Biology subjects

Singh, M.

Publications and source records attributed to Singh, M..

At least 55 records · Page 3Linked to original sources

bioRxiv2025

Genetic Drivers of Sensitivity or Resistance to RAS(ON) Multi-Selective Inhibitors in NRAS-Mutated Melanoma

Most patients with advanced BRAF or NRAS-driven melanoma receive front-line immunotherapy. However, if immunotherapy fails, BRAF-mutated patients have effective second-line therapies, whereas NRAS-mutated patients lack pathway-targeted options. Recently, RAS(ON) multi-selective inhibitors like RMC-7977, and the investigational agent daraxonrasib, were described that, in partnership with cyclophilin-A (CYPA), inhibit RAS[GTP] signaling. Both compounds demonstrate potent anti-proliferative activity against NRAS-mutated melanoma cell lines and robust anti-tumor activity against preclinical melanoma models. However, in preclinical models, resistance to RMC-7977 monotherapy arose through mutations in Ppia (encoding CYPA) or Map2k1 (encoding MEK1). Moreover, two clinical case studies in patients with NRAS-mutated melanoma treated with daraxonrasib demonstrated clear anti-tumor activity in one patient, but progressive disease in another with co-occurring NRAS and MAP2K1 mutations at baseline. These findings support the potential for daraxonrasib in treatment of patients with NRAS-mutated melanoma, and reveal candidate mechanisms of monotherapy resistance, underscoring the need for combination therapies to improve outcomes. SIGNIFICANCEThere are no pathway-targeted therapies for patients with NRAS-mutated melanoma. Here we demonstrate that direct pharmacological inhibition of RAS[GTP] with RMC-7977 or daraxonrasib (RMC-6236) has profound inhibitory effects in preclinical models of NRAS-mutated melanoma. Furthermore, we identify mechanisms of resistance to RMC-7977 through mutational inactivation of CYPA or mutational activation of MEK1.

cancer biology↗

bioRxiv2025

Complexome profile of mitochondrial complexes in the myzozoan parasite of oysters, Perkinsus marinus

Mitochondrial complexes, such as the mitochondrial electron transport chain (mETC), the F1Fo-ATP synthase and the mitochondrial ribosome, are centrally important for mitochondrial function. Recently, an unexpected diversity in the composition of these complexes across unicellular eukaryotic lineages, with the apicomplexan parasites featuring prominently, has been revealed. However, whether the observed enlarged and divergent mitochondrial complexes are conserved across the wider Myzozoan lineage has not been investigated. Here, using a complexome profiling proteomic approach, we have characterised the composition of the mitochondrial complexes of the myzozoan parasite of oysters, Perkinsus marinus. We show that it shares with Plasmodium and Toxoplasma huge ATP synthase and mETC complexes. Moreover, the Perkinsus mitoribosome possesses many of the divergent features recently discovered in apicomplexans, such as an expanded subunit repertoire and the inclusion of RAP-domain and ApiAP2-like proteins as ribosomal proteins. Our study reveals the divergent subunit composition of mitochondrial complexes is an ancestral and highly conserved feature of Myzozoa.

microbiology↗

bioRxiv2025

Natural variation in an NLR pair confers thermostable resistance to a devastating bacterial pathogen

Climate change reshapes host-pathogen interactions by increasing pathogen aggressiveness and weakening plant immune responses, particularly under heat stress. Nucleotide-binding leucine-rich repeat (NLR) immune receptors, key players in pathogen recognition, are altered under elevated temperatures in both plants and mammals, posing a major challenge to disease resistance. In Arabidopsis thaliana, the well-described RPS4/RRS1 NLR pair confers resistance to the worldwide devastating phytopathogenic Ralstonia pseudosolanacearum. Here, by combining the exploration of natural genetic variation with genetic mapping, polymorphism analysis, structural modeling, and functional complementation, we demonstrated that the paucity of full thermostable resistance is primarily associated with a unique RPS4/RRS1 haplotype carrying key substitutions in leucine-rich repeat domains. These findings reveal natural genetic diversity as a source of thermostable resistance, highlighting promising opportunities to engineer climate-resilient plants.

