bluuebunny/crossref_metadata_2025_split huggingface dataset:
SARS-CoV-2 Spike N-Terminal Domain modulates TMPRSS2-dependent viral entry and fusogenicity
Authors: Meng Bo , Datir Rawlings , Choi Jinwook ,   CITIID-NIHR BioResource COVID-19 Collaboration, Bradley John , Smith Kenneth GC , Lee Joo Hyeon , Gupta Ravindra K. 
Published: May 2022

AbstractOver 20 mutations have been identified in the N-Terminal Domain (NTD) of SARS-CoV-2 spike and yet few of them are fully characterised. Here we first examined the contribution of the NTD to infection and cell-cell fusion by constructing different VOC-based chimeric spikes bearing B.1617 lineage (Delta and Kappa variants) NTDs and generating spike pseudotyped lentivirus (PV). We found the Delta NTD on a Kappa or WT background increased spike S1/S2 cleavage efficiency and virus entry, specifically in Calu-3 lung cells and airway organoids, through use of TMPRSS2. We have previously shown Delta spike confers rapid cell-cell fusion kinetics; here we show that increased fusogenicity can be conferred to WT and Kappa variant spikes by transfer of the Delta NTD. Moving to contemporary variants, we found that BA.2 had higher entry efficiency in a range of cell types as compared to BA.1. BA.2 showed higher fusogenic activity than BA.1, but the BA.2 NTD could not confer higher fusion to BA.1 spike. There was low efficiency of TMPRSS2 usage by both BA.1 and BA.2, and chimeras of Omicron BA.1 and BA.2 spikes with a Delta NTD did not result in more efficient use of TMRPSS2 or cell-cell fusogenicity. We conclude that the NTD allosterically modulates S1/S2 cleavage and spike-mediated functions such as entry and cell-cell fusion in a spike context dependent manner, and allosteric interactions may be lost when combining regions from more distantly related spike proteins. These data may explain the lack of successful SARS-CoV-2 inter-variant recombinants bearing breakpoints within spike.
A detailed landscape of genomic alterations in malignant peripheral nerve sheath tumor cell lines challenges the current MPNST diagnosis
Authors: Magallon-Lorenz Miriam , Terribas Ernest , Fernández Marco , Requena Gerard , Rosas Inma , Mazuelas Helena , Uriarte Itziar , Negro Alex , Castellanos Elisabeth , Blanco Ignacio , DeVries George , Kawashima Hiroyuki , Legius Eric , Brems Hilde , Mautner Viktor , Kluwe Lan , Ratner Nancy , Wallace Margaret , Rodriguez Juana Fernández , Lázaro Conxi , Fletcher Jonathan A , Reuss David , Carrió Meritxell , Gel Bernat , Serra Eduard 
Published: May 2022

AbstractBackgroundMalignant peripheral nerve sheath tumors (MPNSTs) are soft tissue sarcomas that arise from the peripheral nervous system. Half of the tumors develop in the context of the genetic disease Neurofibromatosis type 1 (NF1) and the rest are sporadic sarcomas. MPNSTs have a dismal prognosis due to their aggressiveness and tendency to metastasize, and new treatment options are needed. The diagnosis of MPNSTs can be challenging, especially outside of the NF1 context since specific histological criteria have not been completely established. Genomic analysis may both facilitate differential diagnoses and suggest precision medicine strategies.MethodsWe generated a complete genomic resource of a set of widely used human NF1-related and sporadic MPNST cell lines by applying ploidy analysis, whole genome and whole exome sequencing and SNP-array analysis, complemented by methylome-based classification and immunofluorescence of cell identity markers (SOX9, SOX10, S100B).ResultsNF1 MPNST cell lines faithfully recapitulated the genomic copy number profile of primary MPNSTs. Structural variants were key players in the complete inactivation of most recurrently altered tumor suppressor genes (TSGs) (NF1, CDKN2A, SUZ12/EED), while small variants played a minor role in the NF1 context, both concerning TSG inactivation and due to the absence of gain-of-function mutations. In clear contrast, the sporadic cell lines (STS-26T, HS-Sch-2, HS-PSS) did not recapitulate the copy number profile of primary MPNSTs. They carried different TSG inactivation and exhibited gain-of-function mutations by predicted kinase activation or generation of fusion genes. Mutational frequencies and signatures emerged as promising informative tools for aiding in MPNST differential diagnosis. Due to the multiple genomic differences exhibited, we complemented their characterization using a methylome-based classifier. All NF1-related cell lines were assigned within the MPNST group, while sporadic cell lines clustered either with melanomas or with an uncertain MPNST-like sarcoma group. The staining of cell identity markers reinforced the idea of a potential misdiagnose of the MPNSTs used to derive the sporadic cell lines analyzed.ConclusionsDeep genomic analysis, together with methylome-based sarcoma classification and cell identity marker analysis, challenged the MPNST identity of sporadic cell lines. Results presented here open an opportunity to revise MPNST differential diagnosis and classification.
Herpes simplex virus 1 entry glycoproteins form stable complexes prior to and during membrane fusion
Authors: Pataki Zemplen , Viveros Andrea Rebolledo , Heldwein Ekaterina E. 
Published: May 2022

