Biology subjects

Davidson, T.

Publications and source records attributed to Davidson, T..

6 recordsLinked to original sources

bioRxiv2025

Inhibiting SOX18 with propranolol restores vascular integrity in NR2F2-driven malformations

Translating genomic discoveries into therapies for rare genetic disorders remains a significant challenge, particularly for variants of unknown significance (VUS) where molecular mechanisms are unclear. This is particularly relevant in vascular malformations, where venous differentiation remains poorly understood, and the role of transcription factors in specifying venous identity is only beginning to be elucidated. Here, we combine live-cell single-molecule imaging with genomics-based approaches to uncover a biophysical mechanism of transcription factor antagonism that underpins venous identity. We show that SOX18 and NR2F2 antagonistically co-regulate venous differentiation through dynamic feedback between their nuclear populations. This interaction is disrupted in vascular malformation syndrome caused by a de novo heterozygous NR2F2 mutation, presenting with aberrant vascular integrity and bleeding. Treatment with an FDA-approved drug--known to inhibit SOX18--led to marked clinical improvement in the proband. To dissect the molecular mechanism underlying this mutation and the drug response, we used human embryonic stem cells (hESCs) engineered to carry the probands NR2F2 variant. These cells exhibited impaired hESC to venous differentiation with no effect on artery EC differentiation. In silico modelling and live-cell molecular imaging revealed that the NR2F2 variant is hyper-mobile, fails to form homodimers, and cannot recruit SOX18, thereby disrupting a critical transcriptional antagonism that underpins venous endothelial identity. We demonstrate that targeted pharmacological inhibition of SOX18 restores this regulatory balance in hESC-derived venous endothelial cells, rescuing both gene expression and NR2F2 binding dynamics at the single-molecule level. Together, this study uncovers a biophysical mechanism of transcription factor antagonism that governs venous differentiation and offers a framework for developing targeted therapies for rare vascular malformations.

developmental biology↗

bioRxiv2024

Anti-phase clustering of regulatory factors shapes gene bursting

Stem cell self-renewal relies on finely tuned transcriptional oscillations of pluripotency genes, yet the sequence by which transcription factors (TFs) govern "on" and "off" states remains unclear. Here, we integrate trimodal single-molecule imaging - SOX2 mobility, Nanog locus diffusion, and real-time Nanog mRNA synthesis using the STREAMING-tag reporter - to visualise endogenous regulatory dynamics in living cells. We identify two SOX2 binding modes linked to transcriptional priming and termination and show coordinated temporal activity of SOX2, OCT4, BRD4, and MED22 at the Nanog locus. Live-cell and fixed-cell measurements reveal that local RNA fluctuations modulate SOX2 visiting-frequency rates. During the active elongation, high nascent enhancer and mRNA levels transiently sequester SOX2 through non-specific interactions, reducing its effective repetitive rebinding and limiting interference with elongating polymerase. After transcript release, declining RNA density permits SOX2 re-engagement, with high-visiting frequency with longer residency and increased locus mobility. These dynamics reveal RNA-dependent feedback that alternately buffers and primes transcriptional re-initiation.

molecular biology↗

bioRxiv2022

Dynamic Synchronization between Hippocampal Spatial Representations and the Stepping Rhythm

Summary paragraphThe hippocampus is a vertebrate brain structure that expresses spatial representations1 and is critical for navigation2,3. Navigation in turn intricately depends on locomotion; however, current accounts suggest a dissociation between hippocampal spatial representations and the details of locomotor processes. Specifically, the hippocampus is thought to primarily represent higher-order cognitive and locomotor variables like position, speed, and direction of movement4-7, while the limb movements that propel the animal are thought to be computed and represented primarily in subcortical circuits, including the spinal cord, brainstem, and cerebellum8-11. Whether hippocampal representations are actually decoupled from the detailed structure of locomotor processes remains unknown. To address this question, we simultaneously monitored hippocampal spatial representations and ongoing limb movements underlying locomotion at fast timescales. We found that the forelimb stepping cycle in freely behaving rats is rhythmic and peaks at ~8 Hz during movement, matching the ~8 Hz organization of information processing in the hippocampus during locomotion12. We also discovered precisely timed coordination between the time at which the forelimbs touch the ground ( plant times of the stepping cycle) and the hippocampal representation of space. Notably, plant times coincide with hippocampal representations closest to the actual position of the animal, while in-between these plant times, the hippocampal representation progresses towards possible future locations. This synchronization was specifically detectable when animals approached upcoming spatial decisions. Taken together, our results reveal profound and dynamic coordination on a timescale of tens of milliseconds between central cognitive representations and peripheral motor processes. This coordination engages and disengages rapidly in association with cognitive demands and is well suited to support rapid information exchange between cognitive and sensory-motor circuits.

