© Mario Izquierdo

 Resumen de noticias: Nature

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Editorial

· French scientists focus on the big political picture. (18.04.2017) Researchers in France overwhelmingly oppose the far right and can stamp out its rise by turning out to register their disapproval. 269-269.

· US foreign aid saves money as well as lives. (13.04.2017) Cutting the budget for applied research in foreign aid would make the United States less competitive.​ 269-270.

· Social networks push runners to run further and faster than their friends. (18.04.2017) Online data sharing through wearable devices motivates people to do more exercise. 270-270.

Column

· Doom and gloom won't save the world. (18.04.2017) The best way to encourage conservation is to share our success stories, not to write obituaries for the planet, says Nancy Knowlton. 271-271.

Seven Days

· Fake-drug crackdown, tackling misconduct and Europa?s plumes. (19.04.2017) The week in science: 14–20 April 2017. 274-275.

News

· French-election fears unite scientists in defence of liberal democracy. (18.04.2017) Threat of a far-right president galvanizes researchers to put politics first. 277-278.

· Drivers gear up for world?s first nanocar race. (19.04.2017) Chemists will navigate molecular wagons along a tiny golden track. 278-279.

· Unravelling why shoelace knots fail. (12.04.2017) A better understanding of this pedestrian problem could lead to improved surgeons’ knots and fibres. 279-279.

· Republican scientists negotiate the Trump era. (18.04.2017) Conservative academics face a growing tension between their politics and the liberal atmosphere on many US campuses. 280-281.

· Global coalition chips away at neglected tropical diseases. (18.04.2017) Partnerships see some success in eliminating illnesses, but challenges, such as access to treatments, remain. 281-282.

Feature

· DNA's secret weapon against knots and tangles. A simple process seems to explain how massive genomes stay organized and untangled. But no one can agree on what powers it. 284-286.

Comment

· Five hacks for digital democracy. (19.04.2017) Beth Simone Noveck urges researchers to work out how technology can improve public institutions. 287-289.

· Track how technology is transforming work. (13.04.2017) Without data on how artificial intelligence is affecting jobs, policymakers will fly blind into the next industrial revolution, warn Tom Mitchell and Erik Brynjolfsson. 290-292.

Books and Arts

· Human behaviour: Guns and roses. (19.04.2017) Anne Harrington savours Robert Sapolsky's tome on humanity's vacillations. 294-295.

· Books in brief. (19.04.2017) Barbara Kiser reviews five of the week's best science picks. 295-295.

· Perception: Our useful inability to see reality. (19.04.2017) There's some deviant thinking behind perception, discovers Douwe Draaisma. 296-296.

Correspondence

· Marine litter: Sea change for plastic pollution. (19.04.2017) Scientists, policymakers and the public can learn from LITTERBASE, a newly launched online database of information from 1,300 peer-reviewed publications that provides analysis and visualization of human-generated marine litter worldwide (http://litterbase.org).This comprehensive resource will help to coordinate international action against a lethal form 297-297.

· Carbon markets: extend, don't limit. (19.04.2017) In our view, your headline 'Don't link carbon markets' is poor advice to policymakers (J.GreenNature543, 484–486;10.1038/543484a2017). To cut carbon pollution at the pace and scale that science demands, we must create linkages that can 297-297.

· Carbon markets: link with caution. (19.04.2017) Jessica Green's admonition to avoid linking carbon markets is not the consensus among economists and social scientists (Nature543, 484–486;10.1038/543484a2017). This advice seems to misinterpret how carbon-pricing instruments operate.International trade in goods and services has improved 297-297.

· Scientific methods: Teach children to spot fake facts. (19.04.2017) I agree that we should train students how to use the scientific method in their everyday lives (Nature543, 149;10.1038/5431492017 and Nature543, 150;10.1038/5431502017), but this needs to start much earlier than in college 297-297.

Obituary

· Ronald Drever (1931?2017). (19.04.2017) Experimental physicist key to the detection of gravitational waves. 298-298.

Naturejobs

· Retirement: Dollars and sense. (19.04.2017) Don't delay— start saving early and fatten your pension pot. 381-383.

