Biology subjects

Sagar, R.

Publications and source records attributed to Sagar, R..

6 recordsLinked to original sources

bioRxiv2026

Proteomic identification and validation of novel neuronal EV-based markers for Alzheimers disease biomarker discovery

Extracellular vesicles (EVs) circulate in biofluids and carry tissue-specific molecular cargo, offering significant potential for the discovery of minimally invasive biomarkers. However, translation in neurodegenerative diseases has been hindered by the lack of validated neuronal EV surface markers that enable selective isolation from plasma. We hypothesized that proteomic profiling of EVs released from human induced pluripotent stem cell (hiPSC)-derived neurons would identify 1. robust Alzheimers disease (AD)-associated signatures that reflect disease pathogenesis, and 2. surface-accessible neuronal markers capable of enriching disease-relevant cargo. Neurons differentiated from AD patients and age-matched cognitively normal (CN) individuals were used to isolate EVs, which were characterized and analyzed by LC-MS proteomics in both total and membrane-enriched fractions. Proteomic profiling identified numerous dysregulated proteins, with a subset validated across independent AD datasets. We identified CNTNAP2 and STX1B as neuronal, brain-enriched EV surface proteins accessible for selective capture and confirmed their presence in EVs from post-mortem human brain, supporting them as bona fide brain-derived EV markers. Immuno-isolation of plasma EVs showed that CNTNAP2-positive EVs had a robust AD-associated increase in phosphorylated tau, identifying CNTNAP2 as a highly discriminative brain-derived EV marker and supporting its potential for blood-based AD diagnostics. Graphical AbstractPrevious studies indicate that extracellular vesicles (EVs) released from neurons carry disease-relevant cargo, yet the search for the optimal neuronal surface markers for the selective isolation of EVs pertinent to Alzheimers disease (AD) from blood is ongoing. To address this need, we performed proteomic profiling of EVs derived from hiPSC-neurons (iNEVs) of AD patients and cognitively normal individuals (CN). LC-MS analysis of whole and membrane-enriched EV fractions revealed robust protein dysregulation and identified CNTNAP2 and STX1B as surface-exposed neuronal EV proteins, confirmed in human brain-derived EVs (BDEVs). Immuno-isolation of plasma EVs demonstrated that CNTNAP2-positive EVs are enriched for phosphorylated tau in AD, whereas the previously used markers; NrCAM and ATP1A3-positive EVs showed limited discrimination. These findings establish a robust framework for proteomic discovery and nominate CNTNAP2 as a promising EV selection marker for blood-based AD diagnostics. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=146 SRC="FIGDIR/small/720870v1_ufig1.gif" ALT="Figure 1"> View larger version (48K): org.highwire.dtl.DTLVardef@754b45org.highwire.dtl.DTLVardef@a0a566org.highwire.dtl.DTLVardef@cb0134org.highwire.dtl.DTLVardef@1bc0275_HPS_FORMAT_FIGEXP M_FIG C_FIG

neuroscience↗

bioRxiv2026

Polymer-lipid hybrid nanoparticle enhances mRNA delivery and T cell-mediated immunity

mRNA vaccines have transformed prophylactic immunization against infectious diseases as well as therapeutic interventions for cancer. However, their effectiveness against emerging viral variants and a range of malignancies continues to be hindered by suboptimal induction of T cell-mediated immunity. To overcome this limitation, here we developed a polymer-lipid hybrid nanoparticle (PLNP) platform engineered to improve mRNA delivery to antigen-presenting cells (APCs) and to potentiate T cell responses. Relative to conventional mRNA lipid nanoparticle (LNP) vaccines, mRNA PLNP vaccines demonstrated markedly improved lymph node targeting, APC activation, Th1-biased pro-inflammatory cytokine response, and antigen-specific T cell expansion while retaining robust humoral immunity. Remarkably, mRNA-PLNP vaccines generated approximately 50% more antigen-specific CD8+ T cells than mRNA-LNP vaccines across multiple antigens, including SARS-CoV-2 spike, influenza hemagglutinin, and ovalbumin. In prophylactic applications, mRNA PLNP vaccine provided complete protection against SARS-CoV-2 variants. As a therapeutic approach in a melanoma model, mRNA PLNP vaccination resulted in enhanced tumor control and significantly prolonged survival compared to LNP-based formulations. Collectively, these results establish PLNP as a versatile and broadly applicable platform for augmenting mRNA vaccine efficacy through improved mRNA delivery and T cell priming, offering promising implications for infection prevention and cancer immunotherapy.

immunology↗

bioRxiv2025

Foraging ecology drives viral community structure in New Zealand's aquatic birds

Wild migratory birds play a major role in the global spread of viruses, yet the diversity, host range and transmission patterns of viruses harboured by migratory species in Aotearoa/New Zealand remain largely unknown. This knowledge gap is critical given New Zealands position along major migratory flyways spanning Oceania, Antarctica and east Asia, where understanding viral diversity is key to assessing the risk of viral introductions such as highly pathogenic avian influenza virus and viral dispersal across these regions. To address this, we conducted the first large-scale metatranscriptomic survey of wild birds from New Zealand and its subantarctic islands, collecting 1,348 samples from 31 host species spanning four avian orders. We identified 118 avian viruses from 17 families, including 107 novel species, greatly expanding our knowledge of avian viral diversity. Viral communities differed significantly by host order and foraging behaviour, with scavenger birds harbouring more diverse viromes than non-scavengers. Although no HPAI subtypes were detected, we recovered a low-pathogenic avian influenza A/H1N9 virus from red knots (Calidris canutus) and a divergent tobanivirus from Auckland Island teal (Anas aucklandica), the first putative avian member of the Tobaniviridae. Notably, we detected 12 mammalian-associated viruses, primarily in scavenger birds, including Hedgehog hepatovirus, Rabbit haemorrhagic disease virus 2, and sea lion astroviruses, with mammalian host reads confirming their dietary origin. This study establishes the first virome baseline for New Zealands migratory birds, highlighting the ecological role of foraging in shaping viral communities and improving regional preparedness for HPAI and other emerging avian pathogens.