ABSTRACTHerpesviruses – ubiquitous pathogens that cause persistent infections – have some of the most complex cell entry mechanisms. Entry of the prototypical herpes simplex virus 1 (HSV-1) requires coordinated efforts of 4 glycoproteins, gB, gD, gH, and gL. The current model posits that the glycoproteins do not interact prior to receptor engagement and that binding of gD to its receptor causes a “cascade” of sequential pairwise interactions, first activating the gH/gL complex and subsequently activating gB, the viral fusogen. But how these glycoproteins interact remains unresolved. Here, using a quantitative split-luciferase approach, we show that pairwise HSV-1 glycoprotein complexes form prior to fusion, remain stable throughout fusion, and do not depend on the presence of the cellular receptor. Based on our findings, we propose a revised “conformational cascade” model of HSV-1 entry. We hypothesize that all 4 glycoproteins assemble into a complex prior to fusion, with gH/gL positioned between gD and gB. Once gD binds to a cognate receptor, the proximity of the glycoproteins within this complex allows for efficient transmission of the activating signal from the receptor-activated gD to gH/gL to gB through sequential conformational changes, ultimately triggering the fusogenic refolding of gB. Our results also highlight previously unappreciated contributions of the transmembrane and cytoplasmic domains to glycoprotein interactions and fusion. Similar principles could be at play in other multicomponent viral entry systems, and the split luciferase approach used here is a powerful tool for investigating protein-protein interactions in these and a variety of other systems.IMPORTANCEHerpes simplex virus 1 (HSV-1) infects the majority of humans for life and can cause diseases ranging from painful sores to deadly brain inflammation. No vaccines or curative treatments currently exist. HSV-1 infection of target cells requires coordinated efforts of four viral glycoproteins. But how these glycoproteins interact remains unclear. Using a quantitative protein interaction assay, we found that HSV-1 glycoproteins form stable, receptor-independent complexes. We propose that the 4 proteins form a complex, which could facilitate transmission of the entry-triggering signal from the receptor-binding component to the membrane fusogen component through sequential conformational changes. Similar principles could be applicable across other multicomponent protein systems. A revised model of HSV-1 entry could facilitate the development of therapeutics targeting this process.
Analysis of CheW-like domains provides insights into organization of prokaryotic chemotaxis systems
Authors: Vass Luke R. , Bourret Robert B. , Foster Clay A. 
Published: May 2022

