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Aggarwal, N.

Publications and source records attributed to Aggarwal, N..

11 recordsLinked to original sources

EpiATLAS - a reference for human epigenomic research

The sequence of the human genome provides a foundation for understanding cellular processes in health and disease1. The organisation of this primary genetic information into cell-specific structure and function is critical to understanding the cell type-specific interpretation and execution of the genome. Epigenetic processes are essential for packaging and higher-level functional organisation of the genome, and changes therein are increasingly recognised as contributors to human disease. Building on primary data generated by multinational consortia, the International Human Epigenome Consortium2 (IHEC) has uniformly processed a collection of more than 2000 comprehensive human reference epigenomes, collectively referred to as EpiATLAS. This effort involved the development of standardised molecular and bioinformatics protocols, metadata models, and analytical tools to manage, integrate, display, and share vast amounts of epigenomic data. This includes the creation of a publicly available Epigenome Reference Registry, which provides a system for accessing protected human subject datasets and facilitates open searching of de-identified samples and experimental data. The integrated EpiATLAS ecosystem and its comprehensive human reference epigenome maps provide an unprecedented resource for the biosciences, expanding the annotated epigenomic landscape while uncovering previously unappreciated relationships among regulatory layers and revealing how epigenetic inputs underpin fundamental cellular functions and disease associations.

genomics↗

Rosindol: A fluorogen for the quantitative measurement of reactive oxygen species in living cells

Reactive oxygen species (ROS) are key mediators of disease, yet accurate characterization in living systems remains challenging because current probes lack oxidation specificity and produce nonlinear, pH-dependent signals. Here we introduce Rosindol, a novel thioacetal-based fluorogenic probe that overcomes these limitations. Rosindol undergoes an umpolung oxidation in the presence of ROS to generate fluorescence, displaying dose-linear responses to H2O2, O2*-, OH*, and HOCl with minimal background signal. Unlike conventional probes, Rosindol is pH-independent, photostable, water soluble, and agnostic to glucose concentration, esterase expression, and ambient oxygen. Validation in human cells--including PMA-stimulated neutrophils and SOD knockout models--confirms accurate detection of cytosolic and mitochondrial ROS. In pancreatic cancer cells, Rosindol reveals a fourfold increase in mitochondrial O2*- generation capacity via Complex I of the electron transport chain. Glucose stimulation induces twofold higher ROS generation in malignant cells, highlighting a connection between Warburg metabolism and the etiology of oxidative stress in pancreatic cancer. These studies illustrate the utility of Rosindol to provide valuable insight to oxidative stress processes in complex biological environments.

cancer biology↗

Image quality metrics fail to accurately represent biological information in fluorescence microscopy

Image processing methods offer the potential to improve the quality of fluorescence microscopy data, allowing for image acquisition at lower, less phototoxic illumination doses. The training and evaluation of such methods is informed and driven by full-reference image quality metrics (IQMs); however, these metrics derive from applications to natural scene images, not fluorescence microscopy images. Here we investigate the response of IQMs to common properties of fluorescence microscopy data and whether IQMs are capable of reporting the biological information content of images. We find that IQM scores are biased by image content for both raw and processed microscopy data, and that improvements in IQM values reported after processing are not reliably correlated with performance in downstream analysis tasks. As common IQMs are unreliable proxies for guiding image processing developments in biological fluorescence microscopy, image processing performance should be benchmarked according to downstream analysis success.

bioinformatics↗

Integrated flexible DNA methylation-chromatin segmentation modelingenhances epigenomic state annotation

DNA methylation and histone modifications together shape the cell-type-specific epigenomic landscape. To enable a more comprehensive genome-wide annotation, we developed EpiSegMixMeth (ESMM), the first truly integrative segmentation model combining chromatin marks and DNA methylation. ESMM extends hidden Markov models with flexible read count distributions and state duration modeling. Applied to 154 high-quality human epigenomes from the IHEC EpiAtlas, ESMM substantially improves the annotation of broad heterochromatic regions-covering over 60% of the genome, that are frequently missed by chromatin-only models. Additionally, it precisely defines the boundaries of narrow regulatory elements and resolves local chromatin state transitions during cell differentiation. Notably, we demonstrate that DNA methylation can substitute for missing repressive histone marks in segmentation, ensuring robust annotation across diverse cell types. In memory B-cell development, ESMM reveals fine-scale chromatin state shifts that align with 3D genome architecture changes. Our results highlight the power of integrating DNA methylation into genome segmentation and provide a valuable resource for dissecting cell-type-specific epigenomic regulation.

