Biology subjects

Arron, J.

Publications and source records attributed to Arron, J..

9 recordsLinked to original sources

bioRxiv2026

Nuclear Myosin VI stabilises Ku-associated DNA ends during non-homologous end joining

DNA double-strand breaks (DSBs) require rapid signalling and physical stabilisation of broken DNA ends to preserve genome integrity. Here, we identify myosin VI (MVI) as an ATM-regulated component of the DSB response. DNA damage induces rapid nuclear accumulation and nanoscale reorganisation of MVI across multiple cell models, in an ATM-dependent manner. Pharmacological or genetic perturbation of MVI attenuates {gamma}H2AX signalling and disrupts Ku80 organisation, while DNA damage persists. This leads to increased sensitivity to cisplatin and bleomycin. Super-resolution imaging reveals spatial association of MVI with Ku80-containing repair structures, implicating MVI in non-homologous end joining (NHEJ). In a minimal reconstituted system, MVI and actin enhance the proximity of Ku70/80-bound DNA ends. Together, our findings identify MVI as a regulator of DSB repair that links ATM signalling to Ku-associated DNA-end stabilisation and suggest that targeting MVI may sensitise tumour cells to genotoxic therapy.

cancer biology↗

bioRxiv2025

Combined antagonism of Oncostatin M (OSM) and Interleukin 6 (IL-6) provides both anti-fibrotic and anti-inflammatory benefit in pulmonary fibrosis

Interstitial lung diseases (ILDs), including idiopathic pulmonary fibrosis (IPF) and systemic sclerosis-associated ILD (SSc-ILD), are irreversible fibrosing diseases with a mean survival time of less than 5 years for IPF. Poorly understood etiology and complex pathogenesis of these diseases have hampered the identification and development of effective therapeutics. Existing treatments can slow progressive fibrosis and lung function decline but do not stop it entirely, resulting in a minimal impact on patient survival. Thus, novel therapeutic interventions are needed. Tocilizumab, an anti-IL-6 receptor antibody, was recently approved by FDA for the treatment of SSc-ILD based on evidence demonstrating a reduction in the rate of lung function decline. In this study, we have characterized an IL-6-driven feed-forward myeloid axis contributing to lung inflammation providing a mechanistic hypothesis for tocilizumab. Concomitantly we have identified an oncostatin M (OSM) orchestrated lung injury response contributing to epithelial and endothelial cell disruption, myofibroblast activation and fibrosis. Despite dysregulated expression of IL11 in IPF, SSc-ILD, and murine models of fibrosis, we found no evidence for a pro-fibrotic role for IL-11 in vitro or in vivo. Instead, in pre-clinical models of IPF we demonstrate that antagonism of OSM alone, or to a greater degree in combination with IL-6, reduced lung fibrosis and inflammation. Translating these observations, we validated gp130:OSMR, rather than gp130:LIFR, as the dominant human receptor complex used by OSM, identifying OSMR as a potential therapeutic target to stall fibrosis.

immunology↗

bioRxiv2024

Coumarin as a general switching auxiliary to prepare photochromic and spontaneously blinking fluorophores

Single-molecule localization microscopy (SMLM) uses activatable or switchable fluorophores to create non-diffraction limited maps of molecular location in biological samples. Despite the utility of this imaging technique, the portfolio of appropriate labels for SMLM remains limited. Here, we describe a general strategy for the construction of "glitter bomb" labels by simply combining rhodamine and coumarin dyes though an amide bond. Condensation of the ortho-carboxyl group on the pendant phenyl ring of rhodamine dyes with a 7-aminocoumarin yields photochromic or spontaneously blinking fluorophores depending on the parent rhodamine structure. We apply this strategy to prepare labels useful super-resolution experiments in fixed cells using different attachment techniques. This general glitter bomb strategy should lead to improved labels for SMLM, ultimately enabling the creation of detailed molecular maps in biological samples.

cell biology↗

bioRxiv2023

Specialized actin nanoscale layers control focal adhesion turnover

Focal adhesions (FAs) connect inner workings of the cell to the extracellular matrix to control cell adhesion, migration, and mechanosensing1,2. Previous studies demonstrated that FAs contain three vertical layers, which connect extracellular matrix to the cytoskeleton3,4,5. However, cellular processes rely on precisely-regulated FA turnover, but the molecular machineries that control FA assembly and disassembly have remained elusive. By using super-resolution iPALM microscopy, we identified two unprecedented nanoscale layers within FAs, specified by actin filaments bound to tropomyosin isoforms Tpm1.6 and Tpm3.2. The Tpm1.6-actin filaments beneath the previously identified actin-regulatory layer are critical for adhesion maturation and controlled cell motility, whereas the Tpm3.2-actin filament layer towards the bottom of FA facilitates adhesion disassembly. Mechanistically, Tpm3.2 stabilizes KANK-family proteins at adhesions, and hence targets microtubule plus-ends to FAs to catalyse their disassembly. Loss of Tpm3.2 leads to disorganized microtubule network, abnormally stable FAs, and defects in tail retraction during cell migration. Thus, FAs are composed of at least three distinct actin filament layers, each having specific roles in coupling of adhesion to the cytoskeleton, or in controlling adhesion dynamics. In a broader context, these findings demonstrate how distinct actin filament populations can co-exist and perform specific functions within a defined cellular compartment.

