目次

Editorials

実験動物の苦痛を軽減する努力は、哺乳類だけでなく、魚類も含め、全てを対象にすべきだ。

Fish have feelings too p.407

Our obligation to keep the suffering of laboratory animals to a minimum — both in life and in death — does not apply only to mammals.

doi: 10.1038/506407a

数学分野のオンライン共同プロジェクトの成功から、他の分野も多くを学べるだろう。

Parallel lines p.407

A collaborative online mathematics project holds lessons for other disciplines.

doi: 10.1038/506407b

民間による宇宙飛行に必要なのは、ビジョンとハードワークと大いなる「楽観主義」だろう。

Virgin territory p.408

Putting a private craft into space requires vision, hard work and a big dose of optimism.

doi: 10.1038/506408a

News

H7N9鳥インフルエンザが、中国からベトナムへ広がる恐れが。

Vietnam on high alert over flu risk p.415

H7N9 avian influenza may spread from China for first time.

doi: 10.1038/506415a

ゲーム理論の実験によって、サルの社会的協調に関わる神経回路の手がかりが。

Monkey brains wired to share p.416

Game-theory test exposes circuits for social interaction.

doi: 10.1038/506416a

ブラジルのサンパウロ州が、巨大マゼラン望遠鏡計画への参加を検討へ。

São Paulo poised to join megatelescope p.417

Brazilian state mulls support for Giant Magellan Telescope.

doi: 10.1038/506417a

アインシュタインはかつて、ビックバン理論を受け入れがたいがために定常宇宙の可能性を考慮していたことが、昔の直筆原稿から明らかに。

Einstein’s lost theory uncovered p.418

Physicist explored the idea of a steady-state Universe in 1931.

doi: 10.1038/506418a

実験用のゼブラフィッシュの安楽死に用いる薬剤が、かえって苦痛を感じさせているのではないかと疑問が。

Fish-kill method questioned p.419

Common anaesthetic not the most humane option for zebrafish euthanasia, say studies.

doi: 10.1038/506419a

米・独の協同開発による「飛行天文台」SOFIAが、ようやく技術的問題を克服して最大限の性能発揮へ。

SOFIA irons out technical kinks p.420

US–German airborne telescope slow to reach full capability.

doi: 10.1038/506420a

News Features

クラウドソーシング:数の強み

Crowd-sourcing: Strength in numbers p.422

オンラインで多数の力を集めて協同で行うプロジェクトは、適切な問題を選べば、研究のスピードアップに役立つことが分かってきた。

doi: 10.1038/506422a

法廷の科学:病原菌による捜査

Science in court: Disease detectives p.424

微生物の系統関係を推定する強力な手法が考案され、この系統関係が裁判の証拠として用いられるケースが増えているが、その扱いには注意が必要だ。

doi: 10.1038/506424a

News & Views

結核:「手をかけない」創薬

Tuberculosis: Drug discovery goes au naturel p.436

半合成による薬剤設計の可能性を示した研究で、結核菌(Mycobacterium tuberculosis)に対する効力が弱い既存の抗生物質の1つの構造に修飾を加えることで、有効性が高い新種のリード化合物が作られた。

doi: 10.1038/506436a

応用物理学:宇宙鏡向きの光学トラッピング

Applied physics: Optical trapping for space mirrors p.437

光によって決まった位置に保持された微細粒子だけを使って、宇宙望遠鏡用の鏡を作り出すことは可能だろうか。光学的束縛と呼ばれる技術を使った研究によって、この目標が一歩近づいた。

doi: 10.1038/506437a

がん:変異がなくても発生する新しいタイプのがん 

Cancer: Tumours outside the mutation box p.438

脳腫瘍の1つである上衣腫の研究から、あるサブタイプでは遺伝子再編成が見られるが、他の2つにはDNAに変異が生じていないことが分かった。これは、がんのイニシエーションの機構が一般に考えられているよりも幅広いことを示唆している。

doi: 10.1038/nature13061

保全:風に吹かれて

Conservation: Wind blown p.440

モデル化研究と野外観察を組み合わせて、森林の中の空き地は風による種子の散布状況を変化させる可能性があることが明らかにされた。この知見は、植物の保全と関わってくる。

