Rec8 cohesin-mediated axis-loop chromatin architecture is required for meiotic recombination During meiotic prophase, cohesin-dependent axial structures are formed in the synaptonemal complex (SC). However, the functional correlation between these structures and cohesion remains elusive. Here, we examined the formation of cohesin-dependent axial structures in the fission yeast Schizosaccharomyces pombe. This organism forms atypical SCs composed of linear elements (LinEs) resembling the lateral elements of SC but lacking the transverse filaments. Hi-C analysis using a highly synchronous population of meiotic S. pombe cells revealed that the axis-loop chromatin structure formed in meiotic prophase was dependent on the Rec8 cohesin complex. In contrast, the Rec8-mediated formation of the axis-loop structure occurred in cells lacking components of LinEs. To dissect the functions of Rec8, we identified a rec8-F204S mutant that lost the ability to assemble the axis-loop structure without losing cohesion of sister chromatids. This mutant showed defects in the formation of the axis-loop structure and LinE assembly and thus exhibited reduced meiotic recombination. Collectively, our results demonstrate that the Rec8-dependent axis-loop structure provides a structural platform essential for LinE assembly, facilitating meiotic recombination of homologous chromosomes, independently of its role in sister chromatid cohesion.
Pak1 and PP2A antagonize aPKC function to support cortical tension induced by the Crumbs-Yurt complex The Drosophila polarity protein Crumbs is essential for the establishment and growth of the apical domain in epithelial cells. The protein Yurt limits the ability of Crumbs to promote apical membrane growth, thereby defining proper apical/lateral membrane ratio that is crucial for forming and maintaining complex epithelial structures such as tubes or acini. Here, we show that Yurt also increases Myosin-dependent cortical tension downstream of Crumbs. Yurt overexpression thus induces apical constriction in epithelial cells. The kinase aPKC phosphorylates Yurt, thereby dislodging the latter from the apical domain and releasing apical tension. In contrast, the kinase Pak1 promotes Yurt dephosphorylation through activation of the phosphatase PP2A. The Pak1- PP2A module thus opposes aPKC function and supports Yurt-induced apical constriction. Hence, the complex interplay between Yurt, aPKC, Pak1 and PP2A contributes to the functional plasticity of Crumbs. Overall, our data increase our understanding of how proteins sustaining epithelial cell polarization and Myosin-dependent cell contractility interact with one another to control epithelial tissue architecture.
A Facile Alternative Sustainable Process for the Extraction and Purification of Microbial Melanin Conventional techniques for the extraction of the melanin encounter several disadvantages such as poor extraction efficiency, excessive use of acid and alkali, and lengthy time duration. To extract melanin in a more sustainable manner, herein suitability of an aqueous solution of quaternary ammonium hydroxide known as tetrabutylammonium hydroxide (40% w/w TBAOH in water) to extract and purify the pigment from the endophyte Streptomyces hyderabadensis 7VPT5-5R was investigated. The solvent could extract 5.54{+/-}0.03 g/L of pure melanin against 3.31{+/-} 0.02 g/L of pure melanin by conventional method from bacterial culture resulting 66% increase in the yield of the pigment. The quaternary ammonium based solvent was further recycled for 5 consecutive cycles and production of melanin with yield ranging from 5.54{+/-}0.03 g/L to 5.47{+/-} 0.02 g/L was obtained. The yield of the pigment was 38-40% higher in the recycled solvent in comparison to the melanin yield extracted by conventional method. Considering the efficiency of the solvent for effective extraction and purification of melanin and its recyclability potential, it can be considered as a sustainable solvent for the extraction of the pigments from bacterial culture. Furthermore, the developed method for extraction of melanin from microorganisms as a sustainable source would help in reducing the cost of melanin leading to its efficient utilization in diverse fields. A chemical screen based on an interruption of zebrafish gastrulation identifies the HTR2C inhibitor Pizotifen as a suppressor of EMT-mediated metastasis Metastasis is responsible for approximately 90% of cancer-associated mortality but few models exist that allow for rapid and effective screening of anti-metastasis drugs. Current mouse models of metastasis are too expensive and time consuming to use for rapid and high-throughput screening. Therefore, we created a unique screening concept utilizing conserved mechanisms between zebrafish gastrulation and cancer metastasis for identification of potential anti-metastatic drugs. We hypothesized that small chemicals that interrupt zebrafish gastrulation might also suppress metastatic progression of cancer cells and developed a phenotype-based chemical screen to test the hypothesis. The screen used epiboly, the first