Spatial Disorganization Research Articles

Spatial Configuration of Market Spaces: Accessibility and Management Challenges in Bamenda City, Cameroon

Market spaces are fundamental to urban life in Cameroon, serving as key centers for commerce, social interaction, and cultural exchange. However, rapid urbanization has intensified challenges related to the spatial placement and organization of markets, particularly in Bamenda. Poor infrastructure, congestion, spatial disorganization, and inadequate parking facilities hinder accessibility and affect the efficiency of market operations. These challenges not only limit economic activities but also create difficulties for vendors, customers, and other stakeholders who rely on these markets for daily sustenance and business. The research problem centers on the inefficient spatial arrangement and poor management of market spaces in Bamenda, which contribute to accessibility constraints, safety concerns, and overall dissatisfaction among market participants. This study, therefore, aims to examine the spatial location, layout, and design of major markets in Bamenda, including Bamenda Main Market, Nkwen Market, Food Market, and Ntarikon Market. It seeks to analyze how these spatial characteristics impact accessibility and functionality, as well as to identify the major challenges faced by market participants. To achieve these objectives, the study employs both qualitative and quantitative methods, including informant interviews and the administration of 324 questionnaires to vendors, customers, and shop owners. Spatial analysis mapping is utilized to assess market locations, layouts, and proximities, providing a comprehensive understanding of their spatial organization. The findings indicate that congestion, narrow pathways, inadequate infrastructure, and unregulated market expansion significantly impede accessibility and market efficiency. Given these challenges, the study strongly advocates for the effective implementation of Bamenda’s proposed Master Plan to regulate urban spaces, particularly market infrastructure. Additionally, the proper execution of the Plan of Soil Occupation (POS) is recommended to address the haphazard arrangement of market stalls and control illegal market operations.

3 Validity of Visuoconstructional Assessment Methods within Healthy Elderly Greek Australians: Quantitative and Error Analysis

Objective:Visuospatial skills are frequently assessed with drawing tests. Research has suggested that the use of drawing tasks in low educated groups may lack the ability to discriminate healthy individuals from clinical populations. The aims of this study were to investigate the validity of visuoconstructional tests in a sample of older Greek Australian immigrants and compare their performances to a matched sample of patients with Alzheimer’s disease (AD).Participants and Methods:We assessed visuoconstructional performances in a sample of 90 healthy older Greek Australians, with a primary school level of education, and compared performances to a demographically matched sample of 20 Greek Australians with a diagnosis of AD on four visuoconstructional drawing tests: Greek cross, four-pointed star, intersecting pentagons, and the Necker Cube.Results:While healthy participants tended to outperform the AD group on most copy tasks, high fail rates within the healthy sample were observed for the intersecting pentagons and Necker cube (78% and 73% fail rates respectively) when using established clinical cutoff scores. High rates of curved angle, omission, distorted relation between elements, spatial disorganization and three-dimensional design errors were found across the four-pointed star, intersecting pentagons, and the Necker cube in both healthy participants and those with AD. Exploratory receiver operating characteristic curve analysis revealed that, with perhaps the exception of the Greek cross, meaningful sensitivity and specificity could not be reached for the four-pointed star, intersecting pentagons, and Necker cube.Conclusions:Cognitively healthy immigrants with low education appear to be at a disadvantage when completing visuoconstructional drawing tests, as their performance may be misinterpreted as indicating cognitive impairment. Future research is needed to identify alternative approaches to assess visuoconstructional ability in low education older cohorts.

