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Departing from the cultural impacts of physical museums, this article explores two significant virtual benefits of online digitized art collections. Based on empirical research, it speculates that these increasingly interconnected collections have the potential to implement a new model of cultural participation able to sustain power sharing beyond public consultation, and transform the art system’s inherent stratification, viz. modulate the art world’s access barriers to institutional prestige, thus benefiting artists by levelling the playing field. The claim is that they can serve as a digital infrastructure to recruit collective intelligence on a mass scale in order to democratize culture and foster more equality and diversity in the art world. However, these impacts cannot simply be achieved by turning users into citizen curators or leveraging ‘altmetrics’ (i.e., views and likes) to influence selection and modulate order within an aggregated or distributed database. The main obstacle to these virtual impacts is not online access barriers, nor insufficient participation. Multiplying eyeballs, facilitating discovery and promoting public choices are all vital; but, these initiatives cannot hope to transform the art system if the individual judgment being captured is subject to different spheres of influence and network effects driving inequality. To overcome these effects, the article proposes a novel, choice-based, pathfinding tool designed to recruit users’ sensemaking faculty, as opposed to their personal taste, and in so doing, more effectively capture what users find meaningful (and institute a new value proposition for art).

Since the mid-1990s, cultural organizations have increasingly digitized their physical collections and made them available online; however, museums are still puzzled over what to do with these growing digital collections. Meanwhile, art institutions’ reluctance to produce virtual exhibitions, linked to a prevailing skeuomorphic paradigm, has left the matter of curating art digitizations unresolved. While museum computing scholarship has aptly identified the problematic absence of authentically digital curatorial processes, it has largely overlooked the fact that online collections and in-gallery group shows similarly condition artistic reception owing to a shared database logic, subjecting both to a mediation paradox in contemporary culture. This article examines the effects of this shared logic on public engagement, along with recent digital curatorial strategies that have emerged in response around notions of the digital aura and networked objects. The article concludes by proposing three conditions for an alternative curatorial process capable of adequately mediating art digitizations online without sacrificing aesthetic experience to the limited affordances of screen-based information and communications technologies.

Adaptive façades are gaining greater importance in highly efficient buildings under a warming climate. There is an increasing demand for adaptive façades designed to regulate solar and thermal gains/losses, as well as avoid discomfort and glare issues. Occupants and developers of office buildings ask for a healthy and energy-neutral working environment. Adaptive façades are appropriate dynamic solutions controlled automatically or through occupant interaction. However, relatively few studies compared their energy and overheating risk performance, and there is still a vast knowledge gap on occupant behavior in operation. Therefore, we chose to study four dynamic envelopes representing four different façade families: dynamic shading, electrochromic glazing, double-skin, and active ventilative façades. Three control strategies were chosen to study the dynamic aspect of solar control, operative temperature, and glare control. Simulations were realized with EnergyPlus on the BESTEST case 600 from the ASHRAE standard 140/2020 for the temperate climate of Brussels. A sensitivity analysis was conducted to study the most influential parameters. The study findings indicate that dynamic shading devices and electrochromic glazing have a remarkable influence on the annual thermal energy demand, decreasing the total annual loads that can reach 30%. On the other hand, BIPV double-skin façades and active ventilative façades (cavity façades) could be more appropriate for cold climates. The study ranks the four façade technologies and provides novel insights for façade designers and building owners regarding the annual energy performance and overheating risk.

DNA methylation (5-methylcytosine; 5mC) is a repressive gene-regulatory mark required for vertebrate embryogenesis. Genomic 5mC is tightly regulated through the coordinated action of DNA methyltransferases, which deposit 5mC, and TET enzymes, which participate in its active removal through the formation of 5-hydroxymethylcytosine (5hmC). TET enzymes are essential for mammalian gastrulation and activation of vertebrate developmental enhancers, however, to date, a clear picture of 5hmC function, abundance, and genomic distribution in non-vertebrate lineages is lacking. By employing base-resolution 5mC and 5hmC quantification during sea urchin and lancelet embryogenesis, we shed light on the roles of non-vertebrate 5hmC and TET enzymes. We find that these invertebrate deuterostomes employ TET enzymes for targeted demethylation of regulatory regions associated with developmental genes and show that the complement of identified 5hmC-regulated genes is conserved to vertebrates. This work thus demonstrates that active 5mC removal from regulatory regions is a common feature of deuterostome embryogenesis suggestive of unexpected deep conservation of a major gene-regulatory module.

