Biology subjects

Edgar, L. J.

Publications and source records attributed to Edgar, L. J..

9 recordsLinked to original sources

bioRxiv2026

Cell Surface Sialoglycan Engineering Through Exogenous mRNA

All human cells display a dense matrix of structurally diverse glycans that often terminate in monosaccharides belonging to the sialic acid family of sugars. While these sialoglycans are now recognized as critical regulators of human immunity, there is a lack of technologies that provide precise, transient control over their biosynthesis and presentation on a live cell surface. Here, we addressed this unmet need by developing an mRNA-based platform for delivery of transcripts coding for the enzymes that assemble sialoglycans - sialyltransferases - to human cells. We demonstrated that mRNA coding for the 2-6-specific sialyltransferase ST6Gal1 produced active, Golgi-resident enzyme that potentiated levels of 2-6-sialoglycans on the surface of human cell lines. Increased presentation of these sialoglycans was transient and tracked with the degradation kinetics of the delivered mRNA. Importantly, this approach minimally perturbed other classes of glycans and did not broadly alter physiological transcriptional networks beyond those involved in cellular responses to exogenous RNA. Similar on-target effects were observed for the O-linked 2-6-specific sialyltransferase ST6GalNAc4; however, the effects from mRNA coding for the 2-3-specific sialyltransferases ST3Gal1 and ST3Gal4 were more complex. Taken together, this mRNA platform provides a framework for cellular sialoglycoengineering endeavours, where precise and reversible control over glycocalyx composition is desired.

bioengineering↗

bioRxiv2026

Biological recognition of mirror-image glycans

Recent synthesis of essential enzymes, such as DNA and RNA polymerases with opposite chirality, has boosted the feasibility of creating mirror-image life. Such life, if ever produced, will undoubtedly be coated by a dense display of glycans (glycoproteins, glycolipids, polysaccharides) built from enantiomers of common monosaccharides. Recognition of mirror-image glycans by extant glycan-binding proteins (GBPs) may be critical for colonization by or immune response to mirror life organisms. We evaluated recognition of enantiomers of common glycans by a diverse set of purified GBPs (plant and human derived), antibodies (including IgM from human plasma), mammalian cells (including immune cells), and organs in live animals. We found that GBP binding to enantiomers of naturally prevalent glycans is widespread. Notably, L-glucose and L-galactose interact with fucose-binding lectins, including DC-SIGN, a C-type lectin expressed on immune cells. These interactions can be inhibited by soluble "natural" glycan ligands and enantiomeric ones confirming specificity. Binding of L-glycans to diverse immune cell repertoires revealed preferences for specific glycan enantiomers. IgM antibodies from human serum showed donor-specific recognition of L-glycans. We propose that the recognition of L-glycans by extant GBPs arises from their co-evolution over millennia with the L-glycans that are present in the glycocalyx of many microorganisms.

biochemistry↗

bioRxiv2026

Sequential infection reprograms the immune landscape to shape future responses

Mouse models have been instrumental in defining immune mechanisms but often fail to capture the complexity of human immunity, limiting clinical translation. A major limitation is the immunological immaturity of specific pathogen-free (SPF) mice relative to pathogen-experienced adult humans. Here, we use a sequential infection (SI) model that recapitulates cumulative pathogen exposure and define its impact on immune composition and function. Beyond the previously reported expansion of memory T cells, SI induced durable, system-wide remodeling across lymphoid and non-lymphoid tissues, reshaping innate and adaptive immune populations, tissue-resident immunity, and hematopoietic output. Single-cell transcriptomic analyses revealed inflammatory imprinting of naive CD4 and CD8 T cells, whereas memory T cells acquired enhanced effector programs coupled with reduced biosynthetic activity, transcriptional states that more closely resemble those of pathogen-experienced adult humans. Functionally, SI mice recapitulated the human response to anti-CD28 super-agonist and exhibited altered magnitude and differentiation of acute and chronic antiviral T cell responses, demonstrating that cumulative pathogen exposure reshapes both existing immunity and the generation of future immune responses. Thus, cumulative pathogen exposure coordinately remodels hematopoiesis and naive and memory lymphocyte states, establishing a durable inflammation-experienced immune landscape that reshapes both immune memory and future immune responses, with broad implications for the translational fidelity of preclinical mouse models.

