periods can lead to abnormal brain development within the transcription and translation of ASD-related genes mainly in male offspring.

Protonation states at different pH, conformational changes and impact of glycosylation in synapsin Ia

Synapsin I (SynI) is the most abundant brain phosphoprotein present at presynaptic terminals that regulates neurotransmitter release, clustering of synaptic vesicles (SVs) at active zones, and stimulates synaptogenesis and neurite outgrowth. Earlier studies have established that SynI displays pH-dependent tethering of SVs to actin filaments and exhibits a maximum binding around neutral pH, however, the effect of pH shift from acidic to basic on the conformational stability of SynI has not been explored yet. Another important aspect of SynIa is its O-GlcNAcylation (O-GlcNac) at the Thr87 position, which is responsible for the positive regulation of synaptic plasticity linked to learning and memory in mice. Furthermore, reduced levels of O-GlcNAc have been observed in Alzheimer's disease, suggesting a possible link to deficits in synaptic plasticity. In this study, the effect of pH and glycosylation on the structure and functional stability of SynIa is determined through molecular dynamics (MD) simulation approach. The 3D structure of SynIa was established via threading-based homology modeling methods. It was observed that the structure of SynIa adopts extended conformational changes as the pH shifts from acidic to basic, resulting in a compact conformation at pH 8.0. Moreover, the results obtained by comparing the glycosylated and unglycosylated protein indicated that the glycan moiety imparts stability to the protein by forming intramolecular hydrogen bond interactions with the protein residues. The results indicate that although O-GlcNAc moieties do not induce a significant change in SynIa structure they minimize protein dynamics, likely leading to enhanced protein stability.

An updated reappraisal of synapsins: structure, function and role in neurological and psychiatric disorders

Synapsins (Syns) are phosphoproteins strongly involved in neuronal development and neurotransmitter release. Three distinct genes SYN1, SYN2 and SYN3, with elevated evolutionary conservation, have been described to encode for Synapsin I, Synapsin II and Synapsin III, respectively. Syns display a series of common features, but also exhibit distinctive localization, expression pattern, post-translational modifications (PTM). These characteristics enable their interaction with other synaptic proteins, membranes and cytoskeletal components, which is essential for the proper execution of their multiple functions in neuronal cells. These include the control of synapse formation and growth, neuron maturation and renewal, as well as synaptic vesicle mobilization, docking, fusion, recycling. Perturbations in the balanced expression of Syns, alterations of their PTM, mutations and polymorphisms of their encoding genes induce severe dysregulations in brain networks functions leading to the onset of psychiatric or neurological disorders. This review presents what we have learned since the discovery of Syn I in 1977, providing the state of the art on Syns structure, function, physiology and involvement in central nervous system disorders.

Modulation of hippocampal dopamine and synapse-related proteins by electroacupuncture improves memory deficit caused by sleep deprivation

BACKGROUND

Sleep is crucial for proper functioning of the brain, whereas lack of sleep is very common in modern society and can cause memory impairment. Hence, it is of great significance to find effective methods to intervene in the pathogenesis of memory impairment.

OBJECTIVE

We designed this study to explore the mechanism underlying the therapeutic effects of electroacupuncture (EA) on the deficits caused by sleep deprivation (SD).

METHODS

In this study, we first utilized the modified multiple platform method (MMPM) to establish a rat model of SD, which was followed by use of the Y-maze and Morris water maze (MWM) to assess the performance of rats following EA treatment.

RESULTS

We found that EA at GV20 and ST36 significantly decreased the number of error reactions, increased the number of active avoidance responses in the Y-maze and shortened the latency of finding the platform in the MWM test in SD + EA versus untreated SD groups. Moreover, EA treatment partially restored SD-induced reductions in hippocampal dopamine (DA) content and significantly increased the levels of phosphorylated (p) synapsin I, calcium/calmodulin-dependent protein kinase (CaMK) II, and tyrosine hydroxylase, which are related to the synthesis and release of DA.

CONCLUSIONS

In summary, we it appears that EA at GV20 and ST36 may improve SD-induced memory deficits by restoring the quantity of DA in the hippocampus, which is related to activation of CaMK II, synapsin I, and tyrosine hydroxylase. EA may have potential as an alternative therapy for SD and could improve learning and memory deficits among those suffering from sleep deficiency, although this needs verification by prospective clinical studies.

Cystatin C promotes cognitive dysfunction in rats with cerebral microbleeds by inhibiting the ERK/synapsin Ia/Ib pathway

Although higher serum level of cystatin C (CysC) was observed in patients with cerebral microbleeds, its associated role in the disease has not been elucidated. In this work, a rat model of cerebral microbleeds was created with the aim of investigating effects of CysC on cognitive function in rats with cerebral microbleeds and the underlying mechanism. Serum samples of patients with cerebral microbleeds and healthy people of the same age were collected. Levels of cystatin C expression in these samples were measured using CysC kits. Moreover, 48 spontaneously hypertensive rats (SHRs) bred under specific pathogen-free (SPF) conditions were randomly divided into 4 groups: sham surgery control group (sham), model group (CMB), model + empty vector control group (CMB + vehicle), and model + cystatin C overexpression group (CMB + CysC). Expression levels of CysC in hippocampus of rats in each group were measured by western blot analysis. The Y-maze was used to evaluate cognitive function of rats. Hippocampal long-term potentiation (LTP) in rats was assessed by the electrophysiological assay. Alterations in levels of p-ERK1/2 and p-synapsin Ia/b proteins associated with cognitive function were identified by western blot analysis. The serum levels of CysC in patients with cerebral microbleeds were significantly upregulated (P<0.001). After injection of CysC, its expression levels in rat hippocampus were significantly increased (P<0.001), which enhanced the decline in learning and memory function, as well as the decrease of LTP in the rat model of cerebral microbleeds (P<0.001). Western blot results showed that injection of CysC further reduced the levels of p-ERK1/2 and p-synapsin Ia/b in the rat model of microbleeds (P<0.001). CysC was up regulated in serum of patients with cerebral microbleeds. It promoted cognitive dysfunction in rats with microbleeds by inhibiting ERK/synapsin Ia/Ib pathway.