《自然》（20190704出版）一周論文導讀
翻譯 | 唐一塵
Nature, 4 July 2019, Volume 571 Issue 7763
《自然》2019年7月4日，第571卷7763期
生物學Biology
Whole-animal connectomes of both Caenorhabditis elegans sexes
兩種性別秀麗隱桿線蟲的神經系統所有聯結的圖譜
作者：Steven J. Cook、Travis A. Jarrell、Christopher A. Brittin、David H. Hall、Scott W. Emmons，et al
鏈接：
https://www.nature.com/articles/s41586-019-1352-7
摘要：
秀麗隱桿線蟲是神經科學研究的重要模式生物。此前研究描繪了雄性線蟲以及雌雄同體線蟲神經系統切片的聯結圖譜。本論文報道了這兩種性別的成年秀麗隱桿線蟲神經系統內所有聯結的圖譜。
研究人員先利用連續電子顯微鏡圖像繪製出了雄性線蟲頭部環路的圖譜，再將所得圖譜與此前已經發表的顯微圖像相結合，生成了整體動物的聯結圖譜，包括對雌雄同體線蟲的神經系統聯結的重構。
相較於先前的研究，該方法不僅發現了更多的聯結，還能提供每個聯結的位置，並根據其物理大小間接測量出聯結強度。
結果顯示，高達30%的聯結在強度上或具有顯著的性別差異。研究人員表示，由於他們的聯結圖譜來源於多種動物的顯微圖像，因此應被看作概念模型。
這是迄今已發表的最完整的秀麗隱桿線蟲神經聯結圖譜，可用於比較線蟲神經系統的性別差異。該圖譜或能用來破解控制秀麗隱桿線蟲行為的神經環路。
Abstract
Knowledge of connectivity in the nervous system is essential to understanding its function. Here we describe connectomes for both adult sexes of the nematode Caenorhabditis elegans, an important model organism for neuroscience research. We present quantitative connectivity matrices that encompass all connections from sensory input to end-organ output across the entire animal, information that is necessary to model behaviour. Serial electron microscopy reconstructions that are based on the analysis of both newand previously published electron micrographs update previous results and include data on the male head. The nervous system differs between sexes at multiple levels. Several sex-shared neurons that function in circuits for sexual behaviour are sexually dimorphic in structure and connectivity. Inputs from sex-specific circuitry to central circuitry reveal points at which sexual and non-sexual pathways converge. In sex-shared central pathways, a substantial number of connections differ in strength between the sexes. Quantitative connectomes that include all connections serve as the basis for understanding how complex, adaptive behavior is generated.
Hydraulic control of mammalian embryo size and cell fate
哺乳動物胚胎大小和細胞命運的水力控制
作者：Chii Jou Chan, Maria Costanzo, Teresa Ruiz-Herrero, Gregor M?nke, Ryan J. Petrie, Martin Bergert, Alba Diz-Mu?oz, L. Mahadevan & Takashi Hiiragi
鏈接：
https://www.nature.com/articles/s41586-019-1309-x
摘要：
尺寸控制是組織發育和體內平衡的基礎。雖然細胞增殖在這些過程中的作用已得到廣泛研究，但是控制胚胎尺寸的機制，以及這些機制如何影響細胞命運仍是未知的。
這裡，研究人員使用小鼠胚囊作為模型揭示了充滿液體的腔（充液腔）在控制胚胎尺寸和確定細胞命運方面所起的關鍵作用。
研究人員發現在在胚囊發育過程中充液腔壓力增加了兩倍，這種壓力增加轉化為位於充液腔內壁上的滋養外胚層的細胞皮質張力和組織硬度的同時增加。
增加的皮質張力導致紐蛋白機械感測和功能性緊密連接的成熟，從而建立正反饋迴路來適應充液腔生長。當張力達到臨界閾值時，細胞間黏附不能持續保持，這導致滋養外胚層破裂和胚泡塌陷。
一種簡單的水力門控振蕩理論概括了觀察到的尺寸振蕩的動態變化，並預測了胚胎尺寸隨組織體積的變化。
這種理論進一步預測，受到破壞的緊密連接或增加的組織硬度導致較小的胚胎尺寸，研究人員驗證了這一點，並表示充液腔內壓力和尺寸變化能夠影響滋養外胚層的細胞分裂模式，從而影響細胞分配和命運。
Abstract
Size control is fundamental in tissue development and homeostasis. Although the role of cell proliferation in these processes has been widely studied, the mechanisms that control embryo size—and how these mechanisms affect cellfate—remain unknown. Here we use the mouse blastocyst as a model to unravel a key role of fluid-filled lumen in the control of embryo size and specification of cell fate. We find that there is a two fold increase in lumenal pressure during blastocyst development, which translates into a concomitant increase incell cortical tension and tissue stiffness of the trophectoderm that lines the lumen. Increased cortical tension leads to vinculin mechano sensing and maturation of functional tight junctions, which establishes a positive feedback loop to accommodate lumen growth. When the cortical tension reaches a critical threshold, cell–cell adhesion cannot be sustained during mitotic entry, which leads to trophectoderm rupture and blastocyst collapse. A simple theory of hydraulically gated oscillations recapitulates the observed dynamics of size oscillations, and predicts the scaling of embryo size with tissue volume. This theory further predicts that disrupted tight junctions or increased tissue stiffness lead to a smaller embryo size, which we verified by biophysical, embryological, pharmacological and genetic perturbations. Changes in lumenal pressure and size can influence the cell division pattern of the trophectoderm, and thereby affect cell allocation and fate. Our study reveals how lumenal pressure and tissue mechanics control embryo size at the tissue scale, which iscoupled to cell position and fate at the cellular scale.
