《Nature》最新目录要览：2009-09-24出版
时间：2009-09-27 阅读： 我要评论:
《Nature》最新目录要览：2009-09-24出版
封面故事：印度“种姓”的古老历史和遗传渊源
Reconstructing Indian population history
对来自印度25个不同族群的132人的基因变异所做分析显示，两个古老的遗传趋异族群是今天大多数印度人的祖先。其中一个被称为“印度北部先民”的分支在遗传上接近中东人、中亚人和欧洲人。另一个被称为“印度南部先民”的分支与该次大陆以外的任何族群都不相近。这项工作为几个长期未能回答的问题提供了答案。看来，“种姓”数千年来一直是决定印度婚姻关系的一个强大力量，而一些人类学家过去曾认为“种姓”目前所具有的力量是英国殖民主义的一个产物。而且，神秘的安达曼群岛“矮小黑人”也被发现是从“印度南部先民”族群分离出来的一个古老分支。族群间等位基因频率差异很大，部分原因是族群内存在通婚习俗，所以印度有大量隐性疾病可通过基因方法来甄别和分析。本期封面所示为本项研究中取样族群所在地点及每个族群的一个成员。（Article p. 489; News & Views）封面图片：Kumarasamy Thangaraj/ Lalji Singh & F. Amirtharaj。
致癌性前列腺细胞——CARN细胞（Oncogenic prostate cells）
A luminal epithelial stem cell that is a cell of origin for prostate cancer
被称为“CARN细胞”的一个罕见的腔干细胞群已在小鼠前列腺中被发现。CARN细胞在由雄性激素耗尽所诱导的前列腺组织再生过程中生成腔细胞和基细胞两种类型。除了提供自我更新潜力外，这些细胞还能成为致癌转化的一个目标：CARN细胞中肿瘤抑制基因Pten的删除导致再生中的前列腺内肿瘤的形成。这些细胞在没有雄性激素存在时能够存活的能力提出这样一个可能性：独立于雄性激素的癌症可从这个细胞群产生，而且CARN细胞还可能为表现出扩散性前列腺癌恶性特征的细胞的治疗性定位提供了一个途径。（Article p. 495）
白矮星PG 1159–035角动量几乎全部失去（Stars lose their momentum）
Seismic evidence for the loss of stellar angular momentum before the white-dwarf stage
大多数恒星以白矮星的形式结束它们的恒星生命。如果所有恒星在其演化过程中都保持其角动量，那么白矮星的致密性应使其转动极快，周期只有几秒钟。然而，对白矮星所做观测表明，它们的表层转动要慢一些，典型周期在几小时和几十年之间。以前，人们一直没有可能确定它们在光球的表层之下是否自转得更快一些。现在，用星震学方法所做的一项研究显示，脉动白矮星PG 1159–035作为一个固态天体在转动，周期相对较长，大约为33-34小时。这说明它的角动量几乎已经全部失去，很可能发生在白矮星阶段之前。（Letter p. 501; News & Views）
全新世碳周期的最新重建结果（Holocene carbon cycle）
Stable isotope constraints on Holocene carbon cycle changes from an Antarctic ice core
通过对“EPICA Dome C”南极冰心中束缚的空气所做测量获得的一个新的大气δ13C记录，与一个简单的碳模型相结合，为全新世（当前的间冰期，开始于距今约11,000年前）碳周期提供了一幅高分辨率画面。以前的重建工作曾显示大气CO2浓度有显著变化，但造成这些变化的原因却不清楚。新的数据表明，全新世早期大气CO2浓度下降5 p.p.m.v.，是由陆地生物圈吸收约2900亿吨碳、以及为响应陆地碳吸收的碳酸盐补偿作用所发生的海洋中碳的释放共同造成的。在全新世晚期大气CO2浓度增加20 p.p.m.v.，大部分可由早先陆地生物圈碳酸盐补偿及珊瑚礁形成来解释，少部分可由陆地生物圈碳库存少量减少来解释。（Letter p. 507）
新类型厄尔尼诺现象出现比例将增加（El Niño changes its tune）
El Niño in a changing climate
最近几十年，出现了一种截然不同的厄尔尼诺类型。“正常”厄尔尼诺，是与东太平洋异常变暖以及其他地方所发生的从洪涝到干旱在内的各种不同气候变化相关的气候事件。另一种类型的厄尔尼诺，有时称之为“厄尔尼诺Modoki”（ Modoki在日语中意思是“相似但不同的”）。在这种厄尔尼诺现象中，暖池向西移动，其东侧和西侧为较冷的海水。Sang-Wook Yeh及其同事，利用将人为造成的温室气体变化考虑在内的一系列气候模型发现，这种新类型厄尔尼诺现象的出现比例，预计在21世纪末期会增加高达5倍。（Letter p. 511; News & Views）
演化路上开弓没有回头箭（Evolution has no reverse）
An epistatic ratchet constrains the direction of glucocorticoid receptor evolution