morphogenetic movement in gastrulation, as a marker and enabled 100 chemicals to be tested in five hours. The screen tested 1280 FDA-approved drugs and identified Pizotifen, an antagonist for serotonin receptor 2C (HTR2C) as an epiboly-interrupting drug. Pharmacologic and genetic inhibition of HTR2C suppressed metastatic progression in a mouse model. Blocking HTR2C with Pizotifen restored epithelial properties to metastatic cells through inhibition of Wnt-signaling. In contrast, HTR2C induced epithelial to mesenchymal transition (EMT) through activation of Wnt-signaling and promoted metastatic dissemination of human cancer cells in a zebrafish xenotransplantation model. Taken together, our concept offers a novel platform for discovery of anti-metastasis drugs. Using Hierarchical Similarity To Examine The Genetics of Behcet's disease Behcets disease (BD) is a multisystem inflammatory disease that affects patients along the historic silk road. Thus far, the pathogenesis of the disease has proved elusive due to the complex genetic interactions and unknown environmental or viral triggering factors of the disease. In this paper, we seek to clarify the genetic factors of the disease while also uncovering other diseases of interest that present with a similar genotype as BD. To do this, we employ a convergent functional genomics approach by leveraging the hierarchical similarity tool available in Geneweaver. Through our analysis, we were able to ascertain 7 BD consensus genes and 16 autoimmune diseases with genetic overlap with BD. The results of our study will inform further research into the pathogenesis of Behcets Disease. Intron-mediated induction of phenotypic heterogeneity Introns are universally present in the nuclear genomes of eukaryotes1. The budding yeast, an otherwise intron-poor species, preserves two sets of ribosomal protein (RP) genes differing primarily in their introns2-4. Despite recent findings on the role of RP introns under stress and starvation5-7, understanding the contribution of introns to ribosome regulation remains challenging. Here, combining isogrowth profiling8 with single-cell protein measurements9, we found that introns can mediate inducible phenotypic heterogeneity conferring a clear fitness advantage. Osmotic stress leads to bimodal expression of the small ribosomal subunit protein Rps22B, mediated by an intron in the 5 untranslated region of its transcript. The two resulting yeast subpopulations differ in their ability to cope with starvation. Low Rps22B protein levels resulted in prolonged survival under sustained starvation, while high Rps22B levels enabled cells to grow faster after transient starvation. Further, yeast growing at high sugar concentrations - similar to those in ripe grapes - exhibit bimodal Rps22B expression when approaching stationary phase. Differential intron-mediated regulation of RP genes thus provides a way to diversify the population when starvation looms in natural environments. Our findings reveal a new role for introns in inducing phenotypic heterogeneity in changing environments and suggest that duplicated RP genes in yeast contribute to resolving the evolutionary conflict between precise expression control and environmental responsiveness10. A multiscale lipid and cellular atlas of the human kidney The human kidney is composed of over 26 cell types that actively coordinate with each other to form higher-order structures, such as the nephron. It is not yet understood how these structures vary throughout a single organ or amongst the same organs within the human population. We have developed an extensive lipid and cellular atlas of the human kidney consisting of over 3 million cells comprising 75,000 functional tissue units (i.e., glomeruli, proximal tubules, distal tubules, and collecting ducts) from 13 human subjects. This atlas was developed using spatially registered and integrated technologies consisting of imaging mass spectrometry, multiplexed immunofluorescence, stained microscopy, and autofluorescence microscopy, to comprehensively probe large (i.e., centimeter-sized) areas of tissue. The cellular organization and lipid profiles of glomeruli, proximal tubules, distal tubules, and collecting ducts were discovered through these multimodal imaging data as well as their intra- and inter-subject variance. Relating the lipid profiles obtained from imaging mass spectrometry to distinct cell types obtained from immunofluorescence allowed us to hypothesize the functional role of specific phospholipids that have not previously been described. These hypotheses include subject characteristics, such as BMI and sex. The integrated data from the aforementioned datasets provide a valuable reference for kidney researchers, are publicly available through the NIH Human Biomolecular Atlas Program (https://portal.hubmapconsortium.org/), and discussed below. Diverse stem-chondrichthyan oral structures and evidence for an independently acquired acanthodid dentition The teeth of sharks famously form a series of transversely-organised files with conveyor-belt replacement that are borne directly