SenNet recommendations for detecting senescent cells in different tissues.

Once considered a tissue culture-specific phenomenon, cellular senescence has now been linked to various biological processes with both beneficial and detrimental roles in humans, rodents and other species. Much of our understanding of senescent cell biology still originates from tissue culture studies, where each cell in the culture is driven to an irreversible cell cycle arrest. By contrast, in tissues, these cells are relatively rare and difficult to characterize, and it is now established that fully differentiated, postmitotic cells can also acquire a senescence phenotype. The SenNet Biomarkers Working Group was formed to provide recommendations for the use of cellular senescence markers to identify and characterize senescent cells in tissues. Here, we provide recommendations for detecting senescent cells in different tissues based on a comprehensive analysis of existing literature reporting senescence markers in 14 tissues in mice and humans. We discuss some of the recent advances in detecting and characterizing cellular senescence, including molecular senescence signatures and morphological features, and the use of circulating markers. We aim for this work to be a valuable resource for both seasoned investigators in senescence-related studies and newcomers to the field.

Organ Mapping Antibody Panels: a community resource for standardized multiplexed tissue imaging.

Multiplexed antibody-based imaging enables the detailed characterization of molecular and cellular organization in tissues. Advances in the field now allow high-parameter data collection (>60 targets); however, considerable expertise and capital are needed to construct the antibody panels employed by these methods. Organ mapping antibody panels are community-validated resources that save time and money, increase reproducibility, accelerate discovery and support the construction of a Human Reference Atlas.

Validation of an organ mapping antibody panel for cyclical immunofluorescence microscopy on normal human kidneys.

The lack of standardization in antibody validation remains a major contributor to irreproducibility of human research. To address this, we have applied a standardized approach to validate a panel of antibodies to identify 18 major cell types and 5 extracellular matrix compartments in the human kidney by immunofluorescence (IF) microscopy. We have used these to generate an organ mapping antibody panel for two-dimensional (2-D) and three-dimensional (3-D) cyclical IF (CyCIF) to provide a more detailed method for evaluating tissue segmentation and volumes using a larger panel of markers than would normally be possible using standard fluorescence microscopy. CyCIF also makes it possible to perform multiplexed IF microscopy of whole slide images, which is a distinct advantage over other multiplexed imaging technologies that are applicable to limited fields of view. This enables a broader view of cell distributions across larger anatomical regions, allowing a better chance to capture localized regions of dysfunction in diseased tissues. These methods are broadly accessible to any laboratory with a fluorescence microscope, enabling spatial cellular phenotyping in normal and disease states. We also provide a detailed solution for image alignment between CyCIF cycles that can be used by investigators to perform these studies without programming experience using open-sourced software. This ability to perform multiplexed imaging without specialized instrumentation or computational skills opens the door to integration with more highly dimensional molecular imaging modalities such as spatial transcriptomics and imaging mass spectrometry, enabling the discovery of molecular markers of specific cell types, and how these are altered in disease.NEW & NOTEWORTHY We describe here validation criteria used to define on organ mapping panel of antibodies that can be used to define 18 cell types and five extracellular matrix compartments using cyclical immunofluorescence (CyCIF) microscopy. As CyCIF does not require specialized instrumentation, and image registration required to assemble CyCIF images can be performed by any laboratory without specialized computational skills, this technology is accessible to any laboratory with access to a fluorescence microscope and digital scanner.

A modular framework for multiscale, multicellular, spatiotemporal modeling of acute primary viral infection and immune response in epithelial tissues and its application to drug therapy timing and effectiveness.

Simulations of tissue-specific effects of primary acute viral infections like COVID-19 are essential for understanding disease outcomes and optimizing therapies. Such simulations need to support continuous updating in response to rapid advances in understanding of infection mechanisms, and parallel development of components by multiple groups. We present an open-source platform for multiscale spatiotemporal simulation of an epithelial tissue, viral infection, cellular immune response and tissue damage, specifically designed to be modular and extensible to support continuous updating and parallel development. The base simulation of a simplified patch of epithelial tissue and immune response exhibits distinct patterns of infection dynamics from widespread infection, to recurrence, to clearance. Slower viral internalization and faster immune-cell recruitment slow infection and promote containment. Because antiviral drugs can have side effects and show reduced clinical effectiveness when given later during infection, we studied the effects on progression of treatment potency and time-of-first treatment after infection. In simulations, even a low potency therapy with a drug which reduces the replication rate of viral RNA greatly decreases the total tissue damage and virus burden when given near the beginning of infection. Many combinations of dosage and treatment time lead to stochastic outcomes, with some simulation replicas showing clearance or control (treatment success), while others show rapid infection of all epithelial cells (treatment failure). Thus, while a high potency therapy usually is less effective when given later, treatments at late times are occasionally effective. We illustrate how to extend the platform to model specific virus types (e.g., hepatitis C) and add additional cellular mechanisms (tissue recovery and variable cell susceptibility to infection), using our software modules and publicly-available software repository.