演化是否会仅仅通过逆转功能的选择压力而回到某种先祖结构是一个长期未能解决的问题，但也是一个仅靠形态史难以解决的问题。现在，Bridgeman等人以物理方式重构了一种调控蛋白（糖(肾上腺)皮质激素受体），并且以原子分辨率解析了施加在它们功能演化上的结构限制条件（即它们与哪个荷尔蒙结合）。他们发现，一种先祖蛋白中必不可少的氨基酸在一种较新的蛋白中却变成了中性，在那里它们随后会受到“遗传漂变”的侵蚀。（它们的）这种丢失使自然选择丧失了逆转历史替换所需的必要原材料——它们不再像其过去在另一个方向上那样具有“适应性”。从演化上来讲，走回头路是不可能的。（Letter p. 515）
共培养细胞之间存在易感性差异的深层原因（Cells with a difference）
Population context determines cell-to-cell variability in endocytosis and virus infection
对药物治疗或病毒感染的易感性从一个细胞到另一个细胞会有所不同，即便是在放在一起培养的一组基因完全相同的细胞中也是如此。这种异质性在很大程度上一直被归因于内在噪音，如基因表达的变化或信号分子水平的波动。现在，Snijder等人对大量共培养细胞进行了定量分析，并在细胞基本特点（如膜脂组成、或被一些而非另一些病毒感染的可感染性）与一个细胞的种群环境（例如，它们是处在一个粘附细胞岛的中心还是周边）之间发现了决定性的联系。这项工作中采用的评估细胞群的计算机辅助方法也许还可用于药物筛选。（Letter p. 520）
锯蛋白病CWD在鹿群中的发病和传播机制（Prion disease transmission）
Asymptomatic deer excrete infectious prions in faeces
“慢性消耗病”（ CWD）是一种高传染性锯蛋白病，在包括马鹿和驼鹿在内的鹿科动物的几个物种中引起神经退化。CWD自然传播的精确机制尚未解决。人们知道，一旦一个动物表现出这种病的症状，其排泄物会含有传染性锯蛋白。Stanley Prusiner及其同事发现，感染CWD的骡鹿，在表现出这种病的可见症状之前很久，其粪便中就开始含有感染性锯蛋白。这个发现对解释为什么CWD在鹿当中具有高发性、为什么能够高效横向传播提供了一个很有道理的、自然的机制，并且也可能适用于羊所患的同样具有感染性的痒病。（Letter p. 529）
“成形素” 浓度梯度的形成机制（Morphogens keep it simple）
Fgf8 morphogen gradient forms by a source-sink mechanism with freely diffusing molecules
被称为“成形素”的某些分子的浓度梯度已知在胚胎形成过程中控制组织发育。这种梯度怎样形成是一个人们很不了解的问题，Yu等人对此进行了研究。他们采用一种用于在活体中对分子进行成像的先进的高精密度技术（荧光校正光谱）发现，活斑马鱼胚胎中的扩散性FGF8“成形素”梯度由一个简单的源-汇机制形成。（Letter p. 533; News & Views）
活性氧在一些组织中可能有好的一面（Reactive oxygen’s good side）
Reactive oxygen species prime Drosophila haematopoietic progenitors for differentiation
虽然人们研究活性氧（ROS）主要是由于它们在DNA损伤、蛋白/类脂氧化和细胞凋亡中的有害作用，但人们也不断认识到ROS在一些组织中可能有有益作用。在哺乳动物造血系统中，造血干细胞含有低浓度ROS，但出乎意料的是，“共同髓系祖细胞”（ CMP）产生浓度相当高的ROS。Edward Owusu-Ansah和Utpal Banerjee在果蝇的两个先祖细胞类型中，发现了ROS含量的这种差别在功能上的明显重要性。他们发现，先祖细胞中由发育调控的、比较高的ROS含量使它们对分化比较敏感，并且确立了ROS在调控造血干细胞命运中所起的信号作用。（Letter p. 537; News & Views）
核糖核酸酶XRN-2对微RNA的作用（Recycling silencing complexes）
Active turnover modulates mature microRNA activity in Caenorhabditis elegans
在发育过程中，一类被称为“微RNA”的小型RNA在决定基因表达谱中扮演重要角色，它们是通过与某些信使RNA结合、抑制这些信使RNA的翻译或使其沉默的方式发挥作用的。人们认为，微RNA是造成单细胞生物演化成多细胞生物的一个因素。Saibal Chatterjee 和 Helge Großhans报告说，在微RNA作用于一个目标信使RNA之上、并从沉默复合物中释放出来之后，核糖核酸酶XRN-2促进它们的降解。XRN-2以这种方式来起微RNA含量的一种体内平衡调控因子的作用，这个作用在对新的发育提示信号做出反应当中可能具有重要性。（Letter p. 546）
