Biology subjects

Thompson, G.

Publications and source records attributed to Thompson, G..

27 records · Page 2Linked to original sources

bioRxiv2022

Characterization of the growth and morphology of a BSL-2 Coccidioides posadasii strain that persists in the parasitic life cycle at ambient CO2.

Coccidioides is a dimorphic fungus responsible for Valley Fever and is the cause of severe morbidity and mortality in the infected population. Although there is some insight into the genes, pathways, and growth media involved in the parasitic to saprophytic growth transition, the exact determinants that govern this switch are largely unknown. In this work, we examined the growth and morphology of a novel Coccidioides posadasii strain (C. posadasii S/E) that efficiently produces spherules and endospores and persists in the parasitic life cycle at ambient CO2. We demonstrated that C. posadasii S/E remains virulent in an insect infection model. Surprisingly, under spherule-inducing conditions, C. posadasii S/E culture was found to be completely hyphal. Differential interference contrast (DIC) and transmission electron microscopy (TEM) revealed unexpected cellular changes in this strain including cell wall remodeling and formation of septal pores with Woronin bodies. Our study suggests that the C. posadasii S/E strain is a useful BSL-2 model for studying the molecular factors that are active during the parasitic life cycle and the mechanisms underlying the parasitic to saprophytic growth transition - a morphological switch that can impact the pathogenicity of the organism in the host.

microbiology↗

bioRxiv2021

Aneuploidy influences the gene expression profiles in Saccharomyces pastorianus group I and II strains during fermentation.

The lager yeasts, Saccharomyces pastorianus, are hybrids of Saccharomyces cerevisiae and Saccharomyces eubayanus and are divided into two broad groups, Group I and II. The two groups evolved from at least one common hybridisation event but have subsequently diverged with Group I strains losing many S. cerevisiae chromosomes while the Group II strains retain both sub-genomes. The complex genomes, containing orthologous alleles from the parental chromosomes, pose interesting questions regarding gene regulation and its impact on the fermentation properties of the strains. Superimposed on the presence of orthologous alleles are complexities of gene dosage due to the aneuploid nature of the genomes. We examined the contribution of the S. cerevisiae and S. eubayanus alleles to the gene expression patterns of Group I and II strains during fermentation. We show that the relative expression of S. cerevisiae and S. eubayanus orthologues is positively correlated with gene copy number. Despite the reduced S. cerevisiae content in the Group I strain, S. cerevisiae orthologues contribute to biochemical pathways upregulated during fermentation which may explain the retention of specific chromosomes in the strain. Conversely, S. eubayanus genes are significantly overrepresented in the upregulated gene pool in the Group II strain. Comparison of the transcription profiles of Group I and II strains during fermentation identified both common and unique gene expression patterns, with gene copy number being a dominant contributory factor. Thus, the aneuploid genomes create complex patterns of gene expression during fermentation with gene dosage playing a crucial role both within and between strains.

genetics↗

bioRxiv2021

Stem cell-derived macrophages as a new platform for studying host-pathogen interactions in livestock

Infectious diseases of farmed and wild animals pose a recurrent threat to food security and human health. The macrophage, a key component of the innate immune system, is the first line of defence against many infectious agents and plays a major role in shaping the adaptive immune response. However, this phagocyte is a target and host for many pathogens. Understanding the molecular basis of interactions between macrophages and pathogens is therefore crucial for the development of effective strategies to combat important infectious diseases. We explored how pluripotent stem cells (PSCs) can provide a limitless in vitro supply of genetically and experimentally tractable macrophages from livestock. Porcine and bovine PSC-derived macrophages (PSCdMs) exhibited molecular and functional characteristics of ex vivo primary macrophages. Pig PSCdMs were productively infected by Porcine Reproductive and Respiratory Syndrome Virus (PRRSV) and African Swine Fever Virus (ASFV), two of the most economically important and devastating viruses in pig farming. Moreover, Pig PSCdMs were readily amenable to genetic modification by CRISPR/Cas9 gene editing applied in parental stem cells, or directly by lentiviral vector transduction. PSCs and differentiated derivatives therefore provide a useful and ethical experimental platform to investigate the genetic and molecular basis of host-pathogen interactions in livestock.

immunology↗

bioRxiv2021

Defining the pig microglial transcriptome reveals their core signature, regional heterogeneity, and similarity with humans

Microglia play key roles in brain homeostasis as well as responses to neurodegeneration and neuroinflammatory processes caused by physical disease and psychosocial stress. The pig is a physiologically-relevant model species for studying human neurological disorders, many of which are associated with microglial dysfunction. Furthermore, pigs are an important agricultural species, and there is a need to understand how microglial function affects their welfare. As a basis for improved understanding to enhance biomedical and agricultural research, we sought to characterise pig microglial identity at genome-wide scale and conduct inter-species comparisons. We isolated pig hippocampal tissue and microglia from frontal cortex, hippocampus and cerebellum, as well as alveolar macrophages from the lungs and conducted RNA-sequencing (RNAseq). By comparing the transcriptomic profiles between microglia, macrophages, and hippocampal tissue, we derived a set of 365 highly-enriched genes defining the porcine core microglial signature. We found brain regional heterogeneity based on 215 genes showing significant (adjusted p<0.01) regional variations and that cerebellar microglia were most distinct. We compared normalized gene expression for microglia from human, mice and pigs using microglia signature gene lists derived from each species and demonstrated that a core microglial marker gene signature is conserved across species, but that species-specific expression subsets also exist. Importantly, pig and human microglia shared greater similarity than pig and murine microglia. Our data provide a valuable resource defining the pig microglial transcriptome signature that highlights pigs as a useful large animal species bridging between rodents and humans in which to study the role of microglia during homeostasis and disease. Main Points- Defined a pig microglial transcriptome signature comprising 365 genes. - Demonstrated regional variance in the pig microglial transcriptome across the brain. - Revealed greater similarity between pig and human microglia than mouse.