on the jaw cartilages, in contrast to the dermal plate-borne dentition of bony fishes that undergoes site-specific replacement. A major obstacle in understanding how this system evolved is the poorly understood relationships of the earliest chondrichthyans and the profusion of morphologically and terminologically diverse bones, cartilages, splints and whorls that they possess. Here we use tomographic methods to investigate mandibular structures in several early branching  acanthodian-grade stem-chondrichthyans. We show that the dentigerous jaw bones of disparate genera of ischnacanthids are united by a common construction, being growing bones with non-shedding dentition. Mandibular splints, which support the ventro-lateral edge of the Meckels cartilage in some taxa, are formed from dermal bone and may be an acanthodid synapomorphy. We demonstrate that the teeth of Acanthodopsis are borne directly on the mandibular cartilage and that this taxon is deeply nested within an edentulous radiation, representing an unexpected independent origin of teeth. Many or even all of the range of unusual oral structures may be apomorphic, but they should nonetheless be considered when building hypotheses of tooth and jaw evolution, both in chondrichthyans and more broadly. Dramatic differences in male and female mortality trends for selected European cohorts over ~20 years. Longevity is of considerable interest. Collation of recent data after World War II by the Human Mortality Database allowed analyses, previously unattainable, of modal death-ages for sufficient numbers of selected European cohorts. The aim was to track modes and medians/means ([&ge;]60 years old (y)) of all-cause mortality for both sexes. The only highest-quality, large-number Lexis data available were analyzed: from nine countries: Denmark, Finland, France, Iceland, Italy, Netherlands, Norway, Sweden and Switzerland; raw-data modes (and medians/means [&ge;]60y, plus thin-plate-spline averages), were analyzed, plus pooled data. Here we show that for cohorts 1880-[~]1900 dramatic sex differences existed between death-age changes with all countries except Iceland showing male modal negative trends lasting [~]10-20 years and medians in all countries near-constant or negative lasting [~]10-20 years; whereas females from most countries showed fairly constant positive trends (except Finnish modes and Norwegian medians). For cohorts [~]1900-1919 male and female modal trends were positive (except Dutch and Icelandic cohorts and Finnish females). The net results were that male mortality modes for Danish, Icelandic, Italian, Dutch, Swedish and Norwegian 1919 cohorts were roughly the same as for 1880 cohorts, whereas female death-age modes increased. Results clarify previously knowledge concerning sex differences during this period. Despite improved environment in late adulthood over this period, this did not translate into increased male longevity and earlier events might have sealed their fate, especially in Denmark, Italy, Netherlands, Norway, aand Sweden (and, later, Iceland). SERCA function is impaired in skeletal and cardiac muscles from young DBA/2J mdx mice The DBA/2J (D2) mdx mouse has emerged as a more severe model of Duchenne muscular dystrophy when compared to the traditional C57BL/10 (C57) mdx mouse. Here, we questioned whether sarco(endo)plasmic reticulum Ca2+-ATPase (SERCA) function would differ in muscles from young D2 and C57 mdx mice. In gastrocnemius muscles, both D2- and C57 mdx mice exhibited signs of impaired Ca2+ uptake, however, this was more severe in D2 mdx mice. Maximal SERCA activity was lowered only in D2 mdx gastrocnemius muscles and not C57 mdx muscles. Furthermore, in the left ventricle and diaphragm, Ca2+ uptake was impaired in C57 mdx muscles with lowered rates of Ca2+ uptake compared with C57 WT mice, whereas in muscles from D2 mdx mice, rates of Ca2+ uptake were unattainable due to the severe impairments in their ability to transport Ca2+. Overall, our study demonstrates that SERCA function is drastically impaired in young D2 mdx mice. Brominated Lipid Probes Expose Structural Asymmetries in Constricted Membranes Lipids in biological membranes are thought to be functionally organized, but few experimental tools can probe nanoscale membrane structure. Using brominated lipids as contrast probes for cryo-EM and a model ESCRT-III membrane remodeling system, we observed leaflet-level and protein-localized lipid structural patterns within highly constricted and thinned membrane nanotubes. These nanotubes differed markedly from protein-free, flat bilayers in leaflet thickness, lipid diffusion rates, and lipid compositional and conformational asymmetries. Simulations and cryo-EM imaging of brominated SDPC showed how a pair of phenylalanine residues scored the outer leaflet with a helical hydrophobic defect where polyunsaturated docosahexaenoyl (DHA) tails accumulated at the bilayer surface. Combining cryo-EM of halogenated lipids with molecular dynamics thus enables new characterizations of the composition and structure of membranes on molecular length scales.