doi: 10.1038/506440a

基本定数:精度のチームワーク

Fundamental constants: The teamwork of precision p.440

電子の原子質量の新しい値は、素粒子物理学の標準模型の1兆分の1の精度での検証を可能にすると考えられる一連の測定の一環として得られた。

doi: 10.1038/nature13059

細胞生物学:クローン病の厄介な遺伝学

Cell biology: Stressful genetics in Crohn's disease p.441

オートファジー関連タンパク質ATG16L1によく生じる変異は、クローン病のリスク因子である。だが、この遺伝学的変化は、細胞がストレスを受けてATG16L1がカスパーゼ3によって切断される時にだけ正体を現すことが分かった。

doi: 10.1038/nature13060

大気科学:迅速な酸化から生じる不揮発性粒子

Atmospheric science: Involatile particles from rapid oxidation p.442

植生が生産する気化物質から微小なエアロゾル粒子が形成され、さらに大きくなる仕組みについては分かっていない。揮発性有機化合物から高度に酸化された産物が直接形成されるという知見は、解決の糸口になりそうだ。

doi: 10.1038/506442a

Articles

がん:エピゲノミック変化は致死的なCIMP陽性の乳児上衣腫の原因となる

Epigenomic alterations define lethal CIMP-positive ependymomas of infancy p.445

Although genetically bland, the posterior fossa group A subgroup of ependymomas, found often in infants and associated with poor prognosis, exhibit widespread epigenetic alterations, namely a CpG island methylator phenotype; these tumours are shown to be susceptible both in vitro and in vivo to various compounds that target epigenetic modifications, such as DNA methylation and H3K27 tri-methylation.

doi: 10.1038/nature13108

がん:C11orf95–RELA融合は上衣腫で発がん性NF-κBシグナル伝達を駆動する

C11orf95RELA fusions drive oncogenic NF-κB signalling in ependymoma p.451

At least two-thirds of supratentorial ependymomas contain oncogenic fusions between RELA, the principal effector of nuclear factor-κB (NF-κB) signalling, and uncharacterized gene C11orf95; C11orf95–RELA fusion proteins translocate spontaneously to the nucleus to activate NF-κB target genes, and rapidly transform neural stem cells to form tumours in mice

doi: 10.1038/nature13109

細胞生物学:クローン病で見られるAtg16l1変異体はカスパーゼ3による分解を促進する

A Crohn’s disease variant in Atg16l1 enhances its degradation by caspase 3 p.456

The Crohn’s disease risk-conferring T300A variant in the autophagy protein ATG16L1 increases its sensitivity to caspase-3-mediated cleavage; this decreases the induction of autophagy in response to metabolic stress or pathogen infection, leading to increased secretion of inflammatory cytokines.

doi: 10.1038/nature13044

Letters

宇宙:恒星SMSS J031300.36–670839.3における金属の源としての、低エネルギーで鉄に乏しい1個の超新星

A single low-energy, iron-poor supernova as the source of metals in the star SMSS J031300.36−670839.3 p.463

The element abundance ratios of four low-mass stars with extremely low metallicities (abundances of elements heavier than helium) indicate that the gas out of which the stars formed was enriched in each case by at most a few—and potentially only one—low-energy supernova. Such supernovae yield large quantities of light elements such as carbon but very little iron. The dominance of low-energy supernovae seems surprising, because it had been expected that the first stars were extremely massive, and that they disintegrated in pair-instability explosions that would rapidly enrich galaxies in iron. What has remained unclear is the yield of iron from the first supernovae, because hitherto no star has been unambiguously interpreted as encapsulating the yield of a single supernova. Here we report the optical spectrum of SMSS J031300.36−670839.3, which shows no evidence of iron (with an upper limit of 10−7.1 times solar abundance). Based on a comparison of its abundance pattern with those of models, we conclude that the star was seeded with material from a single supernova with an original mass about 60 times that of the Sun (and that the supernova left behind a black hole). Taken together with the four previously mentioned low-metallicity stars, we conclude that low-energy supernovae were common in the early Universe, and that such supernovae yielded light-element enrichment with insignificant iron. Reduced stellar feedback both chemically and mechanically from low-energy supernovae would have enabled first-generation stars to form over an extended period. We speculate that such stars may perhaps have had an important role in the epoch of cosmic reionization and the chemical evolution of early galaxies.

