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PLOS Biology: New Articles

  • The bacterial type three secretion system induces mechanoporation of vacuolar membranes

    by Léa Swistak, Marvin Albert, Camila Valenzuela, Elif Begum Gokerkucuk, François Bontems, Stéphane Tachon, Keith T. Egger, Anastasia D. Gazi, Anna Sartori-Rupp, Cammie F. Lesser, Perrine Paul-Gilloteaux, Jean-Yves Tinevez, Matthijn Vos, Jost Enninga

    Endomembrane breaching is a crucial strategy employed by intracellular pathogens enclosed within vacuoles to access the nutrient-rich cytosol for intracellular replication. While bacteria use various mechanisms to compromise host membranes, the specific processes and factors involved are often unknown. Shigella flexneri, a major human pathogen, accesses the cytosol relying on the Type Three Secretion System (T3SS) and secreted effectors. Using in-cell correlative light and electron microscopy, we tracked the sequential steps of Shigella host cell entry. Moreover, we captured the T3SS, which projects a needle from the bacterial surface, in the process of puncturing holes in the vacuolar membrane. This initial puncture ensures disruption of the vacuole. Together this introduces the concept of mechanoporation via a bacterial secretion system as a crucial process for bacterial pathogen-induced membrane damage.

  • Removing facial features from structural MRI images biases visual quality assessment

    by Céline Provins, Élodie Savary, Thomas Sanchez, Emeline Mullier, Jaime Barranco, Elda Fischi-Gómez, Yasser Alemán-Gómez, Jonas Richiardi, Russell A. Poldrack, Patric Hagmann, Oscar Esteban

    A critical step before data-sharing of human neuroimaging is removing facial features to protect individuals’ privacy. However, not only does this process redact identifiable information about individuals, but it also removes non-identifiable information. This introduces undesired variability into downstream analysis and interpretation. This registered report investigated the degree to which the so-called defacing altered the quality assessment of T1-weighted images of the human brain from the openly available “IXI dataset”. The effect of defacing on manual quality assessment was investigated on a single-site subset of the dataset (N = 185). By comparing two linear mixed-effects models, we determined that four trained human raters’ perception of quality was significantly influenced by defacing by modeling their ratings on the same set of images in two conditions: “nondefaced” (i.e., preserving facial features) and “defaced”. In addition, we investigated these biases on automated quality assessments by applying repeated-measures, multivariate ANOVA (rm-MANOVA) on the image quality metrics extracted with MRIQC on the full IXI dataset (N = 581; three acquisition sites). This study found that defacing altered the quality assessments by humans and showed that MRIQC’s quality metrics were mostly insensitive to defacing.

  • Glial cells diverge in fly brain evolution

    by Yaoyu Jiao, Trevor R. Sorrells

    How animal brains evolve to support ecological specialization is poorly understood. A recent PLOS Biology study reveals that glial cells show the most dramatic molecular and cellular changes in the brains of fruit flies adapted to a toxic niche, highlighting their underappreciated role in brain evolution. How animal brains evolve to support ecological specialization is poorly understood. This Primer explores a recent PLOS Biology study which reveals that glial cells show the most dramatic molecular and cellular changes in the brains of fruit flies adapted to a toxic niche, highlighting their underappreciated role in brain evolution.

  • Variant mutation G215C in SARS-CoV-2 nucleocapsid enhances viral infection via altered genomic encapsidation

    by Hannah C. Kubinski, Hannah W. Despres, Bryan A. Johnson, Madaline M. Schmidt, Sara A. Jaffrani, Allyson H. Turner, Conor D. Fanuele, Margaret G. Mills, Kumari G. Lokugamage, Caroline M. Dumas, David J. Shirley, Leah K. Estes, Andrew Pekosz, Jessica W. Crothers, Pavitra Roychoudhury, Alexander L. Greninger, Keith R. Jerome, Bruno Martorelli Di Genova, David H. Walker, Bryan A. Ballif, Mark S. Ladinsky, Pamela J. Bjorkman, Vineet D. Menachery, Emily A. Bruce

    The evolution of SARS-CoV-2 variants and their respective phenotypes represents an important set of tools to understand basic coronavirus biology as well as the public health implications of individual mutations in variants of concern. While mutations outside of spike are not well studied, the entire viral genome is undergoing evolutionary selection, with several variants containing mutations in the central disordered linker region of the nucleocapsid (N) protein. Here, we identify a mutation (G215C), characteristic of the Delta variant, that introduces a novel cysteine into this linker domain, which results in the formation of a more stable N-N dimer. Using reverse genetics, we determined that this cysteine residue is necessary and sufficient for stable dimer formation in a WA1 SARS-CoV-2 background, where it results in significantly increased viral growth both in vitro and in vivo. Mechanistically, we show that the N:G215C mutant has more encapsidation as measured by increased RNA binding to N, N incorporation into virions, and electron microscopy showing that individual virions are larger, with elongated morphologies.

  • Comparative single-cell transcriptomic atlases of drosophilid brains suggest glial evolution during ecological adaptation

    by Daehan Lee, Michael P. Shahandeh, Liliane Abuin, Richard Benton

    To explore how brains change upon species evolution, we generated single-cell transcriptomic atlases of the central brains of three closely related but ecologically distinct drosophilids: the generalists Drosophila melanogaster and Drosophila simulans, and the noni fruit specialist Drosophila sechellia. The global cellular composition of these species’ brains is well-conserved, but we predicted a few cell types with different frequencies, notably perineurial glia of the blood–brain barrier, which we validate in vivo. Gene expression analysis revealed that distinct cell types evolve at different rates and patterns, with glial populations exhibiting the greatest divergence between species. Compared to the D. melanogaster brain, cellular composition and gene expression patterns are more divergent in D. sechellia than in D. simulans—despite their similar phylogenetic distance from D. melanogaster—indicating that the specialization of D. sechellia is reflected in the structure and function of its brain. Expression changes in D. sechellia include several metabolic signaling genes, suggestive of adaptations to its novel source of nutrition. Additional single-cell transcriptomic analysis on D. sechellia revealed genes and cell types responsive to dietary supplement with noni, pointing to glia as sites for both physiological and genetic adaptation to this fruit. Our atlases represent the first comparative datasets for “whole” central brains and provide a comprehensive foundation for studying the evolvability of nervous systems in a well-defined phylogenetic and ecological framework.