One-Sentence SummaryCryo-EM imaging of halogenated lipids and MD simulations provide molecular-scale insight into constricted bilayer structure. Nanoscale ligand density modulates gap junction intercellular communication of cell condensates during chondrogenesis To unveil the influence of cell-matrix adhesions in the establishment of gap junction intercellular communication (GJIC) during cell condensation in chondrogenesis.

Materials & MethodsPreviously developed nanopatterns of the cell adhesive ligand arginine-glycine-aspartic acid (RGD) were used as cell culture substrates to control cell adhesion at the nanoscale. We conducted in vitro chondrogenesis of mesenchymal stem cells on the nanopatterns. We evaluated cohesion and GJIC in cell condensates.

ResultsMechanical stability and GJIC are enhanced by a nanopattern configuration in which 90% of the surface area presents adhesion sites separated less than 70 nm, thus providing an onset for cell signaling.

ConclusionCell-matrix adhesions regulate GJIC of mesenchymal cell condensates during in vitro chondrogenesis from a threshold configuration at the nanoscale. Trade-offs in biosensor optimization for dynamic pathway engineering Recent progress in synthetic biology allows the construction of dynamic control circuits for metabolic engineering. This technology promises to overcome many challenges encountered in traditional pathway engineering, thanks to their ability to self-regulate gene expression in response to bioreactor perturbations. The central components in these control circuits are metabolite biosensors that read out pathway signals and actuate enzyme expression. However, the construction of metabolite biosensors is a major bottleneck for strain design, and a key challenge is to understand the relation between biosensor dose-response curves and pathway performance. Here we employ multiobjective optimization to quantify performance trade-offs that arise in the design and calibration of metabolite biosensors. Our approach reveals strategies for tuning dose-response curves along an optimal trade-off between production flux and the cost of an increased expression burden on the host. We explore properties of control architectures built in the literature, and identify their advantages and caveats in terms of performance and robustness to growth conditions and leaky promoters. We demonstrate the optimality of a control circuit for glucaric acid production in Escherichia coli, which has been shown to increase titer by 2.5-fold as compared to static designs. Our results lay the groundwork for the automated design of control circuits for pathway engineering, with applications in the food, energy and pharmaceutical sectors. Simulation of foraging behavior using a decision-making agent with Bayesian and inverse Bayesian inference: Temporal correlations and power laws in displacement patterns It has been stated that in human migratory behavior, the step length series may have temporal correlation and that there is some relationship between this time dependency and the fact that the frequency distribution of step length follows a power-law distribution. Furthermore, the frequency of occurrence of the step length in some large marine organisms has been found to switch between power-law and exponential distributions, depending on the difficulty of prey acquisition. However, to date it has not been clarified how the aforementioned three phenomena arise: the positive correlation created in the step length series, the relation between the positive correlation of the step length series and the form of an individuals step length distribution, and the switching between power-law and exponential distributions depending on the abundance of prey. This study simulated foraging behavior using the Bayesian decision-making agent simultaneously performing both knowledge learning and knowledge-based inference to analyze how the aforementioned three phenomena arise. In the agent with learning and inference, past experiences were stored as hypotheses (knowledge) and they were used in current foraging behavior; at the same time, the hypothesis continued to be updated based on new experiences. The simulation results show that the agent with both learning and inference has a mechanism that simultaneously causes all the phenomena. Motor cortical output for skilled forelimb movement is selectively distributed across projection neuron classes The interaction of descending neocortical outputs and subcortical premotor circuits is critical for shaping the skilled movements. Two broad classes of motor cortical output projection neurons provide input to many subcortical motor areas: pyramidal tract neurons (PT), which project throughout the neuraxis; and intratelencephalic neurons (IT), which project within cortex and subcortical striatum. It is unclear whether these classes are functionally in series or whether separable components of descending motor control signals are distributed across these distinct classes of projection neurons. Here we combine large-scale neural recordings across all layers of motor cortex with cell-type specific perturbations to study cortically-dependent mouse motor behaviors: kinematically-variable manipulation of a joystick and a kinematically-precise reach-to-grasp. We find that striatum-projecting IT neuron activity preferentially represents amplitude whereas pons-projecting PT neurons preferentially represent the variable direction of forelimb movements. Thus, separable components of descending motor cortical commands are distributed across motor cortical projection cell classes.

