Biology subjects

Cameron, B.

Publications and source records attributed to Cameron, B..

7 recordsLinked to original sources

bioRxiv2026

Coincident epithelial signals restrain commensal-specific CD8αβ+ T cells in the intestine

The intestinal epithelium harbors a large population of microbiota-dependent CD8{beta}+ T cells whose antigen specificity and regulation are ill-defined. By identifying MHCIa-restricted TCRs and generating tetramers against the gut commensal Segmented Filamentous Bacteria, we demonstrate that a single commensal species drives a clonally expanded, antigen-specific CD8{beta}+ T cell within the intraepithelial lymphocyte compartment. Mechanistically, the intestinal epithelium coordinates coincident signals governing this population: peptide:MHC-dependent TCR engagement drives pIEL accumulation, while v{beta}6-mediated TGF{beta} activation restraints effector cell differentiation. Perturbation of epithelial cell-mediated TGF{beta} activation diverts commensal-specific CD8+ T cells toward inflammatory differentiation states transcriptionally convergent with those observed in ulcerative colitis. The intestinal epithelium thus functions as a dual-signal organizer of commensal-specific CD8+ T cell responses, coupling differentiation to restraint through spatially coincident molecular cues.

immunology↗

bioRxiv2025

The origins and adaptive consequences of polyploidy in a dominant prairie grass

Polyploidy is ubiquitous across North American prairies, which provide essential ecosystem services and rich soil for agriculture. Yet the mechanism driving polyploid abundance is unclear. Multiple hypotheses have been proposed including polyploid abundance is proportional to the opportunity for whole genome duplication (WGD), and WGD alters phenotypes that may increase fitness. We tested these two hypotheses together in the mixed-ploidy species Andropogon gerardi, a dominant grass species in endangered North American tallgrass prairies. Leveraging a novel, phased allopolyploid reference genome, we found the A. gerardi hexaploid arose after the C4 grassland expansion in the early Pleistocene, when glacial cycles likely increased secondary contact between the diploid progenitors. We sequenced A. gerardi from 25 popula-tions and examined cytotype performance and morphology in a controlled environment to investigate the consequences of the contemporary mixed-ploidy populations. We found the 9x A. gerardi cytotype is a neopolyploid and a result of recurrent WGD events. Further, we demonstrate the 9x neopolyploids have greater growth and a decreased stomatal pore index, which is adaptive in xeric climates where the 9x cy-totype is most common. Together, our results support both hypotheses for polyploid abundance in North America: WGD is a product of opportunity and can have immediate fitness consequences. Although the changes to fitness may provide an advantage to 9x A. gerardi, the establishment of 9x may lower overall population fitness due to the lower reproductive viability of 9x individuals. Significance statementPolyploid species are abundant in North American prairies and make up many of the dominant species in the ecosystem. This prominence could be a result of whole genome duplication conferring an advantage that increases the frequency of polyploids or could simply indicate that the opportunity for whole genome duplication is higher in this ecosystem, or both. Through examining three polyploidization events in A. gerardi, the dominant species in endangered tallgrass North American prairies, we found whole genome duplication is both surprisingly common and confers traits that are beneficial in some environments.

plant biology↗

bioRxiv2025

Parallel polygenic urban adaptation despite high gene flow in a coastal marine invertebrate

Urbanization results in novel environments, offering a unique opportunity to investigate natural selection on small spatiotemporal scales. Although each city is different, geographically distinct cities can in some ways represent evolutionary replicates, allowing for the investigation of parallel and predictable evolutionary responses to urban environments. Additionally, there are few examples of urban adaptation in high gene flow marine systems, whose patterns might differ markedly from aquatic and terrestrial systems. Using whole genomes from Pacific purple sea urchins (Strongylocentrotus purpuratus) across three coastal cities spanning >2000km, we investigated genomic signals for adaptation to urban environments. We found genetic variants differentiating urban and nonurban sites within each city region, despite high gene flow and little evidence for differentiation across latitudinal gradients. While these SNP-level candidates for selection were largely non-overlapping, polygenic approaches uncover a distinct parallel signal of urban adaptation across the sampled range. Our results suggest that adaptation over small scale urbanization gradients is possible even in high gene flow systems and the polygenic architecture of adaptation is, at least in part, parallel. More broadly, our work highlights the importance of polygenic methods in ecological genomics in expanding our understanding of how evolutionary forces operate in natural systems.

genomics↗

bioRxiv2024

Suppression of T cell function by phosphoethanolamine, a metabolite enriched in tumor interstitial fluid

