Biology subjects

Wilson, B. A.

Publications and source records attributed to Wilson, B. A..

11 recordsLinked to original sources

bioRxiv2026

Tissue-wide metabolic buffering confers resilience to mosaic mitochondrial dysfunction

Mitochondria and oxidative phosphorylation (OxPhos) are essential for cellular homeostasis. However, the phenotypes caused by mitochondrial dysfunction often display remarkable tissue-specificity. What determines the susceptibility of individual cells to metabolic or mitochondrial defects in a complex in vivo tissue context, remains largely unknown. We find that neural stem cells (NSCs) in the developing Drosophila brain can maintain normal proliferation despite severe cell-autonomous OxPhos-dysfunction, provided that sufficient neighbouring cells remain metabolically intact. This tissue-wide buffering progressively fails as the proportion of NSCs with OxPhos dysfunction increases, indicating that the phenotypic threshold for mitochondrial dysfunction is an emergent property of a tissue rather than only of individual cells or cell-types. Mechanistically, we find that OxPhos-deficient NSCs activate a stress-response associated with ATF4/crc-transcriptional activation. NSCs upregulate lactate dehydrogenase (LDH) expression to maintain glycolysis, but their proliferation remains limited by NAD+ regeneration rather than by ATP production. Non-cell-autonomous rescue of NSC-proliferation depends on LDH-dependent NAD+-production in a brain-wide glial network connected by gap junctions and the glutamate/aspartate-transporter Eaat1. These findings demonstrate that the phenotypic threshold for mitochondrial dysfunction is determined by tissue-wide spare metabolic capacity rather than only of individual cells or cell-types. Tissue heterogeneity thus provides resilience to metabolic dysfunction, evidencing key benefits of diversity, and suggesting new therapeutic strategies to enhance endogenous metabolic buffering.

developmental biology↗

bioRxiv2025

PANK2-mediated de novo CoA synthesis is required for metabolic switching to fatty acid oxidation

Humans have 3 different PANK enzymes (PANK1-3) that catalyze the first step in the de novo synthesis of Coenzyme A (CoA). All PANKs are feedback inhibited by acyl-CoAs but only PANK2 can overcome this inhibition by binding palmitoyl-carnitine. Previous studies, conducted under glucose-replete conditions, have failed to detect a PANK2-mediated contribution to CoA synthesis. We found that exposure to BSA-conjugated palmitate (PAL-BSA) led to activation of fatty acid oxidation (FAO) and the accumulation of both palmitoyl-carnitine and palmitoyl-CoA in HEK293T cells, suggesting that PANK2 is active under these conditions. Isotope tracing experiments with 13C15N-pantothenate showed that PANK2 uniquely sustains de novo CoA synthesis and high production of Acetyl-CoA in the presence of long-chain fatty acids, indicating that FAO is limited by CoA availability in these conditions. Consistent with this mechanism, fibroblasts from PKAN patients exhibited impaired oxidation of palmitoyl-carnitine, confirming the functional relevance of our results in a disease context.

biochemistry↗

bioRxiv2024

A Genetic Screen for regulators of CNS morphology in Drosophila

Despite increasing in mass approximately 100-fold during larval life, the Drosophila CNS maintains its characteristic form during this rapid growth phase. Dynamic interactions between the overlying basement membrane and underlying surface glia are known to regulate CNS structure in Drosophila, but the genes and pathways that establish and maintain CNS morphology during development remain poorly characterized. To identify genes that regulate CNS shape in Drosophila, we conducted an EMS-based, forward genetic screen of the second chromosome, uncovered 50 mutations that disrupt CNS structure, and mapped these alleles to 17 genes. Whole genome sequencing revealed the affected gene for all but one mutation. Identified genes include well characterized regulators of tissue shape, like LanB1, viking, and Collagen type IV alpha1, as well as previously characterized genes, such as Toll-2 and Rme-8, with no known role in regulating CNS structure. We also uncovered that papilin and C1GalTA likely act in the same pathway to regulate CNS structure and found that the fly homolog of a glucuronosyltransferase, B4GAT1/LARGE1, that regulates Dystroglycan function in mammals is required to maintain CNS shape in Drosophila. Finally, we show that the senseless-2 transcription factor is expressed and functions specifically in surface glia found on peripheral nerves but not those on the CNS proper to govern CNS structure, identifying a gene that functionally subdivides a glial subtype along the peripheral-central axis. Future work on these genes should clarify the genetic mechanisms that ensure the homeostasis of CNS shape and form during development.

genetics↗

bioRxiv2024

Dihydroceramide desaturase governs endoplasmic reticulum and lipid droplet homeostasis to promote glial function in the nervous system

