Spine Maturation Research Articles

A zinc finger transcription factor enables social behaviors while controlling transposable elements and immune response in prefrontal cortex

The neurobiological origins of social behaviors are incompletely understood. Here we utilized synthetic biology approaches to reprogram the function of ZFP189, a transcription factor whose expression and function in rodent prefrontal cortex was previously demonstrated to be protective against stress-induced social deficits. We created novel synthetic ZFP189 transcription factors including ZFP189VPR, which activates the transcription of target genes and therefore exerts opposite functional control from the endogenous, transcriptionally repressive ZFP189WT. Following viral delivery of these synthetic ZFP189 transcription factors to mouse prefrontal cortex, we observe that ZFP189-mediated transcriptional control promotes mature dendritic spine morphology on transduced pyramidal neurons. Interestingly, inversion of ZFP189-mediated transcription in this brain area, achieved by viral delivery of synthetic ZFP189VPR, precipitates social behavioral deficits in terms of social interaction, motivation, and the cognition necessary for the maintenance of social hierarchy, without other observable behavioral deficits. RNA sequencing of virally manipulated prefrontal cortex tissues reveals that ZFP189 transcription factors of opposing regulatory function (ZFP189WT versus ZFP189VPR) have opposite influence on the expression of genetic transposable elements as well as genes that participate in adaptive immune functions. Collectively, this work reveals that ZFP189 function in the prefrontal cortex coordinates structural and transcriptional neuroadaptations necessary for complex social behaviors while regulating transposable element-rich regions of DNA and the expression of immune-related genes. Given the evidence for a co-evolution of social behavior and the brain immune response, we posit that ZFP189 may have evolved to augment brain transposon-associated immune function as a way of enhancing an animal’s capacity for functioning in social groups.

Distinct Alterations in Dendritic Spine Morphology in the Absence of β-Neurexins.

Dendritic spines are essential for synaptic function because they constitute the postsynaptic compartment of the neurons that receives the most excitatory input. The extracellularly shorter variant of the presynaptic cell adhesion molecules neurexins, β-neurexin, has been implicated in various aspects of synaptic function, including neurotransmitter release. However, its role in developing or stabilizing dendritic spines as fundamental computational units of excitatory synapses has remained unclear. Here, we show through morphological analysis that the deletion of β-neurexins in hippocampal neurons in vitro and in hippocampal tissue in vivo affects presynaptic dense-core vesicles, as hypothesized earlier, and, unexpectedly, alters the postsynaptic spine structure. Specifically, we observed that the absence of β-neurexins led to an increase in filopodial-like protrusions in vitro and more mature mushroom-type spines in the CA1 region of adult knockout mice. In addition, the deletion of β-neurexins caused alterations in the spine head dimension and an increase in spines with perforations of their postsynaptic density but no changes in the overall number of spines or synapses. Our results indicate that presynaptic β-neurexins play a role across the synaptic cleft, possibly by aligning with postsynaptic binding partners and glutamate receptors via transsynaptic columns.

Cdk5-dependent rapid formation and stabilization of dendritic spines by corticotropin-releasing factor

The neuropeptide corticotropin-releasing factor (CRF) exerts a pivotal role in modulating neuronal activity in the mammalian brain. The effects of CRF exhibit notable variations, depending on factors such as duration of exposure, concentration, and anatomical location. In the CA1 region of the hippocampus, the impact of CRF is dichotomous: chronic exposure to CRF impairs synapse formation and dendritic integrity, whereas brief exposure enhances synapse formation and plasticity. In the current study, we demonstrate long-term effects of acute CRF on the density and stability of mature mushroom spines ex vivo. We establish that both CRF receptors are present in this hippocampal region, and we pinpoint their precise subcellular localization within synapses by electron microscopy. Furthermore, both in vivo and ex vivo data collectively demonstrate that a transient surge of CRF in the CA1 activates the cyclin-dependent kinase 5 (Cdk5)-pathway. This activation leads to a notable augmentation in CRF-dependent spine formation. Overall, these data suggest that upon acute release of CRF in the CA1-SR synapse, both CRF-Rs can be activated and promote synaptic plasticity via activating different downstream signaling pathways, such as the Cdk5-pathway.

Memory consolidation drives the enhancement of remote cocaine memory via prefrontal circuit.

