Subpopulation Of Spines Research Articles

Palmitoylation of A-kinase anchoring protein 79/150 modulates its nanoscale organization, trafficking, and mobility in postsynaptic spines.

A-kinase anchoring protein 79-human/150-rodent (AKAP79/150) organizes signaling proteins to control synaptic plasticity. AKAP79/150 associates with the plasma membrane and endosomes through its N-terminal domain that contains three polybasic regions and two Cys residues that are reversibly palmitoylated. Mutations abolishing palmitoylation (AKAP79/150 CS) reduce its endosomal localization and association with the postsynaptic density (PSD). Here we combined advanced light and electron microscopy (EM) to characterize the effects of AKAP79/150 palmitoylation on its postsynaptic nanoscale organization, trafficking, and mobility in hippocampal neurons. Immunogold EM revealed prominent extrasynaptic membrane AKAP150 labeling with less labeling at the PSD. The label was at greater distances from the spine membrane for AKAP150 CS than WT in the PSD but not in extra-synaptic locations. Immunogold EM of GFP-tagged AKAP79 WT showed that AKAP79 adopts a vertical, extended conformation at the PSD with its N-terminus at the membrane, in contrast to extrasynaptic locations where it adopts a compact or open configurations of its N- and C-termini with parallel orientation to the membrane. In contrast, GFP-tagged AKAP79 CS was displaced from the PSD coincident with disruption of its vertical orientation, while proximity and orientation with respect to the extra-synaptic membrane was less impacted. Single-molecule localization microscopy (SMLM) revealed a heterogeneous distribution of AKAP150 with distinct high-density, nano-scale regions (HDRs) overlapping the PSD but more prominently located in the extrasynaptic membrane for WT and the CS mutant. Thick section scanning transmission electron microscopy (STEM) tomography revealed AKAP150 immunogold clusters similar in size to HDRs seen by SMLM and more AKAP150 labeled endosomes in spines for WT than for CS, consistent with the requirement for AKAP palmitoylation in endosomal trafficking. Hidden Markov modeling of single molecule tracking data revealed a bound/immobile fraction and two mobile fractions for AKAP79 in spines, with the CS mutant having shorter dwell times and faster transition rates between states than WT, suggesting that palmitoylation stabilizes individual AKAP molecules in various spine subpopulations. These data demonstrate that palmitoylation fine tunes the nanoscale localization, mobility, and trafficking of AKAP79/150 in dendritic spines, which might have profound effects on its regulation of synaptic plasticity.

Sepsis after elective neurosurgery: Incidence, outcomes, and predictive factors

Sepsis is a life-threatening condition resulting from systemic infection, with mortality rates approaching 30%. Most neurological surgeries are now performed electively, which permits medical optimization preoperatively. We performed a retrospective cohort analysis of 122,466 adult elective neurosurgical patients from 2012 to 2018 in the National Surgical Quality Improvement Program database. To select for a medically optimized population, patients were included if they arrived from home on the day of surgery, were not pregnant or puerperium, and had no documented evidence of preexisting infection. We analyzed demographic, comorbidity, and operative information; performed multivariate logistic regression to explore factors predictive of postoperative sepsis; and evaluated outcomes for patients who developed sepsis. Overall, 0.87% of patients developed postoperative sepsis (n = 1,067). The rate of sepsis was higher in the cranial subpopulation (1.21%; n = 330) and lower in the spinal subpopulation (0.77%; n = 733). The overall sepsis cohort was older, had more males, was more functionally dependent, had longer operation durations, and had higher rates of medical comorbidities. Minority race and smoking were not associated with sepsis. The sepsis cohort fared worse than the control cohort across all outcome measures, including prolonged length-of-stay (≥90th percentile), discharge anywhere but home, 30-day readmission, 30-day reoperation, and 30-day mortality. Results for the cranial and spine subpopulations follow similar trends. In summary, sepsis in the elective neurosurgical population is an uncommon but devastating cause of excess morbidity and mortality.