Dihydroceramide desaturases convert dihydroceramides to ceramides, the precursors of all complex sphingolipids. Reduction of DEGS1 dihydroceramide desaturase function causes pediatric neurodegenerative disorder hypomyelinating leukodystrophy-18 (HLD-18). We discovered that infertile crescent (ifc), the Drosophila DEGS1 homolog, is expressed primarily in glial cells to promote CNS development by guarding against neurodegeneration. Loss of ifc causes massive dihydroceramide accumulation and severe morphological defects in cortex glia, including endoplasmic reticulum (ER) expansion, failure of neuronal ensheathment, and lipid droplet depletion. RNAi knockdown of the upstream ceramide synthase schlank in glia of ifc mutants rescues ER expansion, suggesting dihydroceramide accumulation in the ER drives this phenotype. RNAi knockdown of ifc in glia but not neurons drives neuronal cell death, suggesting that ifc function in glia promotes neuronal survival. Our work identifies glia as the primary site of disease progression in HLD-18 and may inform on juvenile forms of ALS, which also feature elevated dihydroceramide levels.

developmental biology↗

bioRxiv2023

Glioblastoma Margin as a Diffusion Barrier Revealed by Photoactivation of Plasmonic Nanovesicles

Glioblastoma (GBM) is the most complex and lethal adult primary brain cancer. Adequate drug diffusion and penetration are essential for treating GBM, but how the spatial heterogeneity in GBM impacts drug diffusion and transport is poorly understood. Herein, we report a new method, photoactivation of plasmonic nanovesicles (PANO), to measure molecular diffusion in the extracellular space of GBM. By examining three genetically engineered GBM mouse models that recapitulate key clinical features including angiogenic core and diffuse infiltration, we found that the tumor margin has the lowest diffusion coefficient (highest tortuosity) compared with the tumor core and surrounding brain tissue. Analysis of the cellular composition shows that the tortuosity in the GBM is strongly correlated with neuronal loss and astrocyte activation. Our all-optical measurement reveals the heterogeneous GBM microenvironment and highlights the tumor margin as a diffusion barrier for drug transport in the brain, with implications for therapeutic delivery.

bioengineering↗

bioRxiv2023

Temporal Coordination of the Transcription Factor Response to H2O2 stress

The p53 and FOXO transcription factors (TFs) share many similarities despite their distinct evolutionary origins. Both TFs are activated by a variety of cellular stresses and upregulate genes in similar pathways including cell-cycle arrest and apoptosis. Oxidative stress from excess H2O2 activates both FOXO1 and p53, yet whether they are activated at the same time is unclear. Here we found that cells respond to high H2O2 levels in two temporal phases. In the first phase FOXO1 rapidly shuttles to the nucleus while p53 levels remain low. In the second phase FOXO1 exits the nucleus and p53 levels rise. We found that other oxidative stress induced TFs are activated in the first phase with FOXO1 (NF-kB, NFAT1), or the second phase with p53 (NRF2, JUN) but not both following H2O2 stress. The two TF phases result in large differences in gene expression patterns. Finally, we provide evidence that 2-Cys peroxiredoxins control the timing of the TF phases in response to H2O2.

cell biology↗

bioRxiv2022

Vascular endothelial growth factor A contributes to the increasing of mammalian respiratory epithelial permeability induced by Pasteurella multocida infection

Infections with Pasteurella multocida can cause significant zoonotic respiratory problems in both humans and animals. In vivo tests in mouse infection models were used to investigate the mechanisms of respiratory epithelial barrier dysfunction during respiratory bacterial infection with these pathogens. Results revealed that P. multocida infection significantly increased epithelial permeability and increased expression of vascular endothelial growth factor A (VEGFA) and endothelial nitric oxide synthase (eNOS) in murine tracheae and lungs. In murine lung epithelial cell (MLE-12) models, P. multocida infection decreased the expression of tight junctions (ZO-1) and adherens junctions ({beta}-catenin, E-cadherin), but induced the activation of the hypoxia-inducible factor-1 (HIF-1) and VEGFA signaling. When expression of HIF-1 is suppressed, the induction of VEGFA and ZO-1expression by P. multocida infection is decreased. We also found that intervention of HIF-1 and VEGFA signaling affected infection outcomes caused by respiratory bacteria in mouse models. Most importantly, we demonstrated that P. multocida infection increased permeability of human respiratory epithelial cells and this process was associated with the activation of the HIF-1 and VEGFA signaling and likely contributes to the pathogenesis of P. multocida in humans. ImportanceMammalian respiratory epithelium forms the first line of defense against infections with Pasteurella multocida, an important zoonotic respiratory pathogen. In this study, we found P. multocida infection increased respiratory epithelial permeability and promoted the induction of the hypoxia-HIF-1-VEGFA axis in both mouse and murine cell models. Similar findings were also demonstrated in human respiratory epithelial cells. The results from this study gain important knowledge about the pathogenesis of P. multocida causing infections in both animals and humans.

microbiology↗

bioRxiv2022

Calcium-Mediated Modulation of Blood-Brain Barrier Permeability by Laser Stimulation of Endothelial-Targeted Nanoparticles

