Biology subjects

Kaushik, R.

Publications and source records attributed to Kaushik, R..

At least 19 recordsLinked to original sources

bioRxiv2025

Transcriptional control of neuronal maintenance by SOX2 during inner ear innervation

The cochlear sensory epithelium and the spiral ganglion neurons it supports arise from a common pool of otic progenitors, yet the neurons remain dependent on the epithelium for guidance and survival long after the two lineages diverge. How that dependency is sustained as the progenitor pool generates increasingly restricted cell types is unknown. Here we show that SOX2 maintains this regulatory continuity. Deletion of Sox2 from the cochlear epithelium after cochlear neurogenesis does not affect neuroblast generation, delamination and proliferation; however, peripheral axons failed to reach the epithelium and neurons were progressively lost, identifying a non-cell-autonomous requirement for epithelial SOX2. Transcriptomic profiling revealed a SOX2-dependent epithelial programme enriched for neurotrophic and axon-guidance genes, including Ntf3 and Bdnf. In cochlear organoids, acute Sox2 deletion reduced H3K27ac at regulatory elements while H3K4me1 remained stable, consistent with SOX2 maintaining the activity of previously marked enhancers. Ntf3 and Bdnf exemplified distinct regulatory trajectories. At Ntf3, SOX2 occupied an enhancer whose activity depended on Sox2, whereas at Bdnf it occupied promoter-proximal elements in progenitors before ATOH1 engaged these and a hair-cell-active distal enhancer. Thus, SOX2 links sensory fate specification to epithelial-neuronal communication. More generally, our findings suggest that regulatory competence can persist through lineage restriction, while changing transcription-factor inputs partition its output among descendants to coordinate their development.

developmental biology↗

bioRxiv2025

Junctional Heterogeneity Shapes Epithelial Morphospace

Tissues and organs develop a wide range of shapes, sizes and cellular organisations, linked to their physiological function. How developmental programmes generate this organisational diversity remains poorly understood. Inner ear sensory epithelia in birds, fish, and mammals provide a tractable system to address this question, as their constituent cells arise from a common developmental lineage, share molecular signatures, and have conserved physiological functions, yet assemble into distinct cellular organisations. These epithelia contain two principal cell types, mechanosensory hair cells (HCs) and supporting cells (SCs), organised into mosaics. Here, we developed a three-parameter morphospace that quantitatively captures epithelial organisation, enabling comparisons across species, structures and developmental stages. Combining this framework with genetic perturbation, biochemical analysis and live imaging reveals that the diverse mature organisations emerge from a common early organisational state constrained by Notch-Delta signalling. During subsequent development, the differential localisation of adhesion molecules (Cdh1,2 and Nectin) and contractility-associated proteins (NM2 and -actinin-4) at HC-SC and SC-SC junctions establishes junctional asymmetries. Across species, asymmetry drives stable circular HCs and actively remodelling SCs. The coexistence of these cell shape states drives selective intercalation, guiding each epithelium along a distinct trajectory through morphospace toward its mature organisation. These findings identify cell-shape dynamics as a developmental mechanism for generating organisational diversity in sensory, and potentially other, epithelia.

developmental biology↗

bioRxiv2025

Scratcher: An automated machine-vision tool for dissecting the neural basis of itch

Itch or pruritus invokes a specific reflexive and repetitive directed nocifensive behavioural response, known as scratching. Recent decades have revealed neural circuits that are involved in the sensory and affective-motivational aspects of itch-induced scratching. However, most of these studies relied on manual subjective methods of quantifying scratching in laboratory mice and rats. Recent advances in deep learning have opened avenues for the development of computational tools to analyze animal behaviour in a reliable and automated manner. Further, combined with optogenetic and chemogenetic strategies, these tools can accelerate our understanding of neural circuits underlying itch and scratching. To that end, we have developed Scratcher, a GUI-based computational tool based on a real-time object detection algorithm that allows semi-supervised automated analysis of scratching behaviour in mice in a computationally inexpensive manner. We recorded chloroquine-induced acute itch as it developed and determined the consequence of nail-trimming on acute-itch induced scratching with Scratcher. To probe the neural mechanisms underlying itch, we combined Scratcher with genetic circuit dissection using the Fos-TRAP mouse line. By targeting itch-activated neurons in the lateral parabrachial nucleus (LPBN) - a key brainstem hub for pruritic signal transmission - we demonstrated that LPBN activity modulates itch-evoked scratching. Together, we present a novel, easy-to-use computational tool to dissect molecular, cellular, and circuit mechanisms of itch and scratching.