Dynamic mitochondrial transcription and translation in B cells control germinal center entry and lymphomagenesis

Germinal center (GC) B cells undergo proliferation at very high rates in a hypoxic microenvironment but the cellular processes driving this are incompletely understood. Here we show that the mitochondria of GC B cells are highly dynamic, with significantly upregulated transcription and translation rates associated with the activity of transcription factor A, mitochondrial (TFAM). TFAM, while also necessary for normal B cell development, is required for entry of activated GC precursor B cells into the germinal center reaction; deletion of Tfam significantly impairs GC formation, function and output. Loss of TFAM in B cells compromises the actin cytoskeleton and impairs cellular motility of GC B cells in response to chemokine signaling, leading to their spatial disorganization. We show that B cell lymphoma substantially increases mitochondrial translation and that deletion of Tfam in B cells is protective against the development of lymphoma in a c-Myc transgenic mouse model. Finally, we show that pharmacological inhibition of mitochondrial transcription and translation inhibits growth of GC-derived human lymphoma cells and induces similar defects in the actin cytoskeleton.

Abstract P2-21-01: Decoding Inter- and Intra-Tumor Heterogeneity in Lobular Breast Cancer Using Spatial Transcriptomics and Clustering Analysis

Abstract Background: Invasive lobular breast carcinoma (ILC) represents 5 to 15% of all invasive breast cancers. Recent studies showed the importance of tumor microenvironment (TME) heterogeneity on patient outcome. Here, we aim to characterize TME spatial heterogeneity by performing clustering analysis on spatial transcriptomics (ST) data. Methods: Frozen tumor samples from 43 primary estrogen receptor positive, HER2-negative ILCs were characterized using ST (Visium, 10x Genomics), each ST slide containing 4992 spots. Hematoxylin/eosin (H&E) stained ST slides were annotated (QuPath software) reaching single cell resolution. After performing normalization, hierarchical clustering (STutility R package) across all samples was carried out on principal components computed using highly variable genes. Clusters were characterized using morphological annotation and gene set enrichment analysis for hallmark gene sets from MSigDB (FGSEA R package). A cluster of spots was defined as tumoral or stromal if the average proportion of pixels annotated as tumor or stroma across its constitutive spots was higher than the average proportion of tumor or stroma pixels across all spots of our cohort. Spatial heterogeneity was assessed by comparing the number of contacts between spots belonging to the same cluster (homo-contacts) and the number of contacts between spots belonging to different clusters (hetero-contacts). Comparisons between groups were assessed using Wilcoxon test. Results: Out of the 43 ILC samples, 19 were T2 or T3, 13 were node-positive and 34 were grade 2. Of note, 9 patients experienced disease relapse. Morphological annotation revealed that an average of 20.4%, 61.12%, 11.5%, 0.45%, 3% of the tissues in our dataset corresponded to tumor, stroma, adipose tissue, immune infiltrate and normal structures (vessels, normal breast), respectively. Bioinformatics analysis revealed 7 tumor, 11 stroma, and 6 normal structures clusters, as well as 8 mixed clusters with no predominant morphological structure, with a median of 22 clusters per sample. Tumor and stroma clusters were either shared across all samples or present only in specific samples. Overall, tumor clusters were characterized by an enrichment in estrogen and androgen response related pathways. Moreover, tumor clusters enriched in oxidative phosphorylation, G2M checkpoint and MYC targets were more present in samples with higher histopathological grade (p=0.016), whereas tumor clusters enriched in interferon alpha/gamma response related pathway were associated with a higher tumor stage (p=0.007). A higher number of hetero-contacts among tumor spots were associated with disease relapse (p=0.02). Similarly, a higher number of hetero-contacts among stroma spots including immune and adipose related clusters was also found in samples from patients who experienced disease relapse (p=0.01). Overall, these findings suggest a role of both tumor and stroma spatial disorganization and heterogeneity in tumor progression. Furthermore, clusters capturing the presence of normal breast and in situ carcinoma were enriched in samples from patients who did not relapse (p< 0.001). Conclusion: Our results revealed the substantial inter- and intra-patient heterogeneity of ILC both at the tumor and microenvironment levels. Different tumor and stroma clusters characterized by specific hallmarks were associated to specific clinical features and disease outcome, unraveling potential new targets for optimizing ILC care. Further validation is needed. Citation Format: Matteo Serra, Mattia Rediti, Frédéric Lifrange, David Venet, Nicola Occelli, Laetitia Collet, Delphine Vincent, Ghizlane Rouas, Ligia Craciun, Denis Larsimont, Miikka Vikkula, Francois P. Duhoux, Françoise Rothé, Christos Sotiriou. Decoding Inter- and Intra-Tumor Heterogeneity in Lobular Breast Cancer Using Spatial Transcriptomics and Clustering Analysis [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P2-21-01.