The blood-brain barrier (BBB) maintains an optimal environment for brain homeostasis but excludes most therapeutics from entering the brain. Strategies that can reversibly increase BBB permeability will be essential for treating brain diseases and is the focus of significant preclinical and translational interest. Recently, we reported that picosecond laser excitation of molecular-targeted gold nanoparticles (AuNPs) induced a graded and reversible increase in BBB permeability in vivo (OptoBBB). Here we investigate how to increase the targeting efficiency and how picosecond lase stimulation of AuNP leads to an increase in endothelial paracellular permeability. Our results suggest that targeting brain endothelial glycoproteins leads to >20-fold higher targeting efficiency compared with tight junction targeting. We report that OptoBBB is associated with a transient elevation of Ca2+ that propagates to adjacent endothelial cells after laser excitation and extends the region of BBB opening. The Ca2+ response involves both internal Ca2+ depletion and Ca2+ influx. Furthermore, we demonstrate that the involvement of actin polymerization and Ca2+-dependent phosphorylation of ERK1/2 lead to cytoskeletal activation, increasing paracellular permeability. Taken together, we provide mechanistic insight into how excitation of endothelial targeted AuNPs leads to an increase in BBB permeability. These insights will be critical for guiding the future developments of this technology for brain disease treatment.

bioengineering↗

bioRxiv2021

Probability-based mechanisms in biological networks with parameter uncertainty

Mathematical models of biomolecular networks are commonly used to study cellular processes; however, their usefulness to explain and predict dynamic behaviors is often questioned due to the unclear relationship between parameter uncertainty and network dynamics. In this work, we introduce PyDyNo (Python Dynamic analysis of biochemical NetwOrks), a non-equilibrium reaction-flux based analysis to identify dominant reaction paths within a biochemical reaction network calibrated to experimental data. We first show, in a simplified apoptosis execution model, that Bayesian parameter optimization can yield thousands of parameter vectors with equally good fits to experimental data. Our analysis however enables us to identify the dynamic differences between these parameter sets and identify three dominant execution modes. We further demonstrate that parameter vectors from each execution mode exhibit varying sensitivity to perturbations. We then apply our methodology to JAK2/STAT5 network in colony-forming unit-erythroid (CFU-E) cells to identify its signal execution modes. Our analysis identifies a previously unrecognized mechanistic explanation for the survival responses of the CFU-E cell population that would have been impossible to deduce with traditional protein-concentration based analyses. Impact StatementGiven the mechanistic models of network-driven cellular processes and the associated parameter uncertainty, we present a framework that can identify dominant reaction paths that could in turn lead to unique signal execution modes (i.e., dominant paths of flux propagation), providing a novel statistical and mechanistic insights to explain and predict signal processing and execution.

systems biology↗

bioRxiv2019

Cardiolipin-dependent Properties of Model Mitochondrial Membranes from Molecular Dynamics Simulations

Cardiolipin is a unique anionic lipid found in mitochondrial membranes where it contributes to various mitochondrial functions, including metabolism, mitochondrial membrane fusion/fission dynamics, and apoptosis. Dysregulation of cardiolipin synthesis and remodeling have also been implicated in several diseases, such as diabetes, heart disease and Barth Syndrome. Although cardiolipins structural and dynamic roles have been extensively studied in binary mixtures with other phospholipids, the biophysical properties of cardiolipin in ternary lipid mixtures are still not well resolved. Here, we used molecular dynamics simulations to investigate the cardiolipin-dependent properties of ternary lipid bilayer systems that mimic the major components of mitochondrial membranes. We found that changes to cardiolipin concentration only resulted in minor changes to bilayer structural features, but that the lipid diffusion was significantly affected by those alterations. We also found that cardiolipin position along the bilayer surfaces correlated to negative curvature deflections, consistent with the induction of negative curvature stress in the membrane monolayers. This work contributes to a foundational understanding of the role of CL in altering the properties in ternary lipid mixtures composed of the major mitochondrial phospholipids, providing much needed insights to help understand how cardiolipin concentration modulates the biophysical properties of mitochondrial membranes.

biophysics↗

bioRxiv2017

Progressively more subtle aggregation avoidance strategies mark a long-term direction to protein evolution

To detect a direction to evolution, without the pitfalls of reconstructing ancestral states, we need to compare \"more evolved\" to \"less evolved\" entities. But because all extant species have the same common ancestor, none are chronologically more evolved than any other. However, different gene families were born at different times, allowing us to compare young protein-coding genes to those that are older and hence have been evolving for longer. To be retained during evolution, a protein must not only have a function, but must also avoid toxic dysfunction such as protein aggregation. There is conflict between the two requirements; hydrophobic amino acids form the cores of protein folds, but also promote aggregation. Young genes avoid strongly hydrophobic amino acids, which is presumably the simplest solution to the aggregation problem. Here we show that young genes few hydrophobic residues are clustered near one another along the primary sequence, presumably to assist folding. The higher aggregation risk created by the higher hydrophobicity of older genes is counteracted by more subtle effects in the ordering of the amino acids, including a reduction in the clustering of hydrophobic residues until they eventually become more interspersed than if distributed randomly. This interspersion has previously been reported to be a general property of proteins, but here we find that it is restricted to old genes. Quantitatively, the index of dispersion delineates a gradual trend, i.e. a decrease in the clustering of hydrophobic amino acids over billions of years.

evolutionary biology↗