Spine Density Research Articles

CXCL10 impairs synaptic plasticity and was modulated by cGAS-STING pathway after stroke in mice.

Sensorimotor deficits following stroke remain a major cause of disability, but little is known about the specific pathological mechanisms. Exploring the pathological mechanisms and identifying potential therapeutic targets to promote functional rehabilitation after stroke are essential. CXCL10, also known as interferon-γ-inducible protein 10 (IP-10), plays an important role in multiple brain disorders by mediating synaptic plasticity, yet its role in stroke is still unclear. In this study, mice were subjected to photothrombotic (PT) stroke, and sensorimotor deficits were determined by the ladder walking tests, tape removal tests, and rotarod tests. The density of dendritic spines and synaptic plasticity was determined in Thy1-EGFP mice and evaluated by electrophysiology. We found that photothrombotic stroke induced sensorimotor deficits and upregulated the expression of CXCL10, whereas suppressing the expression of CXCL10 by adeno-associated virus (AAV) ameliorated sensorimotor deficits and increased the levels of synapse-related proteins, the density of dendritic spines, and synaptic strength. Furthermore, the cyclic GMP-AMP (cGAMP) synthase (cGAS)-stimulus of interferon genes (STING) pathway was activated by stroke and induced CXCL10 release, and cGAS or STING antagonists downregulated the levels of CXCL10 and improved synaptic plasticity after stroke. Collectively, our results indicate that cGAS-STING pathway activation promoted CXCL10 release and impaired synaptic plasticity during stroke recovery.NEW & NOTEWORTHY Chemokine-mediated inflammatory response plays a critical role in stroke. CXCL10 plays an important role in multiple brain disorders by mediating synaptic plasticity, yet its role in stroke recovery is still unclear. Herein, we identified a new mechanism that cyclic GMP-AMP (cGAMP) synthase (cGAS)-stimulus of interferon genes (STING) pathway activation promoted CXCL10 release and impaired synaptic plasticity during stroke recovery. Our findings highlight the potential therapeutic strategy of targeting the cGAS-STING pathway to treat stroke.

High-intensity interval training and medium-intensity continuous training may affect cognitive function through regulation of intestinal microbial composition and its metabolite LPS by the gut-brain axis

AimsThe gut-brain axis is the communication mechanism between the gut and the central nervous system, and the intestinal flora and lipopolysaccharide (LPS) play a crucial role in this mechanism. Exercise regulates the gut microbiota composition and metabolite production (i.e., LPS). We aimed to investigate the effects of high-intensity interval training (HIIT) and moderate-intensity continuous training (MICT) on cognitive function in C57BL/6 J mice through gut-brain axis regulation of gut microbiota composition and LPS displacement. Main methodsC57BL/6 J male mice were randomly divided into sedentary, HIIT, and MICT groups. After 12 weeks of exercise intervention, the cognitive function of the brain and mRNA levels of related inflammatory factors were measured. RNA sequencing, Golgi staining, intestinal microbial 16 s rDNA sequencing, and ELISA were performed. Key findingsHIIT and MICT affect brain cognitive function by regulating the gut microbiota composition and its metabolite, LPS, through the gut microbiota-gut-brain axis. HIIT is suspected to have a risk: it can induce “intestinal leakage” by regulating intestinal permeability-related microbiota, resulting in excessive LPS in the blood and brain and activating M1 microglia in the brain, leading to reduced dendritic spine density and affecting cognitive function. SignificanceThis study revealed a potential link between changes in the gut microbiota and cognitive function. It highlighted the possible risk of HIIT in reducing dendritic spine density and affecting cognitive function.

PP1β opposes classic PP1 function, inhibiting spine maturation and promoting LTP.

Protein phosphatase 1 (PP1) regulates synaptic plasticity and has been described as a molecular constraint on learning and memory. There are three neuronal isoforms, PP1α, PP1β, and PP1γ, but little is known about their individual functions. PP1α and PP1γ are assumed to mediate the effects of PP1 on learning and memory based on their enrichment at dendritic spines and their preferential binding to neurabin and spinophilin, major PP1 synaptic scaffolding proteins. However, it was recently discovered that human de novo PP1β mutations cause intellectual disability, suggesting an important but ill-defined role for PP1β. In this study, we investigated the functions of each PP1 isoform in hippocampal synaptic physiology using conditional CA1-specific knockout mice. In stark contrast to classic PP1 function, we found that PP1β promotes synaptic plasticity as well as spatial memory. These changes in synaptic plasticity and memory are accompanied by changes in GluA1 phosphorylation, GluN2A levels, and dendritic spine density and morphology, including silent synapse number. These functions of PP1β reveal a previously unidentified signaling pathway regulating spine maturation and plasticity, broadening our understanding of the complex role of PP1 in synaptic physiology.