· Mental health: Degree and depression. (19.04.2017) 383-383.

Futures

· Running safety tips for humans. (19.04.2017) Exercise caution. 386-386.

Correction

· Correction. (19.04.2017) The News story‘Cassini’s science swan-song’ (Nature 544, 149–150; 2017) erred in implying that the inner rings are known to contain propeller-shaped gaps. The gaps are known to exist in outer rings, but no hints have yet been seen of them in the 282-282.

News& Views

· Ecology: In peril from a perfect pathogen. (19.04.2017) It emerges that a fungal infection killing salamanders has many potential reservoirs, and that environmentally resistant spores transmit disease. Urgent interventions are needed to save susceptible populations from extinction. See Letter p.353 300-301.

· Materials science: Crystals aligned through graphene. (19.04.2017) Graphene has been used as a 'transparent' layer that allows single crystals of a material to be grown on a substrate, and then lifted off— in much the same way that baking paper lets cakes be removed easily from tins. See Letter p.340 301-302.

· Neurodegenerative disease: Two?for?one on potential therapies. (12.04.2017) Molecules that inhibit the synthesis of the ataxin 2 protein can ameliorate the effects of two neurodegenerative diseases in mouse models, raising hopes for the success of this approach in clinical trials. See Letters p.362& p.367 302-303.

· Microbiology: Gut microbes augment neurodegeneration. (12.04.2017) Bacterial residents of the human body often provide beneficial effects, but some can be harmful. The action of gut bacteria has been found to be tightly linked to neurodegeneration in a mouse model of Parkinson's disease. 304-305.

· Materials science: How to print glass. (19.04.2017) From time immemorial, optically transparent fused silica glasses have been treasured for their physical, chemical and aesthetic qualities. When it comes to producing and patterning such glasses, the image that typically springs to mind is of a high-temperature furnace and a sweaty glass-blower skilfully moulding 305-305.

· Glaciology: Ice-shelf stability questioned. (19.04.2017) Surface lakes and streams are forming on Antarctica's ice shelves, making them susceptible to instability and possible collapse. But rivers could mitigate this effect by efficiently exporting meltwater to the ocean. See Letters p.344& p.349 306-307.

· 50& 100 Years Ago. (19.04.2017) 50 Years AgoSome elegantly simple results of Defendi, Ephrussi et al. ... have provided strong support for the general hypothesis that cancer induced by virus results from the addition of genetic information.Uncontrolled growth is the characteristic property that distinguishes all cancer cells 307-307.

· Structural biology: A receptor that might block itself. (05.04.2017) The structure of the angiotensin II type 2 receptor reveals a potential mode of self-blocking action. This might explain its lack of signalling, and opens up avenues of investigation into its function and role in disease. See Article p.327 307-308.

Article

· Virus genomes reveal factors that spread and sustained the Ebola epidemic. (12.04.2017) The 2013–2016 West African epidemic caused by the Ebola virus was of unprecedented magnitude, duration and impact. Here we reconstruct the dispersal, proliferation and decline of Ebola virus throughout the region by analysing 1,610 Ebola virus genomes, which represent over 5% of the known cases. 309-315.

· Postsynaptic synaptotagmins mediate AMPA receptor exocytosis during LTP. (29.03.2017) Strengthening of synaptic connections by NMDA (N-methyl-d-aspartate) receptor-dependent long-term potentiation (LTP) shapes neural circuits and mediates learning and memory. During the induction of NMDA-receptor-dependent LTP, Ca2+ influx stimulates recruitment of synaptic AMPA (α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid) receptors, thereby strengthening synapses. 316-321.

· A B12-dependent radical SAM enzyme involved in oxetanocin A biosynthesis. (27.03.2017) Oxetanocin A (OXT-A) is a potent antitumour, antiviral and antibacterial compound. Biosynthesis of OXT-A has been linked to a plasmid-borne Bacillus megaterium gene cluster that contains four genes: oxsA, oxsB, oxrA and oxrB. Here we show that both the oxsA 322-326.