One-sentence summarySeparable components of cortical motor commands are distributed across distinct glutamatergic projection neuron cell-types. Artificial seawater based long-term culture of colonial ascidians Tunicates are highly diverse marine invertebrate filter-feeders that are vertebrates closest relatives. These organisms, despite a drastically different body plan during their adulthood, have a tissue complexity related to that of vertebrates. Ascidians, which compose most of the Tunicata, are benthic sessile hermaphrodites that reproduce sexually through a motile tadpole larval stage. Over half of the known ascidians species are able to reproduce asexually by budding, typically leading to the formation of colonies where animals, called zooids, are interconnected through an external vascular system. In addition, colonial ascidians are established models for important biological processes including allorecognition, immunobiology, aging, angiogenesis and whole-body regeneration. However, the current paucity in breeding infrastructures limits the study of these animals to coastal regions.

To promote a wider scientific spreading and popularity of colonial ascidians, we have developed a flexible recirculating husbandry setup for their long-term in-lab culture. Our system is inspired both by the flow-through aquariums used by coastal ascidian labs, as well as by the recirculating in-lab systems used for zebrafish research. Our hybrid system thus combines colony breeding, water filtering and food culturing in a semi-automated system where specimens develop on hanging microscopy glass slides. Temperature, light/dark cycles, flow speed and feeding rates can be controlled independently in four different breeding environments to provide room for species-specific optimization as well as for running experiments. This setup is complemented with a quarantine for the acclimatization of wild isolates.

Herein we present our success in breeding Botrylloides diegensis, a species of colonial ascidians, for more than 3 years in recirculating artificial seawater over 600 km away from their natural habitat. We show that colonies adapt well to in-lab culturing provided that a suitable marine microbiome is present, and that a specific strain can be isolated, propagated and efficiently used for research over prolonged periods of time. The flexible and modular structure of our system can be scaled and adapted to the needs of specific species, such as Botryllus schlosseri, as well as of particular laboratory spaces. Overall, we show that Botrylloides diegensis can be proficiently bred in-land and suggest that our results can be extended to other species of colonial ascidians to promote research on these fascinating animals.

HighlightsO_LIFirst artificial seawater based recirculating aquaculture for colonial ascidians
C_LIO_LIOver 3 years of continuous breeding
C_LIO_LISemi-automated setup with minimized maintenance
C_LIO_LIGood biomass production for strain propagation
C_LIO_LI4 different culture conditions for optimized breeding for species of interest
C_LI Non-specific effects of a CINNAMATE-4-HYDROXYLASE inhibitor on auxin homeostasis Chemical inhibitors are often implemented for the functional characterization of genes to overcome the limitations associated with genetic approaches. Although being a powerful tool, off-target effects of these inhibitors are easily overlooked in a complex biological setting. Here we illustrate the implications of such secondary effects by focusing on piperonylic acid (PA), an inhibitor of CINNAMATE-4-HYDROXYLASE (C4H) that is often used to investigate the involvement of lignin during plant growth and development. When supplied to plants, we found that PA is recognized as a substrate by GRETCHEN HAGEN 3.6 (GH3.6), an amido synthetase involved in the formation of the auxin catabolite indole-3-acetic acid (IAA)-Asp. By competing for the same enzyme, PA interferes with auxin conjugation, resulting in an increase in cellular auxin concentrations. These increased auxin levels likely further contribute to an increase in adventitious rooting previously observed upon PA-treatment. Despite the focus on GH3.6 in this report, PA is conjugated by an array of enzymes and their subsequent reduced activity on native substrates could potentially affect a whole set of physiological processes in the plant. We conclude that surrogate occupation of the endogenous conjugation machinery in the plant by exogenous compounds is likely a more general phenomenon that is rarely considered in pharmacological studies. Our results hereby provide an important basis for future reference in studies using chemical inhibitors. The origins and drivers of Neotropical diversity The origins and evolution of the outstanding Neotropical biodiversity are still debated. A comprehensive understanding is hindered by the lack of deep-time comparative data across wide phylogenetic and ecological contexts. Here, we evaluate four evolutionary scenarios assuming different diversification trajectories and drivers of Neotropical diversification, and assess their variation across Neotropical regions and taxa. Our analysis of 150 phylogenies (12,512 species) of seed plants and tetrapods reveals that Neotropical diversity has mostly expanded through time (70% of the clades), while scenarios of saturated and declining diversity also account for 21% and 9% of Neotropical diversity, respectively. We identify five biogeographic areas that represent distinctive units of long-term Neotropical evolution (Pan-Amazonia, Dry