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NEWS AND VIEWS
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Archaeology: Maya, Khmer and Inca pp479-480
Past societies have struggled against environmental problems similar to
those that beset us today. Three publications illuminate the outcomes for
three different tropical civilizations during the period AD 700-1600.
Jared Diamond
doi:10.1038/461479a
http://www.nature.com/nature/journal/v461/n7263/full/461479a.html
Developmental biology: Rise of the source-sink model pp480-481
Gradients of signalling molecules dictate where specific cell types form in
developing tissues, but how these gradients are set up is much debated. A
model proposed 40 years ago by Francis Crick may provide an answer.
Alexander F. Schier and Daniel Needleman
doi:10.1038/461480a
http://www.nature.com/nature/journal/v461/n7263/full/461480a.html
Climate change: The El Nino with a difference pp481-484
Patterns of sea-surface warming and cooling in the tropical Pacific seem
to be changing, as do the associated atmospheric effects. Increased global
warming is implicated in these shifts in El Nino phenomena.
Karumuri Ashok and Toshio Yamagata
doi:10.1038/461481a
http://www.nature.com/nature/journal/v461/n7263/full/461481a.html
Chemical biology: Caught in the activation pp484-485
A crystal structure reveals how a protein kinase is activated by the binding
of a small molecule at a pocket far from the catalytic site. This opens the
door to the design of modulators of protein phosphorylation.
Yi Liu
doi:10.1038/461484a
http://www.nature.com/nature/journal/v461/n7263/full/461484a.html
Astrophysics: Inner workings of a star pp485-486
By borrowing a technique used by seismologists to investigate Earth's interior,
astronomers have probed the hitherto-unknown interior rotation profile of a
white-dwarf star.
Sung-Chul Yoon
doi:10.1038/461485a
http://www.nature.com/nature/journal/v461/n7263/full/461485a.html
Developmental biology: A bad boy comes good pp486-487
Reactive oxygen species are often blamed for the development of cancer and
other diseases. Contrary to their 'bad boy' reputation, these species seem to
be essential for the development of immune cells, at least in the fly.