Remote memory usually decreases over time, whereas remote drug-cue associated memory exhibits enhancement, increasing the risk of relapse during abstinence. Memory system consolidation is a prerequisite for remote memory formation, but neurobiological underpinnings of the role of consolidation in the enhancement of remote drug memory are unclear. Here, we found that remote cocaine-cue associated memory was enhanced in rats that underwent self-administration training, together with a progressive increase in the response of prelimbic cortex (PrL) CaMKII neurons to cues. System consolidation was required for the enhancement of remote cocaine memory through PrL CaMKII neurons during the early period post-training. Furthermore, dendritic spine maturation in the PrL relied on the basolateral amygdala (BLA) input during the early period of consolidation, contributing to remote memory enhancement. These findings indicate that memory consolidation drives the enhancement of remote cocaine memory through a time-dependent increase in activity and maturation of PrL CaMKII neurons receiving a sustained BLA input.

Agathobaculum butyriciproducens improves ageing-associated cognitive impairment in mice

AimsThe gut microbiota is increasingly recognised as a pivotal regulator of immune system homeostasis and brain health. Recent research has implicated the gut microbiota in age-related cognitive impairment and dementia. Agathobaculum butyriciproducens SR79 T (SR79), which was identified in the human gut, has been reported to be beneficial in addressing cognitive deficits and pathophysiologies in a mouse model of Alzheimer's disease. However, it remains unknown whether SR79 affects age-dependent cognitive impairment. Main methodTo explore the effects of SR79 on cognitive function during ageing, we administered SR79 to aged mice. Ageing-associated behavioural alterations were examined using the open field test (OFT), tail suspension test (TST), novel object recognition test (NORT), Y-maze alternation test (Y-maze), and Morris water maze test (MWM). We investigated the mechanisms of action in the gut and brain using molecular and histological analyses. Key findingsAdministration of SR79 improved age-related cognitive impairment without altering general locomotor activity or depressive behaviour in aged mice. Furthermore, SR79 increased mature dendritic spines in the pyramidal cells of layer III and phosphorylation of CaMKIIα in the cortex of aged mice. Age-related activation of astrocytes in the cortex of layers III-V of the aged brain was reduced following SR79 administration. Additionally, SR79 markedly increased IL-10 production and Foxp3 and Muc2 mRNA expression in the colons of aged mice. SignificanceThese findings suggest that treatment with SR79 may be a beneficial microbial-based approach for enhancing cognitive function during ageing.

Effects of esketamine on depression-like behavior and dendritic spine plasticity in the prefrontal cortex neurons of spared nerve injury-induced depressed mice.

The present study utilized the spared nerve injury (SNI) to create a mouse model of depression to investigate the impact of esketamine on depressive-like behaviors, on the expression of PSD-95 and CRMP2 proteins, and on changes in neuronal dendritic spine plasticity in the prefrontal cortex (PFC). Depressive-like behavioral tests were performed 1 h after esketamine treatment, and the PFC tissues were obtained on the fourth day after completing the behavioral tests. Then, dendritic spine density and morphology in the PFC were measured using Golgi staining, and CRMP2 and PSD-95 proteins were obtained from PFC tissue by western blotting. The results of this study showed that esketamine significantly increased the immobility time in the forced swimming test and tail suspension test. In the open field test, esketamine increased the time spent in the open arms, the time spent in the central area, and the total distance covered. It also increased the protein expression levels of CRMP2 and PSD-95 in addition to the total and mature dendritic spine density of the PFC in SNI-depressed mice. Esketamine can significantly improve depression-like behaviors in SNI-depressed mice and promote an increase in dendritic spine density and maturation in the PFC. These effects may be associated with changes in CRMP2 and PSD-95 expression.

Differential Effects of Neonatal Ventral Hippocampus Lesion on Behavior and Corticolimbic Plasticity in Wistar-Kyoto and Spontaneously Hypertensive Rats.

Dysfunction of the corticolimbic system, particularly at the dendritic spine level, is a recognized core mechanism in neurodevelopmental disorders such as schizophrenia. Neonatal ventral hippocampus lesion (NVHL) in Sprague-Dawley rats induces both a schizophrenia-related behavioral phenotype and dendritic spine pathology (reduced total number and mature spines) in corticolimbic areas, which is mitigated by antipsychotics. However, there is limited information on the impact of rat strain on NVHL outcomes and antipsychotic effects. We compared the behavioral performance in the open field, novel object recognition (NORT), and social interaction tests, as well as structural neuroplasticity with the Golgi-Cox stain in Wistar-Kyoto (WKY) and spontaneously hypertensive (SH) male rats with and without NVHL. Additionally, we explored the effect of the atypical antipsychotic risperidone (RISP). WKY rats with NVHL displayed motor hyperactivity without impairments in memory and social behavior, accompanied by dendritic spine pathology in the neurons of the prefrontal cortex (PFC) layer 3 and basolateral amygdala. RISP treatment reduced motor activity and had subtle and selective effects on the neuroplasticity alterations. In SH rats, NVHL increased the time spent in the border area during the open field test, impaired the short-term performance in NORT, and reduced social interaction time, deficits that were corrected after RISP administration. The NVHL caused dendritic spine pathology in the PFC layers 3 and 5 of SH rats, which RISP treatment ameliorated. Our results support the utility of the NVHL model for exploring neuroplasticity mechanisms in schizophrenia and understanding pharmacotherapy.