· Structural basis for selectivity and diversity in angiotensin II receptors. (05.04.2017) The angiotensin II receptors AT1R and AT2R serve as key components of the renin–angiotensin–aldosterone system. AT1R has a central role in the regulation of blood pressure, but the function of AT2R is unclear and it has a 327-332.

Letter

· A temperate rocky super-Earth transiting a nearby cool star. (19.04.2017) M dwarf stars, which have masses less than 60 per cent that of the Sun, make up 75 per cent of the population of the stars in the Galaxy. The atmospheres of orbiting Earth-sized planets are observationally accessible via transmission spectroscopy when the planets pass in front of these stars. Statistical results suggest that the nearest transiting Earth-sized planet in the liquid-water, habitable zone of an M dwarf star is probably around 10.5 parsecs away. A temperate planet has been discovered orbiting Proxima Centauri, the closest M dwarf, but it probably does not transit and its true mass is unknown. Seven Earth-sized planets transit the very low-mass star TRAPPIST-1, which is 12 parsecs away, but their masses and, particularly, their densities are poorly constrained. Here we report observations of LHS 1140b, a planet with a radius of 1.4 Earth radii transiting a small, cool star (LHS 1140) 12 parsecs away. We measure the mass of the planet to be 6.6 times that of Earth, consistent with a rocky bulk composition. LHS 1140b receives an insolation of 0.46 times that of Earth, placing it within the liquid-water, habitable zone. With 90 per cent confidence, we place an upper limit on the orbital eccentricity of 0.29. The circular orbit is unlikely to be the result of tides and therefore was probably present at formation. Given its large surface gravity and cool insolation, the planet may have retained its atmosphere despite the greater luminosity (compared to the present-day) of its host star in its youth. Because LHS 1140 is nearby, telescopes currently under construction might be able to search for specific atmospheric gases in the future. 333-336.

· Three-dimensional printing of transparent fused silica glass. (19.04.2017) Glass is one of the most important high-performance materials used for scientific research, in industry and in society, mainly owing to its unmatched optical transparency, outstanding mechanical, chemical and thermal resistance as well as its thermal and electrical insulating properties. However, glasses and especially high-purity glasses such as fused silica glass are notoriously difficult to shape, requiring high-temperature melting and casting processes for macroscopic objects or hazardous chemicals for microscopic features. These drawbacks have made glasses inaccessible to modern manufacturing technologies such as three-dimensional printing (3D printing). Using a casting nanocomposite, here we create transparent fused silica glass components using stereolithography 3D printers at resolutions of a few tens of micrometres. The process uses a photocurable silica nanocomposite that is 3D printed and converted to high-quality fused silica glass via heat treatment. The printed fused silica glass is non-porous, with the optical transparency of commercial fused silica glass, and has a smooth surface with a roughness of a few nanometres. By doping with metal salts, coloured glasses can be created. This work widens the choice of materials for 3D printing, enabling the creation of arbitrary macro- and microstructures in fused silica glass for many applications in both industry and academia. 337-339.

· Remote epitaxy through graphene enables two-dimensional material-based layer transfer. (19.04.2017) Epitaxy—the growth of a crystalline material on a substrate—is crucial for the semiconductor industry, but is often limited by the need for lattice matching between the two material systems. This strict requirement is relaxed for van der Waals epitaxy, in which epitaxy on layered or two-dimensional (2D) materials is mediated by weak van der Waals interactions, and which also allows facile layer release from 2D surfaces. It has been thought that 2D materials are the only seed layers for van der Waals epitaxy. However, the substrates below 2D materials may still interact with the layers grown during epitaxy (epilayers), as in the case of the so-called wetting transparency documented for graphene. Here we show that the weak van der Waals potential of graphene cannot completely screen the stronger potential field of many substrates, which enables epitaxial growth to occur despite its presence.We use density functional theory calculations to establish that adatoms will experience remote epitaxial registry with a substrate through a substrate–epilayer gap of up to nine ångströms; this gap can accommodate a monolayer of graphene. We confirm the predictions with homoepitaxial growth of GaAs(001) on GaAs(001) substrates through monolayer graphene, and show that the approach is also applicable to InP and GaP. The grown single-crystalline films are rapidly released from the graphene-coated substrate and perform as well as conventionally prepared films when incorporated in light-emitting devices. This technique enables any type of semiconductor film to be copied from underlying substrates through 2D materials, and then the resultant epilayer to be rapidly released and transferred to a substrate of interest. This process is particularly attractive in the context of non-silicon electronics and photonics, where the ability to re-use the graphene-coated substrates allows savings on the high cost of non-silicon substrates. 340-343.