During animal ontogenesis, body axis patterning is finely regulated by complex interactions between several signaling pathways. Nitric Oxide (NO) and Retinoic Acid (RA) are potent morphogens that play a pivotal role in vertebrate development. Their involvement in axial patterning of head and pharynx shows conserved features in the chordate phylum. Indeed, in the cephalochordate amphioxus NO and RA are crucial for the correct development of pharyngeal structures. Here we demonstrate the functional cooperation between NO and RA occurring in amphioxus embryogenesis. During neurulation, NO modulates RA production through the transcriptional regulation of Aldh1a.2 that irreversibly converts retinaldehyde into RA. On the other hand, RA regulates the transcription of Nos genes, probably through RA Response Elements found in their regulatory regions. The reciprocal regulation of NO and RA pathways results to be essential for the normal pharyngeal development in amphioxus and suggests that this regulatory crosstalk could be conserved in vertebrates.

Mammalian brains feature exceptionally high levels of non-CpG DNA methylation alongside the canonical form of CpG methylation. Non-CpG methylation plays a critical regulatory role in cognitive function, which is mediated by the binding of MeCP2, the transcriptional regulator that when mutated causes Rett syndrome. However, it is unclear whether the non-CpG neural methylation system is restricted to mammalian species with complex cognitive abilities or has deeper evolutionary origins. To test this, we investigated brain DNA methylation across 12 distantly related animal lineages, revealing that non-CpG methylation is restricted to vertebrates. We discovered that in vertebrates, non-CpG methylation is enriched within a highly conserved set of developmental genes transcriptionally repressed in adult brains, indicating that it demarcates a deeply conserved regulatory program. We also found that the writer of non-CpG methylation, DNMT3A, and the reader, MeCP2, originated at the onset of vertebrates as a result of the ancestral vertebrate whole-genome duplication. Together, we demonstrate how this novel layer of epigenetic information assembled at the root of vertebrates and gained new regulatory roles independent of the ancestral form of the canonical CpG methylation. This suggests that the emergence of non-CpG methylation may have fostered the evolution of sophisticated cognitive abilities found in the vertebrate lineage., This work was supported by the Australian Research Council (ARC) Centre of Excellence programme in Plant Energy Biology (grant no. CE140100008). R.L. was supported by a Sylvia and Charles Viertel Senior Medical Research Fellowship, ARC Future Fellowship (no. FT120100862) and Howard Hughes Medical Institute International Research Scholarship. A.d.M. was funded by an EMBO long-term fellowship (no. ALTF 144-2014). J.L.G.-S. was supported by the Spanish government (grant no. BFU2016- 74961-P) and the institutional grant Unidad de Excelencia María de Maeztu (no. MDM-2016-0687). B.V. was supported by the Biomedical Research Council of the Agency for Science, Technology and Research of Singapore. F.G. was supported by an ARC Future Fellowship (no. FT160100267). C.W.R. was supported by an NSF grant (no. IOS-1354898). J.R.E. is an investigator of the Howard Hughes Medical Institute. Genomic data was generated at the Australian Cancer Research Foundation Centre for Advanced Cancer Genomics.

International audience; About eight million animal species are estimated to live on Earth, and all except those belonging to one subphylum are invertebrates. Invertebrates are incredibly diverse in their morphologies, life histories, and in the range of the ecological niches that they occupy. A great variety of modes of reproduction and sex determination systems is also observed among them, and their mosaic-distribution across the phylogeny shows that transitions between them occur frequently and rapidly. Genetic conflict in its various forms is a long-standing theory to explain what drives those evolutionary transitions. Here, we review (1) the different modes of reproduction among invertebrate species, highlighting sexual reproduction as the probable ancestral state; (2) the paradoxical diversity of sex determination systems; (3) the different types of genetic conflicts that could drive the evolution of such different systems.

