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Insights into the assembly and activation of the microtubule nucleator gamma-TuRC 期刊论文
NATURE, 2020, 578 (7795) : 467-+
作者:  Cyranoski, David
收藏  |  浏览/下载:38/0  |  提交时间:2020/07/03

Microtubules are dynamic polymers of alpha- and beta-tubulin and have crucial roles in cell signalling, cell migration, intracellular transport and chromosome segregation(1). They assemble de novo from alpha beta-tubulin dimers in an essential process termed microtubule nucleation. Complexes that contain the protein gamma-tubulin serve as structural templates for the microtubule nucleation reaction(2). In vertebrates, microtubules are nucleated by the 2.2-megadalton gamma-tubulin ring complex (gamma-TuRC), which comprises gamma-tubulin, five related gamma-tubulin complex proteins (GCP2-GCP6) and additional factors(3). GCP6 is unique among the GCP proteins because it carries an extended insertion domain of unknown function. Our understanding of microtubule formation in cells and tissues is limited by a lack of high-resolution structural information on the gamma-TuRC. Here we present the cryo-electron microscopy structure of gamma-TuRC from Xenopus laevis at 4.8 angstrom global resolution, and identify a 14-spoked arrangement of GCP proteins and gamma-tubulins in a partially flexible open left-handed spiral with a uniform sequence of GCP variants. By forming specific interactions with other GCP proteins, the GCP6-specific insertion domain acts as a scaffold for the assembly of the gamma-TuRC. Unexpectedly, we identify actin as a bona fide structural component of the gamma-TuRC with functional relevance in microtubule nucleation. The spiral geometry of gamma-TuRC is suboptimal for microtubule nucleation and a controlled conformational rearrangement of the gamma-TuRC is required for its activation. Collectively, our cryo-electron microscopy reconstructions provide detailed insights into the molecular organization, assembly and activation mechanism of vertebrate gamma-TuRC, and will serve as a framework for the mechanistic understanding of fundamental biological processes associated with microtubule nucleation, such as meiotic and mitotic spindle formation and centriole biogenesis(4).


The cryo-EM structure of the gamma-tubulin ring complex (gamma-TuRC) from Xenopus laevis provides insights into the molecular organization of the complex, and shows that actin is a structural component that is functionally relevant to microtubule nucleation.


  
A developmental landscape of 3D-cultured human pre-gastrulation embryos 期刊论文
NATURE, 2020, 577 (7791) : 537-+
作者:  Xiang, Lifeng;  Yin, Yu;  Zheng, Yun;  Ma, Yanping;  Li, Yonggang;  Zhao, Zhigang;  Guo, Junqiang;  Ai, Zongyong;  Niu, Yuyu;  Duan, Kui;  He, Jingjing;  Ren, Shuchao;  Wu, Dan;  Bai, Yun;  Shang, Zhouchun;  Dai, Xi;  Ji, Weizhi;  Li, Tianqing
收藏  |  浏览/下载:34/0  |  提交时间:2020/07/03

Our understanding of how human embryos develop before gastrulation, including spatial self-organization and cell type ontogeny, remains limited by available two-dimensional technological platforms(1,2) that do not recapitulate the in vivo conditions(3-5). Here we report a three-dimensional (3D) blastocyst-culture system that enables human blastocyst development up to the primitive streak anlage stage. These 3D embryos mimic developmental landmarks and 3D architectures in vivo, including the embryonic disc, amnion, basement membrane, primary and primate unique secondary yolk sac, formation of anterior-posterior polarity and primitive streak anlage. Using single-cell transcriptome profiling, we delineate ontology and regulatory networks that underlie the segregation of epiblast, primitive endoderm and trophoblast. Compared with epiblasts, the amniotic epithelium shows unique and characteristic phenotypes. After implantation, specific pathways and transcription factors trigger the differentiation of cytotrophoblasts, extravillous cytotrophoblasts and syncytiotrophoblasts. Epiblasts undergo a transition to pluripotency upon implantation, and the transcriptome of these cells is maintained until the generation of the primitive streak anlage. These developmental processes are driven by different pluripotency factors. Together, findings from our 3D-culture approach help to determine the molecular and morphogenetic developmental landscape that occurs during human embryogenesis.