plant biology↗

bioRxiv2025

A Site-Specific Organometallic Approach for Installing Tyrosine Phosphorylation Mimics to Decipher the Role of Phosphorylation in Alpha-Synuclein (aSyn) Aggregation and Seeding

Several studies have identified phosphorylation of alpha-synuclein (aSyn) at multiple tyrosine residues (Y39, Y125, Y133, and Y136) within Lewy bodies, which are the pathological hallmarks of Parkinsons disease (PD). However, understanding the specific role of phosphorylation at each site, or how multiple phosphorylation sites interact, has been challenging. Herein, we present an efficient method that leverages an organometallic Pd-complex to site-specifically attach phosphomimetic groups via Cys-arylation, closely mimicking natural phosphorylation. Using this approach, we successfully incorporated native-like tyrosine phosphorylation mimics into cysteine-containing proteins like synthetic transcription factor Max and recombinant aSyn, in good yields. To demonstrate the methods versatility, we created a focused library of mono-, di-, and tri-phosphorylated aSyn analogues. This development enabled, for the first time, the investigation of the effect of site-specific phosphorylation at multiple C-terminal tyrosine residues on aSyn fibrillization and aggregation. Our results show that mono-phosphorylation at any of the C-terminal sites has little effect on aggregation, while di- and tri-phosphorylation slows down the process, extending the lag phase compared to wild-type aSyn. Additionally, phosphorylation at Y39 reduces the seeding activity of aSyn fibrils by almost threefold in both mammalian and neuronal models of synuclein pathology. Overall, our strategy provides a rapid, selective, and scalable way to introduce aromatic PTMs, producing homogeneous protein libraries essential for mechanistic studies, biomarker development, and exploring the therapeutic potential of targeting aSyn-phosphorylation for PD and related disorders.

biochemistry↗

bioRxiv2025

Interaction and co-phase separation of SARS-CoV-2 nucleocapsid protein and human hnRNPA1 and its implications for viral life cycle

The nucleocapsid (N) protein of SARS-CoV-2 is central to viral assembly and replication. It binds viral RNA to form a helical nucleocapsid and enabling genome packaging and release into host cells. Human hnRNPA1, one of the most abundant RNA-binding proteins in eukaryotes, regulates key aspects of RNA metabolism, including splicing, transcription, localisation, and transport. Here, we report a direct physical interaction between SARS-CoV-2 N protein and hnRNPA1 with moderate affinity (Kd [~] 0.18 M), primarily mediated through their intrinsically disordered regions. Furthermore, we found that these proteins co-phase separate in vitro and co-localise within stress granules in cells. In vivo studies reveal that hnRNPA1 suppresses viral replication, suggesting that the N protein - hnRNPA1 interaction plays an important role in modulating the viral life cycle.

biochemistry↗

bioRxiv2025

Deconvolution of Sparse-count RNA Sequencing Data for Tumor Cells Using Embedded Negative Binomial Distributions

Estimating tumor-specific transcript proportions from mixed bulk samples has potential to inform novel biology. However, estimation accuracy using existing methods in sparse-count data such as microRNA-seq and spatial transcriptomics has yet to be established. We generated a mixed small RNA benchmark dataset to demonstrate analytical challenges. To resolve them, we developed DeMixNB, a semi-reference-based deconvolution model assuming a sum of negative binomial distributions. Applications to miRNA-seq from 856 patients with breast cancer and 3,755 spatial spots from lung cancer generated either clinical or mechanistic insights into tumor cell plasticity. This supports the important utility of DeMixNB to investigate cancer RNomes.