Dendritic Spines Taxonomy: The Functional and Structural Classification • Time-Dependent Probabilistic Model of Neuronal Activation.

Categorizing spines into four subpopulations, stubby, mushroom, thin, or filopodia, is one of the common approaches in morphological analysis. Most cellular models describing synaptic plasticity, long-term potentiation (LTP), and long-term depression associate synaptic strength with either spine enlargement or spine shrinkage. Unfortunately, although we have a lot of available software with automatic spine segmentation and feature extraction methods, at present none of them allows for automatic and unbiased distinction between dendritic spine subpopulations, or for the detailed computational models of spine behavior. Therefore, we propose structural classification based on two different mathematical approaches: unsupervised construction of spine shape taxonomy based on arbitrary features (SpineTool) and supervised classification exploiting convolution kernels theory (2dSpAn). We compared two populations of spines in a form of static and dynamic data sets gathered at three time points. The dynamic data contain two sets of spines: the active set and the control set. The first population was stimulated with LTP, and the other population in its resting state was used as a control population. We propose one equation describing the distribution of variables that best fits all dendritic spine parameters.

A role for proteolytic regulation of δ-catenin in remodeling a subpopulation of dendritic spines in the rodent brain.

Neural wiring and activity are essential for proper brain function and behavioral outputs and rely on mechanisms that guide the formation, elimination, and remodeling of synapses. During development, it is therefore vital that synaptic densities and architecture are tightly regulated to allow for appropriate neural circuit formation and function. δ-Catenin, a component of the cadherin-catenin cell adhesion complex, has been demonstrated to be a critical regulator of synaptic density and function in the developing central neurons. In this study, we identified forms of δ-catenin that include only the N-terminal (DcatNT) or the C-terminal (DcatCT) regions. We found that these δ-catenin forms are differentially expressed in different regions of the male mouse brain. Our results also indicated that in rat primary cortical culture, these forms are generated in an activity-dependent manner by Ca2+-dependent and calpain-mediated cleavage of δ-catenin or in an activity-independent but lysosome-dependent manner. Functionally, loss of the domain containing the calpain-cleavage sites allowing for generation of DcatCT and DcatNT perturbed the density of a subpopulation of dendritic protrusions in rat hippocampal neurons. This subpopulation likely included protrusions that are either in transition toward becoming mature mushroom spines or in the process of being eliminated. By influencing this subpopulation of spines, proteolytic processing of δ-catenin can likely regulate the balance between mature and immature dendritic protrusions in coordination with neural activity. We conclude that by undergoing cleavage, δ-catenin differentially regulates the densities of subpopulations of dendritic spines and contributes to proper neural circuit wiring in the developing brain.

Computational Approach to Dendritic Spine Taxonomy and Shape Transition Analysis.

The common approach in morphological analysis of dendritic spines of mammalian neuronal cells is to categorize spines into subpopulations based on whether they are stubby, mushroom, thin, or filopodia shaped. The corresponding cellular models of synaptic plasticity, long-term potentiation, and long-term depression associate the synaptic strength with either spine enlargement or spine shrinkage. Although a variety of automatic spine segmentation and feature extraction methods were developed recently, no approaches allowing for an automatic and unbiased distinction between dendritic spine subpopulations and detailed computational models of spine behavior exist. We propose an automatic and statistically based method for the unsupervised construction of spine shape taxonomy based on arbitrary features. The taxonomy is then utilized in the newly introduced computational model of behavior, which relies on transitions between shapes. Models of different populations are compared using supplied bootstrap-based statistical tests. We compared two populations of spines at two time points. The first population was stimulated with long-term potentiation, and the other in the resting state was used as a control. The comparison of shape transition characteristics allowed us to identify the differences between population behaviors. Although some extreme changes were observed in the stimulated population, statistically significant differences were found only when whole models were compared. The source code of our software is freely available for non-commercial use1. Contact: d.plewczynski@cent.uw.edu.pl.