Synthesis of 9-Dechlorochrysophaentin A Enables Studies Revealing Bacterial Cell Wall Biosynthesis Inhibition Phenotype in B. subtilis.

Chrysophaentin A is an antimicrobial natural product isolated from the marine alga C. taylori in milligram quantity. Structurally, chrysophaentin A features a macrocyclic biaryl ether core incorporating two trisubstituted chloroalkenes at its periphery. A concise synthesis of iso- and 9-dechlorochrysophaentin A enabled by a Z-selective ring-closing metathesis (RCM) cyclization followed by an oxygen to carbon ring contraction is described. Fluorescent microscopy studies revealed 9-dechlorochrysophaentins leads to inhibition of bacterial cell wall biosynthesis by disassembly of key divisome proteins, the cornerstone to bacterial cell wall biosynthesis and division.

Phosphate flow between hybrid histidine kinases CheA3 and CheS3 controls Rhodospirillum centenum cyst formation.

Genomic and genetic analyses have demonstrated that many species contain multiple chemotaxis-like signal transduction cascades that likely control processes other than chemotaxis. The Che3 signal transduction cascade from Rhodospirillum centenum is one such example that regulates development of dormant cysts. This Che-like cascade contains two hybrid response regulator-histidine kinases, CheA3 and CheS3, and a single-domain response regulator CheY3. We demonstrate that cheS3 is epistatic to cheA3 and that only CheS3∼P can phosphorylate CheY3. We further show that CheA3 derepresses cyst formation by phosphorylating a CheS3 receiver domain. These results demonstrate that the flow of phosphate as defined by the paradigm E. coli chemotaxis cascade does not necessarily hold true for non-chemotactic Che-like signal transduction cascades.

Surface contact stimulates the just-in-time deployment of bacterial adhesins.

The attachment of bacteria to surfaces provides advantages such as increasing nutrient access and resistance to environmental stress. Attachment begins with a reversible phase, often mediated by surface structures such as flagella and pili, followed by a transition to irreversible attachment, typically mediated by polysaccharides. Here we show that the interplay between pili and flagellum rotation stimulates the rapid transition between reversible and polysaccharide-mediated irreversible attachment. We found that reversible attachment of Caulobacter crescentus cells is mediated by motile cells bearing pili and that their contact with a surface results in the rapid pili-dependent arrest of flagellum rotation and concurrent stimulation of polar holdfast adhesive polysaccharide. Similar stimulation of polar adhesin production by surface contact occurs in Asticcacaulis biprosthecum and Agrobacterium tumefaciens. Therefore, single bacterial cells respond to their initial contact with surfaces by triggering just-in-time adhesin production. This mechanism restricts stable attachment to intimate surface interactions, thereby maximizing surface attachment, discouraging non-productive self-adherence, and preventing curing of the adhesive.

The scaffolding and signalling functions of a localization factor impact polar development.

In the differentiating alphaproteobacterium Caulobacter crescentus, organelle synthesis at cell poles is critical to forming different progeny after cell division. Co-ordination of polar organelle synthesis, including pili and holdfast, and flagellum ejection, is mediated in part by the scaffolding protein PodJ. At the time of cell division, PodJ undergoes regulated processing to a short form that persists at the flagellar pole of swarmer cells. This study analyses how PodJ's role in structural and signalling protein localization impacts organelle synthesis. A PodJ mutant with an internal deletion exhibits reduced sensitivity to pili-tropic phage ΦCbK, resulting from reduced pilA gene expression, which can be linked to altered signalling protein localization. The phage sensitivity defect of a ΔpodJ mutant can be partially suppressed by ectopic pilA expression. Induction of PodJ processing, by manipulation of podJ itself or controlled perP expression, resulted in decreased pilus biogenesis and, when coupled with a podJ mutation that reduced pilA expression, led to complete loss of phage sensitivity. As a whole, the results show that PodJ's scaffolding role for structural and signalling proteins both contribute to flagellar pole organelle development.

