Biology subjects

Dennison, C.

Publications and source records attributed to Dennison, C..

9 recordsLinked to original sources

bioRxiv2026

Vascular endothelial cadherin remodeling is associated with endothelial barrier dysfunction in chronic subdural hematoma

Abstract Background: Chronic subdural hematoma (cSDH) remains a significant and increasingly prevalent cause of morbidity in older adults. Disease progression is sustained by de novo formed highly vascularized pseudomembranes and a persistent cycle of fluid accumulation and hematoma expansion. Although inflammatory and angiogenic pathways have been implicated in cSDH pathogenesis, the endothelial mechanisms underlying persistent vascular leak remain poorly understood. We investigated the cSDH vascular microenvironment in human patients and examined the role of vascular endothelial cadherin (VECAD) remodeling in cSDH endothelial dysfunction. Methods: Human cSDH membranes and fluid were evaluated by multiplex profiling, histology, immunofluorescence, immunoprecipitation, western blotting and exploratory bulk RNA sequencing. A human brain endothelial cell (HBEC) line was exposed to patient-derived cSDH fluid to assess VECAD remodeling, endothelial barrier permeability, and proliferation. Results: Multiplex profiling of patient-derived cSDH fluid detected mediators associated with endothelial cell (EC) activation, extracellular matrix remodeling, inflammation, and angiogenesis. In patient pseudomembranes, discontinuous VECAD coincided with erythrocyte extravasation. Two hyperdense (high-risk) specimens showed more extensive disruption than the hypodense (low-risk) specimen while vessel counts appeared similar. Bulk RNA sequencing identified an angiogenic environment and enrichment in cadherin regulation. A soluble VECAD (sVECAD) isoform was detected in cSDH fluid. Exposure of HBECs to patient-derived cSDH fluid increased EC proliferation, cytoplasmic VECAD (cVECAD) accumulation, and EC barrier permeability. Concurrent dexamethasone or minocycline treatment attenuated VECAD cleavage. Conclusions: VECAD disruption is a prominent feature of cSDH and is associated with EC barrier dysfunction. These findings support further evaluation of soluble VECAD as a candidate biomarker and of junction-preserving pathways as potential therapeutic targets.

pathology↗

bioRxiv2026

Concealed Conduction Vulnerability in Scn1b Haploinsufficiency Emerges with Osmotic Stress

RationaleSCN1B encodes the {beta}-subunits of the main cardiac voltage-gated sodium channel, NaV1.5. Variants are linked to cardiac conduction disease, often with concealed phenotypes. Whether {beta}1-subunits regulate conduction through nanoscale intercalated disc (ID) structures, e.g. perinexi, and ephaptic coupling remains unresolved. ObjectiveTest whether Scn1b haploinsufficiency induces latent conduction abnormalities that are unmasked by perturbations in extracellular nanodomains. Methods and ResultsAdult Scn1b+/- mice and wild-type (WT) littermates underwent multiscale phenotyping (qRT-PCR, Western blot, patch clamp, transmission electron microscopy (TEM), ex vivo optical mapping, in vivo ECG). Scn1b+/- hearts showed [~]50% reductions in Scn1b mRNA and {beta}1 protein without changes in canonical conduction proteins. Peak sodium current, baseline conduction velocity ex vivo, and baseline QRS duration in vivo were unchanged. However, TEM revealed increased baseline perinexal width in Scn1b+/- hearts. Osmotic expansion of the perinexus with mannitol slowed conduction to a greater extent in Scn1b+/- hearts and prolonged QRS duration in vivo. In contrast, perinexal narrowing with dextran 2MDa selectively increased conduction velocity in Scn1b+/- hearts. ConclusionsScn1b haploinsufficiency preserves baseline excitability and conduction but structurally remodels the ID at the nanoscale, increasing sensitivity to extracellular nanodomain perturbations. These data support a structural role for {beta}1-subunits in ephaptic coupling, and that conduction is maintained over a range of perinexal widths with pathological conduction slowing occurring beyond a critical width. Importantly, osmotic stress unmasks a concealed conduction phenotype, identifying extracellular nanodomain stability as a potential therapeutic target to mitigate arrhythmia risk in SCN1B-associated disease.

biophysics↗

bioRxiv2025

Markers of resilience to stony coral tissue loss disease and probiotic potential in the microbiome of the threatened coral, Orbicella faveolata