Diagonal, Bahama-Antilles, Galapagos, and an  elsewhere region) and find that diversity dynamics do not differ across these areas, suggesting no geographic structure in long-term Neotropical diversification. In contrast, diversification dynamics differ substantially across taxa: plant diversity mostly expanded through time (88%), while a substantial fraction (43%) of tetrapod diversity accumulated at a slower pace or declined toward the present. These opposite evolutionary patterns may reflect different capacities for plants and tetrapods to cope with climate change, with potential implications for future adaptation and ecosystem resilience. Cell type-specific differential expression in spatial transcriptomics Spatial transcriptomics enables spatially resolved gene expression measurements at near single-cell resolution. There is a pressing need for computational tools to enable the detection of genes that are differentially expressed (DE) within specific cell types across tissue context. We show that current approaches cannot learn cell type-specific DE due to changes in cell type composition across space and the fact that measurement units often detect transcripts from more than one cell type. Here, we introduce a statistical method, Cell type-Specific Inference of Differential Expression (C-SIDE), that identifies cell type-specific patterns of differential gene expression while accounting for localization of other cell types. We model spatial transcriptomics gene expression as an additive mixture across cell types of general log-linear cell type-specific expression functions. This approach provides a unified framework for defining and identifying gene expression changes in a wide-range of relevant contexts: changes due to pathology, anatomical regions, physical proximity to specific cell types, and cellular microenvironment. Furthermore, our approach enables statistical inference across multiple samples and replicates when such data is available. We demonstrate, through simulations and validation experiments on Slide-seq and MER-FISH datasets, that our approach accurately identifies cell type-specific differential gene expression and provides valid uncertainty quantification. Lastly, we apply our method to characterize spatially-localized tissue changes in the context of disease. In an Alzheimers mouse model Slide-seq dataset, we identify plaque-dependent patterns of cellular immune activity. We also find a putative interaction between tumor cells and myeloid immune cells in a Slide-seq tumor dataset. We make our C-SIDE method publicly available as part of the open source R package https://github.com/dmcable/spacexr. TXN, a Xanthohumol Derivative, Attenuates High-Fat Diet Induced Hepatic Steatosis by Antagonizing PPARγ We previously reported xanthohumol (XN), and its synthetic derivative tetrahydro-XN (TXN) attenuates high-fat diet (HFD) induced obesity and metabolic syndrome in C57BL/6J mice. The objective of the current study was to determine the effect of XN and TXN on lipid accumulation in the liver. Non-supplemented mice were unable to adapt their caloric intake to 60% HFD, resulting in obesity and hepatic steatosis; however, TXN reduced weight gain and decreased hepatic steatosis. Liver transcriptomics indicated TXN might antagonize lipogenic PPAR{gamma} actions in vivo. XN and TXN inhibited rosiglitazone-induced 3T3-L1 cell differentiation concomitant with decreased expression of lipogenesis-related genes. A PPAR{gamma} competitive binding assay showed XN and TXN bind to PPAR{gamma} with an IC50 similar to pioglitazone and 8-10 times stronger than oleate. Molecular docking simulations demonstrated XN and TXN bind in the PPAR{gamma} ligand-binding domain pocket. Our findings are consistent with XN and TXN acting as antagonists of PPAR{gamma}. Live Analysis of Position Effect Variegation (PEV) in Drosophila Reveals Different Modes of Action for HP1a and Su(var)3-9 AO_SCPLOWBSTRACTC_SCPLOWPosition Effect Variegation (PEV) results from the juxtaposition of euchromatic and heterochromatic components of eukaryotic genomes, silencing genes near the new euchromatin/heterochromatin junctions. Silencing is itself heritable through S phase, giving rise to distinctive random patterns of cell clones expressing the genes intermixed with clones in which the genes are silenced. Much of what we know about epigenetic inheritance in the soma stems from work on PEV aimed at identifying the components of the silencing machinery and its mechanism of inheritance. The roles of two central gene activities - the Su(var)3-9-encoded histone H3-Lysine-9 methyltransferase and the Su(var)205-encoded methyl-H3-Lysine-9 binding protein HP1a - have been inferred from terminal phenotypes, leaving considerable gaps in understanding how PEV behaves through development. Here, we investigate the PEV phenotypes of Su(var)3-9 and Su(var)205 mutations in live developing tissues. We discovered that mutation in Su(var)205 compromises the initial establishment of PEV in early embryogenesis. Later gains of heterochromatin-induced gene silencing are possible, but are unstable and lost rapidly. In contrast, a strain with mutation in Su(var)3-9 exhibits robust silencing early in development, but fails to maintain it through subsequent cell divisions. Our analyses show that while the terminal phenotypes of these mutations may appear identical, they have arrived at them through different developmental trajectories. We discuss how our findings expand and clarify existing models for epigenetic inheritance of heterochromatin-induced gene silencing.