Ulrich Theopold
doi:10.1038/461486a
http://www.nature.com/nature/journal/v461/n7263/full/461486a.html
Human genetics: Tracing India's invisible threads pp487-488
One measure of the extraordinary level of human diversity found in India is
the use of 15 languages on its banknotes. The genetic underpinnings of that
population diversity are yielding to whole-genome analysis.
Aravinda Chakravarti
doi:10.1038/461487a
http://www.nature.com/nature/journal/v461/n7263/full/461487a.html
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ARTICLES
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Reconstructing Indian population history pp489-494
Genome-wide analysis of human variation in 25 diverse groups from India
reveals two ancient populations, genetically divergent, that are ancestral
to most Indians today. Traditionally upper caste and Indo-European speakers
tend to be descended from a group that is genetically close to Middle Easterners,
Central Asians and Europeans. The other group, the 'Ancestral South Indians',
does not appear to be close to any group outside the subcontinent.
David Reich et al.
doi:10.1038/nature08365
Abstract: http://www.nature.com/nature/journal/v461/n7263/abs/nature08365.html
Article: http://www.nature.com/nature/journal/v461/n7263/full/nature08365.html
A luminal epithelial stem cell that is a cell of origin for prostate cancer
pp495-500
A known regulator of prostate epithelial differentiation, Nkx3-1, is shown here
to mark a stem cell population that functions during prostate regeneration.
Furthermore, in mice in which the Pten tumour suppressor gene is deleted in a
group of rare cells that express Nkx3-1 in the absence of testicular androgens,
termed CARN cells, there is rapid carcinoma formation after andogen-mediated
regeneration. These observations indicate that prostate cancer can originate in CARN cells.
Xi Wang et al.
doi:10.1038/nature08361
Abstract: http://www.nature.com/nature/journal/v461/n7263/abs/nature08361.html
Article: http://www.nature.com/nature/journal/v461/n7263/full/nature08361.html
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LETTERS
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Seismic evidence for the loss of stellar angular momentum before the
white-dwarf stage pp501-503
The majority of all stars finish their evolution as white dwarf stars. If
white dwarf stars kept the angular momentum of their progenitors, they should
rotate relatively rapidly, with typical periods of the order of a few seconds.
Observations show that they rotate much more slowly, but it is not known whether
a white dwarf could 'hide' some of its original angular momentum below its
superficial layers. Here, a determination of the internal rotation profile of
a white dwarf shows that it rotates as a solid body and with a relatively long period.
S. Charpinet, G. Fontaine and P. Brassard
doi:10.1038/nature08307
Abstract: http://www.nature.com/nature/journal/v461/n7263/abs/nature08307.html
Article: http://www.nature.com/nature/journal/v461/n7263/full/nature08307.html
Violation of Bell's inequality in Josephson phase qubits pp504-506
Bell inequalities are a quantitative measure that can distinguish classically
determined correlations from stronger quantum correlations, and their measurement
provides strong experimental evidence that quantum mechanics provides a complete
description. The violation of a Bell inequality is now demonstrated in a solid-state
system; the experiment provides further strong evidence that a macroscopic
electrical circuit is really a quantum system.
Markus Ansmann et al.
doi:10.1038/nature08363
Abstract: http://www.nature.com/nature/journal/v461/n7263/abs/nature08363.html
Article: http://www.nature.com/nature/journal/v461/n7263/full/nature08363.html
Stable isotope constraints on Holocene carbon cycle changes from an Antarctic
ice core pp507-510
Antarctic ice cores can be used to reconstruct atmospheric CO2 concentrations,
revealing significant changes during the Holocene epoch which started 11,000
years ago. Here, a highly resolved [delta]13C record is presented for the past
11,000 years from measurements on atmospheric CO2 trapped in an Antarctic ice core.
These data are combined with a simplified carbon cycle model to shed light on the
processes responsible for the changes in CO2 concentrations.