Regulation of 3D Organization and Its Role in Cancer Biology.

Three-dimensional (3D) genomics is the frontier field in the post-genomics era, its foremost content is the relationship between chromatin spatial conformation and regulation of gene transcription. Cancer biology is a complex system resulting from genetic alterations in key tumor oncogenes and suppressor genes for cell proliferation, DNA replication, cell differentiation, and homeostatic functions. Although scientific research in recent decades has revealed how the genome sequence is mutated in many cancers, high-order chromosomal structures involved in the development and fate of cancer cells represent a crucial but rarely explored aspect of cancer genomics. Hence, dissection of the 3D genome conformation of cancer helps understand the unique epigenetic patterns and gene regulation processes that distinguish cancer biology from normal physiological states. In recent years, research in tumor 3D genomics has grown quickly. With the rapid progress of 3D genomics technology, we can now better determine the relationship between cancer pathogenesis and the chromatin structure of cancer cells. It is becoming increasingly explicit that changes in 3D chromatin structure play a vital role in controlling oncogene transcription. This review focuses on the relationships between tumor gene expression regulation, tumor 3D chromatin structure, and cancer phenotypic plasticity. Furthermore, based on the functional consequences of spatial disorganization in the cancer genome, we look forward to the clinical application prospects of 3D genomic biomarkers.

Spatial whole transcriptome profiling of the tumor microenvironment in FFPE prostate carcinoma using the Visium platform

Abstract Despite years of prostate cancer research, balancing the risks of treatment complications and tumor progression remains a challenge. The inability to dissect tumor microenvironments (TME) and immune compartments contributes to a knowledge gap. Spatially resolved molecular profiling allows understanding these complexities for potential personalized treatments. We used 10× Genomics Visium Spatial Gene Expression for FFPE tissue for spatial whole transcriptome analysis of two prostate cancer sample TMEs. The tissues were processed over~5,000 molecularly barcoded, spatially encoded capture probes in spots for spatially resolved transcriptional readout. We resolved whole transcriptome tumorigenic profiles in sections of normal, stage III adenocarcinoma, and stage IV acinar cell carcinoma FFPE human prostate tissues. Computational clustering identified spatial gene expression patterns that aligned with pathologist annotations. The data revealed spatial disorganization of basal and luminal cells in tumor samples. T lymphocytes were dispersed throughout the whole tissue in the adenocarcinoma, while plasma B cells were in the peritumoral region impacting patient prognosis. Computational methods inferred copy number variation, identifying aneuploidy regions and specific loci driving the genomic profile of the cancerous regions. We demonstrated that spatial whole transcriptome analysis resolves FFPE prostate samples. Our data rapidly confirms known cell type patterns and tumor region-specific gene expression while enhancing understanding of the TME for drug target or biomarker discovery for tailored therapies and patient stratification.

A spatial Analysis of Crime and Neighborhood Characteristics in Detroit Census Block Groups