· Antarctic ice shelf potentially stabilized by export of meltwater in surface river. (19.04.2017) Meltwater stored in ponds and crevasses can weaken and fracture ice shelves, triggering their rapid disintegration. This ice-shelf collapse results in an increased flux of ice from adjacent glaciers and ice streams, thereby raising sea level globally. However, surface rivers forming on ice shelves could potentially export stored meltwater and prevent its destructive effects. Here we present evidence for persistent active drainage networks—interconnected streams, ponds and rivers—on the Nansen Ice Shelf in Antarctica that export a large fraction of the ice shelf’s meltwater into the ocean. We find that active drainage has exported water off the ice surface through waterfalls and dolines for more than a century. The surface river terminates in a 130-metre-wide waterfall that can export the entire annual surface melt over the course of seven days. During warmer melt seasons, these drainage networks adapt to changing environmental conditions by remaining active for longer and exporting more water. Similar networks are present on the ice shelf in front of Petermann Glacier, Greenland, but other systems, such as on the Larsen C and Amery Ice Shelves, retain surface water at present. The underlying reasons for export versus retention remain unclear. Nonetheless our results suggest that, in a future warming climate, surface rivers could export melt off the large ice shelves surrounding Antarctica—contrary to present Antarctic ice-sheet models, which assume that meltwater is stored on the ice surface where it triggers ice-shelf disintegration. 344-348.

· Widespread movement of meltwater onto and across Antarctic ice shelves. (19.04.2017) Surface meltwater drains across ice sheets, forming melt ponds that can trigger ice-shelf collapse, acceleration of grounded ice flow and increased sea-level rise. Numerical models of the Antarctic Ice Sheet that incorporate meltwater’s impact on ice shelves, but ignore the movement of water across the ice surface, predict a metre of global sea-level rise this century in response to atmospheric warming. To understand the impact of water moving across the ice surface a broad quantification of surface meltwater and its drainageis needed. Yet, despite extensive research in Greenland and observations of individual drainage systems in Antarctica, we have little understanding of Antarctic-wide surface hydrology or how it will evolve. Here we show widespread drainage of meltwater across the surface of the ice sheet through surface streams and ponds (hereafter ‘surface drainage’) as far south as 85° S and as high as 1,300 metres above sea level. Our findings are based on satellite imagery from 1973 onwards and aerial photography from 1947 onwards. Surface drainage has persisted for decades, transporting water up to 120 kilometres from grounded ice onto and across ice shelves, feeding vast melt ponds up to 80 kilometres long. Large-scale surface drainage could deliver water to areas of ice shelves vulnerable to collapse, as melt rates increase this century. While Antarctic surface melt ponds are relatively welldocumented on some ice shelves, we have discovered that ponds often form part of widespread, large-scale surface drainage systems. In a warming climate, enhanced surface drainage could accelerate future ice-mass loss from Antarctic, potentially via positive feedbacks between the extent of exposed rock, melting and thinning of the ice sheet. 349-352.

· Drivers of salamander extirpation mediated by Batrachochytrium salamandrivorans. (19.04.2017) The recent arrival of Batrachochytrium salamandrivorans in Europe was followed by rapid expansion of its geographical distribution and host range, confirming the unprecedented threat that this chytrid fungus poses to western Palaearctic amphibians. Mitigating this hazard requires a thorough understanding of the pathogen’s disease ecology that is driving the extinction process. Here, we monitored infection, disease and host population dynamics in a Belgian fire salamander (Salamandra salamandra) population for two years immediately after the first signs of infection. We show that arrival of this chytrid is associated with rapid population collapse without any sign of recovery, largely due to lack of increased resistance in the surviving salamanders and a demographic shift that prevents compensation for mortality. The pathogen adopts a dual transmission strategy, with environmentally resistant non-motile spores in addition to the motile spores identified in its sister species B. dendrobatidis. The fungus retains its virulence not only in water and soil, but also in anurans and less susceptible urodelan species that function as infection reservoirs. The combined characteristics of the disease ecology suggest that further expansion of this fungus will behave as a ‘perfect storm’ that is able to rapidly extirpate highly susceptible salamander populations across Europe. 353-356.