Overexpression of Motopsin, an Extracellular Serine Protease Related to Intellectual Disability, Promotes Adult Neurogenesis and Neuronal Responsiveness in the Dentate Gyrus.

Motopsin, a serine protease encoded by PRSS12, is secreted by neuronal cells into the synaptic clefts in an activity-dependent manner, where it induces synaptogenesis by modulating Na+/K+-ATPase activity. In humans, motopsin deficiency leads to severe intellectual disability and, in mice, it disturbs spatial memory and social behavior. In this study, we investigated mice that overexpressed motopsin in the forebrain using the Tet-Off system (DTG-OE mice). The elevated agrin cleavage or the reduced Na+/K+-ATPase activity was not detected. However, motopsin overexpression led to a reduction in spine density in hippocampal CA1 basal dendrites. While motopsin overexpression decreased the ratio of mature mushroom spines in the DG, it increased the ratio of immature thin spines in CA1 apical dendrites. Female DTG-OE mice showed elevated locomotor activity in their home cages. DTG-OE mice showed aberrant behaviors, such as delayed latency to the target hole in the Barnes maze test and prolonged duration of sniffing objects in the novel object recognition test (NOR), although they retained memory comparable to that of TRE-motopsin littermates, which normally express motopsin. After NOR, c-Fos-positive cells increased in the dentate gyrus (DG) of DTG-OE mice compared with that of DTG-SO littermates, in which motopsin overexpression was suppressed by the administration of doxycycline, and TRE-motopsin littermates. Notably, the numbers of doublecortin- and 5-bromo-2'-deoxyuridine-labeled cells significantly increased in the DG of DTG-OE mice, suggesting increased adult neurogenesis. Importantly, our results revealed a new function in addition to modulating neuronal responsiveness and spine morphology in the DG: the regulation of neurogenesis.

High‐salt diet enhances Helicobacter pylori infection and increases the prevalence of Alzheimer’s disease

AbstractBackgroundThe American Heart Association recommends that adults consume less than 2,300 milligrams of salt (sodium chloride) daily; anything surpassing this limit is classified as a “high‐salt diet (HSD)” [1]. Research has shown that excessive salt intake stimulates the gastric mucosa, favoring Helicobacter pylori (Hp) colonization [2]. In this review, the relationship between HSD and the susceptibility to Hp infection will be discussed. It is proposed that increased salt consumption will cause neurodegeneration, i.e. Alzheimer’s disease (AD) by way of increased expression of Hp strains in the gastric mucosa.MethodsA complex and specific literature search was conducted across various scientific, international databases for English, peer‐reviewed articles and reviews published in the last decade using the following terms: Helicobacter pylori, amyloid‐β, high‐salt diet, and Alzheimer’s disease. Case reports were excluded. The main objectives were predominantly focused on animal‐based studies.ResultsExperimental data shows HSD enhances Hp growth in mice. The subsequent microglial activation containing H. pylori‐specific IgG, IL‐8 and TNF‐α in the cerebrospinal fluid, induces oxidative damage in neuronal cells. In addition, urease in Hp increases cytosolic [Ca2+] apoptosis and autophagy of neurons. Hp filtrate induces tau hyperphosphorylation at AD‐tau phosphorylation sites such as Thr231 and Ser404. Hp ‐infected mice show a significantly larger GFAP‐positive astrocyte area than non‐infected mice. Immunostaining reveals microglia and astrocytes to be found adjacent to amyloid‐β plaques in Hp‐infected AD model mice. Injection of Hp filtrate impairs the maturation of dendritic spines, increasing Aβ42 production in the hippocampus and cortex, and enhancing expression of PS‐2, resulting in delayed spatial learning and impaired memory in rats.ConclusionThis review provides comprehensive evidence of potential synergistic effects of HSD and Hp on the brain resulting in neurodegeneration and AD progression. Understanding the pathologic consequences of salt consumption on this infection may be key in the prevention of dementia and AD. Thus, further research is required for substantiation of causality, the role of antibiotics and to examine other novel therapeutics.