Anatomical structures, cell types, and biomarkers of the healthy human blood vasculature.

More than 150 scientists from 17 consortia are collaborating on an international project to build a Human Reference Atlas, which maps all 37 trillion cells in the healthy adult human body. The initial release of this atlas provided hierarchical lists of the anatomical structures, cell types, and biomarkers in 11 organs. Here, we describe the methods we used as part of this initiative to build the first open, computer-readable, and comprehensive database of the adult human blood vasculature, called the Human Reference Atlas-Vasculature Common Coordinate Framework (HRA-VCCF). It includes 993 vessels and their branching connections, 10 cell types, and 10 biomarkers. With this paper we are releasing additional details on vessel types and subtypes, branching sequence, anastomoses, portal systems, microvasculature, functional tissue units, mappings to regions vessels supply or drain, geometric properties of vessels, and links to 3D reference objects. Future versions will add variants and connections to the lymph vasculature; and, it will iteratively expand and improve the database as additional experimental data become available through the participating consortia.

Segmentation of human functional tissue units in support of a Human Reference Atlas.

The Human BioMolecular Atlas Program (HuBMAP) aims to compile a Human Reference Atlas (HRA) for the healthy adult body at the cellular level. Functional tissue units (FTUs), relevant for HRA construction, are of pathobiological significance. Manual segmentation of FTUs does not scale; highly accurate and performant, open-source machine-learning algorithms are needed. We designed and hosted a Kaggle competition that focused on development of such algorithms and 1200 teams from 60 countries participated. We present the competition outcomes and an expanded analysis of the winning algorithms on additional kidney and colon tissue data, and conduct a pilot study to understand spatial location and density of FTUs across the kidney. The top algorithm from the competition, Tom, outperforms other algorithms in the expanded study, while using fewer computational resources. Tom was added to the HuBMAP infrastructure to run kidney FTU segmentation at scale-showcasing the value of Kaggle competitions for advancing research.

Specimen, biological structure, and spatial ontologies in support of a Human Reference Atlas.

The Human Reference Atlas (HRA) is defined as a comprehensive, three-dimensional (3D) atlas of all the cells in the healthy human body. It is compiled by an international team of experts who develop standard terminologies that they link to 3D reference objects, describing anatomical structures. The third HRA release (v1.2) covers spatial reference data and ontology annotations for 26 organs. Experts access the HRA annotations via spreadsheets and view reference object models in 3D editing tools. This paper introduces the Common Coordinate Framework (CCF) Ontology v2.0.1 that interlinks specimen, biological structure, and spatial data, together with the CCF API that makes the HRA programmatically accessible and interoperable with Linked Open Data (LOD). We detail how real-world user needs and experimental data guide CCF Ontology design and implementation, present CCF Ontology classes and properties together with exemplary usage, and report on validation methods. The CCF Ontology graph database and API are used in the HuBMAP portal, HRA Organ Gallery, and other applications that support data queries across multiple, heterogeneous sources.

Mapping the lymphatic system across body scales and expertise domains: A report from the 2021 National Heart, Lung, and Blood Institute workshop at the Boston Lymphatic Symposium.

Enhancing our understanding of lymphatic anatomy from the microscopic to the anatomical scale is essential to discern how the structure and function of the lymphatic system interacts with different tissues and organs within the body and contributes to health and disease. The knowledge of molecular aspects of the lymphatic network is fundamental to understand the mechanisms of disease progression and prevention. Recent advances in mapping components of the lymphatic system using state of the art single cell technologies, the identification of novel biomarkers, new clinical imaging efforts, and computational tools which attempt to identify connections between these diverse technologies hold the potential to catalyze new strategies to address lymphatic diseases such as lymphedema and lipedema. This manuscript summarizes current knowledge of the lymphatic system and identifies prevailing challenges and opportunities to advance the field of lymphatic research as discussed by the experts in the workshop.

Tissue registration and exploration user interfaces in support of a human reference atlas.