neuroscience↗

bioRxiv2021

Chronic CNS Pathology is Associated with Abnormal Collagen Deposition and Fibrotic-like Changes

Multiple sclerosis is a chronic debilitating disease of the CNS. The relapsing remitting form of the disease is driven by CNS directed inflammation. However, in the progressive forms of the disease, inflammation has abated and the underlying pathology is less well understood. In this paper, we show that chronic lesions in progressive MS are associated with fibrotic changes, a type of pathology that has previously not thought to occur in the CNS. In an animal model of chronic MS, late stage disease contains no inflammatory infiltrates and is instead characterized by collagen deposition that is histologically similar to fibrosis. In human MS samples, chronic, but not acute lesions, are devoid of inflammatory infiltrates and instead contain significant collagen deposition. Furthermore, we demonstrate that both mouse and human astrocytes are the cellular source of collagen. These results suggest that anti-fibrotic therapy may be beneficial in the treatment of progressive MS.

neuroscience↗

bioRxiv2018

Oligodendrocyte Precursor Cells Are Co-Opted by the Immune System to Cross-Present Antigen and Mediate Cytotoxicity

Oligodendrocyte precursor cells (OPCs) are abundant in the adult CNS and can be recruited to form new oligodendrocytes and myelin in response to injury or disease. However, in multiple sclerosis (MS), oligodendrocyte regeneration and remyelination are often incomplete, suggesting that recruitment and maturation of OPCs is impaired. MS and the rodent model experimental autoimmune encephalomyelitis (EAE) are characterized by infiltration of activated T-cells into the CNS. To investigate the mechanisms by which this neuroinflammatory process influences OPC mobilization, we performed in vivo fate tracing in an inflammatory demyelinating animal model. Results of our studies showed that the OPC differentiation and myelin production are inhibited by either adoptive transfer of CNS infiltrating cytokine producing effector T-cells or CNS production of interferon gamma (IFN{gamma}), using an astrocyte specific IFN{gamma} transgene model. In both systems, IFN{gamma} changes the profile of OPCs by inducing functional expression of the immunoproteasome and upregulation of MHC class I. OPCs exposed to IFN{gamma} are shown to cross present exogenous antigen to cytotoxic CD8 T-cells, which then produce proteases and FasL that results in subsequent caspase 3/7 activation and OPC death, both in vitro and in vivo. Cross presentation by OPCs is dependent on the cytosolic processing pathway and can be inhibited by small molecules targeting MHC class I antigen processing and the immunoproteasome subunits. Finally, the immunoproteasome subunit, PSMB8, is shown to be markedly increased on Sox10+ oligodendrocyte lineage cells only in the demyelinated white matter lesions from patients with MS. These findings support the notion that OPCs have multiple functions beyond differentiation into myelinating cells and adapt to their microenvironment by responding to local cues. In MS, OPCs may be co-opted by the immune system to perpetuate the autoimmune response. Strategies aimed at inhibiting the aberrant immune activation pathways in OPCs may allow more efficient remyelination in MS.

neuroscience↗

bioRxiv2018

Knock-in rats expressing Cre and Flp recombinases at the Parvalbumin locus.

Rats have the ability to learn and perform sophisticated behavioral tasks, making them very useful for investigating neural circuit functions. In contrast to the extensive mouse genetic toolkit, the paucity of recombinase-expressing rat models has limited the ability to monitor and manipulate molecularly-defined neural populations in this species. Here we report the generation and validation of two knock-in rat strains expressing either Cre or Flp recombinase under the control of Parvalbumin (Pvalb), a gene expressed in the critical \"fast-spiking\" subset of inhibitory interneurons (FSIs). These strains were generated with CRISPR-Cas9 gene editing and show highly specific and penetrant labeling of Pvalb-expressing neurons, as demonstrated by in situ hybridization and immunohistochemistry. We validated these models in both prefrontal cortex and striatum using both ex vivo and in vivo approaches, including whole-cell recording, optogenetics, extracellular physiology and photometry. Our results demonstrate the utility of these new transgenic models for a wide range of neuroscience experiments.

neuroscience↗