RGMa and Neogenin control dendritic spine morphogenesis via WAVE Regulatory Complex-mediated actin remodeling.

Structural plasticity, the ability of dendritic spines to change their volume in response to synaptic stimulation, is an essential determinant of synaptic strength and long-term potentiation (LTP), the proposed cellular substrate for learning and memory. Branched actin polymerization is a major force driving spine enlargement and sustains structural plasticity. The WAVE Regulatory Complex (WRC), a pivotal branched actin regulator, controls spine morphology and therefore structural plasticity. However, the molecular mechanisms that govern WRC activation during spine enlargement are largely unknown. Here we identify a critical role for Neogenin and its ligand RGMa (Repulsive Guidance Molecule a) in promoting spine enlargement through the activation of WRC-mediated branched actin remodeling. We demonstrate that Neogenin regulates WRC activity by binding to the highly conserved Cyfip/Abi binding pocket within the WRC. We find that after Neogenin or RGMa depletion, the proportions of filopodia and immature thin spines are dramatically increased, and the number of mature mushroom spines concomitantly decreased. Wildtype Neogenin, but not Neogenin bearing mutations in the Cyfip/Abi binding motif, is able to rescue the spine enlargement defect. Furthermore, Neogenin depletion inhibits actin polymerization in the spine head, an effect that is not restored by the mutant. We conclude that RGMa and Neogenin are critical modulators of WRC-mediated branched actin polymerization promoting spine enlargement. This study also provides mechanistic insight into Neogenin's emerging role in LTP induction.

Antidepressant-like effects of the Punica granatum and citalopram combination are associated with structural changes in dendritic spines of granule cells in the dentate gyrus of rats.

Introduction: Natural products such as phytoestrogens-enriched foods or supplements have been considered as an alternative therapy to reduce depressive symptoms associated with menopause. It is known that the aqueous extract of Punica granatum (AE-PG) exerts antidepressant-like effects by activating β-estrogen receptors and facilitates the antidepressant response of the clinical drug citalopram (CIT). However, the effects on neuroplasticity are unknown. Objectvie investigated the antidepressant-like response of combining AE-PG and CIT at sub-optimal doses, analyzing their effects on the formation and maturation of dendrite spines in granule cells as well as on the dendrite complexity. Methods: Ovariectomized Wistar rats (3-month-old) were randomly assigned to one of the following groups: A) control (saline solution as vehicle of CIT and AE-PG, B) AE-PG at a sub-threshold dose (vehicle of CIT plus AE-PG at 0.125mg/kg), C) CIT at a sub-threshold dose (0.77mg/kg plus vehicle of AE-PG), and D) a combination of CIT plus AE-PG (0.125mg/kg and 0.77mg/kg, respectively). All rats were treated intraperitoneally for 14 days. Antidepressant-like effects were evaluated using the force swimming test test (FST). The complexity of dendrites and the number and morphology of dendrite spines of neurons were assessed in the dentate gyrus after Golgi-Cox impregnation. The expressions of the mature brain-derived neurotrophic factor (mBDNF) in plasma and of mBDNF and synaptophysin in the hippocampus, as markers of synaptogenesis, were also determined. Results: Administration of CIT combined with AE-PG, but not alone, induced a significant antidepressant-like effect in the FST with an increase in the dendritic complexity and the number of dendritic spines in the dentate gyrus (DG) of the hippocampus, revealed by the thin and stubby categories of neurons at the granular cell layer. At the same time, an increase of mBDNF and synaptophysin expression was observed in the hippocampus of rats that received the combination of AE-PG and CIT.

G-CSF improved the memory and dendritic morphology impairments in the hippocampal CA1 pyramidal neurons after brain ischemia in the male rats.