Seventeen international consortia are collaborating on a human reference atlas (HRA), a comprehensive, high-resolution, three-dimensional atlas of all the cells in the healthy human body. Laboratories around the world are collecting tissue specimens from donors varying in sex, age, ethnicity, and body mass index. However, harmonizing tissue data across 25 organs and more than 15 bulk and spatial single-cell assay types poses challenges. Here, we present software tools and user interfaces developed to spatially and semantically annotate ("register") and explore the tissue data and the evolving HRA. A key part of these tools is a common coordinate framework, providing standard terminologies and data structures for describing specimen, biological structure, and spatial data linked to existing ontologies. As of April 22, 2022, the "registration" user interface has been used to harmonize and publish data on 5,909 tissue blocks collected by the Human Biomolecular Atlas Program (HuBMAP), the Stimulating Peripheral Activity to Relieve Conditions program (SPARC), the Human Cell Atlas (HCA), the Kidney Precision Medicine Project (KPMP), and the Genotype Tissue Expression project (GTEx). Further, 5,856 tissue sections were derived from 506 HuBMAP tissue blocks. The second "exploration" user interface enables consortia to evaluate data quality, explore tissue data spatially within the context of the HRA, and guide data acquisition. A companion website is at https://cns-iu.github.io/HRA-supporting-information/ .

Anatomical structures, cell types and biomarkers of the Human Reference Atlas.

The Human Reference Atlas (HRA) aims to map all of the cells of the human body to advance biomedical research and clinical practice. This Perspective presents collaborative work by members of 16 international consortia on two essential and interlinked parts of the HRA: (1) three-dimensional representations of anatomy that are linked to (2) tables that name and interlink major anatomical structures, cell types, plus biomarkers (ASCT+B). We discuss four examples that demonstrate the practical utility of the HRA.

A modular framework for multiscale, multicellular, spatiotemporal modeling of acute primary viral infection and immune response in epithelial tissues and its application to drug therapy timing and effectiveness: A multiscale model of viral infection in epithelial tissues.

Simulations of tissue-specific effects of primary acute viral infections like COVID-19 are essential for understanding disease outcomes and optimizing therapies. Such simulations need to support continuous updating in response to rapid advances in understanding of infection mechanisms, and parallel development of components by multiple groups. We present an open-source platform for multiscale spatiotemporal simulation of an epithelial tissue, viral infection, cellular immune response and tissue damage, specifically designed to be modular and extensible to support continuous updating and parallel development. The base simulation of a simplified patch of epithelial tissue and immune response exhibits distinct patterns of infection dynamics from widespread infection, to recurrence, to clearance. Slower viral internalization and faster immune-cell recruitment slow infection and promote containment. Because antiviral drugs can have side effects and show reduced clinical effectiveness when given later during infection, we studied the effects on progression of treatment potency and time-of-first treatment after infection. In simulations, even a low potency therapy with a drug which reduces the replication rate of viral RNA greatly decreases the total tissue damage and virus burden when given near the beginning of infection. Many combinations of dosage and treatment time lead to stochastic outcomes, with some simulation replicas showing clearance or control (treatment success), while others show rapid infection of all epithelial cells (treatment failure). Thus, while a high potency therapy usually is less effective when given later, treatments at late times are occasionally effective. We illustrate how to extend the platform to model specific virus types (e.g., hepatitis C) and add additional cellular mechanisms (tissue recovery and variable cell susceptibility to infection), using our software modules and publicly-available software repository.

Cell cycle timing and developmental checkpoints in Caulobacter crescentus.

Development in Caulobacter reflects a level of complexity once thought only to exist in eukaryotic cells. The cell cycle and development are not isolated from each other, but are interdependent processes. Checkpoints are in place to ensure that both cell cycle and developmental processes are completed accurately before the next stage is initiated. The timing of these processes is regulated by signal transduction networks that integrate signals from DNA replication, cell division and development. These signal transduction networks achieve precise timing of the cell cycle and development by regulating temporal gene expression, and protein activity by dynamic spatial localization within the cell and timed proteolysis.

MicrobeJ, a tool for high throughput bacterial cell detection and quantitative analysis.

Single-cell analysis of bacteria and subcellular protein localization dynamics has shown that bacteria have elaborate life cycles, cytoskeletal protein networks and complex signal transduction pathways driven by localized proteins. The volume of multidimensional images generated in such experiments and the computation time required to detect, associate and track cells and subcellular features pose considerable challenges, especially for high-throughput experiments. There is therefore a need for a versatile, computationally efficient image analysis tool capable of extracting the desired relationships from images in a meaningful and unbiased way. Here, we present MicrobeJ, a plug-in for the open-source platform ImageJ(1). MicrobeJ provides a comprehensive framework to process images derived from a wide variety of microscopy experiments with special emphasis on large image sets. It performs the most common intensity and morphology measurements as well as customized detection of poles, septa, fluorescent foci and organelles, determines their subcellular localization with subpixel resolution, and tracks them over time. Because a dynamic link is maintained between the images, measurements and all data representations derived from them, the editor and suite of advanced data presentation tools facilitates the image analysis process and provides a robust way to verify the accuracy and veracity of the data.