neuroscience↗

bioRxiv2025

Single neurons act as a memory buffer for space

Neurons are the fundamental units of cognitive processing. The prevailing view holds that neurons are input-output units that fire action potentials only upon receiving sufficient synaptic input. Here, we demonstrate that this may not be the sole operational mode of neurons in vivo during cognitive tasks, by showing that hippocampal place cells actively maintain firing and preserve spatial information through molecularly defined intrinsic mechanisms. Using in vitro and in vivo recordings coupled with molecular manipulation in mice, we reveal that hippocampal persistent firing during spatial working memory is supported by individual neurons via TRPC4 ion channels. Despite the general belief that persistent activity carries working memory content, we demonstrate that this firing maintains immediate spatial representations and is required for spatial working memory performance. These findings redefine neurons as active contributors to information retention, beyond their traditional role as passive input-output units, potentially reshaping our general understanding of computation in the brain.

neuroscience↗

bioRxiv2024

Role Of Pcdh15 In The Development Of Intrinsic Polarity Of Inner Ear Hair Cells

In vertebrates, auditory information is transduced in the cochlea by mechanosensory hair cells (HC) through an eccentrically organised structure known as the hair bundle. This consists of a true cilium, known as the kinocilium, and modified microvilli, known as stereocilia. The hair bundle has a distinct structure with stereocilia organised in graded rows, with the longest abutting the kinocilia. The hair bundles of all HC are aligned to the tissue axis and are planar polarised. Important in the development and physiology of HC are protein bridges consisting of cadherin-23 and protocadherin-15. These link the tips of stereocilia, where they play a role in mechanotransduction, and between the kinocilia and the stereocilia, where they are involved in development. Both cadherin-23 and protocadherin-15 mutations result in defects in planar polarity; however, the mechanism through which this defect arises is unclear. Using a novel mutant for the Pcdh15-CD2 isoform, we show that while the initial deflection of the kinocilium occurs, its peripheral migration to register with Gi3 is perturbed. Pcdh15-CD2 genetically interacts with Gpsm2, perturbing vestibular function. We find that the earliest expression of Pcdh15-CD2 is at the base of the kinocilia, and the defects in morphogenesis occur before the formation of kinocilial links. By re-introducing functional Pcdh15-CD2, we show that polarity can be restored, suggesting that Pcdh15-CD2 couples kinocilial and stereocilial development through a mechanism independent of kinocilial links.

developmental biology↗

bioRxiv2024

Mechanical coupling of compartments drives polarity and patterning of mouse auditory epithelium

Morphogenetic information arises from a combination of genetically encoded cellular properties and emergent cellular behaviours. The spatio-temporal implementation of this information is critical to ensure robust, reproducible tissue shapes, yet the principles underlying its organisation remain unknown. We investigated this principle using the mouse auditory epithelium, the organ of Corti (OC). OC consists of a sensory domain, which transduces sound through polar mechanosensory hair cells (HC), part of a mosaic with supporting cells (SC). On either side of the sensory domain are non-sensory domains. These domains undergo cellular rearrangements, which, together, lead to a spiral cochlea that contains planar polarised HCs. This makes the mammalian cochlea a compelling system to understand coordination across spatial scales. Using genetic and ex-vivo approaches, we found patterning of OC into sensory and non-sensory domains is associated with a combinatorial expression of adhesion molecules, which underpins OC into spatially defined compartments, enabling planar cell polarity (PCP) cues to regulate compartment-specific organisation. Through compartment-specific knockouts of the PCP protein, Vangl2, we find evidence of compartment coupling, a non-linear influence on the organisation within one compartment when cellular organisation is disrupted in another. In the OC, compartment coupling originates from vinculin-dependent junctional mechanics, coordinating cellular dynamics across spatial scales. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=115 SRC="FIGDIR/small/613243v2_ufig1.gif" ALT="Figure 1"> View larger version (45K): org.highwire.dtl.DTLVardef@11d31c1org.highwire.dtl.DTLVardef@1ad85dcorg.highwire.dtl.DTLVardef@12f4a0corg.highwire.dtl.DTLVardef@1a663ab_HPS_FORMAT_FIGEXP M_FIG C_FIG