Stroke remains the leading cause of death and disability in the world. A new potential treatment for stroke is the granulocyte colony-stimulating factor (G-CSF), which exerts neuroprotective effects through multiple mechanisms. Memory impairment is the most common cognitive problem after a stroke. The suggested treatment for memory impairments is cognitive rehabilitation, which is often ineffective. The hippocampus plays an important role in memory formation. This project aimed to study the effect of G-CSF on memory and dendritic morphology of hippocampal CA1 pyramidal neurons after middle cerebral artery occlusion (MCAO)in rats. Male Sprague-Dawley rats were divided into three groups: the sham, control (MCAO + Vehicle), and treatment (MCAO + G-CSF) groups. G-CSF (50µg/kg S.C) was administered at 6, 24, and 48h after brain ischemia induction. The passive avoidance task to evaluate learning and memory was performed on days 6 and 7 post-ischemia. Seven days after MCAO, the brain was removed and the hippocampal slices were stained with Golgi. After that, the neurons were analyzed for dendritic morphology and maturity. The data showed that stroke was associated with a significant impairment in the acquisition and retention of passive avoidance tasks, while the G-CSF improved learning and memory loss. The dendritic length, arborization, spine density, and mature spines of the hippocampus CA1 neurons were significantly reduced in the control group, and treatment with G-CSF significantly increased these parameters. G-CSF, even with three doses, improved learning and memory deficits, and dendritic morphological changes in the CA1 hippocampal neurons resulted from brain ischemia.

Voluntary Running Improves Behavioral and Structural Abnormalities in a Mouse Model of CDKL5 Deficiency Disorder.

Cyclin-dependent kinase-like 5 (CDKL5) deficiency disorder (CDD) is a rare neurodevelopmental disease caused by mutations in the X-linked CDKL5 gene. CDD is characterized by a broad spectrum of clinical manifestations, including early-onset refractory epileptic seizures, intellectual disability, hypotonia, visual disturbances, and autism-like features. The Cdkl5 knockout (KO) mouse recapitulates several features of CDD, including autistic-like behavior, impaired learning and memory, and motor stereotypies. These behavioral alterations are accompanied by diminished neuronal maturation and survival, reduced dendritic branching and spine maturation, and marked microglia activation. There is currently no cure or effective treatment to ameliorate the symptoms of the disease. Aerobic exercise is known to exert multiple beneficial effects in the brain, not only by increasing neurogenesis, but also by improving motor and cognitive tasks. To date, no studies have analyzed the effect of physical exercise on the phenotype of a CDD mouse model. In view of the positive effects of voluntary running on the brain of mouse models of various human neurodevelopmental disorders, we sought to determine whether voluntary daily running, sustained over a month, could improve brain development and behavioral defects in Cdkl5 KO mice. Our study showed that long-term voluntary running improved the hyperlocomotion and impulsivity behaviors and memory performance of Cdkl5 KO mice. This is correlated with increased hippocampal neurogenesis, neuronal survival, spine maturation, and inhibition of microglia activation. These behavioral and structural improvements were associated with increased BDNF levels. Given the positive effects of BDNF on brain development and function, the present findings support the positive benefits of exercise as an adjuvant therapy for CDD.

SNX17 Mediates Dendritic Spine Maturation via p140Cap.

Sorting nexin17 (SNX17) is a member of the sorting nexin family, which plays a crucial role in endosomal trafficking. Previous research has shown that SNX17 is involved in the recycling or degradation of various proteins associated with neurodevelopmental and neurological diseases in cell models. However, the significance of SNX17 in neurological function in the mouse brain has not been thoroughly investigated. In this study, we generated Snx17 knockout mice and observed that the homozygous deletion of Snx17 (Snx17-/-) resulted in lethality. On the other hand, heterozygous mutant mice (Snx17+/-) exhibited anxiety-like behavior with a reduced preference for social novelty. Furthermore, Snx17 haploinsufficiency led to impaired synaptic transmission and reduced maturation of dendritic spines. Through GST pulldown and interactome analysis, we identified the SRC kinase inhibitor, p140Cap, as a potential downstream target of SNX17. We also demonstrated that the interaction between p140Cap and SNX17 is crucial for dendritic spine maturation. Together, this study provides the first in vivo evidence highlighting the important role of SNX17 in maintaining neuronal function, as well as regulating social novelty and anxiety-like behaviors.

Long-term high-fat diet's impact on synaptic plasticity in the visual cortex and hippocampus neurons: an experimental study