bioinformatics↗

bioRxiv2025

Detecting Somatic Mutations in Rare Clones using Single Cell Multi-Omics

BackgroundSomatic mutations are increasingly recognised as drivers of diseases beyond cancer, including autoimmune disorders. However, identifying rare, cell type-specific causal mutations remains challenging due to their low frequency within heterogeneous cell populations. Traditional bulk sequencing approaches lack the resolution to detect rare variants, underscoring the need for novel methods specifically designed for single-cell data of heterogeneous cell populations. MethodsWe present an integrated single-cell multi-omics computational framework, SCARCE (Single-Cell Analysis of Rare Clonal Events), tailored for single-cell DNA sequencing (scDNA-seq) to statistically prioritise rare somatic mutations within defined cell subpopulations. By comparing variant frequencies across subpopulations, identified through either variant-based clustering or cell type annotation from surface marker expression, we identify variants enriched in specific cell populations. Our method applies multiple user-adjustable filters and statistical enrichment tests to distinguish true somatic variants from technical artifacts. ResultsSCARCE successfully identifies rare somatic mutations across three distinct datasets using technologies including MissionBio Tapestri and clonally-amplified whole-genome sequencing of single cells. We demonstrate that SCARCE correctly isolates and identifies true variants in a cell population comprising just 10 of 16,316 cells (0.06% of the total population). Furthermore, in an extensively characterised sample with known causal variants, SCARCE correctly identifies all known pathogenic variants among its top-ranked candidates. ConclusionsSCARCE offers several advantages over existing tools in the field. By integrating genetic and phenotypic information at single-cell resolution, our approach opens new avenues for understanding the clonal origins of diseases driven by somatic mutations in small cell populations.

bioinformatics↗

bioRxiv2025

Transposable Element-Mediated Epigenomic Remodeling Drives Erythropoietin-Induced Neurogenesis in the Adult Hippocampus

Understanding the molecular mechanisms by which erythropoietin (EPO) acts as neurotrophic factor that enhances hippocampal function and learning is essential to harness its therapeutic potential. Here, we employ single-nucleus ATAC-seq and RNA-seq to map the epigenomic and transcriptional landscapes of adult mouse hippocampus under recombinant human EPO (rhEPO) treatment. We discover significant lineage-specific chromatin remodeling predominantly in newly formed and immature excitatory neurons, highlighting a robust EPO-driven neurogenic response as the first direct evidence that an extrinsic factor can induce adult hippocampal neurogenesis. Notably, many EPO-induced accessible regions overlap ancient transposable elements, particularly ancient LINEs and SINEs, that are bound by key neurogenic transcription factors such as NEUROD1/2, NEUROG2, FOXG1, and ASCL1 and are linked to nearby genes governing neuronal differentiation and synaptic plasticity. Our findings uncover a previously unrecognized transposon-mediated mechanism underlying EPO-induced neurogenesis, highlighting an underappreciated role for TE-derived sequences in this process, and establish a publicly available single-nucleus multiomic atlas as a resource for understanding cell-type-specific gene regulation and neuroplasticity in the adult brain.

neuroscience↗

bioRxiv2025

Feasibility of a parent-delivered attention and working memory intervention for early school-aged children born preterm

Preterm birth is a common neurodevelopmental condition that can have lasting impacts on cognition, including attention and working memory. Interventions that strengthen these skills in early childhood could support school readiness. Dino Island is a tablet-based intervention that combines process-specific practice of attention and working memory skills with a compensatory component that teaches metacognitive skills to scaffold learning. In this pilot study, we evaluated the feasibility of parent-delivered Dino Island in young children born preterm (N=10), alongside a control group who played educational games (N=12). Both groups were instructed to play 2-3 times per week for approximately 20 minutes over a 12-week period. Attention and working memory on untrained tasks were assessed before and after completing the intervention. Parents provided fidelity data through tracking sheets and participated in exit interviews to offer feedback and identify barriers and facilitators. We found that the Dino Island program was successfully delivered by parents with high fidelity. Attrition was higher in the Dino Island group, likely reflecting the challenges of delivering cognitive remediation in home settings. Comparison of attention and working memory scores on untrained tasks pre- and post-showed practice effects but no specific benefit of Dino Island. However, parent reports suggested behavioral improvements specific to the Dino Island group, noting far-transfer effects where children applied metacognitive strategies in other contexts. Overall, this work shows feasibility and tolerability of Dino Island in young children born preterm. Future research should examine its potential impact on school readiness and longer-term academic outcomes in this population.