SO_SCPLOWIGNIFICANCEC_SCPLOWCurrent concepts of epigenetic inheritance are exemplified by Position Effect Variegation, a phenomenon whereby heterochromatin can repress genes in clonal cell lineages. Heterochromatin is required for genome protection as it silences toxic transposable elements and prevents instability of repeat sequences. Histone H3 modified by methylation of Lysine-9 and HP1a are critical components of heterochromatin. Using live cell analysis of PEV in mutants in strains with mutations in Su(var)3-9, which encodes the histone methyltransferase, and Su(var)205, which encodes HP1a, we describe an unexpected dynamism in PEV, challenging current models of epigenetics, and revealing unexpectedly different modes of action of these two fundamental components of heterochromatin. Citation needed?Wikipedia bibliometrics during the first waveof the COVID-19 pandemic. BackgroundWith the COVID-19 pandemics outbreak, millions flocked to Wikipedia for updated information. Amid growing concerns regarding an "infodemic", ensuring the quality of information is a crucial vector of public health. Investigating if and how Wikipedia remained up to date and in line with science is key to formulating strategies to counter misinformation. Using citation analyses, we asked: which sources informed Wikipedias COVID-19-related articles before and during the pandemics first wave (January-May 2020).

ResultsWe found that coronavirus-related articles referenced trusted media sources and high-quality academic research. Moreover, despite a surge in COVID-19 preprints, Wikipedia had a clear preference for open-access studies published in respected journals and made little use of preprints. Building a timeline of English COVID-19 articles from 2001-2020 revealed a nuanced trade-off between quality and timeliness. It further showed how preexisting articles on key topics related to the virus created a framework for integrating new knowledge. Supported by a rigid sourcing policy, this "scientific infrastructure" facilitated contextualization and regulated the influx of new information. Lastly, we constructed a network of DOI-Wikipedia articles, which showed the shifting landscape of pandemic-related knowledge on Wikipedia and how academic citations create a web of shared knowledge supporting topics like COVID-19 vaccine development.