Association between serum insulin-like growth factor 1 and osteoporosis risk in Parkinson's disease: a cross-sectional study.

To examine the correlation between serum insulin-like growth factor 1 (IGF-1) and osteoporosis (OP) in Parkinson's disease (PD). We retrospectively analyzed clinical data from 105 PD patients (PD group) and 78 individuals in the health examination group (HC group). We compared general clinical data and serum IGF-1 levels between the two groups. PD patients were further categorized into PD with OP (50 cases) and PD without OP (55 cases) based on dual-energy X-ray absorptiometry (DXA) results for bone density. We compared general clinical data and serum IGF-1 levels between these two subgroups. Pearson correlation coefficient analysis was conducted to assess the relationship between serum IGF-1 levels and bone density at the lumbar spine and left femoral neck. Multifactorial logistic regression analysis was performed to identify risk factors for PD with OP. Serum IGF-1 levels were significantly lower in the PD group compared to the HC group (P < 0.05). Pearson correlation analysis revealed a positive association between serum IGF-1 levels and both lumbar spine and left femoral neck bone densities (r = 0.653, P < 0.001; r = 0.625, P < 0.001). Multivariate logistic regression analysis identified decreased serum IGF-1 levels, lower uric acid levels, and higher H-Y stage as risk factors for PD with OP (P < 0.05). Reduced levels of serum IGF-1, uric acid, and an increased H-Y stage are closely linked to osteoporosis in PD. Elevating serum levels of IGF-1 and uric acid may potentially offer therapeutic avenues for PD with osteoporosis.

The administration of Cerebrolysin elicits neuroprotective and neurorepair effects in an animal model of type 1 diabetes mellitus

Diabetes mellitus (DM) is a metabolic disorder impacting cerebral function. The administration of Streptozotocin (STZ) is a well-known animal model of insulinopenic type 1 DM in rats. STZ-induced DM results in a myriad of alteration in the periphery and central nervous system (CNS). Cerebrolysin (CBL) is a neuropeptide preparation that promotes synaptic and neuronal plasticity in various animal models. In all cases, CBL was administered when the model was established. This research aims to investigate the neuroprotective and neurorepair effect of CBL on the cytoarchitecture of neurons and spine density in pyramidal neurons of the prefrontal (PFC) and the CA1 region of the dorsal hippocampus, as well as spheroidal neurons of the dentate gyrus (DG), in STZ-induced DM. In the first experimental condition, STZ and CBL are administered at the same time to evaluate the potential preventive effect of CBL. In the second experimental condition, CBL was administered two months after establishing the DM model to measure the potential neurorepair effect of CBL. STZ-induced hyperglycemia remained unaltered by the administration of CBL in both experimental conditions. In the first experimental condition, CBL treatment preserved the neuronal morphology in PFC layer 3, PFC layer 5 and the DG of the hippocampus, while also maintaining spine density in the PFC-3, DG and CA1 hippocampus. Furthermore, CBL induced neurorepair in neurons within the PFC-3, PFC-5 and CA1 regions of the hippocampus, along with an increase in spine density in the PFC-3, DG and CA1 hippocampus. These findings suggest that CBL´s effects on neuroplasticity could be observed before or after the damage was evident.