In the last decades, the cephalochordate amphioxus has reached a peculiar place in research laboratories as an excellent animal model to answer Evo/Devo questions. Nevertheless, mainly due to its restricted spawning season and to the small size of its embryos, only a few basic techniques in developmental biology could be used until recently. Fortunately, these last years, and thanks to the development of high-throughput techniques, new technical approaches have been possible, such as comparative transcriptomics and/or genomics. However, classic micromanipulation techniques are still difficult to apply. Here we present simple protocols for the manipulation of amphioxus embryos. First, we present the spawning induction method used with the European amphioxus species Branchiostoma lanceolatum. Second, we explain simple methods to manipulate the developing amphioxus embryo during the first steps of its development (before the hatching stage). These methods open many technical possibilities for future functional studies. Thus, we present here a simple technique to efficiently dechorionate a large number of embryos, we detail a protocol for the dissociation of cells during the first steps of the embryonic development and, finally, we describe micromanipulation approaches for tissue isolation during the gastrula stage.

Signaling pathways control a large number of gene regulatory networks (GRNs) during animal development, acting as major tools for body plan formation1. Remarkably, in contrast to the large number of transcription factors present in animal genomes, only a few of these pathways operate during development2. Moreover, most of them are largely conserved along metazoan evolution3. How evolution has generated a vast diversity of animal morphologies with such a limited number of tools is still largely unknown. Here we show that gain of interconnectivity between signaling pathways, and the GRNs they control, may have played a critical contribution to the origin of vertebrates. We perturbed the retinoic acid, Wnt, FGF and Nodal signaling pathways during gastrulation in amphioxus and zebrafish and comparatively examined its effects in gene expression and cis-regulatory elements (CREs). We found that multiple developmental genes gain response to these pathways through novel CREs in the vertebrate lineage. Moreover, in contrast to amphioxus, many of these CREs are highly interconnected and respond to multiple pathways in zebrafish. Furthermore, we found that vertebrate-specific cell types are more enriched in highly interconnected genes than those tissues with more ancestral origin. Thus, the increase of CREs in vertebrates integrating inputs from different signaling pathways probably contributed to gene expression complexity and the formation of new cell types and morphological novelties in this lineage.

International audience; The cephalochordates amphioxus or lancelets are benthic marine animals representing the earliest divergent evolutionary lineage within chordates. Although amphioxus are present in most of the world's tropical and temperate oceans, only about thirty different species grouped into three different genera, Branchiostoma, Epigonichthys and Asymmetron have been described. In the genus Asymmetron, only two species have been characterized, although for one of them, A. lucayanum, several cryptic lineages exist. In this work we have sequenced and analyzed the mitogenome of an A. lucayanum population previously described in the Red Sea. The phylogenetic study using this complete mitogenome as well as the analysis of COI gene sequences of several individuals of this Red Sea population show that the Red Sea population is a new cryptic species. We propose to call this new species Asymmetron rubrum.