ABSTRACTThe ability to control locomotion in a dynamic environment provides a competitive advantage for microorganisms, thus driving the evolution of sophisticated regulatory systems. Nineteen known categories of chemotaxis systems control motility mediated by flagella or Type IV pili, plus other cellular functions. A key feature that distinguishes chemotaxis systems from generic two-component regulatory systems is separation of receptor and kinase functions into distinct proteins, linked by CheW scaffold proteins. This arrangement allows for formation of varied arrays with remarkable signaling properties. We recently analyzed sequences of CheW-like domains found in CheA kinases and CheW and CheV scaffold proteins. Sixteen Architectures of CheA, CheW, and CheV proteins contain ∼94% of all CheW-like domains and form six Classes with likely functional specializations.We surveyed chemotaxis system categories and proteins containing CheW-like domains in ∼1900 prokaryotic species, the most comprehensive analysis to date, revealing new insights. Co-occurrence analyses suggested that many chemotaxis systems occur in non-random combinations within species, implying synergy or antagonism. Furthermore, many Architectures of proteins containing CheW-like domains occurred predominantly with specific categories of chemotaxis systems, suggesting specialized functional interactions. We propose Class 1 (∼80%) and Class 2 (∼20%) CheW proteins exhibit preferences for distinct chemoreceptor structures. Furthermore, rare (∼1%) Class 6 CheW proteins frequently co-occurred with methyl-accepting coiled coil (MAC) proteins, which contain both receptor and kinase functions and so do not require connection via a CheW scaffold but may benefit from arrays. Lastly, rare multi-domain CheW proteins may interact with different receptors than single domain CheW proteins.
Dynamic HIV-1 spike motion creates vulnerability for its membrane-bound tripod to antibody attack
Authors: Yang Shuang , Hiotis Giorgos , Wang Yi , Chen Junjian , Wang Jia-huai , Kim Mikyung , Reinherz Ellis L. , Walz Thomas 
Published: May 2022

ABSTRACTVaccines targeting HIV-1’s gp160 spike protein are stymied by high viral mutation rates and structural chicanery. gp160’s membrane-proximal external region (MPER) is the target of naturally arising broadly neutralizing antibodies (bnAbs), yet MPER-based vaccines fail to generate bnAbs. Here, nanodisc-embedded spike protein was investigated by cryo-electron microscopy and molecular-dynamics simulations, revealing spontaneous ectodomain tilting that creates vulnerability for HIV-1. While each MPER protomer radiates centrally towards the three-fold axis contributing to a membrane-associated tripod structure that is occluded in the upright spike, tilting provides access to the opposing MPER. Structures of spike proteins with bound 4E10 bnAb Fabs reveal that the antibody binds exposed MPER, thereby altering MPER dynamics, modifying average ectodomain tilt, and imposing strain on the viral membrane and the spike’s transmembrane segments, resulting in the abrogation of membrane fusion and informing future vaccine development.
Activated interstitial macrophages are a predominant target of viral takeover and focus of inflammation in COVID-19 initiation in human lung
Authors: Wu Timothy Ting-Hsuan , Travaglini Kyle J. , Rustagi Arjun , Xu Duo , Zhang Yue , Andronov Leonid , Jang SoRi , Gillich Astrid , Dehghannasiri Roozbeh , Martínez-Colón Giovanny , Beck Aimee , Liu Daniel Dan , Wilk Aaron J. , Morri Maurizio , Trope Winston L. , Bierman Rob , Weissman Irving L. , Shrager Joseph B. , Quake Stephen R. , Kuo Christin S. , Salzman Julia , Moerner W. E. , Kim Peter S. , Blish Catherine A. , Krasnow Mark A. 
Published: May 2022

ABSTRACTEarly stages of deadly respiratory diseases such as COVID-19 have been challenging to elucidate due to lack of an experimental system that recapitulates the cellular and structural complexity of the human lung while allowing precise control over disease initiation and systematic interrogation of molecular events at cellular resolution. Here we show healthy human lung slices culturedex vivocan be productively infected with SARS-CoV-2, and the cellular tropism of the virus and its distinct and dynamic effects on host cell gene expression can be determined by single cell RNA sequencing and reconstruction of “infection pseudotime” for individual lung cell types. This revealed that the prominent SARS-CoV-2 target is a population of activated interstitial macrophages (IMs), which as infection proceeds accumulate thousands of viral RNA molecules per cell, comprising up to 60% of the cellular transcriptome and including canonical and novel subgenomic RNAs. During viral takeover of IMs, there is cell-autonomous induction of a pro-fibrotic program (TGFB1,SPP1), and an inflammatory program characterized by the early interferon response, chemokines (CCL2, 7,8,13, CXCL10) and cytokines (IL6, IL10), along with destruction of cellular architecture and formation of dense viral genomic RNA bodies revealed by super-resolution microscopy. In contrast, alveolar macrophages (AMs) showed neither viral takeover nor induction of a substantial inflammatory response, although both purified AMs and IMs supported production of infectious virions. Spike-dependent viral entry into AMs was neutralized by blockade of ACE2 or Sialoadhesin/CD169, whereas IM entry was neutralized only by DC-SIGN/CD209 blockade. These results provide a molecular characterization of the initiation of COVID-19 in human lung tissue, identify activated IMs as a prominent site of viral takeover and focus of inflammation and fibrosis, and suggest therapeutic targeting of the DC-SIGN/CD209 entry mechanism to prevent IM infection, destruction and early pathology in COVID-19 pneumonia. Our approach can be generalized to define the initiation program and evaluate therapeutics for any human lung infection at cellular resolution.
Histone modifications and DNA methylation act cooperatively in regulating symbiosis genes in the sea anemone Aiptasia
Authors: Nawaz Kashif , Cziesielski Maha J. , Mariappan Kiruthiga G. , Cui Guoxin , Aranda Manuel 
Published: May 2022