ConclusionsUnderstanding how scientific research interacts with the digital knowledge-sphere during the pandemic provides insight into how Wikipedia can facilitate access to science. It also reveals how, aided by what we term its "citizen encyclopedists", it successfully fended off COVID-19 disinformation and how this unique model may be deployed in other contexts. Deep learning: step forward to high-resolution in vivo shortwave infrared imaging Shortwave infrared window (SWIR: 1000-1700 nm) represents a major improvement compared to the NIR-I region (700-900 nm) in terms of temporal and spatial resolutions in depths down to 4 mm. SWIR is a fast and cheap alternative to more precise methods such as X-ray and opto-acoustic imaging. Main obstacles in SWIR imaging are the noise and scattering from tissues and skin that reduce the precision of the method. We demonstrate that the combination of SWIR in vivo imaging in the NIRIIb region (1500-1700 nm) with advanced deep learning image analysis allows to overcome these obstacles and making a large step forward to high resolution imaging: it allows to precisely segment vessels from tissues and noise, provides morphological structure of the vessels network, with learned pseudo-3D shape, their relative position, dynamic information of blood vascularization in depth in small animals and distinguish the vessels types: artieries and veins. For demonstration we use neural network IterNet that exploits structural redundancy of the blood vessels, which provides a useful analysis tool for raw SWIR images. RIG-I immunotherapy overcomes radioresistance in p53-positive malignant melanoma Radiation therapy induces cytotoxic DNA damage, which results in cell-cycle arrest and activation of cell-intrinsic death pathways, but its application has been limited by the radioresistance of tumors, such as in malignant melanoma. RIG-I is a cytosolic immune receptor expressed in all somatic cells, including tumor cells, with a key role in sensing viral RNA. RIG-I specific oligonucleotide ligands elicit a robust cell-intrinsic antiviral response and immunogenic cell death in tumor cells and are being tested in clinical trials. Nonetheless, their potential to overcome radioresistance has not yet been explored. Here, we demonstrate that activation of RIG-I enhances the extent and immunogenicity of irradiation-induced tumor cell death in human and murine melanoma cell lines in vitro and improved survival in the murine B16 melanoma model. Pathway analysis of transcriptomic data revealed a central role for p53 downstream of the combination treatment, which was corroborated using p53-/- B16 cells. In vivo, the effect of irradiation on immune-cell activation and inhibition of tumor growth was absent in mice carrying p53-/- B16 tumors, while the response to RIG-I stimulation in those mice was maintained. Our results identify p53 as pivotal for the synergistic antitumoral effect of RIG-I and irradiation, resulting in potent induction of immunogenic tumor-cell death. Thus, the administration of RIG-I ligands in combination with radiotherapy is a promising therapeutic approach to treating radioresistant tumors with a functional p53 pathway, such as malignant melanoma. Density dependent interactions during growth mask the effect of interactions during flowering in pollinator-sharing annual plants Density dependent interactions are fundamental to community ecology, but studies often reduce the complex nature of species interactions. In plant ecology, interactions during vegetative growth and flowering are often considered separately, though both can affect reproductive output. Here we use communities of annual flowering plants in the genus Clarkia to ask how interactions during growth and flowering contribute to density dependence in plant seed production, and if pollinator behaviors explain apparent patterns in plant interactions during flowering. We measure seed set (seed number per ovule) and total fecundity (whole-plant seed production) of Clarkia focal plants in experimental interaction plots with the effect of pollinators experimentally removed through supplemental pollination or retained. We also observe pollinator behaviors in the plots and experimental arrays to document pollinator preference, constancy and joint attraction. During flowering, pollinators significantly changed the density dependent effects of Clarkia interactions on seed set in 31% of species interactions, and these changes corresponded to pollinator behaviors. Total fecundity, however, did not depend on interactions between Clarkia; instead, earlier-flowering, non-Clarkia forbs limited total fecundity. Our study shows that interactions during vegetative growth can preclude the effect of pollinator- mediated interactions on fecundity by limiting potential reproductive output. Simultaneously studying different types of species interactions allows for understanding the contingency of ecological outcomes. Neurological mechanism of sensory deficits after developmental exposure to non-dioxin-like polychlorinated biphenyls (PCBs) in zebrafish larvae The most abundant polychlorinated biphenyl (PCB) congeners found in the environment and in humans are neurotoxic. This is of particular concern for early life stages because the exposure of the more vulnerable developing nervous system to chemicals can result in neurobehavioral disorders. To uncover currently unknown links between PCB target mechanisms and neurobehavioral deficits, we investigated the effects of the non-dioxin-like (NDL) congener PCB153 on neuronal morphology and synaptic transmission linked to the proper execution of a sensorimotor response using zebrafish as a vertebrate model. Zebrafish that were exposed during development to concentrations similar to those found in human cord blood and PCB contaminated sites showed a delay in startle response. A similar delay was observed for other NDL congeners but not for the potent dioxin-like congener PCB126. Morphological and biochemical data demonstrate that while exposure to PCB153 induced swelling of afferent sensory neurons, the disruption of dopaminergic and GABAergic signaling is the dominant mechanism associated with motor movement. The effects on important and broadly conserved signaling mechanisms in vertebrates suggest that NDL PCBs may contribute to neurodevelopmental abnormalities in humans and, with the startle response being critical for the survival of fish, to evolutionary adaptation in wildlife.