doi: 10.1038/nature12990

素粒子物理学:電子の原子質量の高精度測定

High-precision measurement of the atomic mass of the electron p.467

The quest for the value of the electron’s atomic mass has been the subject of continuing efforts over the past few decades. Among the seemingly fundamental constants that parameterize the Standard Model of physics and which are thus responsible for its predictive power, the electron mass me is prominent, being responsible for the structure and properties of atoms and molecules. It is closely linked to other fundamental constants, such as the Rydberg constant R and the fine-structure constant α (ref. 6). However, the low mass of the electron considerably complicates its precise determination. Here we combine a very precise measurement of the magnetic moment of a single electron bound to a carbon nucleus with a state-of-the-art calculation in the framework of bound-state quantum electrodynamics. The precision of the resulting value for the atomic mass of the electron surpasses the current literature value of the Committee on Data for Science and Technology (CODATA) by a factor of 13. This result lays the foundation for future fundamental physics experiments and precision tests of the Standard Model.

doi: 10.1038/nature13026

量子光学:電子と正孔の量子液滴

Quantum droplets of electrons and holes p.471

Interacting many-body systems are characterized by stable configurations of objects—ranging from elementary particles to cosmological formations—that also act as building blocks for more complicated structures. It is often possible to incorporate interactions in theoretical treatments of crystalline solids by introducing suitable quasiparticles that have an effective mass, spin or charge which in turn affects the material’s conductivity, optical response or phase transitions. Additional quasiparticle interactions may also create strongly correlated configurations yielding new macroscopic phenomena, such as the emergence of a Mott insulator, superconductivity or the pseudogap phase of high-temperature superconductors. In semiconductors, a conduction-band electron attracts a valence-band hole (electronic vacancy) to create a bound pair, known as an exciton, which is yet another quasiparticle. Two excitons may also bind together to give molecules, often referred to as biexcitons, and even polyexcitons may exist. In indirect-gap semiconductors such as germanium or silicon, a thermodynamic phase transition may produce electron–hole droplets whose diameter can approach the micrometre range. In direct-gap semiconductors such as gallium arsenide, the exciton lifetime is too short for such a thermodynamic process. Instead, different quasiparticle configurations are stabilized dominantly by many-body interactions, not by thermalization. The resulting non-equilibrium quantum kinetics is so complicated that stable aggregates containing three or more Coulomb-correlated electron–hole pairs remain mostly unexplored. Here we study such complex aggregates and identify a new stable configuration of charged particles that we call a quantum droplet. This configuration exists in a plasma and exhibits quantization owing to its small size. It is charge neutral and contains a small number of particles with a pair-correlation function that is characteristic of a liquid. We present experimental and theoretical evidence for the existence of quantum droplets in an electron–hole plasma created in a gallium arsenide quantum well by ultrashort optical pulses.

doi: 10.1038/nature12994

大気科学:低揮発性二次有機エアロゾルの大規模発生源

A large source of low-volatility secondary organic aerosol p.476

The link between biogenic volatile organic compounds in the atmosphere and their conversion to aerosol particles is unclear, but a direct reaction pathway is now described by which volatile organic compounds lead to low-volatility vapours that can then condense onto aerosol surfaces, producing secondary organic aerosol.