AbstractThe symbiotic relationship between cnidarians and dinoflagellates is one of the most widespread endosymbiosis in our oceans and provides the ecological basis of coral-reef ecosystems. Although many studies have been undertaken to unravel the molecular mechanisms underlying these symbioses, we still know little about the epigenetic mechanisms that control the transcriptional responses to symbiosis. Here, we used the model organism Exaiptasia diaphana to study the genome-wide patterns and putative functions of the histone modifications H3K27ac, H3K4me3, H3K9ac, H3K36me3 and H3K27me3 in symbiosis. While we find that their functions are generally conserved, we observed that colocalization of more than one modification and or DNA methylation correlated with significantly higher gene expression, suggesting a cooperative action of histone modifications and DNA methylation in promoting gene expression. Analysis of symbiosis genes revealed that activating histone modifications predominantly associated with symbiosis induced genes involved in glucose metabolism, nitrogen transport, amino acid biosynthesis and organism growth while symbiosis suppressed genes were involved in catabolic processes. Our results provide new insights into the mechanisms of prominent histone modifications and their interaction with DNA methylation in regulating symbiosis in cnidarians.
Simultaneous isolation of proximal and distal lung progenitor cells from individual mice using a 3D printed guide reduces proximal cell contamination of distal lung epithelial cell isolations
Authors: Alsafadi Hani N. , Stegmayr John , Ptasinski Victoria , Silva Iran , Mittendorfer Margareta , Murray Lynne , Wagner Darcy E. 
Published: May 2022

SummaryThe respiratory epithelium consists of multiple, functionally distinct cell-types and is maintained by regionally-specific progenitor populations which repair the epithelium following injury. Several in vitro methods exist for studying lung epithelial repair using primary murine lung epithelial cells, but isolation methods are hampered by a lack of surface markers distinguishing epithelial progenitors along the respiratory epithelium. Here, we developed a 3D-printed lobe divider (3DLD) to aid in simultaneous isolation of proximal versus distal lung epithelial progenitors from individual mice which give rise to differentiated epithelia in multiple in vitro assays. In contrast to 3DLD-isolated distal progenitor cells, classic manual tracheal ligation methods followed by lobe removal resulted in co-isolation of rare proximal progenitors with distal cells which altered the transcriptional landscape of distal organoid cultures. Thus, cell isolation with the 3DLD generates reproducible distal versus proximal progenitor populations and minimizes the potential for contaminating populations to confound in vitro assays.Highlights3DLD reproducibly separates lung lobes and extrapulmonary airways (bronchi/trachea)3DLD cell isolation yields consistent isolation of distal epithelial cells (DECs)Contamination of proximal cells in classic DEC isolations may alter in vitro results3DLD allows for simultaneous isolation of proximal and DECs from single animalseTOC blurbAlsafadi et al. describes a new method for simultaneous isolation of lung epithelial proximal and distal progenitors using the aid of a 3D printed device (3DLD). Both isolated cell types differentiate in multiple in vitro assays. The 3DLD guide minimized contamination of proximal cells in distal cell isolations whose presence can alter the transcriptional landscape of distal epithelial organoids.
Coupled organoids reveal that signaling gradients drive traveling segmentation clock waves during human axial morphogenesis
Authors: Yaman Yusuf Ilker , Huang Roya , Ramanathan Sharad 
Published: May 2022