Functional and morphological adaptation of medial prefrontal corticotropin releasing factor receptor 1-expressing neurons in male mice following chronic ethanol exposure

Chronic ethanol dependence and withdrawal activate corticotropin releasing factor (CRF)-containing GABAergic neurons in the medial prefrontal cortex (mPFC), which tightly regulate glutamatergic pyramidal neurons. Using male CRF1:GFP reporter mice, we recently reported that CRF1-expressing (mPFCCRF1+) neurons predominantly comprise mPFC prelimbic layer 2/3 pyramidal neurons, undergo profound adaptations following chronic ethanol exposure, and regulate anxiety and conditioned rewarding effects of ethanol. To explore the effects of acute and chronic ethanol exposure on glutamate transmission, the impact of chronic alcohol on spine density and morphology, as well as persistent changes in dendritic-related gene expression, we employed whole-cell patch-clamp electrophysiology, diOlistic labeling for dendritic spine analysis, and dendritic gene expression analysis to further characterize mPFCCRF1+ and mPFCCRF1− prelimbic layer 2/3 pyramidal neurons. We found increased glutamate release in mPFCCRF1+ neurons with ethanol dependence, which recovered following withdrawal. In contrast, we did not observe significant changes in glutamate transmission in neighboring mPFCCRF1− neurons. Acute application of 44 mM ethanol significantly reduced glutamate release onto mPFCCRF1+ neurons, which was observed across all treatment groups. However, this sensitivity to acute ethanol was only evident in mPFCCRF1− neurons during withdrawal. In line with alterations in glutamate transmission, we observed a decrease in total spine density in mPFCCRF1+ neurons during dependence, which recovered following withdrawal, while again no changes were observed in mPFCCRF− neurons. Given the observed decreases in mPFCCRF1+ stubby spines during withdrawal, we then identified persistent changes at the dendritic gene expression level in mPFCCRF1+ neurons following withdrawal that may underlie these structural adaptations. Together, these findings highlight the varying responses of mPFCCRF1+ and mPFCCRF1− cell-types to acute and chronic ethanol exposure, as well as withdrawal, revealing specific functional, morphological, and molecular adaptations that may underlie vulnerability to ethanol and the lasting effects of ethanol dependence.

Targeting Nr2e3 to Modulate Tet2 Expression: Therapeutic Potential for Depression Treatment.

Epigenetic mechanisms such as DNA methylation and hydroxymethylation play a significant role in depression. This research has shown that Ten-eleven translocation 2 (Tet2) deficiency prompts depression-like behaviors, but Tet2's transcriptional regulation remains unclear. In the study, bioinformatics is used to identify nuclear receptor subfamily 2 group E member 3 (Nr2e3) as a potential Tet2 regulator. Nr2e3 is found to enhance Tet2's transcriptional activity by binding to its promoter region. Nr2e3 knockdown in mouse hippocampus leads to reduced Tet2 expression, depression-like behaviors, decreased hydroxymethylation of synaptic genes, and downregulation of synaptic proteins like postsynaptic density 95 KDa (PSD95) and N-methy-d-aspartate receptor 1 (NMDAR1). Fewer dendritic spines are also observed. Nr2e3 thus appears to play an antidepressant role under stress. In search of potential treatments, small molecule compounds to increase Nr2e3 expression are screened. Azacyclonal (AZA) is found to enhance the Nr2e3/Tet2 pathway and exhibited antidepressant effects in stressed mice, increasing PSD95 and NMDAR1 expression and dendritic spine density. This study illuminates Tet2's upstream regulatory mechanism, providing a new target for identifying early depression biomarkers and developing treatments.

The WUSCHEL-related homeobox transcription factor CsWOX3 negatively regulates fruit spine morphogenesis in cucumber (Cucumis sativus L.).

Cucumber (Cucumis sativus L.) is a widely cultivated crop with rich germplasm resources, holding significant nutritional value. It also serves as an important model for studying epidermal cell fate and sex determination. Cucumbers are covered with multicellular and unbranched trichomes, including a specific type called spines found on the surface of the fruit. The presence and density of these fruit spines determine the visual quality of cucumber fruits. However, the key regulatory genes and mechanisms underlying cucumber fruit spine development remain poorly understood. In this study, we identified a WUSCHEL-related homeobox (WOX) family gene CsWOX3, which functioned as a typical transcriptional repressor and played a negative role in fruit spine development. Spatial-temporal expression analysis revealed that CsWOX3 exhibited a relatively high expression level in the cucumber female floral organs, particularly in the fruit exocarp. Knockout of CsWOX3 using CRISPR/Cas9 resulted in a significant 2-to-3-fold increase in the diameter of fruit spines base, while overexpression led to a 17% decrease in the diameter compared to the wild-type. A SQUAMOSA PROMOTER BINDING PROTEIN-LIKE transcription factor CsSPL15 could directly bind and activate the expression of CsWOX3, thereby suppressing the expression of downstream auxin-related genes, such as CsARF18. Additionally, the RING-finger type E3 ubiquitin ligase CsMIEL1-like interacted with the HD domain of CsWOX3, which might result in the ubiquitination and subsequent alteration in protein stability of CsWOX3. Collectively, our study uncovered a WOX transcription factor CsWOX3 and elucidated its expression pattern and biological function. This discovery enhances our comprehension of the molecular mechanism governing cucumber fruit spine morphogenesis.