neuroscience↗

bioRxiv2025

Generating ecological baselines on short-grass formations or grazing lawns in Central Terai landscape

Short-grass formations or the "grazing lawns" as they are popularly called support large congregations of mammalian herbivores globally. These systems are known to be maintained by cyclic process of grazing and nutrient deposition in the soil by foraging animals. The basic ecological characteristics of these short-grass systems have extensively been studied in the African context with little understanding particularly from the Himalayan foothills in Terai. In this study, we focused on understanding the ecological baselines such as grass species associations and associated nutrient content in these grazing lawns and tall grass formations across two protected areas of the Uttar Pradesh Terai in India. Our results show that, the protected areas had relatively similar grass species composition and associated nutrient content in the short-grass formations. However, when compared with tall grass formations, the grazing lawns differed markedly in both their grass associations and thus forage quality. Therefore, the results from this study indicate the need to maintain such grazing lawn habitats within the characteristic tall-wet grasslands of the Terai. This also indicates the importance of short-grass formations in providing palatable forage to the mammalian herbivores particularly in peak dry seasons of autumn and winters.

ecology↗

bioRxiv2025

Metabolic Signatures of Pulmonary Embolism in COVID-19: Insights from Longitudinal Intensive Care Unit Profiles

ABSTRACTO_ST_ABSBackgroundC_ST_ABSPulmonary embolism is a severe complication of COVID-19 infection, associated with a hypercoagulable state and heightened risk of blood clots. As SARS-CoV-2 has become endemic, understanding pulmonary embolisms metabolic effects in COVID-19 patients is warranted. This study investigated the longitudinal metabolic profiles of 66 Intensive Care Unit-admitted COVID-19 patients at Erasmus Medical Center to identify metabolites and mechanisms associated with pulmonary embolism. MethodA total of 1209 metabolic species were measured, including amines and lipids. Metabolic changes were analysed across four timeframes: i) general analysis of pulmonary embolism, ii) 72 hours prior to pulmonary embolism, iii) 48 hours prior and the day of pulmonary embolism, and iv) the day of and 48 hours post-pulmonary embolism. ResultsThe general analysis revealed significant upregulation of amines, triglycerides, phosphatidylethanolamines, ether-linked phosphatidylethanolamines, and eicosanoids in patients who developed a pulmonary embolism. Phosphatidylethanolamines containing the 20:3 fatty acid side chain were notably elevated. Minimal metabolic dysregulation was observed 72 hours before pulmonary embolism, with subtle increases in lysophosphatidylcholines and lysophosphatidylethanolamines. In contrast, there was a strong metabolic response during and post-pulmonary embolism, phosphatidylethanolamines (47%), ether-linked phosphatidylethanolamines(96%) and sphingosines(40%). ConclusionThese findings underscore the critical role of lipid metabolism in pulmonary embolism, particularly triglycerides and specific lipid species. The limited metabolic perturbations before pulmonary embolism suggest early prediction challenges, emphasising the need for further research into temporal metabolic changes and their clinical applications.

molecular biology↗

bioRxiv2025

Transcriptional dynamics of the oligodendrocyte lineageand its regulation by the brain erythropoietin system

Oligodendrocytes differentiate from oligodendrocyte progenitor cells (OPC) in early postnatal development, but some oligodendrogenesis is maintained throughout adulthood, where oligodendrocyte lineage dynamics may contribute to neuroplasticity, adaptive myelination, and myelin repair. Here, we studied the effect of erythropoietin (EPO) and its receptor (EPOR) on oligodendrocyte lineage dynamics employing murine hippocampus and its myelinated fibers as model region. Using multiple stage-specific markers and single-nuclei-RNA-seq data, we find that EPO stimulates all oligodendroglial lineage cells directly, driving differentiation/maturation. Differential gene expression analysis reveals multiple EPO-regulated mRNAs, including downregulated transcripts for GABA-A receptors, fitting the known inhibition of oligodendrocyte maturation by GABA. Importantly, analogous oligodendrocyte responses are seen when endogenous EPO expression in brain is stimulated by hypoxia. Mice lacking EPOR from mature oligodendrocytes show subtle deficiencies of adult myelination in hippocampal fimbria and mild working memory deficits. These gain- and loss-of-function experiments may further suggest EPO as clinically safe treatment for remyelination therapies.