Abstract. Crime has an inherent geographical quality and when a crime occurs, it happens within a particular space making spatiality essential component in crime studies. To prevent and respond to crimes, it is first essential to identify the factors that trigger crimes and then design policy and strategy based on each factor. This project investigates the spatial dimension of violent crime rates in the city of Detroit for 2019. Crime data were obtained from the City of Detroit Data Portal and demographic data relating to social disorganization theory were obtained from the Census Bureau. In the presence of spatial spill over and spatial dependence, the assumptions of classical statistics are violated, and Ordinary Least Squares estimations are inefficient in explaining spatial dimensions of crime. This paper uses explanatory variables relating to the social disorganization theory of crime and spatial autoregressive models to determine the predictors of violent crime in the City for the period. Using GeoDa 1.18 and ArcGIS Desktop 10.7.1 software package, Spatial Lag Models (SLM) and Spatial Error Models were carried out to determine which model has high performance in identifying predictors of violent crime. SLM outperformed SEM in terms of efficiency with (AIC:5268.52; Breusch-Pagan test: 9.8402; R2: 16% & Log Likelihood: −2627.26) > SEM (AIC: 5275.24; Breusch-Pagan test: 9.7601; R2: 15% & Log Likelihood: −2630.6194). Strong support is found for the spatial disorganization theory of crime. High percent ethnic heterogeneity (% black) and high college graduates are the strongest predictors of violent crime in the study area.

Extracellular Matrix Disparities in an Nkx2-5 Mutant Mouse Model of Congenital Heart Disease.

Congenital heart disease (CHD) affects almost one percent of all live births. Despite diagnostic and surgical reparative advances, the causes and mechanisms of CHD are still primarily unknown. The extracellular matrix plays a large role in cell communication, function, and differentiation, and therefore likely plays a role in disease development and pathophysiology. Cell adhesion and gap junction proteins, such as integrins and connexins, are also essential to cellular communication and behavior, and could interact directly (integrins) or indirectly (connexins) with the extracellular matrix. In this work, we explore disparities in the expression and spatial patterning of extracellular matrix, adhesion, and gap junction proteins between wild type and Nkx2-5+/R52G mutant mice. Decellularization and proteomic analysis, Western blotting, histology, immunostaining, and mechanical assessment of embryonic and neonatal wild type and Nkx2-5 mutant mouse hearts were performed. An increased abundance of collagen IV, fibronectin, and integrin β-1 was found in Nkx2-5 mutant neonatal mouse hearts, as well as increased expression of connexin 43 in embryonic mutant hearts. Furthermore, a ventricular noncompaction phenotype was observed in both embryonic and neonatal mutant hearts, as well as spatial disorganization of ECM proteins collagen IV and laminin in mutant hearts. Characterizing such properties in a mutant mouse model provides valuable information that can be applied to better understanding the mechanisms of congenital heart disease.

Structural alteration of glycosaminoglycan side chains and spatial disorganization of collagen networks in the skin of patients with mcEDS-CHST14

Musculocontractural Ehlers-Danlos syndrome (mcEDS) due to CHST14/D4ST1 deficiency (mcEDS-CHST14) is a recently delineated type of EDS caused by biallelic loss-of-function mutations in CHST14, which results in the depletion of dermatan sulfate (DS). Clinical characteristics of mcEDS-CHST14 consist of multiple malformations and progressive fragility-related manifestations, including skin hyperextensibility and fragility. Skin fragility is suspected to result from the impaired assembly of collagen fibrils caused by alteration of the glycosaminoglycan (GAG) chain of decorin-proteoglycan (PG) from DS to chondroitin sulfate (CS). This systematic investigation of the skin pathology of patients with mcEDS-CHST14 comprised both immunostaining of decorin and transmission electron microscopy-based cupromeronic blue staining to visualize GAG chains. Collagen fibrils were dispersed in the affected papillary to reticular dermis; in contrast, they were regularly and tightly assembled in controls. Moreover, the fibrils exhibited a perpendicular arrangement to the affected epidermis, whereas fibrils were parallel to control epidermis. Affected GAG chains were linear, stretching from the outer surface of collagen fibrils to adjacent fibrils; in contrast, those of controls were curved, maintaining close contact with attached collagen fibrils. This is the first observation of compositional alteration, from DS to CS, of GAG side chains, which caused structural alteration of GAG side chains and resulted in spatial disorganization of collagen networks; this presumably disrupted the ring-mesh structure of GAG side chains surrounding collagen fibrils. McEDS-CHST14 provides a critical example of the importance of DS in GAG side chains of decorin-PG during assembly of collagen fibrils in maintenance of connective tissues.