P 72. Repetitive magnetic stimulation induces coordinated functional and structural plasticity of excitatory postsynapses in mouse entorhino-hippocampal slice cultures

Repetitive transcranial magnetic stimulation (rTMS) is a non-invasive brain stimulation technique, which can modulate cortical excitability of human subjects for hours beyond the stimulation period. It thus has potential as a therapeutic tool in neuropsychiatric disorders associated with alterations in cortical excitability. However, the aftereffects of rTMS on cortical excitability are not well understood at the cellular and molecular level. To learn more about the cellular and molecular mechanisms of repetitive Magnetic Stimulation (rMS)-induced neural plasticity we have established an in vitro model of rMS using mature organotypic mouse entorhino-hippocampal slice cultures. In this model system we assessed the effects of a high-frequency (10 Hz) rMS protocol on functional and structural properties of excitatory synapses of CA1 pyramidal neurons. Whole-cell patch-clamp recordings, immunohistochemistry, and time-lapse imaging techniques revealed that rMS induces a long-lasting increase in glutamatergic synaptic neurotransmission which is accompanied by structural remodeling of dendritic spines. The effects of rMS on spine size were predominantly seen in small spines, suggesting differential effects of rMS on subpopulations of spines. Furthermore, our data indicate that rMS interferes with the molecular machinery which controls the NMDA-receptor dependent accumulation of AMPA-receptors at postsynaptic sites. These results provide first experimental evidence that high-frequency rMS induces coordinated functional and structural changes of excitatory postsynapses, which are consistent with a long-term potentiation (LTP) of excitatory synaptic strength.

Repetitive Magnetic Stimulation Induces Functional and Structural Plasticity of Excitatory Postsynapses in Mouse Organotypic Hippocampal Slice Cultures

Repetitive transcranial magnetic stimulation (rTMS) is a noninvasive brain stimulation technique that can alter cortical excitability in human subjects for hours beyond the stimulation period. It thus has potential as a therapeutic tool in neuropsychiatric disorders associated with alterations in cortical excitability. However, rTMS-induced neural plasticity remains insufficiently understood at the cellular level. To learn more about the effects of repetitive magnetic stimulation (rMS), we established an in vitro model of rMS using mouse organotypic entorhino-hippocampal slice cultures. We assessed the outcome of a high-frequency (10 Hz) rMS protocol on functional and structural properties of excitatory synapses in mature hippocampal CA1 pyramidal neurons. Whole-cell patch-clamp recordings, immunohistochemistry, and time-lapse imaging techniques revealed that rMS induces a long-lasting increase in glutamatergic synaptic strength, which is accompanied by structural remodeling of dendritic spines. The effects of rMS on spine size were predominantly seen in small spines, suggesting differential effects of rMS on subpopulations of spines. Furthermore, our data indicate that rMS-induced postsynaptic changes depend on the NMDA receptor-mediated accumulation of GluA1-containing AMPA receptors. These results provide first experimental evidence that rMS induces coordinated functional and structural plasticity of excitatory postsynapses, which is consistent with a long-term potentiation of synaptic transmission.

Sampling issues in quantitative analysis of dendritic spines morphology

BackgroundQuantitative analysis of changes in dendritic spine morphology has become an interesting issue in contemporary neuroscience. However, the diversity in dendritic spine population might seriously influence the result of measurements in which their morphology is studied. The detection of differences in spine morphology between control and test group is often compromised by the number of dendritic spines taken for analysis. In order to estimate the impact of dendritic spine diversity we performed Monte Carlo simulations examining various experimental setups and statistical approaches. The confocal images of dendritic spines from hippocampal dissociated cultures have been used to create a set of variables exploited as the simulation resources.ResultsThe tabulated results of simulations given in this article, provide the number of dendritic spines required for the detection of hidden morphological differences between control and test groups in terms of spine head-width, length and area. It turns out that this is the head-width among these three variables, where the changes are most easily detected. Simulation of changes occurring in a subpopulation of spines reveal the strong dependence of detectability on the statistical approach applied. The analysis based on comparison of percentage of spines in subclasses is less sensitive than the direct comparison of relevant variables describing spines morphology.ConclusionsWe evaluated the sampling aspect and effect of systematic morphological variation on detecting the differences in spine morphology. The results provided here may serve as a guideline in selecting the number of samples to be studied in a planned experiment. Our simulations might be a step towards the development of a standardized method of quantitative comparison of dendritic spines morphology, in which different sources of errors are considered.