developmental biology↗

bioRxiv2024

Benchmarking Protein Language Models for Protein Crystallization

The problem of protein structure determination is usually solved by X-ray crystallography. Several in silico deep learning methods have been developed to overcome the high attrition rate, cost of experiments and extensive trial-and-error settings, for the predicting the crystallization propensities of proteins based on their sequences. In this work, we benchmark the power of open protein language models (PLMs) through the TRILL platform, a bespoke framework democratizing the usage of PLMs for the task of predicting crystallization propensities of proteins. By comparing LightGBM / XGBoost classifiers built on the embedding representations learned by different PLMs, such as ESM2, Ankh, ProtT5-XL, ProstT5, with the performance of state-of-the-art sequence-based methods like DeepCrystal, ATTCrys and CLPred, we identify the most effective methods for predicting crystallization outcomes. The LightGBM classifiers utilizing embeddings from ESM2 model with 30 and 36 transformer layers and 150 and 3, 000 million parameters respectively have performance gains by 3 - 5% then all compared models for various evaluation metrics, including AUPR (Area Under Precision-Recall Curve), AUC (Area Under the Receiver Operating Characteristic Curve), and F1 score on independent test sets. Furthermore, we fine-tune the ProtGPT2 model available via TRILL to generate crystallizable proteins. Starting with 3, 000 generated proteins and through a step of filtration processes including consensus of all open PLM-based classifiers, sequence identity through CD-HIT, secondary structure compatibility, aggregation screening, homology search and foldability evaluation, we identified a set of 5 novel proteins as potentially crystallizable.

bioinformatics↗

bioRxiv2024

Decoding Protein Aggregation through Computational Approach: Identification and Scoring of Aggregation-Prone Regions in Protein Sequences

Protein aggregation is a critical phenomenon associated with numerous neurodegenerative and systemic diseases. Understanding the propensity of proteins to aggregate is essential for unraveling the molecular basis of these disorders and for design and engineering of novel proteins or modulating the activity/stability of enzymatic proteins. Here, we present APR-Score, a novel machine-learning based computational method designed to identify aggregation-prone regions within protein sequences. ARP-Score leverages a combination of sequence-based features to predict regions of proteins that are prone to aggregate. The APR-Score harnessed the information ingrained in the compiled sequence and structural features to provide state-of-the-art accuracy. The APR-Score is assessed by conducting rigorous cross-validation experiments on the training dataset and further validated on an independent test dataset. The APR-Score prediction models demonstrated robustness and reliability in discriminating aggregation-prone regions from non-aggregating ones on an independent dataset, achieving Mathews correlation coefficient (MCC) 0.81, precision 0.89, and F1-Score 0.91. The APR-Score offers a valuable tool for researchers investigating protein aggregation-related diseases, as it can expedite the identification of aggregation-prone regions, aiding in the development of targeted therapies and diagnostic tools. The computational protein design and engineering regimes can be facilitated through APR-Score based identification and screening of aggregation prone protein sequences.

bioinformatics↗

bioRxiv2024

Neurocan regulates axon initial segment organization and neuronal activity in cultured cortical neurons

The neural extracellular matrix (ECM) accumulates in the form of perineuronal nets (PNNs), particularly around fast-spiking GABAergic interneurons in the cortex and hippocampus, but also in association with the axon initial segments (AIS) and nodes of Ranvier. Increasing evidence highlights the role of Neurocan (Ncan), a brain-specific component of ECM, in the pathophysiology of neuropsychiatric disorders like bipolar disorder and schizophrenia. Ncan localizes at PNNs, nodes of Ranvier and the AIS, highlighting its potential role in regulation of axonal excitability. Here, we used knockdown and knockout approaches in mouse primary cortical neurons in combination with immunocytochemistry, western blotting and electrophysiological techniques to characterize the role of Ncan in the organization of PNNs and AIS and in the regulation of neuronal activity. We found that reduced Ncan levels led to remodeling of PNNs around neurons via upregulated Aggrecan mRNA and protein levels, increased expression of activity-dependent c-Fos and FosB genes and elevated spontaneous synaptic activity. The latter correlated with increased levels of Ankyrin-G in the AIS particularly in excitatory neurons, and with the elevated expression of Nav1.6 channels. Our results suggest that Ncan regulate expression of key proteins in PNNs and AISs and provide new insights into its role in the fine-tuning of neuronal functions.