A 3D culture system to model human embryonic development, together with single-cell transcriptome profiling, provides insights into the molecular developmental landscape during human post-implantation embryogenesis.


  
Population flow drives spatio-temporal distribution of COVID-19 in China 期刊论文
NATURE, 2020
作者:  Fernandez, Diego Carlos;  Komal, Ruchi;  Langel, Jennifer;  Ma, Jun;  Duy, Phan Q.;  Penzo, Mario A.;  Zhao, Haiqing;  Hattar, Samer
收藏  |  浏览/下载:86/0  |  提交时间:2020/07/03

Sudden, large-scale and diffuse human migration can amplify localized outbreaks of disease into widespread epidemics(1-4). Rapid and accurate tracking of aggregate population flows may therefore be epidemiologically informative. Here we use 11,478,484 counts of mobile phone data from individuals leaving or transiting through the prefecture of Wuhan between 1 January and 24 January 2020 as they moved to 296 prefectures throughout mainland China. First, we document the efficacy of quarantine in ceasing movement. Second, we show that the distribution of population outflow from Wuhan accurately predicts the relative frequency and geographical distribution of infections with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) until 19 February 2020, across mainland China. Third, we develop a spatio-temporal '  risk source'  model that leverages population flow data (which operationalize the risk that emanates from epidemic epicentres) not only to forecast the distribution of confirmed cases, but also to identify regions that have a high risk of transmission at an early stage. Fourth, we use this risk source model to statistically derive the geographical spread of COVID-19 and the growth pattern based on the population outflow from Wuhan  the model yields a benchmark trend and an index for assessing the risk of community transmission of COVID-19 over time for different locations. This approach can be used by policy-makers in any nation with available data to make rapid and accurate risk assessments and to plan the allocation of limited resources ahead of ongoing outbreaks.


Modelling of population flows in China enables the forecasting of the distribution of confirmed cases of COVID-19 and the identification of areas at high risk of SARS-CoV-2 transmission at an early stage.


  
Engineering covalently bonded 2D layered materials by self-intercalation 期刊论文
NATURE, 2020, 581 (7807) : 171-+
作者:  Shang, Jian;  Ye, Gang;  Shi, Ke;  Wan, Yushun;  Luo, Chuming;  Aihara, Hideki;  Geng, Qibin;  Auerbach, Ashley;  Li, Fang
收藏  |  浏览/下载:31/0  |  提交时间:2020/07/03

Two-dimensional (2D) materials(1-5) offer a unique platform from which to explore the physics of topology and many-body phenomena. New properties can be generated by filling the van der Waals gap of 2D materials with intercalants(6,7)  however, post-growth intercalation has usually been limited to alkali metals(8-10). Here we show that the self-intercalation of native atoms(11,12) into bilayer transition metal dichalcogenides during growth generates a class of ultrathin, covalently bonded materials, which we name ic-2D. The stoichiometry of these materials is defined by periodic occupancy patterns of the octahedral vacancy sites in the van der Waals gap, and their properties can be tuned by varying the coverage and the spatial arrangement of the filled sites(7,13). By performing growth under high metal chemical potential(14,15) we can access a range of tantalum-intercalated TaS(Se)(y), including 25% Ta-intercalated Ta9S16, 33.3% Ta-intercalated Ta7S12, 50% Ta-intercalated Ta10S16, 66.7% Ta-intercalated Ta8Se12 (which forms a Kagome lattice) and 100% Ta-intercalated Ta9Se12. Ferromagnetic order was detected in some of these intercalated phases. We also demonstrate that self-intercalated V11S16, In11Se16 and FexTey can be grown under metal-rich conditions. Our work establishes self-intercalation as an approach through which to grow a new class of 2D materials with stoichiometry- or composition-dependent properties.