Objective: To investigate the effects and mechanisms of long-term high-fat diet on synaptic plasticity in the visual cortex and hippocampus neurons of juvenile mice. Methods: This was an experimental study. Twenty-four 4-week-old male C57BL/6J mice were randomly divided into two groups, using a randomized numerical table, with 12 mice in each group. The ND group was fed a normal diet, while the HFD group was fed a high-fat diet. After 12 weeks of feeding, mouse body weight, body fat percentage, glucose tolerance, and blood lipid levels were recorded. Six mice from each group were randomly selected using a randomized numerical table, and long-term potentiation (LTP) in the lateral geniculate nucleus (LGN)-primary visual cortex binocular zone (V1B area) and hippocampus CA3-CA1 were recorded in vitro. Field excitatory postsynaptic potentials (fEPSPs) were measured, and the normalized fEPSP slope was calculated to evaluate changes in cortical synaptic plasticity. Subsequently, brain tissue was collected for Golgi staining to observe the development of pyramidal neurons in layers Ⅱ-Ⅲ of the primary visual cortex and CA1 region of the hippocampus, and changes in dendritic spine morphology and quantity were compared. The remaining six mice from each group were euthanized, and brain tissue was collected for transmission electron microscopy to observe ultrastructural changes in the visual cortex V1B area and hippocampus CA1 region neurons. Independent samples t-test was used for statistical analysis. Results: After 12 weeks of feeding, the body weight of mice in the HFD group was (29.17±1.63) g, significantly lower than the ND group which was (37.99±6.87) g (t=4.33, P<0.001). The body fat percentage in the HFD group was 1.09%±0.22%, which was higher than the ND group with 0.85%±0.09% (t=2.50, P=0.032). HFD mice showed a significant increase in blood glucose level 30 minutes after glucose injection, reaching (17.80±3.94) mmol/L, compared to the ND group with (23.10±1.48) mmol/L (t=3.07, P=0.013). At 60 minutes after glucose injection, the difference in blood glucose levels between the ND group [(13.58±2.39) mmol/L] and the HFD group [(23.70±3.56) mmol/L] was statistically significant (t=5.40, P<0.001). Subsequently, both groups showed a decline in blood glucose levels, and at 120 minutes after glucose injection, the blood glucose level in the ND group decreased to (8.50±1.05) mmol/L, while the HFD group remained at a higher level of (16.03±4.17) mmol/L, showing a statistically significant difference (t=3.91, P=0.004). The serum total cholesterol levels in the ND and HFD groups were (4.08±0.35) mmol/L and (10.80±0.90) mmol/L, respectively, with the HFD group higher than the ND group (t=15.23, P<0.001). However, there was no significant difference in triglyceride levels (P>0.05). The high-density lipoprotein cholesterol level in the ND group was (2.12±0.57) mmol/L, while in the HFD group, it was (1.28±0.15) mmol/L, with the HFD group lower than the ND group (t=3.15, P=0.014). Non-high-density lipoprotein cholesterol level in the HFD group was (11.06±1.46) mmol/L, significantly higher than the ND group with (2.28±0.43) mmol/L (t=12.88, P<0.001). In the hippocampal CA3-CA1 pathway, the fEPSP slope increased by 239.1%±88.8% of baseline in the ND group, while in the HFD group, it was only 147.6%±31.6% of baseline, indicating lower LTP compared to the ND group (t=7.20, P<0.001). For the LGN-V1 pathway, the fEPSP slope increased by 204.8%±67.0% of baseline in the ND group, while in the HFD group, it was 121.1%±15.7% of baseline, showing reduced LTP compared to the ND group (t=9.11, P<0.001). Regarding the visual cortex, in the V1B area of the ND group, the number of dendritic spines per 10 μm was (1.31±1.14), while in the HFD group, it was (0.77±0.43), demonstrating a significant decrease in dendritic spine density (t=3.45, P<0.001). The proportion of mature dendritic spines in the ND group was 69.98%, while non-mature dendritic spines accounted for 30.02%. In contrast, the HFD group had 45.76% mature dendritic spines and 54.24% non-mature dendritic spines. Regarding changes in hippocampal CA1 pyramidal neurons, the cell bodies and axons were not damaged, but HFD group neurons exhibited simplified dendritic structures with reduced branching. The number of dendritic spines per 10 μm was (10.25±3.84) in the HFD group and (25.22±8.21) in the ND group, indicating significantly lower dendritic spine density in the HFD group (t=12.42, P<0.001). The proportion of mature dendritic spines in the ND group was 70.88%, while non-mature dendritic spines accounted for 29.12%. In contrast, the HFD group had 47.37% mature dendritic spines and 52.63% non-mature dendritic spines. Moreover, the ultrastructure of neurons in the visual cortex V1B area and hippocampus CA1 region of HFD mice showed evident damage, with disrupted cell structures, swollen and vacuolated mitochondria, reduced or even disappeared mitochondrial cristae, and decreased synaptic quantity with damaged structure. Conclusions: Long-term high-fat diet in juvenile mice leads to abnormal development and functional maturation of synapses in the visual cortex and hippocampal regions. Dendrites, as the foundation of synaptic structures, undergo abnormal development, which can cause alterations in synaptic plasticity of related neural circuits.