neuroscience↗

bioRxiv2024

MATE-Pred: Multimodal Attention-based TCR-Epitope interaction Predictor

An accurate binding affinity prediction between T-cell receptors and epitopes contributes decisively to develop successful immunotherapy strategies. Some state-of-the-art computational methods implement deep learning techniques by integrating evolutionary features to convert the amino acid residues of cell receptors and epitope sequences into numerical values, while some other methods employ pre-trained language models to summarize the embedding vectors at the amino acid residue level to obtain sequence-wise representations. Here, we propose a highly reliable novel method, MATE-Pred, that performs multi-modal attention-based prediction of T-cell receptors and epitopes binding affinity. The MATE-Pred is compared and benchmarked with other deep learning models that leverage multi-modal representations of T-cell receptors and epitopes. In the proposed method, the textual representation of proteins is embedded with a pre-trained bi-directional encoder model and combined with two additional modalities: a) a comprehensive set of selected physicochemical properties; b) predicted contact maps that estimate the 3D distances between amino acid residues in the sequences. The MATE-Pred demonstrates the potential of multi-modal model in achieving state-of-the-art performance (+8.4% MCC, +5.5% AUC compared to baselines) and efficiently capturing contextual, physicochemical, and structural information from amino acid residues. The performance of MATE-Pred projects its potential application in various drug discovery regimes.

bioinformatics↗

bioRxiv2023

A novel highly divergent enteric calicivirus in a bovine calf, India

In 2015, a novel highly divergent bovine calicivirus was detected in an Indian calf with enteritis. Phylogenetic analysis linked it to the Nebovirus with only 38.5% sequence identities, emphasizing the need for separate taxonomic classification. Furthermore, PCR screening detected these unique caliciviruses widely in Indias northern states.

microbiology↗

bioRxiv2023

Depletion of neurocan in the prefrontal cortex impairs temporal order recognition, cognitive flexibility and perisomatic GABAergic innervation

The condensed form of neural extracellular matrix (ECM), perineuronal nets (PNNs), is predominantly associated with parvalbumin-expressing (PV+) interneurons in the cortex and hippocampus. PNNs are enriched in several lecticans, including neurocan (Ncan). A polymorphism in the human Ncan gene has been associated with alterations in hippocampus-dependent memory function, variation of prefrontal cortex structure, and a higher risk for schizophrenia or bipolar disorder. Ncan knockout (KO) mice show related behavioral abnormalities, such as hyperactivity. Here we focused on studying how dysregulation of Ncan specifically in the mPFC may affect cognitive and synaptic functions. Intracortical adeno-associated virus (AAV) delivery was used to express shRNA against Ncan. Analysis of PNNs in Ncan shRNA-injected mice revealed a reduction in PNNs labelling by Wisteria floribunda agglutinin (WFA) around PV+ interneurons. Reduced Ncan expression resulted in a loss of the mPFC-dependent temporal order recognition and impairment of reversal spatial learning in a labyrinth (dry maze) task. As a potential synaptic substrate of these cognitive abnormalities, we report a robust reduction in the perisomatic GABAergic innervation of PV+ cells in Ncan KO and Ncan shRNA-injected mice. We also observed an increase in the density of vGLUT1-immunopositive synaptic puncta in the neuropil of Ncan shRNA-injected mice, which was, however, compensated in Ncan KO mice. Thus, our findings highlight a functional role of Ncan in supporting perisomatic GABAergic inhibition, temporal order recognition memory and cognitive flexibility, as one of the important cognitive resources depleted in neuropsychiatric disorders. Contribution to the fieldIn this study, we asked if the extracellular matrix proteoglycan neurocan (Ncan) plays a functional role in the prefrontal cortex (PFC) of mice. Using viral delivery and expression of shRNA to knock down the expression of Ncan in the PFC, we provide evidence that neuronal Ncan is essential for the maintenance of perineuronal nets enveloping perisomatic interneurons by influencing the expression of glycoepitopes stained with Wisteria floribunda agglutinin and by modulating mRNA expression levels of other PNNs constituents. At the behavioral level, the knockdown of Ncan in mPFC impaired the temporal order recognition memory and consolidation/retrieval of spatial memories after reversal learning in the dry maze task. At the synaptic level, we found that Ncan knockdown reduced perisomatic GABAergic innervation of perisomatic interneurons and increased the density of vGLUT1+ excitatory presynaptic terminals in the neuropil of the PFC. Moreover, knockdown of Ncan changed the expression levels of several genes involved in activity-dependent synaptic remodeling. In summary, we conclude that neuronal Ncan is essential for multiple cognitive flexibility-related synaptic and cognitive functions in the PFC.