機械工程學/物理學
Mechanical Engineering/Physics
Electrolytic vascular systems for energy-dense robots
能量密集機器人的電解血管系統
作者：Cameron A. Aubin、Snehashis Choudhury、Rhiannon Jerch、Robert F. Shepherd，et al
鏈接：
https://www.nature.com/articles/s41586-019-1313-1
摘要：
機器人一般由執行特定任務、相互獨立的系統組成。
例如，一種材料可能只具有電池的功能，但這也意味著升級系統需要添加額外的電池組，不但會增加機器人自重，維持其性能可能還需要進行一番改進。解決該問題的一種方法是使用具有多功能的電池。
這裡，研究人員認為機器人內部用於傳遞動力的液壓液還具有儲存能量的潛力。
他們讓含有液體電解質的碘化鋅液流電池互聯，製作而成了一種合成血管系統，嵌入仿獅子魚的機器人體內。這種液體會在機器人的周身循環，通過電化學反應驅動機器人內部搭載的泵和電子器件。
與此同時，液體的泵送還能向魚鰭傳遞機械功，幫助機器魚游泳。在測試中，機器魚能以每分鐘大於1.5倍體長的速度長時間逆流遊動（理論最長續航能力為36小時以上）。
研究結果有望提升未來機器人設計的能量儲存、效率和自主性。
Abstract
Modern robots lack the multifunctional interconnected systems found in living organisms and are consequently unable to reproduce their efficiency and autonomy. Energy-storage systems are among the most crucial limitations to robot autonomy, but their size, weight, material and design constraints can bere-examined in the context of multifunctional, bio-inspired applications. Here we present a synthetic energy-dense circulatory system embedded in an untethered, aquatic soft robot. Modelled after redox flow batteries, this synthetic vascular system combines the functions of hydraulic for cetransmission, actuation and energy storage into a single integrated design that geometrically increases the energy density of the robot to enable operation for long durations (up to 36 hours). The fabrication techniques and flexible materials used in its construction enable the vascular system to be created with complex form factors that continuously deform with the robot』s movement. This use of electrochemical energy storage in hydraulic fluids could facilitate increased energy density, autonomy, efficiency and multifunctionality in future robot designs.
Spin–orbit-driven band inversion in bilayer graphene by the van der Waals proximity effect
研究測量石墨烯自旋軌道耦合
作者：J. O. Island、X. Cui、M. P. Zaletel、A. F. Young，et al
鏈接：
https://www.nature.com/articles/s41586-019-1304-2
摘要：
石墨烯的自旋軌道耦合（SOC）是實現物質逆時不變拓撲相的關鍵。Kane和Mele預測SOC將穩定量子自旋霍爾絕緣體，但是單層石墨烯的弱本徵SOC阻礙了該材料的實驗觀察。
本論文報道了利用范德華力與半導體過渡金屬硫族化合物結合，實現了一種層選擇鄰近效應，從而在超清潔雙層石墨烯中設計出Kane-Mele預測的SOC。
研究人員利用高解析度電容測量方法研究了大容量電子壓縮性，發現SOC在導致電荷中性時形成明顯的、不可壓縮的、有間隙的相。實驗數據與簡單的理論模型在數量上是一致的，其中新相由SOC驅動帶反轉產生。
該研究結果為石墨烯異質結構強自旋軌道體系中強拓撲絕緣體及其相關的量子相的研究奠定了基礎。
Abstract
Spin–orbit coupling (SOC) is the key to realizing time-reversal-invariant topological phases of matter. SOC was predicted by Kane and Mele to stabilize a quantum spin Hall insulator; however, the weak intrinsic SOC in monolayer graphene has precluded experimental observation in this material. Here we exploit a layer-selective proximity effect—achieved via a van der Waals contact with a semiconducting transition-metal dichalcogenide—to engineer Kane–Mele SOC in ultra clean bilayer graphene. Using high-resolution capacitance measurements to probe the bulk electronic compressibility, we find that SOC leads to the formation of a distinct, incompressible, gapped phase at charge neutrality. The experimental data agree quantitatively with a simple theoretical model in which the new phase results from SOC-driven band inversion. In contrast to Kane–Mele SOC in monolayer graphene, the inverted phase is not expected to be atime-reversal-invariant topological insulator, despite being separated from conventional band insulators by electric-field-tuned phase transitions where crystal symmetry mandates that the bulk gap must close. Our electrical transport measurements reveal that the inverted phase has a conductivity of approximately e2/h (where e is the electron charge and hPlanck』s constant), which is suppressed by exceptionally small in-plane magnetic fields. The high conductivity and anomalous magneto resistance are consistent with theoretical models that predict helical edge states within the inverted phase that are protected from back scattering by an emergent spin symmetry that remains robust even for large Rashba SOC. Our results pave the way for proximity engineering of strong topological insulators as well as correlated quantum phases in the strong spin–orbit regime in graphene hetero structures.