Autism-related KLHL17 and SYNPO act in concert to control activity-dependent dendritic spine enlargement and the spine apparatus.

Dendritic spines, the tiny and actin-rich protrusions emerging from dendrites, are the subcellular locations of excitatory synapses in the mammalian brain that control synaptic activity and plasticity. Dendritic spines contain a specialized form of endoplasmic reticulum (ER), i.e., the spine apparatus, required for local calcium signaling and that is involved in regulating dendritic spine enlargement and synaptic plasticity. Many autism-linked genes have been shown to play critical roles in synaptic formation and plasticity. Among them, KLHL17 is known to control dendritic spine enlargement during development. As a brain-specific disease-associated gene, KLHL17 is expected to play a critical role in the brain, but it has not yet been well characterized. In this study, we report that KLHL17 expression in mice is strongly regulated by neuronal activity and KLHL17 modulates the synaptic distribution of synaptopodin (SYNPO), a marker of the spine apparatus. Both KLHL17 and SYNPO are F-actin-binding proteins linked to autism. SYNPO is known to maintain the structure of the spine apparatus in mature spines and contributes to synaptic plasticity. Our super-resolution imaging using expansion microscopy demonstrates that SYNPO is indeed embedded into the ER network of dendritic spines and that KLHL17 is closely adjacent to the ER/SYNPO complex. Using mouse genetic models, we further show that Klhl17 haploinsufficiency and knockout result in fewer dendritic spines containing ER clusters and an alteration of calcium events at dendritic spines. Accordingly, activity-dependent dendritic spine enlargement and neuronal activation (reflected by extracellular signal-regulated kinase (ERK) phosphorylation and C-FOS expression) are impaired. In addition, we show that the effect of disrupting the KLHL17 and SYNPO association is similar to the results of Klhl17 haploinsufficiency and knockout, further strengthening the evidence that KLHL17 and SYNPO act together to regulate synaptic plasticity. In conclusion, our findings unravel a role for KLHL17 in controlling synaptic plasticity via its regulation of SYNPO and synaptic ER clustering and imply that impaired synaptic plasticity contributes to the etiology of KLHL17-related disorders.

Mechanism of Robo1 in the pentylenetetrazol-kindled epilepsy mouse model.

The neural network hypothesis is one of the important pathogenesis of drug-resistant epilepsy. Axons guide molecules through synaptic remodeling and brain tissue remodeling, which may result in the formation of abnormal neural networks. Therefore, axon guidance plays a crucial role in disease progression. However, although Robo1 is one of the important components of axon guidance, the role of Robo1 in epilepsy remains unclear. In this study, we aimed to explore the mechanism of Robo1 in epilepsy. Male adult C57BL/6 mice were intraperitoneally injected with pentylenetetrazol to establish an epilepsy model. Lentivirus (LV) was given via intracranial injection 2 weeks before pentylenetetrazol injection. Different expressions of Robo1 between the control group, LV-mediated Robo1 short hairpin RNA group, empty vector control LV group, and normal saline group were analyzed using Western blot, immunofluorescence staining, Golgi staining, and video monitoring. Robo1 was increased in the hippocampus in the pentylenetetrazol-induced epilepsy mouse model; lentiviral Robo1 knockdown prolonged the latency of seizure and reduced the seizure grade in mice and resulted in a decrease in dendritic spine density, while the number of mature dendritic spines was maintained. We speculate that Robo1 has been implicated in the development and progression of epilepsy through its effects on dendritic spine morphology and density. Epileptic mice with Robo1 knockdown virus intervention had lower seizure grade and longer latency. Follow-up findings suggest that Robo1 may modulate seizures by affecting dendritic spine density and morphology. Downregulation of Robo1 may negatively regulate epileptogenesis by decreasing the density of dendritic spines and maintaining a greater number of mature dendritic spines.

Impaired erythropoietin-producing hepatocellular B receptors signaling in the prefrontal cortex and hippocampus following maternal immune activation in male rats.

