Snapshots of Science

365 days highlights from news & views 2019 Snapshots of science

Neurodegeneration Planetary science Condensed-matter physics Selective clearance A new moon Superconductivity of mutant for Neptune near room huntingtin protein temperature In 1989, the NASA spacecraft Huntington’s disease is caused Voyager 2 detected six moons Materials known as by an abnormally long stretch of Neptune that are interior to superconductors transmit of glutamine amino-acid the orbit of the planet’s largest electrical energy with 100% residues in the huntingtin moon, Triton. Showalter et al. efficiency. They have a wide (HTT) protein. Cells degrade report the discovery of a seventh range of applications, such as the mutant huntingtin (mHTT) inner moon, Hippocamp. magnetic resonance imaging through autophagy — a Originally designated as in hospitals. However, these clearance mechanism that S/2004 N 1 and Neptune XIV, applications have been involves engulfment of this moon was found in images hampered, largely by the fact proteins by a vesicle called taken by NASA’s Hubble Space that the superconducting state the autophagosome. Li et al. Telescope in 2004–05 and exists only at temperatures hypothesized that compounds 2009, and then confirmed well below room temperature that bind to both the mutant in further images captured (295 kelvin). Drozdov et al. polyglutamine tract and the in 2016. Hippocamp is only report several key results protein LC3B, which resides in 34 kilometres wide, which that confirm that, when the autophagosome, would lead makes it diminutive compared compressed to pressures of to engulfment and enhanced with its larger siblings, and it more than one million times clearance of mHTT. The authors orbits Neptune (pictured) just Earth’s atmospheric pressure, conducted small-molecule inside the orbit of Proteus — the lanthanum hydride compounds, screens to identify candidate planet’s second-largest moon. which are rich in hydrogen, compounds, and used wild-type The discovery of Hippocamp become superconducting at HTT in a counter-screen to rule is intriguing because of the 250 K. In the next few years, out compounds that bind to the moon’s relationship to Proteus experiments will probably normal version of the protein. and the role that both objects focus on searching for They found encouraging might have had in the history of superconductivity in other evidence that four compounds Neptune’s inner system. pressurized hydrogen-rich could produce functional materials. Given that only improvements in models of Anne J. Verbiscer writing in a small fraction of possible Huntington’s disease across Nature 566, 328–329 (2019). hydrogen-rich systems have Fisheries three species. This therapeutic Original research: Nature 566, been subjected to experiments strategy might also be useful 350–353 (2019). at these tremendous pressures, for other diseases involving it seems more likely than Micronutrient expanded polyglutamine tracts. ever that the dream of room- temperature superconductivity richness of Huda Y. Zoghbi writing in Nature might be realized in the near global fish 575, 57–58 (2019). future. Original research: Nature 575, catches 203–209 (2019). James J. Hamlin writing in Nature 569, 491–492 (2019). Original research: Nature 569, 528–531 (2019). L TO R: NASA/JPL; SYLVAIN CHERKAOUI/REUTERS; LAUREN ANDREWS/NASA LAUREN CHERKAOUI/REUTERS; R: NASA/JPL; SYLVAIN L TO

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Genetic engineering CRISPR tool enables precise genome editing

Tremendous progress has been made in developing gene- editing tools. But a seemingly fundamental limit to the efficiency and precision of gene editing had been reached, owing to the tools’ reliance on complex and competing cellular Glaciology processes. Anzalone et al. now describe ‘search-and-replace’ Greenland’s genome editing, which enables the genome to be altered subglacial methane precisely. In their process, the released ‘search’ part of an RNA guide directs a Cas9 protein to a Sediments beneath glaciers specific sequence in a DNA and ice sheets harbour carbon target, where it cuts one of the reserves that, under certain two DNA strands. A reverse conditions, can be converted to transcriptase enzyme then methane, a potent greenhouse produces DNA complementary gas. Lamarche-Gagnon et al. to the sequence in the ‘replace’ present direct measurements part of the guide, and installs it of dissolved methane in water at one of the cut ends, where it discharged from a land- takes the place of the original terminating glacier of the DNA sequence. DNA repair then Greenland Ice Sheet (pictured) produces a fully edited duplex. during the summer. The water Imperfect edits are almost was supersaturated with entirely avoided. methane, and the amount Fish are a source of micronutrients that help to of methane released to the prevent nutrient-deficiency diseases. For 43 countries, Randall J. Platt writing in Nature atmosphere rivals that from 576, 48–49 (2019). other terrestrial rivers. Hicks et al. mapped the relationship between the Original research: Nature 576, Subglacial sediments can fish-derived nutrients available from fisheries’ 149–157 (2019). therefore act as a local source catches and the prevalence of such diseases. Their of methane, corroborating data demonstrate that catches in some developing the results of other studies. countries should be enough to meet the key Lamarche-Gagnon et al. go further by demonstrating micronutrient needs of their populations. However, that the continuous flux of in many developing tropical countries, a substantial methane from the Greenland proportion of local fish catches are either exported subglacial environment varies or processed locally to generate fishmeal that is then with the efficiency of subglacial exported and used to feed farmed fish. Many of the meltwater drainage. The study provides an example of how local fisheries (pictured), which had traditionally our planet’s icy domains can supplied the regional markets, now instead supply interact with the surrounding fishmeal plants. This does not reduce the pressure on Earth system in unexpected and wild fish. Moreover, it deprives people on low incomes potentially important ways. of previously affordable, nutritious local fish. Lauren C. Andrews writing in Daniel Pauly writing in Nature 574, 41–42 (2019). Nature 565, 31–32 (2019). Original research: Nature 574, 95–98 (2019). Original research: Nature 565, 73–77 (2019).

