Biology subjects

McDermott, E.

Publications and source records attributed to McDermott, E..

4 recordsLinked to original sources

bioRxiv2022

Centrosome Amplification promotes cell invasion via cell-cell contact disruption and Rap-1 activation

Centrosome amplification (CA) is a prominent feature of human cancers linked to genomic instability and tumourigenesis in vivo. CA is observed as early as pre-malignant metaplasia, with CA incidence increasing as the disease progresses from dysplasia to neoplasia. However, the mechanistic contributions of CA to tumourigenesis (tumour architecture and remodelling) are poorly understood. Using non-tumourigenic breast cells (MCF10A), we demonstrate that CA induction (by CDK1 inhibition or PLK4 overexpression) alone increased both cell migration, invasion and Extracellular Matrix (ECM) remodeling. Mechanistically, CA induction activated small GTPase Rap-1. We demonstrated the key role of Rap-1 mediated signalling in CA induced tumourigenesis through Rap-1 inhibition (using GGTI-298) which blocked CA-induced migration, invasion and ECM attachment. CA induction in a long-term MCF10A cell culture system disrupted epithelial cell-cell junction integrity, via dysregulation of expression and subcellular localisation of cell junction proteins (ZO-1, Occludin, JAM-A & {beta}-catenin). At the ultrastructural level, CA significantly inhibited apical junctional complex formation, as visualized by transmission electron microscopy. CA induction in the luminal A breast cancer cell line MCF7 revealed similar trends in cell junction disruption. Furthermore, CA induction in MCF10A elevated expression of integrin {beta}-3, matrix metalloprotease MMP1 and MMP13 facilitating the observed ECM attachment, degradation and cell invasion phenotype. In vivo validation using a Chicken Embryo xenograft model, showed CA positive (CA+) MCF10A cells invaded into the chicken mesodermal layer, characterised by inflammatory cell infiltration and a marked focal reaction between chorioallantoic membrane and cell graft. This reaction was inhibited by pre-treatment of CA+ MCF10A cells with GGTI-298. Interestingly, in metastatic breast cancer cells with high levels of endogenous CA (triple negative cell line MDA-MB-231) inhibition of this CA-signalling pathway (using PLK4 inhibitor Centrinone B) abrogated their metastatic capacity in vitro. This demonstrates dual roles for CA signalling, for initiating and maintaining the CA-induced metastatic phenotype. Here, we demonstrated that CA induction in normal non-tumourigenic cells acts through Rap-1-dependent signaling to confer early pro-tumourigenic changes promoting tumour progression, mediated by ECM disruption, and altered cell-cell contacts. These insights reveal that in normal cells, CA induction alone (without additional pro-tumorigenic alterations) is sufficient to induce tumourigenesis and CA-mediated signaling supports a metastatic phenotype. StatementCentrosome amplification alone drives early tumourigenic change in normal breast epithelial cells

cell biology↗

bioRxiv2022

In vitro evolution of Listeria monocytogenes reveals selective pressure for loss of SigB and AgrA function at different incubation temperatures.