Aggregate Size Optimization in Microwells for Suspension-based Cardiac Differentiation of Human Pluripotent Stem Cells

Cardiac differentiation of human pluripotent stems cells (hPSCs) is typically carried out in suspension cell aggregates. Conventional aggregate formation of hPSCs involves dissociating cell colonies into smaller clumps, with size control of the clumps crudely controlled by pipetting the cell suspension until the desired clump size is achieved. One of the main challenges of conventional aggregate-based cardiac differentiation of hPSCs is that culture heterogeneity and spatial disorganization lead to variable and inefficient cardiomyocyte yield. We and others have previously reported that human embryonic stem cell (hESC) aggregate size can be modulated to optimize cardiac induction efficiency. We have addressed this challenge by employing a scalable, microwell-based approach to control physical parameters of aggregate formation, specifically aggregate size and shape. The method we describe here consists of forced aggregation of defined hPSC numbers in microwells, and the subsequent culture of these aggregates in conditions that direct cardiac induction. This protocol can be readily scaled depending on the size and number of wells used. Using this method, we can consistently achieve culture outputs with cardiomyocyte frequencies greater than 70%.

Aggregate Size Optimization in Microwells for Suspension-based Cardiac Differentiation of Human Pluripotent Stem Cells.

Cardiac differentiation of human pluripotent stems cells (hPSCs) is typically carried out in suspension cell aggregates. Conventional aggregate formation of hPSCs involves dissociating cell colonies into smaller clumps, with size control of the clumps crudely controlled by pipetting the cell suspension until the desired clump size is achieved. One of the main challenges of conventional aggregate-based cardiac differentiation of hPSCs is that culture heterogeneity and spatial disorganization lead to variable and inefficient cardiomyocyte yield. We and others have previously reported that human embryonic stem cell (hESC) aggregate size can be modulated to optimize cardiac induction efficiency. We have addressed this challenge by employing a scalable, microwell-based approach to control physical parameters of aggregate formation, specifically aggregate size and shape. The method we describe here consists of forced aggregation of defined hPSC numbers in microwells, and the subsequent culture of these aggregates in conditions that direct cardiac induction. This protocol can be readily scaled depending on the size and number of wells used. Using this method, we can consistently achieve culture outputs with cardiomyocyte frequencies greater than 70%.

RP-CARS reveals molecular spatial order anomalies in myelin of an animal model of Krabbe disease.

Krabbe disease (KD) is a rare demyelinating sphingolipidosis, often fatal in the first years of life. It is caused by the inactivation of the galactocerebrosidase (GALC) enzyme that causes an increase in the cellular levels of psychosine considered to be at the origin of the tissue-level effects. GALC is inactivated also in the Twitcher (TWI) mouse: a genetic model of KD that is providing important insights into the understating of the pathogenetic process and the development of possible treatments. In this article an innovative optical technique, RP-CARS, is proposed as a tool to study the degree of order of the CH2 bonds inside the myelin sheaths of TWI-mice sciatic-nerve fibres. RP-CARS, a recently developed variation of CARS microscopy, is able to combine the intrinsic chemical selectivity of CARS microscopy with molecular-bond-spatial-orientation sensibility. This is the first time RP-CARS is applied to the study of a genetic model of a pathology, leading to the demonstration of a post-onset progressive spatial disorganization of the myelin CH2 bonds. The presented result could be of great interest for a deeper understanding of the pathogenic mechanisms underlying the human KD and, moreover, it is an additional proof of the experimental validity of this microscopy technique. RP-CARS image (2850cm-1 , CH2 bonds) of a sciatic-nerve optical longitudinal section from a Twitcher P23 (symptomatic) mouse. Scale bar: 10microns. The image was constructed by colour-mapping the degree of molecular order of the CH2 bonds inside the myelin walls, as displayed in the colour bar on the right.