MiR-181a expressed in the dorsal hippocampus regulates the reinstatement of cocaine CPP by targeting PRKAA1

Neuroadaptive changes in the hippocampus underlie addictive-like behaviors in humans or animals chronically exposed to cocaine. miR-181a, which is widely expressed in the hippocampus, acts as a regulator for synaptic plasticity, while its role in drug reinstatement is unclear. In this study, we found that miR-181a regulates the reinstatement of cocaine conditioned place preference(CPP), and altered miR-181a expression changes the complexity of hippocampal neurons and the density and morphology of dendritic spines. By using a luciferase gene reporter, we found that miR-181a targets PRKAA1, an upstream molecule in the mTOR pathway. High miR-181a expression reduced the expression of the PRKAA1 mRNA and promoted mTOR activity and the reinstatement of cocaine CPP. These results indicate that miR-181a is involved in neuronal structural plasticity induced by reinstatement of cocaine CPP, possibly through the activation of the mTOR signaling pathway. This study provides new microRNA targets and a theoretical foundation for the prevention of cocaine-induced reinstatement.

Impaired neurogenesis induced by fluoride via the Notch1 signaling and effects of carvacrol intervention

The negative regulation on neurogenesis has been implicated in fluoride neurotoxicity, while the evidence is limited. To explore whether fluoride interferes with neurogenesis via the Notch1 signaling and the potential alleviation effects of carvacrol (CAR), we conducted in vivo and in vitro experiments, as well as epidemiological analyses in this study. The results showed that urinary fluoride levels and circulating Notch1 levels were associated with IQ levels in boys. NaF-treated rats had fewer neurons, lower densities of dendritic spines, depressed neurogenesis, and impaired learning and memory abilities. In vitro experiments using undifferentiated PC12 cells mimicking neurogenesis revealed that NaF suppressed differentiation and neurite outgrowth. Besides, Notch1 signaling activation was detected in vivo and in vitro. The latter was confirmed using an in vitro model supplemented with DAPT, a potent Notch1 inhibitor. Furthermore, CAR supplementation negatively regulated NICD1 and Hes1 expressions and promoted hippocampal neurogenesis, thereby improving neurological functions in NaF-treated rats. These findings indicated that the inhibition of neurogenesis in hippocampi induced by fluoride via Notch1 signaling activation may be one of the underlying mechanisms of its neurotoxicity, and that CAR significantly alleviated the neurotoxicity of NaF via the Notch1 signaling.

Enhanced hippocampal LTP but normal NMDA receptor and AMPA receptor function in a rat model of CDKL5 deficiency disorder

BackgroundMutations in the X-linked gene cyclin-dependent kinase-like 5 (CDKL5) cause a severe neurological disorder characterised by early-onset epileptic seizures, autism and intellectual disability (ID). Impaired hippocampal function has been implicated in other models of monogenic forms of autism spectrum disorders and ID and is often linked to epilepsy and behavioural abnormalities. Many individuals with CDKL5 deficiency disorder (CDD) have null mutations and complete loss of CDKL5 protein, therefore in the current study we used a Cdkl5−/y rat model to elucidate the impact of CDKL5 loss on cellular excitability and synaptic function of CA1 pyramidal cells (PCs). We hypothesised abnormal pre and/or post synaptic function and plasticity would be observed in the hippocampus of Cdkl5−/y rats.MethodsTo allow cross-species comparisons of phenotypes associated with the loss of CDKL5, we generated a loss of function mutation in exon 8 of the rat Cdkl5 gene and assessed the impact of the loss of CDLK5 using a combination of extracellular and whole-cell electrophysiological recordings, biochemistry, and histology.ResultsOur results indicate that CA1 hippocampal long-term potentiation (LTP) is enhanced in slices prepared from juvenile, but not adult, Cdkl5−/y rats. Enhanced LTP does not result from changes in NMDA receptor function or subunit expression as these remain unaltered throughout development. Furthermore, Ca2+ permeable AMPA receptor mediated currents are unchanged in Cdkl5−/y rats. We observe reduced mEPSC frequency accompanied by increased spine density in basal dendrites of CA1 PCs, however we find no evidence supporting an increase in silent synapses when assessed using a minimal stimulation protocol in slices. Additionally, we found no change in paired-pulse ratio, consistent with normal release probability at Schaffer collateral to CA1 PC synapses.ConclusionsOur data indicate a role for CDKL5 in hippocampal synaptic function and raise the possibility that altered intracellular signalling rather than synaptic deficits contribute to the altered plasticity.LimitationsThis study has focussed on the electrophysiological and anatomical properties of hippocampal CA1 PCs across early postnatal development. Studies involving other brain regions, older animals and behavioural phenotypes associated with the loss of CDKL5 are needed to understand the pathophysiology of CDD.