The alternative sigma factor B ({sigma}B) contributes to the stress tolerance of the foodborne pathogen Listeria monocytogenes by upregulating the General Stress Response. We previously showed that {sigma}B loss-of-function mutations arise frequently in strains of L. monocytogenes, and suggested that mild stresses might favour the selection of such mutations. In this study, we performed in vitro evolution experiments (IVEE) where L. monocytogenes was allowed to evolve over 30 days at elevated (42{degrees}C) or lower (30{degrees}C) incubation temperatures. Isolates purified throughout the IVEE revealed the emergence of sigB operon mutations at 42{degrees}C. However, at 30{degrees}C independent alleles in the agr locus arose, resulting in the inactivation of the Agr quorum sensing. Colonies of both sigB- and agr- strains exhibited a greyer colouration on 7-days-old agar plates compared with the parental strain. Scanning electron microscopy revealed a more complex colony architecture in the wild type than in the mutant strains. sigB- strains outcompeted the parental strain at 42{degrees}C, but not at 30{degrees}C, whilst agr- strains showed a small increase in competitive fitness at 30{degrees}C. Analysis of 40,080 L. monocytogenes publicly available genome sequences revealed a high occurrence rate of premature stop codons in both the sigB and agrCA loci. An analysis of a local L. monocytogenes strain collection revealed 5 out of 168 strains carrying agrCA alleles. Our results suggest that the loss of {sigma}B or Agr confer an increased competitive fitness in some specific conditions and this likely contributes to the emergence of these alleles in strains of L. monocytogenes. ImportanceTo withstand environmental aggressions L. monocytogenes upregulates a large regulon through the action of the alternative sigma factor B ({sigma}B). However, {sigma}B becomes detrimental for L. monocytogenes growth under mild stresses, which confer a competitive advantage to {sigma}B loss-of-function alleles. Temperatures of 42{degrees}C, a mild stress, are often employed in mutagenesis protocols of L. monocytogenes and promote the emergence of {sigma}B loss-of-function alleles in the sigB operon. In contrast, lower temperatures of 30{degrees}C promote the emergence of Agr loss-of-function alleles, a cell-cell communication mechanism in L. monocytogenes. Our findings demonstrate that loss-of-function alleles emerge spontaneously in laboratory-grown strains. These alleles rise in the population as a consequence of the trade-off between growth and survival imposed by the activation of {sigma}B in L. monocytogenes. Additionally, our results demonstrate the importance of identifying unwanted hitchhiker mutations in newly constructed mutant strains.

molecular biology↗

bioRxiv2021

Cryptic costs of viral infection in a model social insect

Declining insect populations emphasize the importance of understanding the drivers underlying reductions in insect fitness. Here, we investigated viruses as a threat to social insect reproduction, using honey bees as a model species. We report that in a sample of N = 93 honey bee (Apis mellifera) queens from nine beekeeping operations across a wide geographic range, high levels of natural viral infection are associated with decreased ovary mass. We confirmed this finding in an independent sample of N = 54 queens. Failed (poor quality) queens displayed higher levels of viral infection, reduced sperm viability, smaller ovaries, and altered ovary protein composition compared to healthy queens. We experimentally infected queens with Israeli acute paralysis virus (IAPV) and found that the ovary masses of IAPV-injected queens were significantly smaller than control queens, demonstrating a causal relationship between viral infection and ovary size. Queens injected with IAPV also had significantly lower expression of vitellogenin, the main source of nutrition deposited into developing oocytes, and higher levels of heat-shock proteins (HSPs), which are part of the honey bees antiviral response. This work together shows that viral infections occurring naturally in the field are compromising queen reproductive success.

systems biology↗

bioRxiv2021

Honey bee queen health is unaffected by contact exposure to pesticides commonly found in beeswax

Honey bee queen health is crucial for colony health and productivity, and pesticides have been previously associated with queen loss and premature supersedure. Prior research has investigated the effects of indirect pesticide exposure on queens via workers, as well as direct effects on queens during development. However, as adults, queens are in constant contact with wax as they walk on comb and lay eggs; therefore, direct pesticide contact with adult queens is a relevant but seldom investigated exposure route. Here, we conducted laboratory and field experiments to investigate the impacts of topical pesticide exposure on adult queens. We tested dose-response relationships of six pesticides commonly found in wax: coumaphos, tau-fluvalinate, atrazine, 2,4-DMPF, chlorpyriphos, chlorothalonil, and a cocktail of all six, each dosed up to 32 times the concentrations typically found in wax. We found no effect of any treatment on queen mass or sperm viability. Furthermore, none of the 1,568 proteins quantified in the queens fat bodies (a major site of detoxification enzyme production) were differentially expressed. In a field trial with N = 30 queens exposed to either a handling control, a solvent control, or a pesticide cocktail, we again found no impact on queen egg-laying pattern, mass, or emergence mass of daughter workers. Further, of the 3,127 proteins identified in fluid from the spermatheca (sperm storage organ), none were differentially expressed. These experiments consistently show that at realistic exposure levels, pesticides commonly found in wax have no direct impact on queen performance, reproduction, or quality metrics. We suggest that previously reported associations between high levels of pesticide residues in wax and queen failure are most likely driven by indirect effects of worker exposure (either through wax or other hive products) on queen care or queen perception.

pharmacology and toxicology↗