生態學Ecology
Insectegg size and shape evolve with ecology but not developmental rate
昆蟲卵的大小和形狀隨生態而進化
作者：Samuel H. Church、Bruno A. S. de Medeiros、Cassandra G. Extavour，et al
鏈接：
https://www.nature.com/articles/s41586-019-1302-4
摘要：
在進化的過程中，生物體的大小出現了顯著多樣化。大小的變化被認為是由於發育、形態和/或生態壓力造成的。
為了對這些壓力的潛在影響進行系統發育測試，研究人員生成了一個包含10000多個昆蟲卵描述的數據集，並將這些數據集與昆蟲的基因和生活史數據集結合起來。
分析顯示，蟲卵大小與發育速率無關，而且很多昆蟲的蟲卵大小與成蟲體型大小也無關聯性。研究人員表示，昆蟲卵大小與形狀的進化取決於產卵時的生態環境，而不是普遍的異速生長常數。
Abstract
Over the course of evolution, organism size has diversified markedly. Changes insize are thought to have occurred because of developmental, morphological and/or ecological pressures. To perform phylogenetic tests of the potential effects of these pressures, here we generated a dataset of more than ten thousand descriptions of insect eggs, and combined these with genetic and life-history datasets. We show that, across eight orders of magnitude of variation in egg volume, the relationship between size and shape itself evolves, such that previously predicted global patterns of scaling do not adequately explain the diversity in egg shapes. We show that egg size is not correlated with developmental rate and that, for many insects, egg size is not correlated with adult body size. Instead, we find that the evolution of parasitoidism and aquatic oviposition help to explain the diversification in the size and shape of insect eggs. Our study suggests that where eggs are laid, rather than universal allometric constants, underlies the evolution of insect egg size and shape.
Location-level processes drive the establishment of alien bird populations worldwide
世界範圍內外來鳥類種群的建立
作者：David W. Redding、Salit Kark、Tim M. Blackburn，et al
鏈接：
https://www.nature.com/articles/s41586-019-1292-2
摘要：
人類介導的物種向自然分布區以外地區的遷移是人類世的一個重要特徵，也是生物多樣性喪失和環境變化的主要驅動力。
阻止外來物種入侵需要理解為什麼有些物種不能「入侵」新區域，而另一些物種卻能成功。這就需要綜合物種引入地的特徵、引入物種和具體引入事件的影響。
由於環境變化可能影響種群生存的空間、時間和系統發育軸，因此很難確定影響種群建立成功的位置級因素。
在此，研究人員將貝葉斯層次回歸分析應用於外來鳥類引入事件資料庫，顯示引入地點的環境條件，特別是氣候適宜性和其他外來物種群體的存在，是「入侵鳥類」成功建立種群的主要決定因素。
而物種水平的性狀和創始種群的大小對成功起著次要但重要的作用。因此，當前人為環境變化很可能會影響未來外來物種的入侵，預測未來的入侵將需要綜合位置、物種和事件級別等多種特徵。
Abstract
Human-mediated translocation of species to areas beyond their natural distribution (which results in "alien" populations) is a key signature of the Anthropocene, and is a primary global driver of biodiversity loss and environmental change. Stemming the tide of invasions requires understanding why some species fail to establishalien populations, and others succeed. To achieve this, we need to integrate the effects of features of the introduction site, the species introduced and the specific introduction event. Determining which, if any, location-level factors affect the success of establishment has proven difficult, owing to the multiple spatial, temporal and phylogenetic axes along which environmental variation may influence population survival. Here we apply Bayesian hierarchical regression analysis to a global spatially and temporally explicit database of introduction events of alien birds to show that environmental conditions at the introduction location, notably climatic suitability and the presence of other groups of alien species, are the primary determinants of successful establishment. Species-level traits and the size ofthe founding population (propagule pressure) exert secondary, but important, effects on success. Thus, current trajectories of anthropogenic environmental change will most probably facilitate future incursions by alien species, but predicting future invasions will require the integration of multiple location-, species- and event-level characteristics.
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