Biology subjects

Mason, J.

Publications and source records attributed to Mason, J..

5 recordsLinked to original sources

bioRxiv2018

Non-enzymatic roles of human RAD51 at stalled replication forks

The central recombination enzyme RAD51 has been implicated in replication fork processing and restart in response to replication stress. Here, we use a separation-of-function allele of RAD51 that retains DNA binding, but not strand exchange activity, to reveal mechanistic aspects of RAD51s roles in the response to replication stress. We find that cells lacking RAD51 strand exchange activity protect replication forks from MRE11-dependent degradation, as expected from previous studies. Unexpectedly we find that RAD51s strand exchange activity is not required to convert stalled forks to a form that can be degraded by DNA2. Such conversion was shown previously to require replication fork reversal, supporting a model in which fork reversal depends on a non-enzymatic function of RAD51. We also show RAD51 promotes replication restart by both strand exchange-dependent and strand exchange-independent mechanisms.

molecular biology↗

bioRxiv2018

Sclerostin Deficiency Alters Peripheral B Lymphocyte Responses in Mice

Understanding how changes in bone physiology and homeostasis affect immune responses will inform how to retain strong immunity in patients with bone disease and in aged individuals. We previously identified sclerostin (Sost) as a mediator of cell communication between the skeletal and the immune system. Elevated bone mineral density in Sost-knockout (Sost-/-) mice contributes to an altered bone marrow microenvironment and adversely affects B cell development. B cells originate from hematopoietic stem cells within the bone marrow and mature in peripheral lymphoid organs to produce antibodies in response to infection and/or vaccination. In this study, we investigated whether the aberrant B cell development observed in the bone marrow of Sost-/- mice extends to peripheral B cells in the spleen during immune challenge, and if these changes were age-dependent. Concomitant with more severe changes in bone architecture, B cell development in the bone marrow and in the spleen worsened with age in Sost-/- mice. B cell responses to T-independent antigens were enhanced in young Sost-/- mice, whereas responses to T-dependent antigens were impaired. Our results support the hypothesis that the adverse effects of B cell development in the Sost-deficient bone marrow microenvironment extends to the peripheral B cell immune response to protein antigens, and suggest that the B cell response to routine vaccinations should be monitored regularly in patients being treated with sclerostin antibody therapy. In addition, our results open the possibility that Sost regulates the T-independent B cell response, which might be applicable to the improvement of vaccines towards non-protein antigens.

immunology↗

bioRxiv2018

PDX Finder: A Portal for Patient-Derived tumor Xenograft Model Discovery

Patient-derived tumor xenograft (PDX) mouse models are a versatile oncology research platform for studying tumor biology and for testing chemotherapeutic approaches tailored to genomic characteristics of individual patients tumors. PDX models are generated and distributed by a diverse group of academic labs, research organizations, multi-institution consortia, and contract research organizations. The distributed nature of PDX repositories and the use of different standards in the associated metadata presents a significant challenge to finding PDX models relevant to specific cancer research questions. The Jackson Laboratory and EMBL-EBI are addressing these challenges by co-developing PDX Finder, a comprehensive open global catalog of PDX models and their associated datasets. Within PDX Finder, model attributes are harmonized and integrated using a previously developed community minimal information standard to support consistent searching across the originating resources. Links to repositories are provided from the PDX Finder search results to facilitate model acquisition and/or collaboration. The PDX Finder resource currently contains information for more than 1900 PDX models of diverse cancers including those from large resources such as the Patient-Derived Models Repository, PDXNet, and EurOPDX. Individuals or organizations that generate and distribute PDXs are invited to increase the \"findability\" of their models by participating in the PDX Finder initiative at www.pdxfinder.org.

cancer biology↗

bioRxiv2018

Markov chain models of cancer metastasis

Abstract.We describe the use of Markov chain models for the purpose of quantitative forecasting of metastatic cancer progression. Each site (node) in the Markov network (directed graph) is an organ site where a secondary tumor could develop with some probability. The Markov matrix is an N x N matrix where each entry represents a transition probability of the disease progressing from one site to another during the course of the disease. The initial state-vector has a 1 at the position corresponding to the primary tumor, and 0s elsewhere (no initial metastases). The spread of the disease to other sites (metastases) is modeled as a directed random walk on the Markov network, moving from site to site with the estimated transition probabilities obtained from longitudinal data. The stochastic model produces probabilistic predictions of the likelihood of each metastatic pathway and corresponding time sequences obtained from computer Monte Carlo simulations. The main challenge is to empirically estimate the N^2 transition probabilities in the Markov matrix using appropriate longitudinal data.

cancer biology↗

bioRxiv2017

Filopodyan: An Open-Source Pipeline For The Analysis Of Filopodia

Filopodia have important sensory and mechanical roles in motile cells. The recruitment of actin regulators, such as ENA/VASP proteins, to sites of protrusion underlies diverse molecular mechanisms of filopodia formation and extension. We developed Filopodyan (filopodia dynamics analysis) in Fiji and R to measure fluorescence in filopodia and at their tips and bases concurrently with their morphological and dynamic properties. Filopodyan supports high-throughput phenotype characterization as well as detailed interactive editing of filopodia reconstructions through an intuitive graphical user interface. Our highly customizable pipeline is widely applicable, capable of detecting filopodia in four different cell types in vitro and in vivo. We use Filopodyan to quantify the recruitment of ENA and VASP preceding filopodia formation in neuronal growth cones, and uncover a molecular heterogeneity whereby different filopodia display markedly different responses to changes in the accumulation of ENA and VASP fluorescence in their tips over time.\n\neTOC summary: Urban[c]i[c] et al. developed an open-source platform called Filopodyan (filopodia dynamics analysis) in Fiji and R to measure fluorescence in filopodia, at their tips, and bases, concurrently with their morphological and dynamic properties. This customizable tool therefore enables researchers to determine the relationship between protein localization and filopodium behavior.

cell biology↗