An environmental risk factor for schizophrenia (SZ) is maternal infection, which exerts longstanding effects on the neurodevelopment of offspring. Accumulating evidence suggests that synaptic disturbances may contribute to the pathology of the disease, but the underlying molecular mechanisms remain poorly understood. Erythropoietin-producing hepatocellular B (EphB) receptor signaling plays an important role in synaptic plasticity by regulating the formation and maturation of dendritic spines and regulating excitatory neurotransmission. We examined whether EphB receptors and downstream associated proteins are susceptible to environmental risk factors implicated in the etiology of synaptic disturbances in SZ. Using an established rodent model, which closely imitates the characteristics of SZ, we observed the behavioral performance and synaptic structure of male offspring in adolescence and early adulthood. We then analyzed the expression of EphB receptors and associated proteins in the prefrontal cortex and hippocampus. Maternal immune activation offspring showed significantly progressive cognitive impairment and pre-pulse inhibition deficits together with an increase in the expression of EphB2 receptors and NMDA receptor subunits. We also found changes in EphB receptor downstream signaling, in particular, a decrease in phospho-cofilin levels which may explain the reduced dendritic spine density. Besides, we found that the AMPA glutamate, another glutamate ionic receptor associated with cofilin, decreased significantly in maternal immune activation offspring. Thus, alterations in EphB signaling induced by immune activation during pregnancy may underlie disruptions in synaptic plasticity and function in the prefrontal cortex and hippocampus associated with behavioral and cognitive impairment. These findings may provide insight into the mechanisms underlying SZ.

Effects of Tropomodulin 2 on Dendritic Spine Reorganization and Dynamics.

Dendritic spines are actin-rich protrusions that receive a signal from the axon at the synapse. Remodeling of cytoskeletal actin is tightly connected to dendritic spine morphology-mediated synaptic plasticity of the neuron. Remodeling of cytoskeletal actin is required for the formation, development, maturation, and reorganization of dendritic spines. Actin filaments are highly dynamic structures with slow-growing/pointed and fast-growing/barbed ends. Very few studies have been conducted on the role of pointed-end binding proteins in the regulation of dendritic spine morphology. In this study, we evaluated the role played by tropomodulin 2 (Tmod2)-a brain-specific isoform, on the dendritic spine re-organization. Tmod2 regulates actin nucleation and polymerization by binding to the pointed end via actin and tropomyosin (Tpm) binding sites. We studied the effects of Tmod2 overexpression in primary hippocampal neurons on spine morphology using confocal microscopy and image analysis. Tmod2 overexpression decreased the spine number and increased spine length. Destroying Tpm-binding ability increased the number of shaft synapses and thin spine motility. Eliminating the actin-binding abilities of Tmod2 increased the number of mushroom spines. Tpm-mediated pointed-end binding decreased F-actin depolymerization, which may positively affect spine stabilization; the nucleation ability of Tmod2 appeared to increase shaft synapses.

Biomechanical evaluation of a novel minimally invasive pedicle bone cement screw applied to the treatment of Kümmel's disease in porcine vertebrae.

Background and objective: Treatment of Kümmel's Disease (KD) with pure percutaneous kyphoplasty carries a greater likelihood of bone cement displacement due to hardened bone and defect of the peripheral cortex. In this study, we designed a novel minimally invasive pedicle bone cement screw and evaluate the effectiveness and safety of this modified surgical instruments in porcine vertebrae. Methods: 18 mature porcine spine specimens were obtained and soaked in 10% formaldehyde solution for 24h. 0.5000mmol/L EDTA-Na2 solution was used to develop in vitro osteoporosis models of porcine vertebrae. They were all made with the bone deficiency at the anterior edge of L1. These specimens were randomly divided into 3 groups for different ways of treatment: Group A: pure percutaneous kyphoplasty (PKP) group; Group B: unilateral novel minimally invasive pedicle bone cement screw fixation combined with PKP group; Group C: bilateral novel minimally invasive pedicle bone cement screw fixation combined with PKP group. The MTS multi-degree of freedom simulation test system was used for biomechanical tests, including axial loading of 500N pressure, range of motion (ROM) in flexion, extension, left/right lateral bending, and left/right axial rotation at 5Nm, and the displacement of bone cement mass at maximum angles of 5° and 10°. Result: The three groups were well filled with bone cement, no leakage or displacement of bone cement was observed, and the height of the vertebrae was higher than pre-operation (p < 0.05). In the left/right axial rotation, the specimens were still significantly different (p < 0.05) from the intact specimens in terms of ROM after PKP. In other directions, ROM of all group had no significant difference (p < 0.05) and was close to the intact vertebrae. Compared with PKP group, the relative displacement of bone cement in groups B and C was smaller (p < 0.05). Conclusion: In the in vitro animal vertebral models, the treatment of KD with the placement of novel pedicle minimally invasive bone cement screw combined with PKP can effectively restore the vertebral height, improve the stability of the affected vertebra and prevent the displacement of bone cement. Biomechanically, there is no significant difference between bilateral and unilateral fixation.