neuroscience↗

bioRxiv2025

Erythropoietin alleviates intellectual disability and autism-like behavior of mice caused by Zbtb20 haploinsufficiency, a construct-valid model of Primrose syndrome

Among the known genetic causes of syndromic autism spectrum disorders (ASD) are transcription factor deficiencies. In this regard, haploinsufficiency of the zinc finger and broad complex, tramtrack, bric and brac domain-containing protein 20 (ZBTB20) leads to a prototypical clinical picture, referred to as Primrose syndrome, comprising severe ASD symptoms together with intellectual disability. Here, we present a comprehensive behavioral and phenotypical characterization of Zbtb20+/- mice, a construct valid model of this thus far untreatable human condition. Zbtb20+/- mice exhibit diminished sociability, reduced vocalization, distinct repetitive behaviors, impaired cognitive flexibility, hyperactivity and hypoalgesia. Magnetic resonance imaging reveals increased volumes of hippocampus, cerebellum, brain matter, and whole brain, confirmed by postmortem brain weight measurements. Due to our previous observation of enhanced ZBTB20 expression in CA1 pyramidal neurons upon recombinant human erythropoietin (rhEPO) injections, we anticipated a mitigating effect through rhEPO treatment of Zbtb20 deficiency/Primrose syndrome. Indeed, after three weeks of alternate-day rhEPO injections, a remarkable improvement in the behavioral phenotype was observed. Our results highlight rhEPO as a first promising treatment for Primrose syndrome.

neuroscience↗

bioRxiv2025

Forebrain-specific loss of erythropoietin provokes compensatory upregulation of different EPO receptors

The procognitive growth factor erythropoietin (EPO) and its canonical receptor, EPOR, have long been recognized to be expressed by most cell types in the brain. Cognitive domains, improved by injections of exogenous EPO or by endogenous, hypoxia-stimulated EPO, include important forebrain functions, namely attention, working memory, drive, and executive performance. To gain mechanistic insight into the involvement of forebrain-expressed EPO, we deleted EPO in mice using as specific cre-driver Emx1. Here, we report that these mutant mice act comparably to their wildtype littermates in a comprehensive behavioral test battery. Importantly, we find that the transcripts of both EPOR and a novel, brain-expressed EPO receptor, EphB4, respond to EPO deletion with compensatory upregulation. EphB4 expression in brain and its increase upon forebrain erasure of EPOR are confirmed by in situ hybridization and immunohistochemistry. The augmented expression of both EPOR and EphB4 and their regulatory intercorrelation may explain why EmxEPO mutants show an even superior performance in the most challenging working memory task. Using the previously published single-nuclei-RNA-seq dataset, we further confirm the suggested compensatory mechanism, wherein EPO loss or reduction drives elevated EPOR expression, adding another layer to the intricate regulation of EPO signaling in hippocampal pyramidal neurons. Collectively, these data may explain the lack of behavioral and negative cognitive consequences upon forebrain-wide EPO elimination.

neuroscience↗

bioRxiv2025

Macrophages drive a fibrogenic gene program of periductal fibroblasts in pediatric primary sclerosing cholangitis