bioinformatics↗

The development of trait anxiety in nonhuman primates during the first year of life

Anxious Temperament (AT) is a nonhuman primate phenotype that models childhood behavioral inhibition, a prominent risk factor for anxiety disorders and stress-related psychopathology. To understand its earliest antecedents, we characterized ATs developmental trajectory over the first year of life. Infant monkeys (n=35, 24 female) were longitudinally phenotyped for AT by assessing threat-related increases in freezing behavior, reductions in coo-calling, and increases in circulating cortisol at 1.5, 6, 12, 24, and 52 weeks. AT levels increased linearly, reaching mature levels by 52 weeks. Individual differences in AT, and its components, were stable across development. These findings support further studies during early primate life aimed to uncover neurobiological factors mediating development of this phenotype, which in humans is linked to stress-related psychopathology.

animal behavior and cognition↗

Characterisation and correction of polarisation effects in fluorescently labelled fibres

Many biological structures take the form of fibres and filaments, and quantitative analysis of fibre organisation is important for understanding their functions in both normal physiological conditions and disease. In order to visualise these structures, fibres can be fluorescently labelled and imaged, with specialised image analysis methods available for quantifying the degree and strength of fibre alignment. Here we show that fluorescently labelled fibres can display polarised emission, with the strength of this effect varying depending on structure and fluorophore identity. This can bias automated analysis of fibre alignment and mask the true underlying structural organisation. We present a method for quantifying and correcting these polarisation effects without requiring polarisation resolved microscopy, and demonstrate its efficacy when applied to images of fluorescently labelled collagen gels, allowing for more reliable characterisation of fibre microarchitecture.

cell biology↗

EpiSegMix: A Flexible Distribution Hidden Markov Model with Duration Modeling for Chromatin State Discovery

MotivationAutomated chromatin segmentation based on ChIP-seq data reveals insights into the epigenetic regulation of chromatin accessibility. Existing segmentation methods are constrained by simplifying modeling assumptions, which may have a negative impact on the segmentation quality. ResultsWe introduce EpiSegMix, a novel segmentation method based on a hidden Markov model with flexible read count distribution types and state duration modeling, allowing for a more flexible modeling of both histone signals and segment lengths. In a comparison with two existing tools, ChromHMM, Segway and EpiCSeg, we show that EpiSegMix is more predictive of cell biology, such as gene expression. Its flexible framework enables it to fit an accurate probabilistic model, which has the potential to increase the biological interpretability of chromatin states. Availability and implementationSource code: https://gitlab.com/rahmannlab/episegmix.

bioinformatics↗

DREADD-mediated amygdala activation is sufficient to induce anxiety-like responses in young nonhuman primates

Anxiety disorders are among the most prevalent psychiatric disorders, with symptoms often beginning early in life. To model the pathophysiology of human pathological anxiety, we utilized Designer Receptors Exclusively Activated by Designer Drugs (DREADDs) in a nonhuman primate model of anxious temperament to selectively increase neuronal activity of the amygdala. Subjects included 10 young rhesus macaques; 5 received bilateral infusions of AAV5-hSyn-HA-hM3Dq into the dorsal amygdala, and 5 served as controls. Subjects underwent behavioral testing in the human intruder paradigm following clozapine or vehicle administration, prior to and following surgery. Behavioral results indicated that clozapine treatment post-surgery increased freezing across different threat-related contexts in hM3Dq subjects. This effect was again observed approximately 1.9 years following surgery, indicating the long-term functional capacity of DREADD-induced neuronal activation. [11C]deschloroclozapine PET imaging demonstrated amygdala hM3Dq-HA specific binding, and immunohistochemistry revealed that hM3Dq-HA expression was most prominent in basolateral nuclei. Electron microscopy confirmed expression was predominantly on neuronal membranes. Together, these data demonstrate that activation of primate amygdala neurons is sufficient to induce increased anxiety-related behaviors, which could serve as a model to investigate pathological anxiety in humans.