Disulfiram-induced cytotoxicity and endo-lysosomal sequestration of zinc in breast cancer cells

Disulfiram, a clinically used alcohol-deterrent has gained prominence as a potential anti-cancer agent due to its impact on copper-dependent processes. Few studies have investigated zinc effects on disulfiram action, despite it having high affinity for this metal. Here we studied the cytotoxic effects of disulfiram in breast cancer cells, and its relationship with both intra and extracellular zinc. MCF-7 and BT474 cancer cell lines gave a striking time-dependent biphasic cytotoxic response between 0.01 and 10μM disulfiram. Co-incubation of disulfiram with low-level zinc removed this effect, suggesting that availability of extracellular zinc significantly influences disulfiram efficacy. Live-cell confocal microscopy using fluorescent endocytic probes and the zinc dye Fluozin-3 revealed that disulfiram selectively and rapidly increased zinc levels in endo-lysosomes. Disulfiram also caused spatial disorganization of late endosomes and lysosomes, suggesting they are novel targets for this drug. This relationship between disulfiram toxicity and ionophore activity was consolidated via synthesis of a new disulfiram analog and overall we demonstrate a novel mechanism of disulfiram-cytotoxicity with significant clinical implications for future use as a cancer therapeutic.

Retinal neurodegenerative changes in the adult insulin receptor substrate-2 deficient mouse

Insulin receptor substrate-2 (Irs2) mediates peripheral insulin action and is essential for retinal health. Previous investigations have reported severe photoreceptor degeneration and abnormal visual function in Irs2-deficient mice. However, molecular changes in the Irs2−/− mouse retina have not been described. In this study, we examined retinal degenerative changes in neuronal and glial cells of adult (9- and 12-week old) Irs2−/− mice by immunohistochemistry. 9-week old Irs2−/− mice showed significant thinning of outer retinal layers, concomitant to Müller and microglial cell activation. Photoreceptor cells displayed different signs of degeneration, such as outer/inner segment atrophy, redistribution of rod- and cone-opsins and spatial disorganization of cone cells. This was accompanied by synaptic changes at the outer plexiform layer, including the retraction of rod-spherules, reduction of photoreceptor synaptic ribbons and synaptic remodeling in second order neurons (i.e. loss and sprouting of dendritic processes in rod bipolar and horizontal cells). By 12 weeks of age, the thickness of inner retinal layers was severely affected. Although inner plexiform layer stratification remained unchanged at this stage, rod bipolar cell axon terminals were significantly depleted. Significant loss of Brn3a+ retinal ganglion cells occurred in 12-week old Irs2−/− mice, in contrast to younger ages. Adult Irs2−/− mice showed clear hallmarks of neurodegeneration and disruption of the inner retina with increasing age. Pharmacological stimulation of Irs2 signaling pathway may provide additional neuroprotection in certain degenerative retinopathies.

Nonlinear measures and dynamics in psychophysiology of consciousness.

According to recent findings nonlinear dynamic processes related to neural chaos and complexity likely play a crucial role in neural synchronization of distributed neural activities that enable information integration and conscious experience. Disturbances in these interactions produce patterns of temporal and spatial disorganization with decreased or increased functional connectivity and complexity that underlie specific changes of perceptual and cognitive states. These perceptual and cognitive changes may be characterized by neural chaos with significantly increased brain sensitivity that may underlie sensitization and kindling, and cognitive hypersensitivity in some mental disorders. Together these findings suggest that processes related to more irregular neural states with higher complexity that may lead to neural chaos, negatively affect information integration and processing in the brain, and may influence disintegrated conscious experience.