Cis-regulatory elements (CREs) are non-coding DNA regions involved in the spatio-temporal regulation of gene expression. Gene regulatory changes drive animal development and play major roles during evolution of animal body plans. Therefore, we believe that determining CREs at different developmental stages and across animal lineages is critical to understand how evolution operates through development. The Assay for Transposase-Accessible Chromatin followed by high-throughput sequencing (ATAC-seq) is a powerful technique for the study of CREs that takes advantage of Tn5 transposase activity. Starting from fewer than 105 cells, in a 1-day procedure, it is possible to detect, at a genome-wide level, CREs located in open chromatin regions with high resolution. Here, we describe a detailed step-by-step ATAC-seq protocol for invertebrate chordate marine embryos. We have successfully applied this technique to amphioxus and two species of tunicate embryos. We also show an easy workflow to analyze data generated with this technique. Moreover, we point out that this method and our bioinformatic pipeline are efficient to detect CREs associated with Wnt signaling pathway by simply using embryos treated with a drug that perturbs this pathway. This approach can be extended to other signaling pathways and also to embryo mutants for critical genes. Our results therefore demonstrate the power of ATAC-seq for the identification of CREs that play essential functions during animal development in a wide range of invertebrate or vertebrate animals., This project has received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 Research and Innovation Program (Grant Agreement No. 740041), the Spanish Ministerio de Economía y Competitividad (Grant No. BFU2016-74961-P), and the Andalusian Government (Grant No. BIO-396). This work was also supported by the institutional grant Unidad de Excelencia María de Maeztu (MDM-2016-0687 to the Department of Gene regulation and morphogenesis of Centro Andaluz de Biología del Desarrollo) and by the EMBO short-term fellowship. The laboratory of HE and SB was supported by the Centre National de la Recherche Scientifique (CNRS) and the Agence Nationale de la Recherche (Grant No. ANR-16-CE12-0008-01).

In the last decades, the cephalochordate amphioxus has reached a peculiar place in research laboratories as an excellent animal model to answer Evo/Devo questions. Nevertheless, mainly due to its restricted spawning season and to the small size of its embryos, only a few basic techniques in developmental biology could be used until recently. Fortunately, these last years, and thanks to the development of high-throughput techniques, new technical approaches have been possible, such as comparative transcriptomics and/or genomics. However, classic micromanipulation techniques are still difficult to apply. Here we present simple protocols for the manipulation of amphioxus embryos. First, we present the spawning induction method used with the European amphioxus species Branchiostoma lanceolatum. Second, we explain simple methods to manipulate the developing amphioxus embryo during the first steps of its development (before the hatching stage). These methods open many technical possibilities for future functional studies. Thus, we present here a simple technique to efficiently dechorionate a large number of embryos, we detail a protocol for the dissociation of cells during the first steps of the embryonic development and, finally, we describe micromanipulation approaches for tissue isolation during the gastrula stage.

The evolution of vertebrates from an ancestral chordate was accompanied by the acquisition of a predatory lifestyle closely associated to the origin of a novel anterior structure, the highly specialized head. While the vertebrate head mesoderm is unsegmented, the paraxial mesoderm of the earliest divergent chordate clade, the cephalochordates (amphioxus), is fully segmented in somites. We have previously shown that fibroblast growth factor signalling controls the formation of the most anterior somites in amphioxus; therefore, unravelling the fibroblast growth factor signalling downstream effectors is of crucial importance to shed light on the evolutionary origin of vertebrate head muscles. By using a comparative RNA sequencing approach and genetic functional analyses, we show that several transcription factors, such as Six1/2, Pax3/7 and Zic, act in combination to ensure the formation of three different somite populations. Interestingly, these proteins are orthologous to key regulators of trunk, and not head, muscle formation in vertebrates. Contrary to prevailing thinking, our results suggest that the vertebrate head mesoderm is of visceral and not paraxial origin and support a multistep evolutionary scenario for the appearance of the unsegmented mesoderm of the vertebrates new ‘head’., The laboratory of H.E. was supported by the Centre national de la recherche scientifique and Agence nationale de la recherche (ANR) grant no. ANR-16-CE12-0008-01; S.B. was supported by the Institut Universitaire de France. D.A. holds a fellowship from Conicyt Becas Chile. J-L.G-S. was supported by the Spanish government (grant no. BFU2016-74961-P), the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant no. 740041) and the institutional grant Unidad de Excelencia María de Maeztu (no. MDM-2016-0687). I.M. was funded by an EMBO short-term fellowship (ASTF 377-2014) and by the Spanish Government with a Juan de la Cierva postdoctoral contract (JCI-2012-13495). H.E. and S.M. were supported by the ECOS-CONICYT C15S02 grant.