TAF15 downregulation contributes to the benefits of physical training on dendritic spines and working memory in aged mice.

Moderate physical training has been shown to hinder age-related memory decline. While the benefits of physical training on hippocampal memory function are well-documented, little is known about its impact on working memory, which is linked to the prelimbic cortex (PrL), one major subdivision of the prefrontal cortex. Here, we examined the effects of physical training on spatial working memory in a well-established animal model of physical training, starting at 16 months of age and continuing for 5 months (running wheel 1 h/day and 5 days/week). This training strategy improved spatial working memory in aged mice (22-month-old), which was accompanied by an increased spine density and a lower TAF15 expression in the PrL. Specifically, physical training affected both thin and mushroom-type spines on PrL pyramidal cells, and prevented age-related loss of spines on selective segments of apical dendritic branches. Correlation analysis revealed that increased TAF15-expression was detrimental to the dendritic spines. However, physical training downregulated TAF15 expression in the PrL, preserving the dendritic spines on PrL pyramidal cells and improving working memory in trained aged mice. When TAF15 was overexpressed in the PrL via a viral approach, the benefits of physical training on the dendritic spines and working memory were abolished. These data suggest that physical training at a moderate pace might downregulate TAF15 expression in the PrL, which favors the dendritic spines on PrL pyramidal cells, thereby improving spatial working memory.

Effects of Kv1.3 knockout on pyramidal neuron excitability and synaptic plasticity in piriform cortex of mice.

Kv1.3 belongs to the voltage-gated potassium (Kv) channel family, which is widely expressed in the central nervous system and associated with a variety of neuropsychiatric disorders. Kv1.3 is highly expressed in the olfactory bulb and piriform cortex and involved in the process of odor perception and nutrient metabolism in animals. Previous studies have explored the function of Kv1.3 in olfactory bulb, while the role of Kv1.3 in piriform cortex was less known. In this study, we investigated the neuronal changes of piriform cortex and feeding behavior after smell stimulation, thus revealing a link between the olfactory sensation and body weight in Kv1.3 KO mice. Coronal slices including the anterior piriform cortex were prepared, whole-cell recording and Ca2+ imaging of pyramidal neurons were conducted. We showed that the firing frequency evoked by depolarization pulses and Ca2+ influx evoked by high K+ solution were significantly increased in pyramidal neurons of Kv1.3 knockout (KO) mice compared to WT mice. Western blotting and immunofluorescence analyses revealed that the downstream signaling molecules CaMKII and PKCα were activated in piriform cortex of Kv1.3 KO mice. Pyramidal neurons in Kv1.3 KO mice exhibited significantly reduced paired-pulse ratio and increased presynaptic Cav2.1 expression, proving that the presynaptic vesicle release might be elevated by Ca2+ influx. Using Golgi staining, we found significantly increased dendritic spine density of pyramidal neurons in Kv1.3 KO mice, supporting the stronger postsynaptic responses in these neurons. In olfactory recognition and feeding behavior tests, we showed that Kv1.3 conditional knockout or cannula injection of 5-(4-phenoxybutoxy) psoralen, a Kv1.3 channel blocker, in piriform cortex both elevated the olfactory recognition index and altered the feeding behavior in mice. In summary, Kv1.3 is a key molecule in regulating neuronal activity of the piriform cortex, which may lay a foundation for the treatment of diseases related to piriform cortex and olfactory detection.

