Biology subjects

O'Brien, L.

Publications and source records attributed to O'Brien, L..

7 recordsLinked to original sources

bioRxiv2026

Developmental origins of thymic B-cell lymphomas

The thymus provides a specialized niche for lymphocyte differentiation, yet the developmental trajectories of its rare B-cell population and their relationship to thymic B-cell lymphomagenesis remain poorly understood. Here, we integrate single-cell multiomics and spatial profiling across human tissues to delineate a B-cell differentiation program selectively represented in the human thymus. This program links CCL17 and germinal center-like B-cell states along a trajectory distinct from canonical germinal center differentiation and can be recapitulated in vitro by signals operating in the thymic medulla. Extending this framework across human B-cell lymphomas, we identify an inherent malignant cell state in PMBCL that shares transcriptional and epigenetic features with CCL17 thymic B cells. This malignant state associates with early clonal positions in reconstructed B-cell receptor phylogenies and persists within tumor microenvironments distinct from the thymic niche. Together, these findings support a model in which thymus-specific B-cell differentiation programs are redeployed during thymic B-cell lymphomagenesis.

cancer biology↗

bioRxiv2026

Vascular waveform analysis using Bayesian pulse deconvolution

Vascular waveforms, which measure bulk flow in blood vessels, are widely used to measure vital signs, diagnose conditions, and predict long-term health outcomes. Analyzing vascular waveforms depends on three fundamentally interdependent tasks: signal filtering, pulse timing detection, and pulse shape extraction. We hypothesized that Bayesian pulse deconvolution can achieve improved performance on all three tasks by solving them jointly. This method uses an analytical, generative model of vascular waveforms with priors informed by physical and biological domain knowledge. In simulations, Bayesian pulse deconvolution achieves better performance on all tasks compared with existing algorithms: 90% reduction of median filtering error, 60% reduction in pulse timing error, and 85% reduction in shape extraction error. The advantages in simulations extend to human recordings of photoplethysmography waveforms. Taking real time-synchronized electrocardiogram R-R intervals as a proxy ground truth, Bayesian pulse deconvolution achieves 40% lower pulse interval estimation error (RMSE = 5.1 ms) compared with typical algorithms (RMSE = 8.3 ms, p=1e-10). By extracting more accurate and informative insights from vascular waveforms, Bayesian pulse deconvolution could advance a wide array of health technologies that rely on interpreting signals from blood vessels.

bioengineering↗

bioRxiv2025

Somites are a source of nephron progenitors in zebrafish

For over a century it has been believed that the vertebrate kidney arises exclusively from the intermediate mesoderm. Here, we overturn this paradigm by demonstrating that some nephrons, the functional units of the kidney, originate from the somites--blocks of paraxial mesoderm best known for their contribution to muscle and connective tissues. Using a combination of the GESTALT technique to assign developmental ancestry, somite transplantation experiments and Cre-lox fate-mapping, we show that somites can contribute to the nephrons in the adult zebrafish kidney. Our findings uncover an unexpected developmental connection between the somites and kidneys, potentially offering new pathways for developing regenerative treatments for kidney diseases.

developmental biology↗

bioRxiv2024

Altered renal vascular patterning reduces ischemic kidney injury and limits vascular loss associated with aging

The kidney vasculature has a complex arrangement, which runs in both series and parallel to perfuse the renal tissue and appropriately filter plasma. Recent studies have demonstrated that the development of this vascular pattern is dependent on netrin-1 secreted by renal stromal progenitors. Mice lacking netrin-1 develop an arterial tree with stochastic branching, particularly of the large interlobar vessels. The current study investigated whether abnormalities in renal vascular pattern altered kidney function or response to injury. To examine this, we analyzed kidney function at baseline as well as in response to recovery from a model of bilateral ischemic injury and measured vascular dynamics in aged mice. We found no differences in kidney function or morphology at baseline between mice with an abnormal arterial pattern compared to control. Interestingly, male and female mutant mice with stochastic vascular patterning showed a reduction in tubular injury in response to ischemia. Similarly, mutant mice also had a preservation of perfused vasculature with aging compared to a reduction in the control group. These results suggest that guided and organized patterning of the renal vasculature may not be required for normal kidney function; thus, modulating renal vascular patterning may represent an effective therapeutic strategy. Understanding how patterning and maturation of the arterial tree affects physiology and response to injury or aging has important implications for enhancing kidney regeneration and tissue engineering strategies.

cell biology↗

bioRxiv2024

Hedgehog signaling controls cytotoxic T cell migration in the tumour microenvironment.