Mutations in DivL and CckA rescue a divJ null mutant of Caulobacter crescentus by reducing the activity of CtrA.

Polar development and cell division in Caulobacter crescentus are controlled and coordinated by multiple signal transduction proteins. divJ encodes a histidine kinase. A null mutation in divJ results in a reduced growth rate, cell filamentation, and mislocalized stalks. Suppressor analysis of divJ identified mutations in genes encoding the tyrosine kinase (divL) and the histidine kinase (cckA). The divL and cckA suppressor alleles all have single amino acid substitutions, some of which confer a temperature-sensitive phenotype, particularly in a wild-type background. Analysis of transcription levels from several positively regulated CtrA-dependent promoters reveals high expression in the divJ mutant, suggesting that DivJ normally serves to reduce CtrA activity. The divL and cckA suppressors reduce the amount of transcription from promoters positively regulated by CtrA, indicating that the mutations in divL and cckA are suppressing the defects of the divJ mutant by reducing the abnormally high level of CtrA activity. Immunoblotting showed no major perturbations in the CtrA protein level in any of these strains, suggesting that the high amount of CtrA activity seen in the divJ mutant and the reduced amount of activity in the suppressors are regulated at the level of activation and not transcription, translation, or degradation. In vivo phosphorylation assays confirmed that divJ mutants have elevated levels of CtrA phosphorylation and that this level is reduced in the suppressors with mutations in divL.

DNA replication initiation is required for mid-cell positioning of FtsZ rings in Caulobacter crescentus.

Polymerization of the GTPase FtsZ to form a structure called the Z-ring is the earliest known step in bacterial cell division. Mid-cell Z-ring assembly coincides with the beginning of the replication cycle in the differentiating bacterium Caulobacter crescentus. Z-ring disassembly occurs at the end of the division cycle, resulting in the complete degradation of FtsZ from both stalked and swarmer progeny cells. New Z-rings can only form in the replicative stalked cell. Conditional mutants in DNA replication were used to determine what role DNA replication events play in the process of Z-ring assembly at different stages in the cell cycle. Z-ring assembly occurred even when early stages of DNA replication were blocked; however, the Z-rings were localized at a subpolar region of the cell. Z-rings only assembled at the proper mid-cell location if DNA replication had initiated. Z-ring assembly coincided with areas containing little or no DNA, and Z-rings could not form over an unreplicated chromosome. Overexpressed FtsZ in the absence of DNA replication did not stimulate productive mid-cell Z-ring assembly but, instead, caused the ends of cells to constrict over an extended area away from the nucleoid. These results indicate that the state of chromosome replication is a major determinant of Z-ring localization in Caulobacter.

Proteomic analysis of the Caulobacter crescentus stalk indicates competence for nutrient uptake.

Caulobacter crescentus, a Gram-negative alpha-purple proteobacterium, is an oligotroph that lives in aquatic environments dilute in nutrients. This bacterium divides asymmetrically. Part of this asymmetric cell division involves the formation of a prosthecum at one pole, referred to as the stalk, which replaces the flagellum of the motile swarmer cell. Little is known about the synthesis or function of the stalk. The stalk is an extension of the cell membranes and peptidoglycan layer, and stalk elongation is stimulated by phosphate starvation. In this study, we have taken advantage of two-dimensional gel (2D gel) electro-phoresis as well as the fully sequenced genome of Caulobacter to study the proteome of the stalk. We modified a stalk-shedding mutant strain of Caulobacter crescentus to increase the yield of stalk material shed and performed 2D gel electrophoresis of purified stalks and cellular fractions. Comparison of the stalk 2D gel with the 2D gels of cell membrane and soluble fractions showed that the stalk is mostly free of cytoplasmic proteins and has a profile very similar to that of the cell membrane. Of the 172 proteins on a stalk 2D gel, we report the identification of 64 spots, corresponding to 39 different proteins present in the stalk of Caulobacter. The identifications include several TonB-dependent receptors, two OmpA family proteins, a dipeptidase, GlpQ, two alkaline phosphatases, 3-phytase, a putative TolC protein and 11 proteins of unknown function. These identifications are consistent with the hypothesis that the stalk plays a role in nutrient uptake.