Joachim Elsig et al.
doi:10.1038/nature08393
Abstract: http://www.nature.com/nature/journal/v461/n7263/abs/nature08393.html
Article: http://www.nature.com/nature/journal/v461/n7263/full/nature08393.html
El Nino in a changing climate pp511-514
A distinctly different type of El Nino event, causing global climate effects
dramatically different from those caused by the canonical El Nino, was observed
in the late twentieth century. Using data from projected global warming scenarios
it is now demonstrated that this new type of El Nino event is likely to become
progressively more common in the future as a result of anthropogenic climate change.
Sang-Wook Yeh et al.
doi:10.1038/nature08316
Abstract: http://www.nature.com/nature/journal/v461/n7263/abs/nature08316.html
Article: http://www.nature.com/nature/journal/v461/n7263/full/nature08316.html
An epistatic ratchet constrains the direction of glucocorticoid receptor evolution
pp515-519
Whether evolution can go back to an ancestral structure by reversing the selection
pressure on function has long fascinated biologists. Here, the evolution of hormone
specificity in the vertebrate glucocorticoid receptor is used as a case-study to
investigate this issue; the mutations that optimized the new specificity of the
glucocorticoid receptor are found to have destabilized elements of the protein
structure that were required to support the ancestral conformation.
Jamie T. Bridgham, Eric A. Ortlund and Joseph W. Thornton
doi:10.1038/nature08249
Abstract: http://www.nature.com/nature/journal/v461/n7263/abs/nature08249.html
Article: http://www.nature.com/nature/journal/v461/n7263/full/nature08249.html
Population context determines cell-to-cell variability in endocytosis and virus
infection pp520-523
Susceptibility to drug treatment or viral infection can vary greatly from one cell
to another even in a population of genetically identical cells cultured together,
but until now the causes of this heterogeneity had not been investigated. Here,
deterministic links are revealed between fundamental cellular features and a cell's
population context - for example, whether a cell is localized at the centre or
at the periphery of an island of adhering cells.
Berend Snijder et al.
doi:10.1038/nature08282
Abstract: http://www.nature.com/nature/journal/v461/n7263/abs/nature08282.html
Article: http://www.nature.com/nature/journal/v461/n7263/full/nature08282.html
Integration of neuronal clones in the radial cortical columns by EphA and ephrin-A
signalling pp524-528
During development of the cerebral cortex, excitatory projection neurons migrate
to form a cellular infrastructure of radial columns. However, some of these
clonally related neurons undergo a lateral shift to intermix with neurons
originating from neighbouring proliferative units. This process is now shown
to be dependent on Eph receptor A and ephrin A signalling, a so far unrecognized
mechanism for lateral neuronal dispersion that seems to be essential for the
proper intermixing of neuronal types in the cortical columns.
Masaaki Torii, Kazue Hashimoto-Torii, Pat Levitt and Pasko Rakic
doi:10.1038/nature08362
Abstract: http://www.nature.com/nature/journal/v461/n7263/abs/nature08362.html
Article: http://www.nature.com/nature/journal/v461/n7263/full/nature08362.html
Asymptomatic deer excrete infectious prions in faeces pp529-532
Infectious prion diseases are transmitted naturally within affected host
populations, for example of sheep and deer. Once an animal is symptomatic its
excretions may contain contagious prions, but the biological importance of these
sources in sustaining epidemics remains unclear. Here it is shown that asymptomatic
mule deer infected with chronic wasting disease excrete infectious prions in their
faeces long before they develop clinical signs of prion disease.
Gultekin Tamguney et al.
doi:10.1038/nature08289
Abstract: http://www.nature.com/nature/journal/v461/n7263/abs/nature08289.html
Article: http://www.nature.com/nature/journal/v461/n7263/full/nature08289.html
Fgf8 morphogen gradient forms by a source-sink mechanism with freely diffusing
molecules pp533-536
Concentration gradients of certain molecules termed 'morphogens' are known to
control tissue development during embryogenesis, but how exactly these gradients
are formed remains unclear. Using the technique of fluorescence correlation
spectroscopy, Fgf8 morphogen gradients are now shown to be established and
maintained in living zebrafish by two essential factors: free diffusion of
single molecules away from the source and a sink function of the receiving cells.