Impairment of synaptic plasticity by the stress mediator CRH involves selective destruction of thin dendritic spines via RhoA signaling

Stress is ubiquitous in modern life and exerts profound effects on cognitive and emotional functions. Thus, whereas acute stress enhances memory, longer episodes exert negative effects through as yet unresolved mechanisms. We report a novel, hippocampus-intrinsic mechanism for the selective memory defects that are provoked by stress. CRH (corticotropin-releasing hormone), a peptide released from hippocampal neurons during stress, depressed synaptic transmission, blocked activity-induced polymerization of spine actin and impaired synaptic plasticity in adult hippocampal slices. Live, multiphoton imaging demonstrated a selective vulnerability of thin dendritic spines to this stress hormone, resulting in depletion of small, potentiation-ready excitatory synapses. The underlying molecular mechanisms required activation and signaling of the actin-regulating small GTPase, RhoA. These results implicate the selective loss of dendritic spine sub-populations as a novel structural and functional foundation for the clinically important effects of stress on cognitive and emotional processes.

Single-Synapse Analysis of a Diverse Synapse Population: Proteomic Imaging Methods and Markers

A lack of methods for measuring the protein compositions of individual synapses insitu has so far hindered the exploration and exploitation of synapse molecular diversity. Here, we describe the use of array tomography, a new high-resolution proteomic imaging method, to determine the composition of glutamate and GABA synapses in somatosensory cortex of Line-H-YFP Thy-1 transgenic mice. We find that virtually all synapses are recognized by antibodies to the presynaptic phosphoprotein synapsin I, while antibodies to 16 other synaptic proteins discriminate among 4 subtypes of glutamatergic synapses and GABAergic synapses. Cell-specific YFP expression in the YFP-H mouse line allows synapses to be assigned to specific presynaptic and postsynaptic partners and reveals that a subpopulation of spines on layer 5 pyramidal cells receives both VGluT1-subtype glutamatergic and GABAergic synaptic inputs. These results establish a means for the high-throughput acquisition of proteomic data from individual cortical synapses insitu.

Impaired Spine Stability Underlies Plaque-Related Spine Loss in an Alzheimer's Disease Mouse Model

Dendritic spines, the site of most excitatory synapses in the brain, are lost in Alzheimer's disease and in related mouse models, undoubtedly contributing to cognitive dysfunction. We hypothesized that spine loss results from plaque-associated alterations of spine stability, causing an imbalance in spine formation and elimination. To investigate effects of plaques on spine stability in vivo, we observed cortical neurons using multiphoton microscopy in a mouse model of amyloid pathology before and after extensive plaque deposition. We also observed age-matched nontransgenic mice to study normal effects of aging on spine plasticity. We found that spine density and structural plasticity are maintained during normal aging. Tg2576 mice had normal spine density and plasticity before plaques appeared, but after amyloid pathology is established, severe disruptions were observed. In control animals, spine formation and elimination were equivalent over 1 hour of observation ( approximately 5% of observed spines), resulting in stable spine density. However, in aged Tg2576 mice spine elimination increased, specifically in the immediate vicinity of plaques. Spine formation was unchanged, resulting in spine loss. These data show a small population of rapidly changing spines in adult and even elderly mouse cortex; further, in the vicinity of amyloid plaques, spine stability is markedly impaired leading to loss of synaptic structural integrity.