· Neanderthal behaviour, diet, and disease inferred from ancient DNA in dental calculus. (08.03.2017) Recent genomic data have revealed multiple interactions between Neanderthals and modern humans, but there is currently little genetic evidence regarding Neanderthal behaviour, diet, or disease. Here we describe the shotgun-sequencing of ancient DNA from five specimens of Neanderthal calcified dental plaque (calculus) and the characterization of regional differences in Neanderthal ecology. At Spy cave, Belgium, Neanderthal diet was heavily meat based and included woolly rhinoceros and wild sheep (mouflon), characteristic of a steppe environment. In contrast, no meat was detected in the diet of Neanderthals from El Sidrón cave, Spain, and dietary components of mushrooms, pine nuts, and moss reflected forest gathering. Differences in diet were also linked to an overall shift in the oral bacterial community (microbiota) and suggested that meat consumption contributed to substantial variation within Neanderthal microbiota. Evidence for self-medication was detected in an El Sidrón Neanderthal with a dental abscess and a chronic gastrointestinal pathogen (Enterocytozoon bieneusi). Metagenomic data from this individual also contained a nearly complete genome of the archaeal commensal Methanobrevibacter oralis (10.2× depth of coverage)—the oldest draft microbial genome generated to date, at around 48,000 years old. DNA preserved within dental calculus represents a notable source of information about the behaviour and health of ancient hominin specimens, as well as a unique system that is useful for the study of long-term microbial evolution. 357-361.

· Antisense oligonucleotide therapy for spinocerebellar ataxia type 2. (12.04.2017) There are no disease-modifying treatments for adult human neurodegenerative diseases. Here we test RNA-targeted therapies in two mouse models of spinocerebellar ataxia type 2 (SCA2), an autosomal dominant polyglutamine disease. Both models recreate the progressive adult-onset dysfunction and degeneration of a neuronal network that are seen in patients, including decreased firing frequency of cerebellar Purkinje cells and a decline in motor function. We developed a potential therapy directed at the ATXN2 gene by screening 152 antisense oligonucleotides (ASOs). The most promising oligonucleotide, ASO7, downregulated ATXN2 mRNA and protein, which resulted in delayed onset of the SCA2 phenotype. After delivery by intracerebroventricular injection to ATXN2-Q127 mice, ASO7 localized to Purkinje cells, reduced cerebellar ATXN2 expression below 75% for more than 10 weeks without microglial activation, and reduced the levels of cerebellar ATXN2. Treatment of symptomatic mice with ASO7 improved motor function compared to saline-treated mice. ASO7 had a similar effect in the BAC-Q72 SCA2 mouse model, and in both mouse models it normalized protein levels of several SCA2-related proteins expressed in Purkinje cells, including Rgs8, Pcp2, Pcp4, Homer3, Cep76 and Fam107b. Notably, the firing frequency of Purkinje cells returned to normal even when treatment was initiated more than 12 weeks after the onset of the motor phenotype in BAC-Q72 mice. These findings support ASOs as a promising approach for treating some human neurodegenerative diseases. 362-366.