Shuizi Rachel Yu et al.
doi:10.1038/nature08391
Abstract: http://www.nature.com/nature/journal/v461/n7263/abs/nature08391.html
Article: http://www.nature.com/nature/journal/v461/n7263/full/nature08391.html
Reactive oxygen species prime Drosophila haematopoietic progenitors for
differentiation pp537-541
Reactive oxygen species (ROS) are generally considered to be deleterious to
cells. Despite the fact that, in mammals, haematopoietic stem cells contain
low levels of ROS, common myeloid progenitors (CMPs) unexpectedly produce
relatively high levels of ROS. Here it is shown that the equivalent class of
cells to CMPs in Drosophila display increased levels of ROS in vivo, apparently
priming them for differentiation.
Edward Owusu-Ansah and Utpal Banerjee
doi:10.1038/nature08313
Abstract: http://www.nature.com/nature/journal/v461/n7263/abs/nature08313.html
Article: http://www.nature.com/nature/journal/v461/n7263/full/nature08313.html
A dimerization-dependent mechanism drives RAF catalytic activation pp542-545
Activation of the kinase RAF, a member of the ERK (extracellular signal-regulated kinase)
pathway, is triggered by the binding of growth factors to receptor tyrosine kinases.
Activating mutations in RAF can lead to unbridled signalling through the ERK pathway
and have been linked to several human cancers. Here, the activation mechanism of RAF
is shown to involve a specific mode of dimerization of its kinase domain, which is
relevant for the action of the RAF activator KSR and certain oncogenic mutations.
Thanashan Rajakulendran et al.
doi:10.1038/nature08314
Abstract: http://www.nature.com/nature/journal/v461/n7263/abs/nature08314.html
Article: http://www.nature.com/nature/journal/v461/n7263/full/nature08314.html
Active turnover modulates mature microRNA activity in Caenorhabditis elegans pp546-549
MicroRNAs have important roles in shaping gene expression profiles during development,
repressing target messenger RNAs to control various biological processes. The
degradation of mature microRNAs in the nematode Caenorhabditis elegans, mediated
by the 5[prime][rarr]3[prime] exoribonuclease XRN-2, is now found to affect
functional microRNA homeostasis in vivo.
Saibal Chatterjee and Helge Groszhans