  
Lactonization as a general route to beta-C(sp(3))-H functionalization 期刊论文
NATURE, 2020, 577 (7792) : 656-+
作者:  Washington, Harriet A.
收藏  |  浏览/下载:29/0  |  提交时间:2020/07/03

Functionalization of the beta-C-H bonds of aliphatic acids is emerging as a valuable synthetic disconnection that complements a wide range of conjugate addition reactions(1-5). Despite efforts for beta-C-H functionalization in carbon-carbon and carbon-heteroatom bond-forming reactions, these have numerous crucial limitations, especially for industrial-scale applications, including lack of mono-selectivity, use of expensive oxidants and limited scope(6-13). Notably, the majority of these reactions are incompatible with free aliphatic acids without exogenous directing groups. Considering the challenge of developing C-H activation reactions, it is not surprising that achieving different transformations requires independent catalyst design and directing group optimizations in each case. Here we report a Pd-catalysed beta-C(sp(3))-H lactonization of aliphatic acids enabled by a mono-N-protected beta-amino acid ligand. The highly strained and reactive beta-lactone products are versatile linchpins for the mono-selective installation of diverse alkyl, alkenyl, aryl, alkynyl, fluoro, hydroxyl and amino groups at the beta position of the parent acid, thus providing a route to many carboxylic acids. The use of inexpensive tert-butyl hydrogen peroxide as the oxidant to promote the desired selective reductive elimination from the Pd(IV) centre, as well as the ease of product purification without column chromatography, render this reaction amenable to tonne-scale manufacturing.


  
Deciphering human macrophage development at single-cell resolution 期刊论文
NATURE, 2020
作者:  Oberst, Polina;  Fievre, Sabine;  Baumann, Natalia;  Concetti, Cristina;  Bartolini, Giorgia;  Jabaudon, Denis
收藏  |  浏览/下载:36/0  |  提交时间:2020/07/03

Macrophages are the first cells of the nascent immune system to emerge during embryonic development. In mice, embryonic macrophages infiltrate developing organs, where they differentiate symbiotically into tissue-resident macrophages (TRMs)(1). However, our understanding of the origins and specialization of macrophages in human embryos is limited. Here we isolated CD45(+) haematopoietic cells from human embryos at Carnegie stages 11 to 23 and subjected them to transcriptomic profiling by single-cell RNA sequencing, followed by functional characterization of a population of CD45(+)CD34(+)CD44(+) yolk sac-derived myeloid-biased progenitors (YSMPs) by single-cell culture. We also mapped macrophage heterogeneity across multiple anatomical sites and identified diverse subsets, including various types of embryonic TRM (in the head, liver, lung and skin). We further traced the specification trajectories of TRMs from either yolk sac-derived primitive macrophages or YSMP-derived embryonic liver monocytes using both transcriptomic and developmental staging information, with a focus on microglia. Finally, we evaluated the molecular similarities between embryonic TRMs and their adult counterparts. Our data represent a comprehensive characterization of the spatiotemporal dynamics of early macrophage development during human embryogenesis, providing a reference for future studies of the development and function of human TRMs.


Single-cell RNA sequencing of haematopoietic cells from human embryos at different developmental stages sheds light on the development and specification of macrophages in different tissues.