Visuoconstructional Abilities in Cognitively Healthy Illiterate Turkish Immigrants: A Quantitative and Qualitative Investigation

Assessment of visuospatial function is an integral part of most neuropsychological assessments and is frequently assessed by visuoconstructional tests. A significant impact of limited schooling and illiteracy has been found on numerous neuropsychological tests and it can be difficult to interpret test results from illiterate individuals. In this study, quantitative and qualitative aspects of performance of elderly cognitively healthy illiterate and literate Turkish immigrants were compared on five commonly used visuoconstructional tests. Significantly poorer performances of illiterate compared to literate subjects were found in copying of two- and three-dimensional geometric designs, and in Clock Drawing Test performance. A systematic qualitative analysis found lacking three-dimensionality, “curved angles”, omissions, distorted relation between elements, and spatial disorganization to be common error types in illiterate subjects. Performances were not found to be influenced by duration of residence in Denmark or level of acculturation. The results warrant caution in the interpretation of visuoconstructional test performances in illiterate subjects, as they can easily be misinterpreted as signs of cognitive dysfunction.

Spatial rotational orientation ability in standing children with cerebral palsy

This study quantified perception and reorientation ability after passive horizontal rotations in thirteen children with cerebral palsy (CP). They stood barefoot on a platform in front of a fixed reference point (static posture task, SPT) and were then blindfolded and passively rotated with six velocity profiles (maximum angular velocity: 57°/s; rotation amplitudes: ±90°, ±180° and ±360°). After the perturbation, the blindfolded children were asked to point to the fixed reference point with their preferred hand (pointing task, PT) and to step back to the initial position on the stationary platform (reorientation task, RT). In order to gain further insight into rotational attitude, the results were comparatively examined with body segment rotations determined using standardized gait analysis (gait task, GT).The kinematic evaluations were conducted using an optoelectronic system: for SPT, PT and RT we confined the analysis, in the horizontal plane, to the head and upper pointing arm of the subject and to the platform; for GT a full body analysis was performed.When CP children were passively rotated towards their more affected side, they overestimated the imposed angle in PT but under-reproduced it in RT. A higher variability emerged in left-hemiplegic children, confirming that the spatial disorganization is predominantly related to right brain lesion. Patients tended to rotate in GT towards the more affected side while in RT they showed an opposite trend.

Cholesterol-Lowering Drugs Inhibit Lectin-Like Oxidized Low-Density Lipoprotein-1 Receptor Function by Membrane Raft Disruption

Lectin-like oxidized low-density lipoprotein (LOX-1), the primary receptor for oxidized low-density lipoprotein (ox-LDL) in endothelial cells, is up-regulated in atherosclerotic lesions. Statins are the principal therapeutic agents for cardiovascular diseases and are known to down-regulate LOX-1 expression. Whether the effect on the LOX-1 receptor is related to statin-mediated cholesterol-lowering activity is unknown. We investigate the requirement of cholesterol for LOX-1-mediated lipid particle internalization, trafficking, and processing and the role of statins as inhibitors of LOX-1 function. Disruption of cholesterol-rich membrane microdomains by acute exposure of cells to methyl-β-cyclodextrin or chronic exposure to different statins (lovastatin and atorvastatin) led to a spatial disorganization of LOX-1 in plasma membranes and a marked loss of specific LOX-1 function in terms of ox-LDL binding and internalization. Subcellular fractionation and immunochemical studies indicate that LOX-1 is naturally present in caveolae-enriched lipid rafts and, by cholesterol reduction, the amount of LOX-1 in this fraction is highly decreased (≥60%). In contrast, isoprenylation inhibition had no effect on the distribution and function of LOX-1 receptors. Furthermore, in primary cultures from atherosclerotic human aorta lesions, we confirm the presence of LOX-1 in caveolae-enriched lipid rafts and demonstrate that lovastatin treatment led to down-regulation of LOX-1 in lipid rafts and rescue of the ox-LDL-induced apoptotic phenotype. Taken together, our data reveal a previously unrecognized essential role of membrane cholesterol for LOX-1 receptor activity and suggest that statins protect vascular endothelium against the adverse effect of ox-LDL by disruption of membrane rafts and impairment of LOX-1 receptor function.