RNA interference (RNAi) requires RNA-dependent RNA polymerases (RdRPs) in many eukaryotes, and RNAi amplification constitutes the only known function for eukaryotic RdRPs. Yet in animals, classical model organisms can elicit RNAi without possessing RdRPs, and only nematode RNAi was shown to require RdRPs. Here we show that RdRP genes are much more common in animals than previously thought, even in insects, where they had been assumed not to exist. RdRP genes were present in the ancestors of numerous clades, and they were subsequently lost at a high frequency. In order to probe the function of RdRPs in a deuterostome (the cephalochordate Branchiostoma lanceolatum), we performed high-throughput analyses of small RNAs from various Branchiostoma developmental stages. Our results show that Branchiostoma RdRPs do not appear to participate in RNAi: we did not detect any candidate small RNA population exhibiting classical siRNA length or sequence features. Our results show that RdRPs have been independently lost in dozens of animal clades, and even in a clade where they have been conserved (cephalochordates) their function in RNAi amplification is not preserved. Such a dramatic functional variability reveals an unexpected plasticity in RNA silencing pathways., Author summary RNA interference (RNAi) is a conserved gene regulation system in eukaryotes. In non-animal eukaryotes, it necessitates RNA-dependent RNA polymerases (“RdRPs”). Among animals, only nematodes appear to require RdRPs for RNAi. Yet additional animal clades have RdRPs and it is assumed that they participate in RNAi. Here, we find that RdRPs are much more common in animals than previously thought, but their genes were independently lost in many lineages. Focusing on a species with RdRP genes (a cephalochordate), we found that it does not use them for RNAi. While RNAi is the only known function for eukaryotic RdRPs, our results suggest additional roles. Eukaryotic RdRPs thus have a complex evolutionary history in animals, with frequent independent losses and apparent functional diversification.

Vertebrates have greatly elaborated the basic chordate body plan and evolved highly distinctive genomes that have been sculpted by two whole-genome duplications. Here we sequence the genome of the Mediterranean amphioxus (Branchiostoma lanceolatum) and characterize DNA methylation, chromatin accessibility, histone modifications and transcriptomes across multiple developmental stages and adult tissues to investigate the evolution of the regulation of the chordate genome. Comparisons with vertebrates identify an intermediate stage in the evolution of differentially methylated enhancers, and a high conservation of gene expression and its cis-regulatory logic between amphioxus and vertebrates that occurs maximally at an earlier mid-embryonic phylotypic period. We analyse regulatory evolution after whole-genome duplications, and find that—in vertebrates—over 80% of broadly expressed gene families with multiple paralogues derived from whole-genome duplications have members that restricted their ancestral expression, and underwent specialization rather than subfunctionalization. Counter-intuitively, paralogues that restricted their expression increased the complexity of their regulatory landscapes. These data pave the way for a better understanding of the regulatory principles that underlie key vertebrate innovations., This research was funded primarily by the European Research Council (ERC) under the European Union’s Horizon 2020 and Seventh Framework Program FP7 research and innovation programs (ERC-AdG-LS8-740041 to J.L.G.-S., ERC-StG-LS2-637591 to M.I., a Marie Sklodowska-Curie Grant (658521) to I.M. and a FP7/2007-2013-ERC-268513 to P.W.H.H.), the Spanish Ministerio de Economía y Competitividad (BFU2016-74961-P to J.L.G.-S., RYC-2016-20089 to I.M., BFU2014-55076-P and BFU2017-89201-P to M.I. and BFU2014-55738-REDT to J.L.G.-S, M.I. and J.R.M.-M), the ‘Centro de Excelencia Severo Ochoa 2013-2017’(SEV-2012-0208), the ‘Unidad de Excelencia María de Maetzu 2017-2021’(MDM-2016-0687), the People Program (Marie Curie Actions) of the European Union’s Seventh Framework Program FP7 under REA grant agreement number 607142 (DevCom) to J.L.G.-S., and the CNRS and the ANR (ANR16-CE12-0008-01) to H.E. O.B. was supported by an Australian Research Council Discovery Early Career Researcher Award (DECRA; DE140101962).