  
Accurate compound-specific C-14 dating of archaeological pottery vessels 期刊论文
NATURE, 2020, 580 (7804) : 506-+
作者:  Yin, Yafei;  Lu, J. Yuyang;  Zhang, Xuechun;  Shao, Wen;  Xu, Yanhui;  Li, Pan;  Hong, Yantao;  Cui, Li;  Shan, Ge;  Tian, Bin;  Zhang, Qiangfeng Cliff;  Shen, Xiaohua
收藏  |  浏览/下载:35/0  |  提交时间:2020/05/13

Pottery is one of the most commonly recovered artefacts from archaeological sites. Despite more than a century of relative dating based on typology and seriation(1), accurate dating of pottery using the radiocarbon dating method has proven extremely challenging owing to the limited survival of organic temper and unreliability of visible residues(2-4). Here we report a method to directly date archaeological pottery based on accelerator mass spectrometry analysis of C-14 in absorbed food residues using palmitic (C-16:0) and stearic (C-18:0) fatty acids purified by preparative gas chromatography(5-8). We present accurate compound-specific radiocarbon determinations of lipids extracted from pottery vessels, which were rigorously evaluated by comparison with dendrochronological dates(9,10) and inclusion in site and regional chronologies that contained previously determined radiocarbon dates on other materials(11-15). Notably, the compound-specific dates from each of the C-16:0 and C-18:0 fatty acids in pottery vessels provide an internal quality control of the results(6) and are entirely compatible with dates for other commonly dated materials. Accurate radiocarbon dating of pottery vessels can reveal: (1) the period of use of pottery  (2) the antiquity of organic residues, including when specific foodstuffs were exploited  (3) the chronology of sites in the absence of traditionally datable materials  and (4) direct verification of pottery typochronologies. Here we used the method to date the exploitation of dairy and carcass products in Neolithic vessels from Britain, Anatolia, central and western Europe, and Saharan Africa.


Using lipid residues absorbed in potsherds, the ages of pottery from various archaeological sites are determined and validated using sites for which the dates are well known from other methods.


  
The fate of carbon in a mature forest under carbon dioxide enrichment 期刊论文
NATURE, 2020, 580 (7802) : 227-+
作者:  Sun, P. Z.;  Yang, Q.;  Kuang, W. J.;  Stebunov, Y. V.;  Xiong, W. Q.;  Yu, J.;  Nair, R. R.;  Katsnelson, M. I.;  Yuan, S. J.;  Grigorieva, I. V.;  Lozada-Hidalgo, M.;  Wang, F. C.;  Geim, A. K.
收藏  |  浏览/下载:90/0  |  提交时间:2020/05/13

Carbon dioxide enrichment of a mature forest resulted in the emission of the excess carbon back into the atmosphere via enhanced ecosystem respiration, suggesting that mature forests may be limited in their capacity to mitigate climate change.


Atmospheric carbon dioxide enrichment (eCO(2)) can enhance plant carbon uptake and growth(1-5), thereby providing an important negative feedback to climate change by slowing the rate of increase of the atmospheric CO2 concentration(6). Although evidence gathered from young aggrading forests has generally indicated a strong CO2 fertilization effect on biomass growth(3-5), it is unclear whether mature forests respond to eCO(2) in a similar way. In mature trees and forest stands(7-10), photosynthetic uptake has been found to increase under eCO(2) without any apparent accompanying growth response, leaving the fate of additional carbon fixed under eCO(2) unclear(4,5,7-11). Here using data from the first ecosystem-scale Free-Air CO2 Enrichment (FACE) experiment in a mature forest, we constructed a comprehensive ecosystem carbon budget to track the fate of carbon as the forest responded to four years of eCO(2) exposure. We show that, although the eCO(2) treatment of +150 parts per million (+38 per cent) above ambient levels induced a 12 per cent (+247 grams of carbon per square metre per year) increase in carbon uptake through gross primary production, this additional carbon uptake did not lead to increased carbon sequestration at the ecosystem level. Instead, the majority of the extra carbon was emitted back into the atmosphere via several respiratory fluxes, with increased soil respiration alone accounting for half of the total uptake surplus. Our results call into question the predominant thinking that the capacity of forests to act as carbon sinks will be generally enhanced under eCO(2), and challenge the efficacy of climate mitigation strategies that rely on ubiquitous CO2 fertilization as a driver of increased carbon sinks in global forests.