immunology↗

bioRxiv2026

An atlas of the human metabolome

Despite the emergence of cellular atlases like the Human Protein Atlas, no equivalent atlas exists for the human metabolome. Here, we present the Human Metabolome Atlas (HMA, hma.ccbr.utoronto.ca), a comprehensive map containing metabolomic profiles of 70 human cell lines across 22 tissues. With an [~]8-fold increase in coverage compared to other resources, the HMA contains quantitative data for 1768 metabolites at the highest identification confidence, encompassing over 50 lipid classes and a broad range of metabolic pathways. This constitutes the most extensive human metabolomic atlas available. Leveraging the HMA, we identified specific metabolic regulation within pathways and cell types and characterized metabolic processes like glycosylation and ferroptosis. Lastly, we developed a publicly available, interactive web-portal to facilitate custom data analysis for the broader scientific community.

systems biology↗

bioRxiv2025

Sialoglycans on human T cells attenuate death programs executed through the Fas pathway

T cells are critical executors of adaptive immune responses and their persistence is tightly regulated. Part of this regulation relies on programmed cell death driven by the Tumor Necrosis Factor (TNF) receptor superfamily. The addition of glycans that terminate in the monosaccharide sialic acid (sialoglycans) to these cell death receptors has been shown to attenuate their apoptotic functions. While this is now understood to be a pro-survival mechanism in settings of cancer pathophysiology, the specific roles of sialoglycans in regulating cell death receptor activity on human T cells remains unexplored. This is of particular importance given the rising interest in T cell glycan editing for therapeutic benefit. Here, we address this gap using both immortalized (Jurkat) and primary human T cells deficient in sialoglycans. We found that T cell sialoglycans suppressed apoptosis induced by the Fas receptor (FasR) but not other TNF receptor superfamily members such as TNFR1 and TRAIL-R1. Dynamic reorganization of FasR was increased on sialoglycan-deficient Jurkat cells, suggesting that these glycans limit receptor clustering. This model was further supported by phosphoproteomics results, which confirmed that loss of sialoglycans negatively regulated the pro-survival MAPK/ERK signalling pathway. Finally, we used a recombinant sialic acid cleaving enzyme (sialidase) to confirm that sialoglycans on primary human T cells are bona fide immunophysiological regulators of FasR-driven programmed cell death. Combined, our results demonstrate that sialoglycan remodelling on T cells influences cell fate driven by the Fas pathway and provide motivation to further characterize the immunoregulatory roles of the glycocalyx in health and disease.

immunology↗

bioRxiv2025

Characterization of a novel mouse model of Dopamine Transporter Deficiency Syndrome and pharmacological therapeutic strategies

The dopamine transporter (DAT) is an essential protein in the maintenance of dopamine homeostasis in the brain. Thus, single amino acid changes in the gene that encodes for DAT can be sufficient to induce disease, such as Dopamine Transporter Deficiency Syndrome (DTDS). DTDS-associated variants are posited to cause DAT protein misfolding, retention in the endoplasmic reticulum, and a consequent depletion or loss of DAT at the cell surface. In turn, proper dopaminergic regulation is lost. Current treatments for DTDS are largely ineffective, and improved therapeutic options are greatly needed. To this end, we have created a novel mouse model of DTDS harboring the A313V knock-in DAT variant, a proxy for the DTDS-causing A314V variant in humans. We show that the A313V knock-in DAT mice are hyperactive, have increased striatal tissue content of dopamine and its metabolites homovanillic acid (HVA) and DOPAC, and impaired dopamine uptake. We demonstrate that FDA approved compounds alpha-methyl-para-tyrosine ([a]MPT) and amphetamine (AMPH) ameliorate hyperactivity in this mouse model. Moreover, [a]MPT may be a disease-modifying treatment by addressing the hyperdopaminergic tone underlying this hyperactivity. In contrast, noribogaine, a pharmacological chaperone for DAT, is unable to rescue DAT expression. Taken together, these findings show that the A313V knock-in DAT variant mice recapitulate several defining phenotypes seen in patients with DTDS, and provide evidence for two novel treatments for the disease.