Nutrient stress represents a significant barrier for antitumor immunity, and tumor interstitial fluid (TIF) often contains metabolites that hinder immune function. However, it is difficult to isolate the effects of tumor nutrient stress from other suppressive factors. Thus, we employed a chemically-defined cell culture medium based on the metabolomic profile of TIF: Tumor Interstitial Fluid Medium (TIFM). Culture of CD8+ T cells in TIFM limited cell expansion and impaired CD8+ T cell effector functions upon restimulation, suggesting tumor nutrient stress alone is sufficient to drive T cell dysfunction. We identified phosphoethanolamine (pEtn), a phospholipid intermediate, as a driver of T cell dysfunction. pEtn dampened TCR signaling by depleting T cells of diacylglycerol required for TCR signal transduction. Reduction of pEtn accumulation in tumors improved intratumoral T cell function and tumor control, suggesting pEtn accumulation plays a dominant role in TME immunosuppression.

immunology↗

bioRxiv2023

Epithelial-Mesenchymal Transition: An Organizing Principle of Mammalian Regeneration

The MRL mouse strain is one of the few examples of a mammal capable of healing appendage wounds by regeneration, a process that begins with the formation of a blastema, a structure containing de-differentiating mesenchymal cells. HIF-1 expression in the nascent MRL wound site blastema is one of the earliest identified events and is sufficient to initiate the complete regenerative program. However, HIF-1 regulates many cellular processes modulating the expression of hundreds of genes. A later signal event is the absence of a functional G1 checkpoint leading to G2 cell cycle arrest with increased cellular DNA but little cell division seen in the blastema. This lack of mitosis in MRL blastema cells is also a hallmark of regeneration in classical invertebrate and vertebrate regenerators such as the planaria, hydra, and newt. Here, we explore the cellular events occurring between HIF-1 upregulation and its regulation of the genes involved in G2 arrest (EVI-5, {gamma}H3, Wnt5a, and ROR2), and identify EMT (Twist, Slug) and chromatin remodeling (EZH-2 and H3K27me3) as key intermediary processes. The locus of these cellular events is highly regionalized within the blastema, occurring in the same cells as determined by double staining using immunohistochemistry and FACS analysis, and appear as EMT and chromatin remodeling followed by G2 arrest determined by kinetic expression studies.

developmental biology↗

bioRxiv2022

Temperature and depth dependence of the spatial distribution of snow crab

The cascading effects of rapid climate change is a reality with which all biota are challenged. In this context, we examine the spatiotemporal probability of occurrence of snow crab as a means to express viable habitat. This is attempted for three demographic components, morphometrically mature males and females and immature adolescent crab in the Scotian Shelf region of the northwest Atlantic, Canada. We use a robust approach, known as Conditional AutoRegressive models, to define viable habitat. Further, we focus upon viable habitat, conditioned on the marginal influence of temperature and depth as they are known to be important constraints on snow crab. We observe some niche partitioning in terms of depth and temperature. We also note declines in viable habitat marginal to depth and temperature since 2010 for all demographic groups. This population representing the southern-most distribution of snow crab in the northwest Atlantic are vulnerable to degradation of viable habitat attributable to rapid climate change. One-Sentence SummaryRapid climate change and a decadal scale change in the viable habitat of snow crab of the Scotian Shelf ecosystem.

ecology↗

bioRxiv2022

Ocean currents drive the worldwide colonization of the most widespread marine plant, eelgrass (Zostera marina)

Currents are unique drivers of oceanic phylogeography and so determine the distribution of marine coastal species, along with past glaciations and sea level changes. Here, we reconstruct the worldwide colonization history of eelgrass (Zostera marina L.), the most widely distributed marine flowering plant or seagrass from its origin in the Northwest Pacific, based on nuclear and chloroplast genomes. We identified two divergent Pacific clades with evidence for admixture along the East Pacific coast. Multiple west to east (trans-Pacific) colonization events support the key role of the North Pacific Current. Time-calibrated nuclear and chloroplast phylogenies yielded concordant estimates of the arrival of Z. marina in the Atlantic through the Canadian Arctic, suggesting that eelgrass-based ecosystems, hotspots of biodiversity and carbon sequestration, have only been present since [~]208 Kya (thousand years ago). Mediterranean populations were founded [~]53 Kya while extant distributions along western and eastern Atlantic shores coincide with the end of the Last Glacial Maximum ([~]20 Kya). The recent colonization and 5-to 7-fold lower genomic diversity of Atlantic compared to the Pacific populations raises concern and opportunity about how Atlantic eelgrass might respond to rapidly warming coastal oceans.

evolutionary biology↗