International audience; In 2016, Kaji et al. concluded that the amphioxus mouth has the quality of a coelomoduct and is, therefore, not homologous to the oral opening of any other animal. They studied a Japanese population of Branchiostoma japonicum and based their conclusion, in part, on the larval expression of BMP2/4 in cells that reportedly joined the rim of the forming mouth. They did not detect transcription of that gene in any other tissues in the anterior region of the larva. Their results were almost the inverse of findings for B. floridae by Panopoulou et al. (1998), who detected BMP2/4 expression in several anterior tissues, but not in cells intimately associated with the nascent mouth. To resolve this discrepancy, we have studied BMP2/4 in a Chinese population of B. japonicum as well as in an additional species, the European B. lanceolatum. In both species, larval expression of BMP2/4 closely resembles the pattern previously reported for B. floridaedthat is, transcription is undetectable in tissues juxtaposed to the forming mouth, but is seen in several other anterior structures (most conspicuously in the lining of the rostral coelom and the club-shaped gland). In sum, we could not repeat the BMP2/4 expression pattern of Kaji et al. (2016) even in the same species, and their findings for this gene, at least, cannot be counted as a support for their hypothesis for a coelomoduct mouth.

International audience; During embryonic development, cells of metazoan embryos need to communicate in order to construct the correct bodyplan. To do so, they use several signals that usually act through interactions between ligands and receptors. Interestingly, only a few pathways are known to be fundamental during animal development, and they are usually found in all the major metazoan clades, raising the following question: how have evolution of the actors and of the functions of these pathways participated in the appearance of the current diversity of animal morphologies? The chordate lineage comprises vertebrates, their sister group the urochordates, and the cephalochordates (i.e. amphioxus). Urochordates are quite derived relative to the chordate ancestor, whereas cephalochordates and vertebrates share many morphological traits. Thus, comparing embryonic development between vertebrates and cephalochordates should give us some insight into the ancestral characters present in chordates and into the morphological evolution in this clade. However, while much is known about the function of different signalling pathways in vertebrates, data are still scarce in the literature for cephalochordates. In this review, we summarize the current state of the field concerning the expression of actors and the function of the major cell-cell communication pathways, including Hedgehog (Hh), Notch, Nuclear Receptor (NR), Receptor Tyrosine Kinase (RTK), Transforming Growth Factor-β (TGF-β) and Wingless/Int (Wnt), in amphioxus.

Complex metazoan bodies require cell-to-cell communication for development, a process often mediated by signaling molecules binding to specific receptors. Relatively few signaling pathways have been recruited during evolution to build multicellular animals from unicellular zygotes. Of these few signaling pathways, one of particular importance is the receptor tyrosine kinase (RTK) pathway. In metazoans, fibroblast growth factors (FGFs) bind to receptors in the RTK family, but the origin of the FGF gene family has so far remained a mystery. Here we show that extant bona fide FGFs most likely originated from proteins bearing an FGF-like domain that arose in a choanoflagellate/metazoan ancestor. We found orthologous genes closely related to FGF in choanoflagellates as well as in many metazoans such as sponges, acoels, protostomes, or nonvertebrate deuterostomes. We also show that these genes have a common evolutionary history with Retinitis Pigmentosa 1 (RP1). Even if some metazoan signaling pathways emerged long before multicellularity, we show that FGFs, like their receptors, originated in a eumetazoan ancestor.

Cet article est un compte-rendu du livre : Stéphanie Fonvielle & Jean-Christophe Pellat, Préludes à l’argumentation proustienne. Perspectives linguistiques et stylistiques, Paris : Éditions Classiques Garnier, coll. « Bibliothèque proustienne », 2015, 723 p., EAN 9782812447235.

Cet article est un compte-rendu du livre : Littératures, n° 72, 2015 : « Imaginaires de la ponctuation dans le discours littéraire (fin xixe‑début xxie siècle) », sous la direction de Stéphane Biakolo et Julien Rault, , 276 p., EAN 9782810703876.