365 days highlights from news & views 2019

Genetics Synthesis Fate of a father’s Chemical libraries READERS’ mitochondria from a double click CHOICE The DNA of eukaryotic A copper-catalysed reaction, We asked readers to vote organisms (such as animals, known as the CuAAC reaction, for a News & Views article plants and fungi) is stored in is the poster child for click to be included as part of two cellular compartments: in chemistry. A reaction is defined our round-up of the year. the nucleus and in organelles as click chemistry if it is (among This is the one they chose. called mitochondria. A healthy other things) operationally individual’s mitochondrial DNA simple, high-yielding, Palaeoanthropology (mtDNA) molecules are mostly applicable to a broad range of identical. However, in people compounds, yet exceptionally Unknown human with diseases caused by mtDNA selective — the chemical groups mutations, normal and mutant that undergo the reaction relative found mtDNA molecules typically must react only with each in Asia coexist in a single cell — a other. CuAAC reactions are situation termed heteroplasmy. used in many disciplines, but Détroit et al. report the Mitochondrial DNA was their applications would be remarkable discovery of

thought to derive exclusively even broader if structurally a human relative that will AG PÉTER FANKHAUSER/ANYBOTICS from maternal egg cells, with complex azide compounds no doubt ignite plenty of Artificial intelligence no paternal contribution, but (which contain N3 groups) were scientific debate. This newly Luo et al. challenge this dogma, Robots on the run more widely available to use as identified species was found identifying three families with reactants. Meng et al. report that in the Philippines and named mtDNA heteroplasmy caused Young animals gallop across fluorosulfuryl azide (FSO2N3) Homo luzonensis. Rapidly by biparental mitochondrial fields, climb trees and reacts with almost any primary changing knowledge about inheritance. Previous work has immediately find their feet amine (compounds that contain hominin evolution in Asia is shown that mitophagy, the with enviable grace after they NH2 groups) to achieve a nearly forcing the re-examination process by which cells ‘eat’ their fall. And like our primate 100% yield of the corresponding of ideas about early hominin own mitochondria, has a role cousins, humans can deploy azide, and used their reagent to dispersals from Africa to in the selective elimination of opposable thumbs and fine make a library of 1,224 azides. Eurasia. Homo luzonensis paternal mitochondria. These motor skills to complete tasks Their reaction meets the speed, provides yet more evidence rare instances of paternal such as effortlessly peeling a breadth and efficiency criteria that hints that Homo erectus mtDNA transmission might clementine or feeling for the for click chemistry. Moreover, might not have been the therefore be attributed to correct key in a dark hallway. the prepared azide solutions only globe-trotting early defective mitochondrial Although walking and grasping can be used directly in CuAAC hominin. The interesting turnover. are easy for many living things, reactions. mix of features observed in robots have been notoriously H. luzonensis raises questions Thomas G. McWilliams and poor at gaited locomotion and Joseph J. Topczewski and about the species’ ancestry Anu Suomalainen writing in manual dexterity. Even a robot En-Chih Liu writing in Nature 574, and its relationships with Nature 565, 296–297 (2019). that performs beautifully in 42–43 (2019). other human relatives. Original research: Proc. Natl simulation will stumble and Original research: Nature 574, One thing can be said for Acad. Sci. USA 115, 13039–13044 fall after a few encounters 86–89 (2019). certain — our picture of (2018). with seemingly minor physical hominin evolution in Asia obstacles. Writing in Science just got even messier, more Robotics, Hwangbo et al. report complicated and a whole lot that a data-driven approach to more interesting. designing robotic software can improve the locomotion skills Matthew W. Tocheri writing in of robots. They demonstrate Nature 568, 176–178 (2019). their method using the ANYmal Original research: Nature 568, robot (pictured) — a medium- 181–186 (2019). dog-sized quadrupedal system.

Hod Lipson writing in Nature 568, 174–175 (2019). Original research: Sci. Robot. 4, eaau5872 (2019).

Correction The citation for the original research in the ‘Robots on the run’ section was incorrect. It should have been Sci. Robot. 4, eaau5872 (2019).