doi: 10.1038/nature13032

地球化学:低温で保存されたマグマ結晶の急速な再流動

Rapid remobilization of magmatic crystals kept in cold storage p.480

The processes involved in the formation and storage of magma within the Earth’s upper crust are of fundamental importance to volcanology. Many volcanic eruptions, including some of the largest, result from the eruption of components stored for tens to hundreds of thousands of years before eruption. Although the physical conditions of magma storage and remobilization are of paramount importance for understanding volcanic processes, they remain relatively poorly known. Eruptions of crystal-rich magma are often suggested to require the mobilization of magma stored at near-solidus conditions; however, accumulation of significant eruptible magma volumes has also been argued to require extended storage of magma at higher temperatures. What has been lacking in this debate is clear observational evidence linking the thermal (and therefore physical) conditions within a magma reservoir to timescales of storage—that is, thermal histories. Here we present a method of constraining such thermal histories by combining timescales derived from uranium-series disequilibria, crystal sizes and trace-element zoning in crystals. At Mount Hood (Oregon, USA), only a small fraction of the total magma storage duration (at most 12 per cent and probably much less than 1 per cent) has been spent at temperatures above the critical crystallinity (40–50 per cent) at which magma is easily mobilized. Partial data sets for other volcanoes also suggest that similar conditions of magma storage are widespread and therefore that rapid mobilization of magmas stored at near-solidus temperatures is common. Magma storage at low temperatures indicates that, although thermobarometry calculations based on mineral compositions may record the conditions of crystallization, they are unlikely to reflect the conditions of most of the time that the magma is stored. Our results also suggest that largely liquid magma bodies that can be imaged geophysically will be ephemeral features and therefore their detection could indicate imminent eruption.

doi: 10.1038/nature12991

古生物学:複数の絶滅海生爬虫類に見られる皮膚での色素沈着は、メラニン形成が収斂的に起こったことの証拠となる

Skin pigmentation provides evidence of convergent melanism in extinct marine reptiles p.484

Throughout the animal kingdom, adaptive colouration serves critical functions ranging from inconspicuous camouflage to ostentatious sexual display, and can provide important information about the environment and biology of a particular organism. The most ubiquitous and abundant pigment, melanin, also has a diverse range of non-visual roles, including thermoregulation in ectotherms. However, little is known about the functional evolution of this important biochrome through deep time, owing to our limited ability to unambiguously identify traces of it in the fossil record. Here we present direct chemical evidence of pigmentation in fossilized skin, from three distantly related marine reptiles: a leatherback turtle, a mosasaur and an ichthyosaur. We demonstrate that dark traces of soft tissue in these fossils are dominated by molecularly preserved eumelanin, in intimate association with fossilized melanosomes. In addition, we suggest that contrary to the countershading of many pelagic animals, at least some ichthyosaurs were uniformly dark-coloured in life. Our analyses expand current knowledge of pigmentation in fossil integument beyond that of feathers, allowing for the reconstruction of colour over much greater ranges of extinct taxa and anatomy. In turn, our results provide evidence of convergent melanism in three disparate lineages of secondarily aquatic tetrapods. Based on extant marine analogues, we propose that the benefits of thermoregulation and/or crypsis are likely to have contributed to this melanisation, with the former having implications for the ability of each group to exploit cold environments.

doi: 10.1038/nature12899

微生物学:細菌での発生調節因子の転用による連続的な形態進化

Sequential evolution of bacterial morphology by co-option of a developmental regulator p.489

What mechanisms underlie the transitions responsible for the diverse shapes observed in the living world? Although bacteria exhibit a myriad of morphologies, the mechanisms responsible for the evolution of bacterial cell shape are not understood. We investigated morphological diversity in a group of bacteria that synthesize an appendage-like extension of the cell envelope called the stalk. The location and number of stalks varies among species, as exemplified by three distinct subcellular positions of stalks within a rod-shaped cell body: polar in the genus Caulobacter and subpolar or bilateral in the genus Asticcacaulis. Here we show that a developmental regulator of Caulobacter crescentus, SpmX, is co-opted in the genus Asticcacaulis to specify stalk synthesis either at the subpolar or bilateral positions. We also show that stepwise evolution of a specific region of SpmX led to the gain of a new function and localization of this protein, which drove the sequential transition in stalk positioning. Our results indicate that changes in protein function, co-option and modularity are key elements in the evolution of bacterial morphology. Therefore, similar evolutionary principles of morphological transitions apply to both single-celled prokaryotes and multicellular eukaryotes.