neuroscience↗

bioRxiv2023

Heparan sulfates regulate axonal excitability and context generalization through Ca2+/calmodulin-dependent protein kinase II

Our previous studies demonstrated that enzymatic removal of highly sulfated heparan sulfates with heparinase 1 impaired axonal excitability and reduced expression of ankyrin G at the axon initial segments in the CA1 region of the hippocampus ex vivo, impaired context discrimination in vivo, and elevated Ca2+/calmodulin-dependent protein kinase II (CaMKII) activity in vitro. Here, we show that in vivo delivery of heparinase 1 in the CA1 region of the hippocampus elevated autophosphorylation of CaMKII 24 hours after injection in mice. Patch-clamp recording in CA1 neurons revealed no significant heparinase effects on the amplitude or frequency of miniature excitatory and inhibitory postsynaptic currents, while the threshold for action potential generation was increased and fewer spikes were generated in response to current injection. Delivery of heparinase on the next day after contextual fear conditioning induced context overgeneralization 24 hours after injection. Co-administration of heparinase with the CaMKII inhibitor (autocamtide-2-related inhibitory peptide) rescued neuronal excitability and expression of ankyrin G at the axon initial segment. It also restored context discrimination, suggesting a key role of CaMKII in neuronal signaling downstream of heparan sulfate proteoglycans and highlighting a link between impaired CA1 pyramidal cell excitability and context generalization during recall of contextual memories.

neuroscience↗

bioRxiv2023

A shift in the mechanisms controlling hippocampal engram formation during brain maturation

The ability to form precise, episodic memories develops with age, with young children only able to form gist-like memories that lack precision. The cellular and molecular events in the developing hippocampus that underlie the emergence of precise, episodic-like memory formation are unclear. In mice, the absence of a competitive neuronal engram allocation process in the immature hippocampus precluded the formation of sparse engrams and precise memories until the fourth postnatal week, when inhibitory circuits in the hippocampus mature. This age-dependent shift in precision of episodic-like memories involved the functional maturation of parvalbumin-expressing interneurons in subfield CA1 by extracellular perineuronal nets which is necessary and sufficient for the onset of competitive neuronal allocation, sparse engram formation, and memory precision. One-Sentence SummaryEpisodic-like memory precision requires maturation of hippocampal inhibitory interneurons by the extracellular matrix.

neuroscience↗

bioRxiv2022

A novel consensus-based computational pipeline for rapid screening of antibody therapeutics for efficacy against SARS-CoV-2 variants of concern including omicron variant