pharmacology and toxicology↗

bioRxiv2024

Loss of PARP7 increases type I interferon signalling and prevents pancreatic tumour growth by enhancing immune cell infiltration

Pancreatic ductal adenocarcinoma (PDAC) is one of the most lethal forms of cancer, and despite low incidence rates, it remains the sixth leading cause of cancer related deaths worldwide. Immunotherapy, which aims to enhance the immune systems ability to recognize and eliminate cancer cells, has emerged as a promising approach in the battle against PDAC. PARP7, a mono-ADP-ribosyltransferase, is a negative regulator of the type I interferon (IFN-I) pathway and has been reported to reduce anti-tumour immunity. Using murine pancreatic cancer cells, we found that loss of Parp7 elevated the levels of interferon stimulated gene factor 3 (ISGF3) and its downstream target genes, even in the absence of STING. Cancer cells deficient in Parp7 produced smaller tumours when injected into immunocompetent mice. Transcriptomic analyses revealed that tumours knocked out for Parp7 (Parp7KO) had increased expression of genes involved in immunoregulatory interactions and interferon signalling pathways. Characterization of tumour infiltrating leukocyte (TIL) populations showed that Parp7KO tumours had higher proportions of natural killer cells, CD8 T cells and a lower proportion of anti-inflammatory macrophages (M2). The overall TIL profile of Parp7KO tumours was suggestive of a less suppressive microenvironment. Our data show that loss of Parp7 reduces PDAC tumour growth by increasing the infiltration of immune cells and enhancing anti-tumour immunity. These findings provide support to pursue PARP7 as a therapeutic target for PDAC.

cancer biology↗

bioRxiv2024

A Unified Atlas of T cell Glycophysiology

Glycans are emerging as important regulators of T cell function but remain poorly characterized across the functionally distinct populations that exist in vivo. Here, we couple single-cell analysis technologies with soluble lectins and chemical probes to interrogate glycosylation patterns on major T cell populations across multiple mouse and human tissues. Our analysis focused on terminal glycan epitopes with immunomodulatory functions, including sialoglycan ligands for Siglecs. We demonstrate that glycosylation patterns are diverse across the resting murine T cell repertoire and dynamically remodelled in response to antigen-specific stimulation. Surprisingly, we find that human T cell populations do not share the same glycoprofiles or glycan remodelling dynamics as their murine counterparts. We show that these differences can be explained by divergent regulation of glycan biosynthesis pathways between the species. These results highlight fundamental glycophysiological differences between mouse and human T cells and reveal features that are critical to consider for glycan-targeted therapies.

immunology↗

bioRxiv2021

Sialic acid ligands of CD28 block co-stimulation of T cells

Effector T cells comprise the cellular arm of the adaptive immune system and are essential for mounting immune responses against pathogens and cancer. To reach effector status, co-stimulation through CD28 is required. Here, we report that sialic acid-containing glycans on the surface of both T cells and APCs are alternative ligands of CD28 that compete with binding to its well-documented activatory ligand CD80 on the APC, resulting in attenuated co-stimulation. Removal of sialic acids enhances T cell activation and enhances the activity of effector T cells made hypofunctional via chronic viral infection through a mechanism that is synergistic with antibody blockade of the inhibitory PD-1 axis. These results reveal a previously unrecognized role for sialic acids in attenuation of CD28 mediated co-stimulation of T cells. One Sentence SummarySialic acids attenuate the second signal required for T cell activation.

immunology↗