  
The projected timing of abrupt ecological disruption from climate change 期刊论文
NATURE, 2020, 580 (7804) : 496-+
作者:  Gorgulla, Christoph;  Boeszoermenyi, Andras;  Wang, Zi-Fu;  Fischer, Patrick D.;  Coote, Paul W.;  Padmanabha Das, Krishna M.;  Malets, Yehor S.;  Radchenko, Dmytro S.;  Moroz, Yurii S.;  Scott, David A.;  Fackeldey, Konstantin;  Hoffmann, Moritz;  Iavniuk, Iryna;  Wagner, Gerhard;  Arthanari, Haribabu
收藏  |  浏览/下载:81/0  |  提交时间:2020/05/13

As anthropogenic climate change continues the risks to biodiversity will increase over time, with future projections indicating that a potentially catastrophic loss of global biodiversity is on the horizon(1-3). However, our understanding of when and how abruptly this climate-driven disruption of biodiversity will occur is limited because biodiversity forecasts typically focus on individual snapshots of the future. Here we use annual projections (from 1850 to 2100) of temperature and precipitation across the ranges of more than 30,000 marine and terrestrial species to estimate the timing of their exposure to potentially dangerous climate conditions. We project that future disruption of ecological assemblages as a result of climate change will be abrupt, because within any given ecological assemblage the exposure of most species to climate conditions beyond their realized niche limits occurs almost simultaneously. Under a high-emissions scenario (representative concentration pathway (RCP) 8.5), such abrupt exposure events begin before 2030 in tropical oceans and spread to tropical forests and higher latitudes by 2050. If global warming is kept below 2 degrees C, less than 2% of assemblages globally are projected to undergo abrupt exposure events of more than 20% of their constituent species  however, the risk accelerates with the magnitude of warming, threatening 15% of assemblages at 4 degrees C, with similar levels of risk in protected and unprotected areas. These results highlight the impending risk of sudden and severe biodiversity losses from climate change and provide a framework for predicting both when and where these events may occur.


Using annual projections of temperature and precipitation to estimate when species will be exposed to potentially harmful climate conditions reveals that disruption of ecological assemblages as a result of climate change will be abrupt and could start as early as the current decade.


  
Convergent genes shape budding yeast pericentromeres 期刊论文
NATURE, 2020
作者:  Yin, Xuefan;  Jin, Jicheng;  Soljacic, Marin;  Peng, Chao;  Zhen, Bo
收藏  |  浏览/下载:41/0  |  提交时间:2020/07/03

The three-dimensional structure of pericentromeres in budding yeast is defined by convergent genes, which mark pericentromere borders and trap cohesin complexes loaded at centromeres, generating an architecture that allows correct chromosome segregation.


The three-dimensional architecture of the genome governs its maintenance, expression and transmission. The cohesin protein complex organizes the genome by topologically linking distant loci, and is highly enriched in specialized chromosomal domains surrounding centromeres, called pericentromeres(1-6). Here we report the three-dimensional structure of pericentromeres in budding yeast (Saccharomyces cerevisiae) and establish the relationship between genome organization and function. We find that convergent genes mark pericentromere borders and, together with core centromeres, define their structure and function by positioning cohesin. Centromeres load cohesin, and convergent genes at pericentromere borders trap it. Each side of the pericentromere is organized into a looped conformation, with border convergent genes at the base. Microtubule attachment extends a single pericentromere loop, size-limited by convergent genes at its borders. Reorienting genes at borders into a tandem configuration repositions cohesin, enlarges the pericentromere and impairs chromosome biorientation during mitosis. Thus, the linear arrangement of transcriptional units together with targeted cohesin loading shapes pericentromeres into a structure that is competent for chromosome segregation. Our results reveal the architecture of the chromosomal region within which kinetochores are embedded, as well as the restructuring caused by microtubule attachment. Furthermore, we establish a direct, causal relationship between the three-dimensional genome organization of a specific chromosomal domain and cellular function.