microbiology↗

bioRxiv2024

Pleotropic effects of a recessive COL1A2 mutation occurring in a mouse model of severe osteogenesis imperfecta

Approximately 85-90% of individuals with Osteogenesis Imperfecta (OI) have dominant pathogenic variants in the COL1A1 or COL1A2 genes. This leads to decreased or abnormal Collagen type I production. Subsequently, bone formation is strongly reduced, causing bone fragility and liability to fractures throughout life. OI is clinically classified in 5 types with the severity ranging from mild to lethal depending on the gene and the type and location of the OI-causative variant and the subsequent effect on (pro) collagen type I synthesis. However, the specific effects on the phenotype and function of osteoblasts are not fully understood. To investigate this, the OI murine model was used, with the oim/oim (OIM) mice closest resembling severely deforming OI type 3 in humans. We showed that in OIM, COL1 mutation results in a multifactorial inhibition of the osteogenic differentiation and maturation as well as inhibition of osteoclastogenesis. The phenotype of differentiated OIM osteoblasts also differs from that of wild type mature osteoblasts, with upregulated oxidative cell stress and autophagy pathways, possibly in response to the intracellular accumulation of type I collagen mRNA. The extracellular accumulation of defective type I collagen fibres contributes to activation of the TGF-{beta} signalling pathway and activates the inflammatory pathway. These effects combine to destabilise the balance of bone turnover, increasing bone fragility. Together, these findings identify the complex mechanisms underlying OI bone fragility in the OIM model of severe OI and can potentially enable identification of clinically relevant endpoints to assess the efficacy of innovative pro-osteogenic treatment for patients with OI.

genetics↗

bioRxiv2023

Excitatory neurons derived from human induced Pluripotent Stem Cells show transcriptomic differences in Alzheimers patients from controls

The recent advances in creating pluripotent stem cells from somatic cells and differentiating them into a variety of cell types is allowing us to study them without the caveats associated with disease related changes. We have generated induced Pluripotent Stem Cells (iPSCs) from eight Alzheimers disease (AD) patients and six controls and used lentiviral delivery to differentiate them into excitatory glutamatergic neurons. We have performed RNA sequencing on these neurons and compared the Alzheimers and control transcriptomes. We find that 621 genes show differences in expression levels at adjusted p<0.05 between the case and control derived neurons. These genes show significant overlap and direction concordance with genes reported from a Single cell transcriptome study of Alzheimers patients, they contain 5 genes implicated with AD from genome wide association studies and they appear to be part of a larger functional network as indicated by an excess of interactions between them observed in the protein-protein interaction database STRING. Exploratory analysis with Uniform Manifold Approximation and Projection (UMAP) suggests distinct clusters of patients, based on gene expression, who maybe clinically different. If confirmed this finding will to contribute to precision medicine approaches to subgroup Alzheimers disease.

genetics↗

bioRxiv2021

How perception and attention participate in reading skill?

Reading creates accessibility to the outer world information and is an integral skill for academic achievement. It involves visual perception, reasoning at symbolic level (text reading) and phonological processing. But does perception, visuospatial processing at pre-symbolic level affect reading skill? To understand and untangle the mechanism fifty children with reading problem (developmental dyslexia, DDC) and twentyfive age-matched typical readers (healthy controls, HC) were studied. In DDC, the variable-performance of non-symbolic visual search (pictorial-level) was associated with bilateral brain activity (functional MRI) of ventral stream (inferior occipital and fusiform) and greater involvement of frontal-prefrontal regions, suggesting the modified dorsal route-gating for figure-ground filtering. Performance variability in picture-concept reasoning (71.9% and significant group mean difference) and visuospatial-organization (51.3%) of DDC children indicate attentional or executive differences at nonsymbolic level. In symbolic discrimination performance, no significant difference observed for single alphabet or number (digit) reading but significant differences at word level for visual and phonological performance (considering orthographic differences), attributes to distractor-inhibition problems. Nonsymbolic to symbolic coding/decoding speed and writing error (copying) differences are suggestive of execution variability rather than motor coordination in DDC. In HC, the top-down dorsal route gating and hypoactivity induced in right frontal-anterior cingulate cortices, play a major role in reading by allocating spatial attention and inhibiting distractors. It has been elaborated in the "neurobiological model". How perception and attention participate in reading skill?O_ST_ABSResearch HighlightsC_ST_ABSO_LIVisuospatial attention, executive control (nonsymbolic level) and visual discrimination (symbolic level) performance contribute to reading. C_LIO_LIIn children with reading problems (dyslexia) pictorial visual processing task (fMRI) recruited higher activation in right hemispheric frontal, inferior parietal and anterior cingulate regions. C_LIO_LIBilateral activation of occipital-striate, extra-striate, fusiform for nonsymbolic is associated with significantly more errors at bigger-symbol-string, in dyslexia. C_LIO_LIAuditory discrimination differences in shallow-deep orthography. C_LIO_LICorrelation of non-symbolic executive and symbolic performances. C_LIO_LIRole of the prelexical visual perception and dorsal-route gating in reading skill explained as neurobiological model. C_LI

neuroscience↗