doi:10.1038/nature08349
Abstract: http://www.nature.com/nature/journal/v461/n7263/abs/nature08349.html
Article: http://www.nature.com/nature/journal/v461/n7263/full/nature08349.html
Reconstructing Indian population history
对来自印度25个不同族群的132人的基因变异所做分析显示，两个古老的遗传趋异族群是今天大多数印度人的祖先。其中一个被称为“印度北部先民”的分支在遗传上接近中东人、中亚人和欧洲人。另一个被称为“印度南部先民”的分支与该次大陆以外的任何族群都不相近。这项工作为几个长期未能回答的问题提供了答案。看来，“种姓”数千年来一直是决定印度婚姻关系的一个强大力量，而一些人类学家过去曾认为“种姓”目前所具有的力量是英国殖民主义的一个产物。而且，神秘的安达曼群岛“矮小黑人”也被发现是从“印度南部先民”族群分离出来的一个古老分支。族群间等位基因频率差异很大，部分原因是族群内存在通婚习俗，所以印度有大量隐性疾病可通过基因方法来甄别和分析。本期封面所示为本项研究中取样族群所在地点及每个族群的一个成员。（Article p. 489; News & Views）封面图片：Kumarasamy Thangaraj/ Lalji Singh & F. Amirtharaj。
致癌性前列腺细胞——CARN细胞（Oncogenic prostate cells）
A luminal epithelial stem cell that is a cell of origin for prostate cancer
被称为“CARN细胞”的一个罕见的腔干细胞群已在小鼠前列腺中被发现。CARN细胞在由雄性激素耗尽所诱导的前列腺组织再生过程中生成腔细胞和基细胞两种类型。除了提供自我更新潜力外，这些细胞还能成为致癌转化的一个目标：CARN细胞中肿瘤抑制基因Pten的删除导致再生中的前列腺内肿瘤的形成。这些细胞在没有雄性激素存在时能够存活的能力提出这样一个可能性：独立于雄性激素的癌症可从这个细胞群产生，而且CARN细胞还可能为表现出扩散性前列腺癌恶性特征的细胞的治疗性定位提供了一个途径。（Article p. 495）
白矮星PG 1159–035角动量几乎全部失去（Stars lose their momentum）
Seismic evidence for the loss of stellar angular momentum before the white-dwarf stage
大多数恒星以白矮星的形式结束它们的恒星生命。如果所有恒星在其演化过程中都保持其角动量，那么白矮星的致密性应使其转动极快，周期只有几秒钟。然而，对白矮星所做观测表明，它们的表层转动要慢一些，典型周期在几小时和几十年之间。以前，人们一直没有可能确定它们在光球的表层之下是否自转得更快一些。现在，用星震学方法所做的一项研究显示，脉动白矮星PG 1159–035作为一个固态天体在转动，周期相对较长，大约为33-34小时。这说明它的角动量几乎已经全部失去，很可能发生在白矮星阶段之前。（Letter p. 501; News & Views）
全新世碳周期的最新重建结果（Holocene carbon cycle）
Stable isotope constraints on Holocene carbon cycle changes from an Antarctic ice core
通过对“EPICA Dome C”南极冰心中束缚的空气所做测量获得的一个新的大气δ13C记录，与一个简单的碳模型相结合，为全新世（当前的间冰期，开始于距今约11,000年前）碳周期提供了一幅高分辨率画面。以前的重建工作曾显示大气CO2浓度有显著变化，但造成这些变化的原因却不清楚。新的数据表明，全新世早期大气CO2浓度下降5 p.p.m.v.，是由陆地生物圈吸收约2900亿吨碳、以及为响应陆地碳吸收的碳酸盐补偿作用所发生的海洋中碳的释放共同造成的。在全新世晚期大气CO2浓度增加20 p.p.m.v.，大部分可由早先陆地生物圈碳酸盐补偿及珊瑚礁形成来解释，少部分可由陆地生物圈碳库存少量减少来解释。（Letter p. 507）
新类型厄尔尼诺现象出现比例将增加（El Niño changes its tune）
El Niño in a changing climate
最近几十年，出现了一种截然不同的厄尔尼诺类型。“正常”厄尔尼诺，是与东太平洋异常变暖以及其他地方所发生的从洪涝到干旱在内的各种不同气候变化相关的气候事件。另一种类型的厄尔尼诺，有时称之为“厄尔尼诺Modoki”（ Modoki在日语中意思是“相似但不同的”）。在这种厄尔尼诺现象中，暖池向西移动，其东侧和西侧为较冷的海水。Sang-Wook Yeh及其同事，利用将人为造成的温室气体变化考虑在内的一系列气候模型发现，这种新类型厄尔尼诺现象的出现比例，预计在21世纪末期会增加高达5倍。（Letter p. 511; News & Views）
演化路上开弓没有回头箭（Evolution has no reverse）