doi: 10.1038/nature12900

遺伝学:酵母の大集団における単一細胞タンパク質量の変動の遺伝学的特徴

Genetics of single-cell protein abundance variation in large yeast populations p.494

Variation among individuals arises in part from differences in DNA sequences, but the genetic basis for variation in most traits, including common diseases, remains only partly understood. Many DNA variants influence phenotypes by altering the expression level of one or several genes. The effects of such variants can be detected as expression quantitative trait loci (eQTL). Traditional eQTL mapping requires large-scale genotype and gene expression data for each individual in the study sample, which limits sample sizes to hundreds of individuals in both humans and model organisms and reduces statistical power. Consequently, many eQTL are probably missed, especially those with smaller effects. Furthermore, most studies use messenger RNA rather than protein abundance as the measure of gene expression. Studies that have used mass-spectrometry proteomics reported unexpected differences between eQTL and protein QTL (pQTL) for the same genes, but these studies have been even more limited in scope. Here we introduce a powerful method for identifying genetic loci that influence protein expression in the yeast Saccharomyces cerevisiae. We measure single-cell protein abundance through the use of green fluorescent protein tags in very large populations of genetically variable cells, and use pooled sequencing to compare allele frequencies across the genome in thousands of individuals with high versus low protein abundance. We applied this method to 160 genes and detected many more loci per gene than previous studies. We also observed closer correspondence between loci that influence protein abundance and loci that influence mRNA abundance of a given gene. Most loci that we detected were clustered in ‘hotspots’ that influence multiple proteins, and some hotspots were found to influence more than half of the proteins that we examined. The variants that underlie these hotspots have profound effects on the gene regulatory network and provide insights into genetic variation in cell physiology between yeast strains.

doi: 10.1038/nature12904

生化学:ヒト腸内の特定のバクテロイデス門細菌群が持つキシログルカン代謝能は、独立した1個の遺伝子座によってもたらされている

A discrete genetic locus confers xyloglucan metabolism in select human gut Bacteroidetes p.498

A well-balanced human diet includes a significant intake of non-starch polysaccharides, collectively termed ‘dietary fibre’, from the cell walls of diverse fruits and vegetables. Owing to the paucity of alimentary enzymes encoded by the human genome, our ability to derive energy from dietary fibre depends on the saccharification and fermentation of complex carbohydrates by the massive microbial community residing in our distal gut. The xyloglucans (XyGs) are a ubiquitous family of highly branched plant cell wall polysaccharides whose mechanism(s) of degradation in the human gut and consequent importance in nutrition have been unclear. Here we demonstrate that a single, complex gene locus in Bacteroides ovatus confers XyG catabolism in this common colonic symbiont. Through targeted gene disruption, biochemical analysis of all predicted glycoside hydrolases and carbohydrate-binding proteins, and three-dimensional structural determination of the vanguard endo-xyloglucanase, we reveal the molecular mechanisms through which XyGs are hydrolysed to component monosaccharides for further metabolism. We also observe that orthologous XyG utilization loci (XyGULs) serve as genetic markers of XyG catabolism in Bacteroidetes, that XyGULs are restricted to a limited number of phylogenetically diverse strains, and that XyGULs are ubiquitous in surveyed human metagenomes. Our findings reveal that the metabolism of even highly abundant components of dietary fibre may be mediated by niche species, which has immediate fundamental and practical implications for gut symbiont population ecology in the context of human diet, nutrition and health.

doi: 10.1038/nature12907

免疫:固着性の肺胞マクロファージは肺胞上皮と連絡して免疫を調節する

Sessile alveolar macrophages communicate with alveolar epithelium to modulate immunity p.503