G272V and P301L Mutations Induce Isoform Specific Tau Mislocalization to Dendritic Spines and Synaptic Dysfunctions in Cellular Models of 3R and 4R Tau Frontotemporal Dementia.

Tau pathologies are detected in the brains of some of the most common neurodegenerative diseases including Alzheimer's disease (AD), Lewy body dementia (LBD), chronic traumatic encephalopathy (CTE), and frontotemporal dementia (FTD). Tau proteins are expressed in six isoforms with either three or four microtubule-binding repeats (3R tau or 4R tau) due to alternative RNA splicing. AD, LBD, and CTE brains contain pathological deposits of both 3R and 4R tau. FTD patients can exhibit either 4R tau pathologies in most cases or 3R tau pathologies less commonly in Pick's disease, which is a subfamily of FTD. Here, we report the isoform-specific roles of tau in FTD. The P301L mutation, linked to familial 4R tau FTD, induces mislocalization of 4R tau to dendritic spines in primary hippocampal cultures that were prepared from neonatal rat pups of both sexes. Contrastingly, the G272V mutation, linked to familial Pick's disease, induces phosphorylation-dependent mislocalization of 3R tau but not 4R tau proteins to dendritic spines. The overexpression of G272V 3R tau but not 4R tau proteins leads to the reduction of dendritic spine density and suppression of mEPSCs in 5-week-old primary rat hippocampal cultures. The decrease in mEPSC amplitude caused by G272V 3R tau is dynamin-dependent whereas that caused by P301L 4R tau is dynamin-independent, indicating that the two tau isoforms activate different signaling pathways responsible for excitatory synaptic dysfunction. Our 3R and 4R tau studies here will shed new light on diverse mechanisms underlying FTD, AD, LBD, and CTE.

Astragaloside IV mediates radiation-induced neuronal damage through activation of BDNF-TrkB signaling

BackgroundElectromagnetic radiation is relevant to human life, and radiation can trigger neurodegenerative diseases by altering the function of the central nervous system through oxidative stress, mitochondrial dysfunction, and protein degradation. Astragaloside IV (AS-IV) is anti-oxidative, anti-apoptotic, activates the BDNF-TrkB pathway and enhances synaptic plasticity in radiated mice, which can exert its neuroprotection. However, the exact molecular mechanisms are still unclear. PurposeThis study investigated whether AS-IV could play a neuroprotective role by regulating BDNF-TrkB pathway in radiation damage and its underlying molecular mechanisms. MethodsTransgenic mice (Thy1-YFP line H) were injected with AS-IV (40 mg/kg/day body weight) by intraperitoneal injection daily for 4 weeks, followed by X-rays. PC12 cells and primary cortical neurons were also exposed to UVA after 24 h of AS-IV treatment (25 μg/ml and 50 μg/ml) in vitro. The impact of radiation on learning and cognitive functions was visualized in the Morris water maze assay. Subsequently, Immunofluorescence and Golgi-Cox staining analyses were utilized to investigate the structural damage of neuronal dendrites and the density of dendritic spines. Transmission electron microscopy was performed to examine how the radiation affected the ultrastructure of neurons. Finally, western blotting analysis and Quantitative RT-PCR were used to evaluate the expression levels and locations of proteins in vitro and in vivo. ResultsRadiation induced BDNF-TrkB signaling dysregulation and decreased the levels of neuron-related functional genes (Ngf, Bdnf, Gap-43, Ras, Psd-95, Arc, Creb, c-Fos), PSD-95 and F-actin, which subsequently led to damage of neuronal ultrastructure and dendrites, loss of dendritic spines, and decreased dendritic complexity index, contributing to spatial learning and memory deficits. These abnormalities were prevented by AS-IV treatment. In addition, TrkB receptor antagonists antagonized these neuroprotective actions of AS-IV. 7,8-dihydroxyflavone and AS-IV had neuroprotective effects after radiation. ConclusionAS-IV inhibits morphological damage of neurons and cognitive dysfunction in mice after radiation exposure, resulting in a neuroprotective effect, which were mediated by activating the BDNF-TrkB pathway.