Multiple severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants continue to evolve carrying flexible amino acid substitutions in the spike proteins receptor binding domain (RBD). These substitutions modify the binding of the SARS-CoV-2 to human angiotensin-converting enzyme 2 (hACE2) receptor and have been implicated in altered host fitness, transmissibility and efficacy against antibody therapeutics and vaccines. Reliably predicting the binding strength of SARS-CoV-2 variants RBD to hACE2 receptor and neutralizing antibodies (NAbs) can help assessing their fitness, and rapid deployment of effective antibody therapeutics, respectively. Here, we introduced a two-step computational framework with three-fold validation that first identified dissociation constant as a reliable predictor of binding affinity in hetero-dimeric and -trimeric protein complexes. The second step implements dissociation constant as descriptor of the binding strengths of SARS-CoV-2 variants RBD to hACE2 and NAbs. Then, we examined several variants of concern (VOCs) such as Alpha, Beta, Gamma, Delta, and Omicron and demonstrated that these VOCs RBD bind to the hACE2 with enhanced affinity. Furthermore, the binding affinity of Omicron variants RBD was reduced with majority of the RBD-directed NAbs, which is highly consistent with the experimental neutralization data. By studying the atomic contacts between RBD and NAbs, we revealed the molecular footprints of four NAbs (GH-12, P2B-1A1, Asarnow_3D11, and C118) -- that may likely neutralize the recently emerged omicron variant -- facilitating enhanced binding affinity. Finally, our findings suggest a computational pathway that could aid researchers identify a range of current NAbs that may be effective against emerging SARS-CoV-2 variants.

bioinformatics↗

bioRxiv2022

A novel structure-based approach for identification of vertebrate susceptibility to SARS-CoV-2: implications for future surveillance programmes

Understanding the origin of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has been a highly debatable and unsolved challenge for the scientific communities across the world. A key to dissect the susceptibility profiles of animal species to SARS-CoV-2 is to understand how virus enters into the cells. The interaction of SARS-CoV-2 ligands (RBD on spike protein) with its host cell receptor, angiotensin-converting enzyme 2 (ACE2), is a critical determinant of host range and cross-species transmission. In this study, we developed and implemented a rigorous computational approach for predicting binding affinity between 299 ACE2 orthologs from diverse vertebrate species and the SARS-CoV-2 spike protein. The findings show that the spike protein of SARS-CoV-2 can bind to many vertebrate species carrying evolutionary divergent ACE2, implying a broad host range at the virus entry level, which may contribute to cross-species transmission and further viral evolution. Additionally, the present study facilitated the identification of genetic determinants that may differentiate susceptible from the resistant host species based on the conservation of ACE2-spike protein interacting residues in vertebrate host species known to facilitate SARS-CoV-2 infection; however, these genetic determinants warrant in vivo experimental confirmation. The molecular interactions associated with varied binding affinity of distinct ACE2 isoforms in a specific bat species were identified using protein structure analysis, implying the existence of diversified susceptibility of bat species to SARS-CoV-2. The findings from current study highlight the importance of intensive surveillance programs aimed at identifying susceptible hosts, particularly those with the potential to transmit zoonotic pathogens, in order to prevent future outbreaks.

bioinformatics↗

bioRxiv2020

Extracellular matrix remodeling through endocytosis and resurfacing of Tenascin-R

The brain extracellular matrix (ECM) assembles around neurons and synapses, and is thought to change only rarely, through proteolysis and renewed protein synthesis. We report here an alternative ECM remodeling mechanism, based on the recycling of ECM molecules. We found that a key ECM protein, Tenascin-R, is frequently endocytosed, and later resurfaces, preferentially near synapses. The TNR molecules complete this cycle within [~]3 days, in an activity-dependent fashion.

neuroscience↗

bioRxiv2020

A synthetic synaptic organizer protein restores glutamatergic neuronal circuits

Neuronal synapses undergo structural and functional changes throughout life, essential for nervous system physiology. However, these changes may also perturb the excitatory/inhibitory neurotransmission balance and trigger neuropsychiatric and neurological disorders. Molecular tools to restore this balance are highly desirable. Here, we report the design and characterization of CPTX, a synthetic synaptic organizer combining structural elements from cerebellin-1 and neuronal pentraxin-1 to interact with presynaptic neurexins and postsynaptic AMPA-type ionotropic glutamate receptors. CPTX induced the formation of excitatory synapses in vitro and in vivo and restored synaptic functions, motor coordination, spatial and contextual memories, and locomotion in mouse models for cerebellar ataxia, Alzheimers disease and spinal cord injury, respectively. Thus, CPTX represents a prototype for novel structure-guided biologics that can efficiently repair or remodel neuronal circuits. One Sentence SummaryStructural biology information was used to design CPTX, a synthetic protein that induces functional excitatory synapses and restores normal behaviors in mouse models of neurological diseases.

neuroscience↗