The tissue-resident macrophages of barrier organs constitute the first line of defence against pathogens at the systemic interface with the ambient environment. In the lung, resident alveolar macrophages (AMs) provide a sentinel function against inhaled pathogens. Bacterial constituents ligate Toll-like receptors (TLRs) on AMs, causing AMs to secrete proinflammatory cytokines that activate alveolar epithelial receptors, leading to recruitment of neutrophils that engulf pathogens. Because the AM-induced response could itself cause tissue injury, it is unclear how AMs modulate the response to prevent injury. Here, using real-time alveolar imaging in situ, we show that a subset of AMs attached to the alveolar wall form connexin 43 (Cx43)-containing gap junction channels with the epithelium. During lipopolysaccharide-induced inflammation, the AMs remained sessile and attached to the alveoli, and they established intercommunication through synchronized Ca2+ waves, using the epithelium as the conducting pathway. The intercommunication was immunosuppressive, involving Ca2+-dependent activation of Akt, because AM-specific knockout of Cx43 enhanced alveolar neutrophil recruitment and secretion of proinflammatory cytokines in the bronchoalveolar lavage. A picture emerges of a novel immunomodulatory process in which a subset of alveolus-attached AMs intercommunicates immunosuppressive signals to reduce endotoxin-induced lung inflammation.

doi: 10.1038/nature12902

微生物学:代謝的に細胞壁を標識する新しい方法により明らかになったトラコーマクラミジアのペプチドグリカン 

A new metabolic cell-wall labelling method reveals peptidoglycan in Chlamydia trachomatis p.507

Peptidoglycan (PG), an essential structure in the cell walls of the vast majority of bacteria, is critical for division and maintaining cell shape and hydrostatic pressure. Bacteria comprising the Chlamydiales were thought to be one of the few exceptions. Chlamydia harbour genes for PG biosynthesis and exhibit susceptibility to ‘anti-PG’ antibiotics, yet attempts to detect PG in any chlamydial species have proven unsuccessful (the ‘chlamydial anomaly’). We used a novel approach to metabolically label chlamydial PG using d-amino acid dipeptide probes and click chemistry. Replicating Chlamydia trachomatis were labelled with these probes throughout their biphasic developmental life cycle, and the results of differential probe incorporation experiments conducted in the presence of ampicillin are consistent with the presence of chlamydial PG-modifying enzymes. These findings culminate 50 years of speculation and debate concerning the chlamydial anomaly and are the strongest evidence so far that chlamydial species possess functional PG.

doi: 10.1038/nature12892

細胞:腸の広範囲に許容状態にあるクロマチンは側方抑制と細胞の可塑性の基盤となる

Broadly permissive intestinal chromatin underlies lateral inhibition and cell plasticity p.511

Cells differentiate when transcription factors bind accessible cis-regulatory elements to establish specific gene expression programs. In differentiating embryonic stem cells, chromatin at lineage-restricted genes becomes sequentially accessible, probably by means of ‘pioneer’ transcription factor activity, but tissues may use other strategies in vivo. Lateral inhibition is a pervasive process in which one cell forces a different identity on its neighbours, and it is unclear how chromatin in equipotent progenitors undergoing lateral inhibition quickly enables distinct, transiently reversible cell fates. Here we report the chromatin and transcriptional underpinnings of differentiation in mouse small intestine crypts, where notch signalling mediates lateral inhibition to assign progenitor cells into absorptive or secretory lineages. Transcript profiles in isolated LGR5+ intestinal stem cells and secretory and absorptive progenitors indicated that each cell population was distinct and the progenitors specified. Nevertheless, secretory and absorptive progenitors showed comparable levels of H3K4me2 and H3K27ac histone marks and DNase I hypersensitivity—signifying accessible, permissive chromatin—at most of the same cis-elements. Enhancers acting uniquely in progenitors were well demarcated in LGR5+ intestinal stem cells, revealing early priming of chromatin for divergent transcriptional programs, and retained active marks well after lineages were specified. On this chromatin background, ATOH1, a secretory-specific transcription factor, controls lateral inhibition through delta-like notch ligand genes and also drives the expression of numerous secretory lineage genes. Depletion of ATOH1 from specified secretory cells converted them into functional enterocytes, indicating prolonged responsiveness of marked enhancers to the presence or absence of a key transcription factor. Thus, lateral inhibition and intestinal crypt lineage plasticity involve interaction of a lineage-restricted transcription factor with broadly permissive chromatin established in multipotent stem cells.

doi: 10.1038/nature12903

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