SummaryAxial development of mammals is a dynamic process involving several coordinated morphogenetic events including axial elongation, somitogenesis, and neural tube formation. How different signals control the dynamics of human axial morphogenesis remains largely unknown. By inducing anteroposterior symmetry breaking of spatially coupled epithelial cysts derived from human pluripotent stem cells, we were able to generate hundreds of axially elongating organoids. Each organoid was composed of a neural tube flanked by presomitic mesoderm that was sequentially segmented into somites. Periodic activation of the somite differentiation gene MESP2 coincided in space and time with anteriorly traveling segmentation clock waves in the presomitic mesoderm of the organoids, recapitulating key aspects of somitogenesis. Through timed perturbations of organoids, we demonstrated that FGF and WNT signaling play distinct roles in axial elongation and somitogenesis, and that the segmentation clock waves are driven by FGF signaling gradients. By generating and perturbing organoids that robustly recapitulate the architecture and dynamics of multiple axial tissues in human embryos, this work offers a means to dissect complex mechanisms underlying human embryogenesis.
Cooperative RNA degradation stabilizes intermediate epithelial-mesenchymal states and supports a phenotypic continuum
Authors: Nordick Benjamin , Park Mary Chae-Yeon , Quaranta Vito , Hong Tian 
Published: May 2022

AbstractEpithelial-mesenchymal transition (EMT) is a change in cell shape and mobility that occurs during normal development or cancer metastasis. Multiple intermediate EMT states reflecting hybrid epithelial and mesenchymal phenotypes were observed in various physiological and pathological conditions. Previous theoretical models explaining the intermediate EMT states rely on multiple regulatory loops involving transcriptional feedback. These models produce three or four attractors with a given set of rate constants, which is incompatible with experimentally observed non-genetic heterogeneity reflecting a continuum-like EMT spectrum. EMT is regulated by many microRNAs that typically bind transcripts of EMT-related genes via multiple binding sites. It was unclear whether post-transcriptional regulations associated with the microRNA binding sites alone can stabilize intermediate EMT states. Here, we used models describing the post-transcriptional regulations with elementary reaction networks, finding that cooperative RNA degradation via multiple microRNA binding sites can generate four-attractor systems without transcriptional feedback. We identified many specific, experimentally supported instances of network structures predicted to permit intermediate EMT states. Furthermore, transcriptional feedback and the newly identified intermediates-enabling circuits can be combined to produce even more intermediate EMT states in both modular and emergent manners. Finally, multisite-mediated cooperative RNA degradation can increase the distribution of gene expression in the EMT spectrum and support the phenotypic continuum without the need of higher noise. Our work reveals a previously unknown role of cooperative RNA degradation and microRNA in EMT, providing a theoretical framework that can help to bridge the gap between mechanistic models and single-cell experiments.
Identification of cancer drivers from tumor-only RNA-seq with RNA-VACAY
Authors: Akutagawa Jon , Mak Allysia J , Aspden Julie L , Brooks Angela N 
Published: May 2022

AbstractDetecting somatic mutations is a cornerstone of cancer genomics and clinical genotyping; however, there has been little systematic evaluation of the utility of RNA sequencing (RNA-seq) for somatic variant detection and driver mutation analysis. Variants found in RNA-Seq are also expressed, reducing the identification of passenger mutations and would not suffer from annotation bias observed in whole-exome sequencing (WES). We developed RNA-VACAY, a containerized pipeline that automates somatic variant calling from tumor RNA-seq data, alone, and evaluated its performance on simulated data and 1,349 RNA-seq samples with matched whole-genome sequencing (WGS). RNA-VACAY was able to detect at least 1 putative driver gene in 15 out of 16 cancer types and identified known driver mutations in 5’ and 3’ UTRs. The computational cost and time to generate and analyze RNA-seq data is lower than WGS or WES, which decreases the resources necessary for somatic variant detection. This study demonstrates the utility of RNA-seq to detect cancer drivers.