Sensory-motor deficits and neurofilament disorganization in gigaxonin-null mice

BackgroundGiant Axonal Neuropathy (GAN) is a fatal neurodegenerative disorder with early onset characterized by a severe deterioration of the peripheral and central nervous system, involving both the motor and the sensory tracts and leading to ataxia, speech defect and intellectual disabilities. The broad deterioration of the nervous system is accompanied by a generalized disorganization of the intermediate filaments, including neurofilaments in neurons, but the implication of this defect in disease onset or progression remains unknown. The identification of gigaxonin, the substrate adaptor of an E3 ubiquitin ligase, as the defective protein in GAN allows us to now investigate the crucial role of the gigaxonin-E3 ligase in sustaining neuronal and intermediate filament integrity. To study the mechanisms controlled by gigaxonin in these processes and to provide a relevant model to test the therapeutic approaches under development for GAN, we generated a Gigaxonin-null mouse by gene targeting.ResultsWe investigated for the first time in Gigaxonin-null mice the deterioration of the motor and sensory functions over time as well as the spatial disorganization of neurofilaments. We showed that gigaxonin depletion in mice induces mild but persistent motor deficits starting at 60 weeks of age in the 129/SvJ-genetic background, while sensory deficits were demonstrated in C57BL/6 animals. In our hands, another gigaxonin-null mouse did not display the early and severe motor deficits reported previously. No apparent neurodegeneration was observed in our knock-out mice, but dysregulation of neurofilaments in proximal and distal axons was massive. Indeed, neurofilaments were not only more abundant but they also showed the abnormal increase in diameter and misorientation that are characteristics of the human pathology.ConclusionsTogether, our results show that gigaxonin depletion in mice induces mild motor and sensory deficits but recapitulates the severe neurofilament dysregulation seen in patients. Our model will allow investigation of the role of the gigaxonin-E3 ligase in organizing neurofilaments and may prove useful in understanding the pathological processes engaged in other neurodegenerative disorders characterized by accumulation of neurofilaments and dysfunction of the Ubiquitin Proteasome System, such as Amyotrophic Lateral Sclerosis, Huntington's, Alzheimer's and Parkinson's diseases.

Classifying fractionated electrograms in human atrial fibrillation using monophasic action potentials and activation mapping: Evidence for localized drivers, rate acceleration, and nonlocal signal etiologies

Complex fractionated electrograms (CFAEs) detected during substrate mapping for atrial fibrillation (AF) reflect etiologies that are difficult to separate. Without knowledge of local refractoriness and activation sequence, CFAEs may represent rapid localized activity, disorganized wave collisions, or far-field electrograms. The purpose of this study was to separate CFAE types in human AF, using monophasic action potentials (MAPs) to map local refractoriness in AF and multipolar catheters to map activation sequence. MAP and adjacent activation sequences at 124 biatrial sites were studied in 18 patients prior to AF ablation (age 57 ± 13 years, left atrial diameter 45 ± 8 mm). AF cycle length, bipolar voltage, and spectral dominant frequency were measured to characterize types of CFAE. CFAE were observed at 91 sites, most of which showed discrete MAPs and (1) pansystolic local activity (8%); (2) CFAE after AF acceleration, often with MAP alternans (8%); or (3) nonlocal (far-field) signals (67%). A fourth CFAE pattern lacked discrete MAPs (17%), consistent with spatial disorganization. CFAE with discrete MAPs and pansystolic activation (consistent with rapid localized AF sites) had shorter cycle length (P <.05) and lower voltage (P <.05) and trended to have higher dominant frequency than other CFAE sites. Many CFAEs, particularly at the septa and coronary sinus, represented far-field signals. CFAEs in human AF represent distinct functional types that may be separated using MAPs and activation sequence. In a minority of cases, CFAEs indicate localized rapid AF sites. The majority of CFAEs reflect far-field signals, AF acceleration, or disorganization. These results may help to interpret CFAE during AF substrate mapping.