· Therapeutic reduction of ataxin-2 extends lifespan and reduces pathology in TDP-43 mice. (12.04.2017) Amyotrophic lateral sclerosis (ALS) is a rapidly progressing neurodegenerative disease that is characterized by motor neuron loss and that leads to paralysis and death 2–5 years after disease onset. Nearly all patients with ALS have aggregates of the RNA-binding protein TDP-43 in their brains and spinal cords, and rare mutations in the gene encoding TDP-43 can cause ALS. There are no effective TDP-43-directed therapies for ALS or related TDP-43 proteinopathies, such as frontotemporal dementia. Antisense oligonucleotides (ASOs) and RNA-interference approaches are emerging as attractive therapeutic strategies in neurological diseases. Indeed, treatment of a rat model of inherited ALS (caused by a mutation in Sod1) with ASOs against Sod1 has been shown to substantially slow disease progression. However, as SOD1 mutations account for only around 2–5% of ALS cases, additional therapeutic strategies are needed. Silencing TDP-43 itself is probably not appropriate, given its critical cellular functions. Here we present a promising alternative therapeutic strategy for ALS that involves targeting ataxin-2. A decrease in ataxin-2 suppresses TDP-43 toxicity in yeast and flies, and intermediate-length polyglutamine expansions in the ataxin-2 gene increase risk of ALS. We used two independent approaches to test whether decreasing ataxin-2 levels could mitigate disease in a mouse model of TDP-43 proteinopathy. First, we crossed ataxin-2 knockout mice with TDP-43 (also known as TARDBP) transgenic mice. The decrease in ataxin-2 reduced aggregation of TDP-43, markedly increased survival and improved motor function. Second, in a more therapeutically applicable approach, we administered ASOs targeting ataxin-2 to the central nervous system of TDP-43 transgenic mice. This single treatment markedly extended survival. Because TDP-43 aggregation is a component of nearly all cases of ALS, targeting ataxin-2 could represent a broadly effective therapeutic strategy. 367-371.

· Modulating the therapeutic response of tumours to dietary serine and glycine starvation. (19.04.2017) The non-essential amino acids serine and glycine are used in multiple anabolic processes that support cancer cell growth and proliferation (reviewed in ref. 1). While some cancer cells upregulate de novo serine synthesis, many others rely on exogenous serine for optimal growth. Restriction of dietary serine and glycine can reduce tumour growth in xenograft and allograft models. Here we show that this observation translates into more clinically relevant autochthonous tumours in genetically engineered mouse models of intestinal cancer (driven by Apc inactivation) or lymphoma (driven by Myc activation). The increased survival following dietary restriction of serine and glycine in these models was further improved by antagonizing the anti-oxidant response. Disruption of mitochondrial oxidative phosphorylation (using biguanides) led to a complex response that could improve or impede the anti-tumour effect of serine and glycine starvation. Notably, Kras-driven mouse models of pancreatic and intestinal cancers were less responsive to depletion of serine and glycine, reflecting an ability of activated Kras to increase the expression of enzymes that are part of the serine synthesis pathway and thus promote de novo serine synthesis. 372-376.

· Rad51-mediated double-strand break repair and mismatch correction of divergent substrates. (12.04.2017) The Rad51 (also known as RecA) family of recombinases executes the critical step in homologous recombination: the search for homologous DNA to serve as a template during the repair of DNA double-strand breaks (DSBs). Although budding yeast Rad51 has been extensively characterized in vitro, the stringency of its search and sensitivity to mismatched sequences in vivo remain poorly defined. Here, in Saccharomyces cerevisiae, we analysed Rad51-dependent break-induced replication in which the invading DSB end and its donor template share a 108-base-pair homology region and the donor carries different densities of single-base-pair mismatches. With every eighth base pair mismatched, repair was about 14% of that of completely homologous sequences. With every sixth base pair mismatched, repair was still more than 5%. Thus, completing break-induced replication in vivo overcomes the apparent requirement for at least 6–8 consecutive paired bases that has been inferred from in vitro studies. When recombination occurs without a protruding nonhomologous 3′ tail, the mismatch repair protein Msh2 does not discourage homeologous recombination. However, when the DSB end contains a 3′ protruding nonhomologous tail, Msh2 promotes the rejection of mismatched substrates. Mismatch correction of strand invasion heteroduplex DNA is strongly polar, favouring correction close to the DSB end. Nearly all mismatch correction depends on the proofreading activity of DNA polymerase-δ, although the repair proteins Msh2, Mlh1 and Exo1 influence the extent of correction. 377-380.

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