Primary sclerosing cholangitis (PSC) is an autoimmune, cholestatic liver disease characterized by inflammation and fibrosis surrounding bile ducts. The cellular crosstalk driving periductal fibrosis remains poorly defined. This study applied a multi-omics approach integrating MERSCOPE spatial transcriptomics, bulk RNA-seq, and SomaScan proteomics to characterize fibrotic periductal regions and their cell-cell communications. Macrophages (MP) expressing moderate-to-high CD163 were found co-localized with cholangiocytes, T cells, and collagen-producing hepatic stellate cells (HSC). Cell niche analysis identified periductal regions with elevated fibrotic signals, in which cell-cell communication analysis revealed MP-HSC interactions involving 17 fibrotic driver genes in MP (e.g., IFNGR1, CSF1R, CD163) and six fibrotic effector genes in HSC (e.g., COL1A2, VCAN, MMP2). In validation analyses, bulk RNA-seq data showed higher driver and effector gene scores in PSC with established fibrosis compared to early-stage PSC and autoimmune hepatitis (AIH). Plasma proteins encoded by MP driver genes were elevated in autoimmune liver disease (AILD) and in patients with elevated ([≥]3.29 kPa) liver stiffness on MR elastography. These findings suggest that macrophages engage in localized crosstalk with HSC, activating fibrotic gene programs and contributing to periductal fibrosis in PSC, thereby identifying potential molecular targets for therapeutic intervention.

immunology↗

bioRxiv2025

Genetic mechanisms of resistance to targeted KRAS inhibition

KRAS mutations are among the most prevalent oncogenic drivers in non-small cell lung cancer (NSCLC), yet the mechanisms of therapeutic resistance to KRAS inhibitors in these cancers remains poorly understood. Here, we deploy high-throughput CRISPR base editing screens to systematically map resistance mutations to three mechanistically distinct KRAS-targeted therapies, including KRAS-G12C(OFF) inhibitor (adagrasib), RAS(ON) G12C-selective tri-complex inhibitor (RMC-4998), and RAS(ON) multi-selective tri-complex inhibitor (RMC-7977). Using both a saturation Kras tiling approach and cancer-associated mutation library, we identify common and compound-selective second-site resistance mutations in Kras, as well as gain-of-function and loss-of-function variants across cancer-associated genes that rewire signaling networks in a context-dependent manner. Notably, we identify a recurrent missense mutation in capicua (Cic), that promotes resistance to RMC-7977 in vitro and in vivo. Moreover, we show that targeting NF{kappa}B signaling in CIC-mutant cells can resensitize them to RAS pathway inhibition and overcome resistance.

cancer biology↗

bioRxiv2025

XAI-based Data Visualization in Multimodal Medical Data

Explainable Artificial Intelligence (XAI) is crucial in healthcare as it helps make intricate machine learning models understandable and clear, especially when working with diverse medical data, enhancing trust, improving diagnostic accuracy, and facilitating better patient outcomes. This paper thoroughly examines the most advanced XAI techniques used in multimodal medical datasets. These strategies include perturbation-based methods, concept-based explanations, and example-based explanations. The value of perturbation-based approaches such as LIME and SHAP in explaining model predictions in medical diagnostics is explored. The paper discusses using concept-based explanations to connect machine learning results with concepts humans can understand. This helps to improve the interpretability of models that handle different types of data, including electronic health records (EHRs), behavioural, omics, sensors, and imaging data. Example-based strategies, such as prototypes and counterfactual explanations, are emphasised for offering intuitive and accessible explanations for healthcare judgments. The paper also explores the difficulties encountered in this field, which include managing data with high dimensions, balancing the tradeoff between accuracy and interpretability, and dealing with limited data by generating synthetic data. Recommendations in future studies focus on improving the practicality and dependability of XAI in clinical settings.

bioengineering↗

bioRxiv2025

Examining the Role of Notch Signaling in Dysplastic Lung Repair

Severe lung injury promotes the appearance of ectopic basal cells in the alveolar space. Since these cells appear to contribute to barrier restoration but demonstrate very inefficient differentiation into normal alveolar epithelium, this represents a dysplastic repair response. Prior work demonstrated the necessity of Notch signaling for expansion of these cells directly and indirectly via interactions with activated fibroblasts, but the original studies largely relied on {gamma}-secretase inhibitors which lack specificity for the Notch pathway. Here we use transgenic mice expressing a dominant-negative MAML construct to confirm that Notch signaling to dysplastic cells impacts their expansion post-influenza. However, Notch inhibition at later time points did not appreciably increase differentiation into alveolar epithelial cells. These results confirm earlier studies and reiterate the advantages of genetic approaches to directly inhibit Notch over less specific pharmacological approaches.

molecular biology↗