bioinformatics↗

bioRxiv2020

Localization and Functional Characterization of the Alternative Oxidase in Naegleria

The Alternative oxidase (AOX) is a protein involved in maintaining the Krebs cycle in instances where the respiratory chain has been inhibited, while allowing for the maintenance of cell growth and necessary metabolic processes for survival. Among eukaryotes, alternative oxidases have disperse distribution and are found in plants, fungi and a few protists, including Naegleria ssp. Naegleria species are free-living unicellular amoeboflagellates, and include the pathogenic species of N. fowleri, the so-called brain eating amoeba. Using a multidisciplinary approach, we aimed to understand the evolution, localization and function of AOX and the role that plays in Naeglerias biology. Our analyses suggest that the protein was present in last common ancestor of the genus and structure prediction showed that all functional residues are also present in Naegleria species. Using a combination of cellular and biochemical techniques, we also functionally characterize N. gruberis AOX in its mitochondria and we demonstrate that its inactivation affects its proliferation. Consequently, we discuss the benefits of the presence of this protein in Naegleria species, along with its potential pathogenicity role in N. fowleri. We predict that our findings will spearhead new explorations to understand the cell biology, metabolism and evolution of Naegleria and other free-living relatives.

microbiology↗

bioRxiv2020

Organized cannabinoid receptor distribution in neurons revealed by super-resolution fluorescence imaging

G-protein-coupled receptors (GPCRs) play important roles in cellular functions. However, their intracellular organization is largely unknown. Through investigation of the cannabinoid receptor 1 (CB1), we discovered periodically repeating clusters of CB1 hotspots within the axons of neurons. We observed these CB1 hotspots interact with the membrane-associated periodic skeleton (MPS) forming a complex crucial in the regulation of CB1 signaling. Furthermore, we found that CB1 hotspot periodicity increased upon CB1 agonist application, and these activated CB1 displayed less dynamic movement compared to non-activated CB1. Our results suggest that CB1 forms periodic hotspots organized by the MPS as a mechanism to increase signaling efficacy when being activated.

neuroscience↗

bioRxiv2019

Crystal structure of the M5 muscarinic acetylcholine receptor

The human M5 muscarinic acetylcholine receptor (mAChR) has recently emerged as an exciting therapeutic target for treating a range of disorders, including drug addiction. However, a lack of structural information for this receptor subtype has limited further drug development and validation. Here we report a high-resolution crystal structure of the human M5 mAChR bound to the clinically used inverse agonist, tiotropium. This structure allowed for a comparison across all five mAChR family members that revealed important differences in both orthosteric and allosteric sites that could inform the rational design of selective ligands. These structural studies together with chimeric swaps between the extracellular regions of the M2 and M5 mAChR further revealed the structural insight into \"kinetic-selectivity\", where ligands show differential residency times between related family members. Collectively, our study provides important insights into the nature of orthosteric and allosteric ligand interaction across the mAChR family that could be exploited for the design of selective ligands.\n\nSignificance StatementThe five subtypes of the muscarinic acetylcholine receptors (mAChRs) are expressed throughout the central and peripheral nervous system where they play a vital role in physiology and pathologies. Recently, the M5 mAChR subtype has emerged as an exciting drug target for the treatment of drug addiction. We have determined the atomic structure of the M5 mAChR bound to the clinically used inverse agonist tiotropium. The M5 mAChR structure now allows for a full comparison of all five mAChR subtypes and reveals subtle differences in the extracellular loop (ECL) regions of the receptor that mediate orthosteric and allosteric ligand selectivity. Together these findings open the door for future structure-based design of selective drugs that target this therapeutically important class of receptors.

pharmacology and toxicology↗

bioRxiv2019

Strong population structure in Venezuelan populations of Coccidioides posadasii

Coccidioides posadasii is a pathogenic fungus that causes coccidioidomycosis in many arid regions of the Americas. One of these regions is bordered by the Caribbean Sea, and the surrounding landscape may play an important role in the dispersion of C. posadasii across South America through southeastern Mexico, Honduras, Guatemala and Venezuela. Comparative phylogenomic analyses of C. posadasii reveal that clinical strains from Venezuela are genetically distinct from the North American populations found in Arizona (AZ), Texas, Mexico, and the rest of South America (TX/MX/SA). We find evidence for admixture between the Venezuela and the North American populations of C. posadasii in Central America. As expected, the proportion of Venezuelan alleles in the admixed population decreases as latitude (and distance from Venezuela) increases. Our results indicate that the population in Venezuela may have been subjected to a recent bottleneck, and shows strong population structure. This analysis provides insight into potential for Coccidioides spp. to invade new regions.

evolutionary biology↗

bioRxiv2019

Alcohol increases aggression in flies

Alcohol-induced aggression is a destructive and widespread phenomenon, but we understand very little about the mechanisms that produce this behavior. We found that two different alcohol exposures potentiate aggression in male flies. (1) A pharmacologically relevant dose of alcohol increases aggression and decreases a goal-directed behavior in male flies. (2) In addition, the odor of alcohol itself enhances intermale aggression by potentiating olfactory signaling by cis-vaccenyl acetate (cVa), a volatile male pheromone. Characterizing these behaviors in the genetically tractable fruit fly can lead to a better understanding of the molecular correlates that regulate alcohol-induced aggression in humans and provide insights into an ethologically relevant behavior.\n\nOne Sentence SummaryWe identified two pathways through which alcohol stimulates intermale aggression in flies; one acts by potentiating a male olfactory pheromone while the other is mediated by the systemic effects of alcohol.

ecology↗