Stony coral tissue loss disease (SCTLD) is widespread within the Caribbean and affects at least 22 species of reef-building coral. Bacteria have been implicated in the etiology of SCTLD, but the community of bacteria and archaea may also contribute to SCTLD resistance. To identify potential mechanisms through which microbes contribute to SCTLD resistance, we sequenced metagenomes from 41 colonies of the threatened coral, Orbicella faveolata, in the lower Florida Keys. All colonies were fate-tracked for three to five years and disease lesions were treated with amoxicillin. By 2024, 20% were never diseased, 10% had lesions before sampling but recovered, 22% were apparently healthy but were eventually susceptible to infection, and 49% had regular repeated infections. Within the coral microbiome, diseased and yet-to-be diseased colonies exhibited higher variability in functional genes. In contrast, corals that remained unaffected or recovered had less variable microbiomes with greater abundances of vitamin and antibiotic biosynthesis, secretion system, and quorum sensing genes that may support host health and resilience to pathogens. Though on some colonies antibiotic treatments were applied repeatedly, there was no effect on the diversity of beta-lactamases, antibiotic resistance genes that may confer amoxicillin resistance. Additional potentially probiotic gene clusters for the production of antimicrobial and bioactive compounds were present in many colonies regardless of fate. Taken together, we find significant probiotic potential in the coral microbiome to armor host O. faveolata corals against SCTLD infection, which may underpin intraspecific variation in stony coral tissue loss disease resilience and susceptibility.

microbiology↗

bioRxiv2025

A connexin 43 targeting peptide prevents blood vessel neointima formation

The gap junction protein connexin 43 (Cx43) is associated with human pathological vascular smooth muscle cell (SMC) proliferation and neointima formation. We previously identified mitogen-activated protein kinase (MAPK) phosphorylation of Cx43 results in binding with the cell cycle protein cyclin E, facilitating neointima formation in mice. However, the specific nature of these interactions and their relevance to human disease have not been elucidated. Using an ex vivo human saphenous vein model of neointima formation, we identified increased MAPK-phosphorylated Cx43 and cyclin E in explant tissues. We used peptide arrays to define a cyclin E-Cx43 binding region and generated CycliCx, a stearate-linked Cx43 phospho-mimetic peptide. In human coronary artery SMC, CycliCx inhibits platelet-derived growth factor-BB (PDGF-{beta})-induced changes in Cx43 trafficking and interactions with cyclin E, and stimulation of proliferation. RNAseq analysis identified CycliCx significantly inhibits PDGF-{beta}-induced proliferative pathways in SMC by limiting PDGF-{beta}-induced early G1/S phase cell cycle progression transcripts. Finally, we show CycliCx limits neointima formation in mice in vivo and in ex vivo human saphenous vein explants. Our data provide strong evidence for selective targeting of Cx43 as a viable therapeutic strategy for preventing neointimal formation in humans.

physiology↗

bioRxiv2025

Injury Induced Connexin 43 Expression Regulates Endothelial Wound Healing

Endothelial cell (EC) injury is a major contributing factor to vascular surgical failure. As such, understanding the mechanisms of endothelial healing is essential to the development of vascular therapeutics and procedures. Gap junctions formed by connexin 43 (Cx43) are implicated in regulating skin wound healing, but their role in endothelial healing is unknown. Secondary analysis of RNAseq data from in vivo injured mouse aortas (GEO: GSE115618), identified significant Cx43 upregulation in EC post-injury. We developed a novel in vivo model of EC injury using mouse carotid artery ligation to test the role of Cx43. We identified that EC immediately adjacent to the wound edge upregulate Cx43 protein expression, predominantly at cell-cell junctions. We show significantly delayed EC healing in a mouse model of inducible EC-specific Cx43 deletion (EC-Cx43 KO) at 24 hr post ligation. Single cell RNAseq analysis of 10,829 cells from 18 hr injured EC-WT and EC-Cx43 KO carotids revealed a Cx43-associated reduction in enrichment of EC pathways associated with migration, proliferation, and ERK/MAPK signaling pathways. Finally, the importance of Cx43 phosphorylation on EC healing was tested in mice with single-point alanine mutations (phospho-null) in known phosphorylation sites that alter Cx43 channel assembly and opening. Mice containing alanine mutations at ERK phosphorylated Cx43 serines (Cx43S255/262/279/282A) reduces healing rates similar to EC-Cx43 KO. These data suggest that EC injury-induced Cx43 upregulation, and subsequent Cx43 gap junction-mediated cell-to-cell communication are required for normal EC migration during wound healing after vascular injury. New and NoteworthyThese findings demonstrate for the first time that mechanical injury to large artery endothelium induces the expression of gap junction protein Cx43. This upregulation improves migratory and proliferative capacity of endothelial cells at the wound edge, facilitating timely wound closure. This phenomenon is dependent on appropriate gap junction function and turnover.

physiology↗

bioRxiv2024

Random adversarial threshold search enables automated DNA screening

Custom DNA synthesis underpins modern biology, but controlled genes in the wrong hands could threaten many lives and public trust in science. In .1992, a virology-trained mass murderer tried and failed to obtain physical samples of Ebola; today, viruses can be assembled from synthetic DNA fragments. Screening orders for controlled sequences is unreliable and expensive because current similarity search algorithms yield false alarms requiring expert human review. Exact-match search can achieve perfect specificity among short known sequences by detecting subsequences unique to controlled genes, but can be trivially evaded by incorporating mutations. Here we rescue exact-match search by additionally screening for predicted functional variants of pseudo-randomly chosen subsequences that arent found in known unregulated genes. To experimentally assess robustness, we protected nine windows from the M13 bacteriophage virus, then invited a "red team" to launch up to 21,000 attacks at each window and measure the fitness of their designed mutants. We identified defensible windows from regulated pathogens, built a test database that our experiments indicate will block 99.999% of functional attacks, and verified its sensitivity against redesigned enzymes. Exact-match search with functional variant prediction offers a promising way to safeguard biotechnology by automating DNA synthesis screening. SummarySearching for exact matches to pre-computed functional variants unique to controlled genes enables sensitive, secure, and automated DNA synthesis screening.