cell biology↗

bioRxiv2022

Actin nano-architecture of phagocytic podosomes

Podosomes are actin-enriched adhesion structures important for multiple cellular processes, including migration, bone remodeling, and phagocytosis. Here, we characterized the structure and organization of phagocytic podosomes using interferometric photoactivated localization microscopy (iPALM), a super-resolution microscopy technique capable of 15-20 nm resolution, together with structured illumination microscopy (SIM) and localization-based superresolution microscopy. Phagocytic podosomes were observed during frustrated phagocytosis, a model in which cells attempt to engulf micro-patterned IgG antibodies. For circular patterns, this resulted in regular arrays of podosomes with well-defined geometry. Using persistent homology, we developed a pipeline for semi-automatic identification and measurement of podosome features. These studies revealed an "hourglass" shape of the podosome actin core, a protruding "knob" at the bottom of the core, and two actin networks extending from the core. Additionally, the distributions of paxillin, talin, myosin II, -actinin, cortactin, and microtubules relative to actin were characterized.

cell biology↗

bioRxiv2022

Autophagy receptor NDP52 alters DNA conformation to modulate RNA Polymerase II transcription

NDP52 is an autophagy receptor involved in the recognition and degradation of invading pathogens and damaged organelles. Although NDP52 was first identified in the nucleus and is expressed throughout the cell, to date, there is no clear nuclear function for NDP52. Here, we use a multidisciplinary approach to characterise the biochemical properties and nuclear roles of NDP52. We found that NDP52 clusters with RNA Polymerase II (RNAPII) at transcription initiation sites and that its overexpression promotes the formation of additional transcriptional clusters. We also show that depletion of NDP52 impacts overall gene-expression levels in two model mammalian cells, and that transcription inhibition affects the spatial organisation and molecular dynamics of NDP52 in the nucleus. This directly links NDP52 to a role in RNAPII-dependent transcription. Furthermore, we also show that NDP52 binds specifically and with high affinity to double-stranded DNA (dsDNA) and that this interaction leads to changes in DNA structure in vitro. This, together with our proteomics data indicating enrichment for interactions with nucleosome remodelling proteins and DNA structure regulators, suggests a possible function for NDP52 in chromatin regulation. Overall, here we uncover novel nuclear roles for NDP52 in gene expression and DNA structure regulation.

biophysics↗

bioRxiv2020

Binding partners regulate unfolding of myosin VI to activate the molecular motor

Myosin VI is the only minus-end actin motor and is coupled to various cellular processes ranging from endocytosis to transcription. This multi-potent nature is achieved through alternative isoform splicing and interactions with a network of binding partners. There is a complex interplay between isoforms and binding partners to regulate myosin VI. Here, we have compared the regulation of two myosin VI splice isoforms by two different binding partners. By combining biochemical and single-molecule approaches, we propose that myosin VI regulation follows a generic mechanism, independently of the spliced isoform and the binding partner involved. We describe how myosin VI adopts an autoinhibited backfolded state which is released by binding partners. This unfolding activates the motor, enhances actin binding and can subsequently trigger dimerization. We have further expanded our study by using single molecule imaging to investigate the impact of binding partners upon myosin VI molecular organisation and dynamics.

biophysics↗

bioRxiv2020

Nuclear myosin VI regulates the spatial organization of mammalian transcription initiation.

During transcription, RNA Polymerase II (RNAPII) is spatially organised within the nucleus into clusters that correlate with transcription activity. While this is a hallmark of genome regulation in mammalian cells, the mechanisms concerning the assembly, organisation and stability which underpin the function these transcription factories remain unknown. Here, we have used combination of single molecule imaging and genomic approaches to explore the role of nuclear myosin VI in the nanoscale organisation of RNAPII. We reveal that myosin VI acts as the molecular anchor that holds RNAPII into transcription factories. Perturbation of myosin VI leads to the disruption of RNAPII localisation, changes in chromatin organisation and subsequently a decrease in gene expression. Overall, we uncover the fundamental role of myosin VI in the spatial regulation of gene expression during the rapid response to changes in the cellular environment.

cell biology↗

bioRxiv2019

Super resolution imaging of a distinct chromatin loop in human lymphoblastoid cells

The three-dimensional genome structure plays a fundamental role in gene regulation and cellular functions. Recent studies in genomics based on sequencing technologies inferred the very basic functional chromatin folding structures of the genome known as chromatin loops, the long-range chromatin interactions that are often mediated by protein factors. To visualize the looping structure of chromatin we applied super-resolution microscopy iPALM to image a specific chromatin loop in GM12878 cells. Totally, we have generated six images of the target chromatin region at the single molecule resolution. To infer the chromatin structures from the captured images, we modeled them as looping conformations using different computational algorithms and then evaluated the models by comparing with Hi-C data to examine the concordance. The results showed a good correlation between the imaging data and sequencing data, suggesting the visualization of higher-order chromatin structures for the very short genomic segments can be realized by microscopic imaging.

molecular biology↗