Cytotoxic T lymphocytes effectively eliminate cancer cells. Their abundance in the tumour microenvironment is one of the strongest pan-cancer predictors of clinical response. Here, we show that Hedgehog (Hh) signaling regulates T cell migration into tumours. Using conditional knockout mouse models of central Hh signaling components Ihh, Smo and Gli1 in CD8 T cells, we show that Smo deletion greatly impairs the anti-tumour response in vivo due to diminished CD8 T cell migration into the tumour microenvironment. The migration defect is mediated exclusively by Smo, both in in vivo cancer models and in vitro migration assays. This effect is independent of the canonical Hh pathway and relies on the GPCR function of Smo to regulate the migration of murine and human CD8 T cells via RhoA. Hh signaling is critical during embryonic development and adult stem cell homeostasis, but is also amplified in multiple cancer types. Hh inhibitors targeting SMO have been clinically-approved and shown efficacy in the treatment of Hh-driven basal cell carcinoma and medulloblastoma but have failed in clinical trials in other solid cancers with upregulated Hh signaling. We demonstrate that SMO inhibitors specifically decrease CD8 T cell migration into the tumour microenvironment, both in murine cancer models and resected BCCs from patients treated with the SMO inhibitor vismodegib, providing the first mechanistic explanation as to why Hh inhibitors have failed in solid cancers. Our data establishes a novel link between Hh inhibition in vivo and the anti-tumour immune response and reveals a fundamental mechanism controlling T cell migration. The work provides the basis for improved Hh targeting approaches in the clinic and new entry points into enhancing migration in T cell therapies.

immunology↗

bioRxiv2021

Evaluation of the SARS-CoV-2 inactivation efficacy associated with buffers from three kits used on high-throughput RNA extraction platforms

Rapid and demonstrable inactivation of SARS-CoV-2 is crucial to ensure operator safety during high-throughput testing of clinical samples. The inactivation efficacy of SARS-CoV-2 was evaluated using commercially available lysis buffers from three viral RNA extraction kits used on two high-throughput (96-well) RNA extraction platforms (Qiagen QiaCube HT and the ThermoFisher Kingfisher Flex) in combination with thermal treatment. Buffer volumes and sample ratios were chosen for their optimised suitability for RNA extraction rather than inactivation efficacy and tested against a representative sample type; SARS-CoV-2 spiked into viral transport medium (VTM). A lysis buffer from the MagMax Pathogen RNA/DNA kit (ThermoFisher), used on the Kingfisher Flex, which included guanidinium isothiocycnate (GITC), a detergent, and isopropanol demonstrated a minimum inactivation efficacy of 1 x 105 TCID50/ml. An alternative lysis buffer from the MagMax Viral/Pathogen Nucleic Acid kit (Thermofisher) also used on the Kingfisher Flex and the lysis buffer from QIAamp 96 Virus QIAcube HT Kit (Qiagen) used on the QiaCube HT (both of which contained GITC and a detergent) reduced titres by 1 x 104 TCID50/ml but did not completely inactivate the virus. Heat treatment alone (15 minutes, 68 {degrees}C) did not completely inactivate the virus, demonstrating a reduction of 1 x 103 TCID50/ml. When inactivation methods included both heat treatment and addition of lysis buffer, all methods were shown to completely inactivate SARS-CoV-2 inactivation against the viral titres tested. Results are discussed in the context of the operation of a high-throughput diagnostic laboratory.

microbiology↗

bioRxiv2021

Non-canonical Hedgehog signaling through L-type voltage gated Ca2+ channels controls CD8+ T cell killing

Cytotoxic CD8+ T lymphocytes (CTLs) are critical to the immune response against intracellular pathogens and cancer and act by eliminating infected and malignant cells through targeted secretion of cytotoxic granules. Hedgehog (Hh) signaling has been shown to be critical for CTL killing. Interestingly, Hh signaling in CD8+ T cells is not induced by extracellular Hh ligands but is initiated upon T cell receptor (TCR) engagement. How the TCR induces the Hh pathway independently of extracellular Hh ligands is unknown. Here we show that the Hh transcription factor Gli1 is essential for efficient CTL function and is induced downstream of the TCR by an extracellular Ca2+ influx selectively controlled by L-type voltage gated Ca2+ channels localized at the plasma membrane. We demonstrate that this novel mode of Hh signaling induction is independent of the canonical Hh pathway and represents the primary mechanism of Gli1 induction in naive CD8+ T cells, while CTLs can also activate Gli1 via MAP Kinase signaling. Importantly, we show that this L-type voltage gated Ca2+ channel-controlled Gli1 induction is functionally required for CTL killing in mice and humans. Gli inhibitors are currently in clinical trials against various cancers and our observations indicate that they likely inhibit the anti-tumor response. Significance statementCytotoxic CD8+ T cells (CTLs) kill infected and malignant cells by targeted secretion of cytotoxic granules. Hedgehog signaling is critical for effective CTL killing and is activated by the T cell receptor (TCR) independently of exogenous Hedgehog ligands. This study shows that Hedgehog transcription factor Gli1 is required for CTL killing and identifies L-type voltage gated Ca2+ channels (Cav1) as essential regulators of CTL killing in mouse and human, by virtue of their ability to activate Gli1 downstream of the TCR. This Cav1-Gli1 axis operates independently of canonical Hedgehog signaling. Our work suggests that caution is required when using Gli inhibitors, currently in trials as anti-cancer therapeutics, since they may dampen the anti-tumor response.

immunology↗