neuroscience↗

AIM2 inflammasome activation in astrocytes occurs during the late phase of EAE

Inflammasomes are a class of innate immune signaling platforms that activate in response to an array of cellular damage and pathogens. Inflammasomes promote inflammation under many circumstances to enhance immunity against pathogens and inflammatory responses through their effector cytokines, IL-1{beta} and IL-18. Multiple sclerosis and its animal model, experimental autoimmune encephalomyelitis (EAE), are such autoimmune conditions influenced by inflammasomes. Despite work investigating inflammasomes during EAE, little remains known concerning the role of inflammasomes in the central nervous system (CNS) during the disease. Here we use multiple genetically modified mouse models to monitor activated inflammasomes in situ based on ASC oligomerization in the spinal cord. Using inflammasome reporter mice, we found heightened inflammasome activation in astrocytes after the disease peak. In contrast, microglia and CNS-infiltrated myeloid cells had few activated inflammasomes in the CNS during EAE. Astrocyte inflammasome activation was dependent on AIM2, but low IL-1{beta} expression and no significant signs of cell death were found in astrocytes during EAE. Thus, the AIM2 inflammasome activation in astrocytes may have a distinct role from traditional inflammasome-mediated inflammation. SIGNIFICANCE STATEMENTInflammasome activation in the peripheral immune system is pathogenic in multiple sclerosis (MS) and its animal model, experimental autoimmune encephalomyelitis (EAE). However, inflammasome activity in the central nervous system (CNS) is largely unexplored. Here, we used genetically modified mice to determine inflammasome activation in the CNS during EAE. Our data indicated heightened AIM2 inflammasome activation in astrocytes after the disease peak. Unexpectedly, neither CNS-infiltrated myeloid cells nor microglia were the primary cells with activated inflammasomes in SC during EAE. Despite AIM2 inflammasome activation, astrocytes did not undergo apparent cell death and produced little of the proinflammatory cytokine, IL-1{beta}, during EAE. This study showed that CNS inflammasome activation occurs during EAE without associating with IL-1{beta}-mediated inflammation.

immunology↗

Isolation and characterization of SARS-CoV-2 VOC, 20H/501Y.V2, from UAE travelers

Multiple SARS-CoV-2 variants have been emerged and created serious public health in the affected countries. The variant of Concern associated with high transmissibility, disease severity and escape mutations is threat to vaccination program across the globe. Travel has been important factor in spread of SARS-CoV-2 variants worldwide. India has also witnessed the dreadful effect of these SARS-CoV-2 variants. Here, we report the Isolation and characterization of SARS-CoV-2 VOC, 20H/501Y.V2 (B.1.351), from UAE travelers to India. The virus isolate would be useful to determine the efficacy of the currently available vaccines in India.

microbiology↗

Dectin-1 limits central nervous system autoimmunity through a non-canonical pathway

Pathologic roles for innate immunity in neurologic disorders are well-described, but protective aspects of the immune response are less understood. Dectin-1, a C-type lectin receptor (CLR), is largely known to induce inflammation. However, we found that Dectin-1 is protective in experimental autoimmune encephalomyelitis (EAE), while its canonical signaling mediator, Card9, promotes the disease. Notably, Dectin-1 does not respond to heat-killed Mycobacteria, an adjuvant to induce EAE. Myeloid cells mediate the protective function of Dectin-1 in EAE and upregulate gene expression of neuroprotective molecules, including Oncostatin M (Osm) through a non-canonical Card9-independent pathway, mediated by NFAT. Furthermore, we found that the Osm receptor (OsmR) functions specifically in astrocytes to reduce EAE severity. Our study revealed a new mechanism of protective myeloid-astrocyte crosstalk regulated by a non-canonical Dectin-1 pathway and identifies novel therapeutic targets for CNS autoimmunity. Graphical AbstractO_LIDectin-1 is a protective C-type lectin receptor (CLR) in experimental autoimmune encephalomyelitis (EAE) C_LIO_LIDectin-1 promotes expression of Osm, a neuroprotective IL-6 family cytokine, in myeloid cells C_LIO_LIOsmR signaling in astrocytes limits EAE progression and promotes remission C_LIO_LINon-canonical Card9-independent signaling drives a distinct Dectin-1-mediated transcriptional program to induce expression of Osm and other factors with protective or anti-inflammatory functions C_LI O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=166 SRC="FIGDIR/small/080481v1_ufig1.gif" ALT="Figure 1"> View larger version (35K): org.highwire.dtl.DTLVardef@885aa2org.highwire.dtl.DTLVardef@1f68087org.highwire.dtl.DTLVardef@70263aorg.highwire.dtl.DTLVardef@ddc3b4_HPS_FORMAT_FIGEXP M_FIG C_FIG

immunology↗