Application of confocal laser microscopy for identification of modern and fossil pollen grains, an example in palm Mauritiinae

Confocal scanning laser microscopy (CSLM) is becoming a powerful tool for palynological studies. CSLM allows palynomorph image sectioning, internal and surface structures visualization, and 3D reconstruction at a higher resolution than standard light microscopy without extra processing. CSLM images are suitable for several image analysis techniques that could help improve the accuracy and reproducibility of taxa identification. Here, using the palm subtribe Mauritiinae (Arecaceae: Calamoideae: Lepidocaryeae) as a model group, we identify modern and fossil pollen grains using CSLM images coupled with ImageJ/Fiji 1.54f plugins and machine learning statistical analyses. Modern taxa pollen grains including Lepidocaryum tenue Mart., Mauritia flexuosa L.f., Mauritiella armata (Mart.) Burret and Mauritiella aculeata (Kunth) Burret were obtained from Smithsonian Tropical Research Institute (STRI) pollen collection or herbarium exsiccates. Fossil pollen of Grimsdalea magnaclavata Germeraad et al. 1968, and Mauritiidites franciscoi (van der Hammen) van der Hammen & Garcia de Mutis 1966, both from Miocene, and Mauritia pollen type from Holocene were obtained from STRI collection. We measured nine shape and exine quantitative parameters, and one qualitative parameter (pollen aperture). Pollen volume was the most important variable (28.270 mean decrease accuracy), followed by pollen aperture (15.003), Skewness (13.466), and spine density (10.246). The machine learning analysis, which included CART and Random Forests, correctly identified both fossil and extant grains. CSLM and the quantitative analysis of morphological traits are a new frontier in palynological studies.

Mecp2 Deficiency in Peripheral Sensory Neuron Improves Cognitive Function by Enhancing Hippocampal Dendritic Spine Densities in Mice.

Methyl-CpG-binding protein 2 (Mecp2) is an epigenetic modulator and numerous studies have explored its impact on the central nervous system manifestations. However, little attention has been given to its potential contributions to the peripheral nervous system (PNS). To investigate the regulation of Mecp2 in the PNS on specific central regions, we generated Mecp2fl/flAdvillincre mice with the sensory-neuron-specific deletion of the Mecp2 gene and found the mutant mice had a heightened sensitivity to temperature, which, however, did not affect the sense of motion, social behaviors, and anxiety-like behavior. Notably, in comparison to Mecp2fl/fl mice, Mecp2fl/flAdvillincre mice exhibited improved learning and memory abilities. The levels of hippocampal synaptophysin and PSD95 proteins were higher in Mecp2fl/flAdvillincre mice than in Mecp2fl/fl mice. Golgi staining revealed a significant increase in total spine density, and dendritic arborization in the hippocampal pyramidal neurons of Mecp2fl/flAdvillincre mice compared to Mecp2fl/fl mice. In addition, the activation of the BDNF-TrkB-CREB1 pathway was observed in the hippocampus and spinal cord of Mecp2fl/flAdvillincre mice. Intriguingly, the hippocampal BDNF/CREB1 signaling pathway in mutant mice was initiated within 5 days after birth. Our findings suggest a potential therapeutic strategy targeting the BDNF-TrkB-CREB1 signaling pathway and peripheral somasensory neurons to treat learning and cognitive deficits associated with Mecp2 disorders.

GluR2 can Drive Neuroinflammation and Cognitive Impairments Following Peripherally Repeated Lipopolysaccharide Exposures.