synthetic biology↗

bioRxiv2023

Low-cost camera-based estrous tracking enables transgenesis in Peromyscus leucopus, the primary reservoir for Lyme disease

CRISPR/Cas9 technology has revolutionized the production of animal models by reducing experimental timelines, slashing costs and streamlining gene editing, leading to a rapid expansion in the number of unique models for the study of human disease and gene function. However, most non-model animals, many of which are important in cancer and aging research, remain recalcitrant to genome engineering due to our limited understanding of their reproductive biology. Many wild rodents that transmit human diseases remain particularly challenging to engineer due to low pregnancy rates, the lack of external copulatory plugs, and susceptibility to premature termination of pregnancy. Here, we present low-cost activity-based estrous tracking for the efficient generation of timed pregnant and pseudopregnant white-footed mice and extend this tracking method to both lab mice and hamsters. Leveraging this technology, we demonstrate the generation of engineered Peromyscus leucopus, the primary reservoir for Lyme disease-causing bacteria and a putative model organism for studies of aging. These tools have broad implications for biomedical research and ecological engineering. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=107 SRC="FIGDIR/small/563285v1_ufig1.gif" ALT="Figure 1"> View larger version (45K): org.highwire.dtl.DTLVardef@19a3fb2org.highwire.dtl.DTLVardef@1cbce4corg.highwire.dtl.DTLVardef@1551e0corg.highwire.dtl.DTLVardef@127c028_HPS_FORMAT_FIGEXP M_FIG C_FIG

bioengineering↗

bioRxiv2022

Microbiome signatures in Acropora cervicornis are associated with genotypic resistance to elevated nutrients and heat stress

The staghorn coral, Acropora cervicornis, was once abundant in the Caribbean, but now is listed as critically endangered. To recover A. cervicornis populations, restoration efforts have focused on preserving genetic diversity and increasing coral cover. However, identifying stress-resistant corals can help to increase restoration success, by allocating genotypes to reefs where they are more likely to survive. We assessed the performance (growth, survivorship, and photochemical efficiency) and characterized the microbiome (prokaryotes) of six A. cervicornis genotypes that were maintained at control temperatures (~26 {degrees}C) and either ambient nutrients or elevated nutrients (elevated NH4, and elevated NH4 + PO4) for > 2 months. We then compared how these parameters changed when the corals were exposed to heat-stress (3-weeks at ~31.5 {degrees}C). We found that exposure to elevated nutrients reduced A. cervicornis performance under control temperatures and heat stress. However, there was a wide range of variation among genotypes, with three genotypes maintaining relatively higher survivorship and growth rates when exposed to nutrients alone, and nutrients followed by heat stress. Heat stress alone changed the microbial composition among genotypes more than elevated nutrients alone, but heat stress also interacted with nutrient pre-exposure to affect microbial communities. The relative abundance of Midichloriaceae and Spirochaetaceae varied by coral genotype and a high abundance of these bacterial taxa was a positive predictor of coral survivorship rate, suggesting a microbial signature that could aid in identifying resistant A. cervicornis genotypes. Our findings suggest there is significant variation among genotypes in the response of A. cervicornis to elevated nutrients and temperatures. Resistant genotypes may be identifiable via their microbiomes and prioritized for outplanting at sites characterized by high levels of nutrient pollution. Large-scale microbiome screening may help expedite targeted outplanting and could be tested and extended to facilitate the identification of genotypes with other resistance characteristics.

ecology↗

bioRxiv2022

Intracellular copper storage and delivery in a bacterium

A family of cytosolic copper (Cu) storage proteins (the Csps) are widespread in bacteria. The Csps can bind large quantities of Cu(I) via their Cys-lined four-helix bundles, and the majority are cytosolic (Csp3s). This is inconsistent with the current dogma that bacteria, unlike eukaryotes, have evolved not to maintain intracellular pools of Cu due to its potential toxicity. Sporulation in Bacillus subtilis has been used to investigate if a Csp3 can store Cu(I) in the cytosol for a target enzyme. The activity of the Cu-requiring endospore multi-Cu oxidase BsCotA (a laccase) increases under Cu-replete conditions in wild type B. subtilis, but not in the strain lacking BsCsp3. Cuprous ions readily transfer from BsCsp3, but not from the cytosolic copper metallochaperone BsCopZ, to BsCotA in vitro producing active enzyme. Both BsCsp3 and BsCotA are upregulated during late sporulation. The hypothesis we propose is that BsCsp3 acquires and stores Cu(I) in the cytosol for BsCotA.

biochemistry↗