Neuroinflammation is being increasingly recognized as a vital factor in the development of various neurological and neuropsychiatric diseases. Lipopolysaccharides (LPS), an outer membrane component of gram-negative bacteria, can trigger innate immune responses, resulting in neuroinflammation and subsequent cognitive deficits. The expression of glutamate receptors (GluRs) on glial cells can induce glial activation. Therefore, we hypothesized that repeated LPS exposure can increase GluR levels, promoting microglial activation and ultimately affecting synaptic plasticity and cognitive function. In this study, C57/BL6 mice were repeatedly exposed to LPS to construct a neuroinflammation animal model. The levels of GluRs, inflammatory cytokines, ionized calcium-binding adaptor molecule 1, postsynaptic density protein 95, synaptophysin 38, NMDA receptor 2A, and NMDA receptor 2B (GluN2B) were measured in the hippocampi. Furthermore, dendritic spine density in the CA1 hippocampal region was determined. Repeated LPS exposure induced cognitive impairments and microglial activation and increased GluR1 and GluR2 levels. This was accompanied by a significant decrease in GluN2B expression and dendritic spine density in the hippocampi. However, CFM-2, an α-amino-3- hydroxy-5-methyl-4-isoxazolepropionate receptor antagonist, reversed these anomalies. Furthermore, minocycline, a microglial inhibitor, reversed these anomalies and downregulated GluR2 but not GluR1 expression. In summary, we demonstrated that GluR2 plays an essential role in microglia-induced neuroinflammation, resulting in synaptic plasticity and cognitive impairment induced by repeated exposure to LPS.

A C-terminal motif containing a PKC phosphorylation site regulates γ-Protocadherin-mediated dendrite arborization in the cerebral cortex in vivo.

The Pcdhg gene cluster encodes 22 γ-Protocadherin (γ-Pcdh) cell adhesion molecules that critically regulate multiple aspects of neural development, including neuronal survival, dendritic and axonal arborization, and synapse formation and maturation. Each γ-Pcdh isoform has unique protein domains-a homophilically interacting extracellular domain and a juxtamembrane cytoplasmic domain-as well as a C-terminal cytoplasmic domain shared by all isoforms. The extent to which isoform-specific versus shared domains regulate distinct γ-Pcdh functions remains incompletely understood. Our previous in vitro studies identified protein kinase C (PKC)phosphorylation of a serine residue within a shared C-terminal motif as a mechanism through which γ-Pcdh promotion of dendrite arborization via myristoylated alanine-rich C-kinase substrate (MARCKS) is abrogated. Here, we used CRISPR/Cas9 genome editing to generate two new mouse lines expressing only non-phosphorylatable γ-Pcdhs, due either to a serine-to-alanine mutation (PcdhgS/A) or to a 15-amino acid C-terminal deletion resulting from insertion of an early stop codon (PcdhgCTD). Both lines are viable and fertile, and the density and maturation of dendritic spines remain unchanged in both PcdhgS/A and PcdhgCTD cortex. Dendrite arborization of cortical pyramidal neurons, however, is significantly increased in both lines, as are levels of active MARCKS. Intriguingly, despite having significantly reduced levels of γ-Pcdh proteins, the PcdhgCTD mutation yields the strongest phenotype, with even heterozygous mutants exhibiting increased arborization. The present study confirms that phosphorylation of a shared C-terminal motif is a key γ-Pcdh negative regulation point and contributes to a converging understanding of γ-Pcdh family function in which distinct roles are played by both individual isoforms and discrete protein domains.

Cognitive integrity in Non-Demented Individuals with Alzheimer's Neuropathology is associated with preservation and remodeling of dendritic spines.

Individuals referred to as Non-Demented with Alzheimer's Neuropathology (NDAN) exhibit cognitive resilience despite presenting Alzheimer's disease (AD) histopathological signs. Investigating the mechanisms behind this resilience may unveil crucial insights into AD resistance. DiI labeling technique was used to analyze dendritic spine morphology in control (CTRL), AD, and NDAN post mortem frontal cortex, particularly focusing on spine types near and far from amyloid beta (Aβ) plaques. NDAN subjects displayed a higher spine density in regions distant from Aβ plaques versus AD patients. In distal areas from the plaques, NDAN individuals exhibited more immature spines, while AD patients had a prevalence of mature spines. Additionally, our examination of levels of Peptidyl-prolyl cis-trans isomerase NIMA-interacting 1 (Pin1), a protein associated with synaptic plasticity and AD, showed significantly lower expression in AD versus NDAN and CTRL. These results suggest that NDAN individuals undergo synaptic remodeling, potentially facilitated by Pin1, serving as a compensatory mechanism to preserve cognitive function despite AD pathology. Spine density is reduced near Aβ plaques compared to the distal area in CTRL, AD, and NDAN dendrites. NDAN shows higher spine density than AD in areas far from Aβ plaques. Far from Aβ plaques, NDAN has a higher density of immature spines, AD a higher density of mature spines. AD individuals show significantly lower levels of Pin1 compared to NDAN and CTRL.