An epistatic ratchet constrains the direction of glucocorticoid receptor evolution
演化是否会仅仅通过逆转功能的选择压力而回到某种先祖结构是一个长期未能解决的问题，但也是一个仅靠形态史难以解决的问题。现在，Bridgeman等人以物理方式重构了一种调控蛋白（糖(肾上腺)皮质激素受体），并且以原子分辨率解析了施加在它们功能演化上的结构限制条件（即它们与哪个荷尔蒙结合）。他们发现，一种先祖蛋白中必不可少的氨基酸在一种较新的蛋白中却变成了中性，在那里它们随后会受到“遗传漂变”的侵蚀。（它们的）这种丢失使自然选择丧失了逆转历史替换所需的必要原材料——它们不再像其过去在另一个方向上那样具有“适应性”。从演化上来讲，走回头路是不可能的。（Letter p. 515）
共培养细胞之间存在易感性差异的深层原因（Cells with a difference）
Population context determines cell-to-cell variability in endocytosis and virus infection
对药物治疗或病毒感染的易感性从一个细胞到另一个细胞会有所不同，即便是在放在一起培养的一组基因完全相同的细胞中也是如此。这种异质性在很大程度上一直被归因于内在噪音，如基因表达的变化或信号分子水平的波动。现在，Snijder等人对大量共培养细胞进行了定量分析，并在细胞基本特点（如膜脂组成、或被一些而非另一些病毒感染的可感染性）与一个细胞的种群环境（例如，它们是处在一个粘附细胞岛的中心还是周边）之间发现了决定性的联系。这项工作中采用的评估细胞群的计算机辅助方法也许还可用于药物筛选。（Letter p. 520）
锯蛋白病CWD在鹿群中的发病和传播机制（Prion disease transmission）
Asymptomatic deer excrete infectious prions in faeces
“慢性消耗病”（ CWD）是一种高传染性锯蛋白病，在包括马鹿和驼鹿在内的鹿科动物的几个物种中引起神经退化。CWD自然传播的精确机制尚未解决。人们知道，一旦一个动物表现出这种病的症状，其排泄物会含有传染性锯蛋白。Stanley Prusiner及其同事发现，感染CWD的骡鹿，在表现出这种病的可见症状之前很久，其粪便中就开始含有感染性锯蛋白。这个发现对解释为什么CWD在鹿当中具有高发性、为什么能够高效横向传播提供了一个很有道理的、自然的机制，并且也可能适用于羊所患的同样具有感染性的痒病。（Letter p. 529）
“成形素” 浓度梯度的形成机制（Morphogens keep it simple）
Fgf8 morphogen gradient forms by a source-sink mechanism with freely diffusing molecules
被称为“成形素”的某些分子的浓度梯度已知在胚胎形成过程中控制组织发育。这种梯度怎样形成是一个人们很不了解的问题，Yu等人对此进行了研究。他们采用一种用于在活体中对分子进行成像的先进的高精密度技术（荧光校正光谱）发现，活斑马鱼胚胎中的扩散性FGF8“成形素”梯度由一个简单的源-汇机制形成。（Letter p. 533; News & Views）
活性氧在一些组织中可能有好的一面（Reactive oxygen’s good side）
Reactive oxygen species prime Drosophila haematopoietic progenitors for differentiation
虽然人们研究活性氧（ROS）主要是由于它们在DNA损伤、蛋白/类脂氧化和细胞凋亡中的有害作用，但人们也不断认识到ROS在一些组织中可能有有益作用。在哺乳动物造血系统中，造血干细胞含有低浓度ROS，但出乎意料的是，“共同髓系祖细胞”（ CMP）产生浓度相当高的ROS。Edward Owusu-Ansah和Utpal Banerjee在果蝇的两个先祖细胞类型中，发现了ROS含量的这种差别在功能上的明显重要性。他们发现，先祖细胞中由发育调控的、比较高的ROS含量使它们对分化比较敏感，并且确立了ROS在调控造血干细胞命运中所起的信号作用。（Letter p. 537; News & Views）
核糖核酸酶XRN-2对微RNA的作用（Recycling silencing complexes）
Active turnover modulates mature microRNA activity in Caenorhabditis elegans
在发育过程中，一类被称为“微RNA”的小型RNA在决定基因表达谱中扮演重要角色，它们是通过与某些信使RNA结合、抑制这些信使RNA的翻译或使其沉默的方式发挥作用的。人们认为，微RNA是造成单细胞生物演化成多细胞生物的一个因素。Saibal Chatterjee 和 Helge Großhans报告说，在微RNA作用于一个目标信使RNA之上、并从沉默复合物中释放出来之后，核糖核酸酶XRN-2促进它们的降解。XRN-2以这种方式来起微RNA含量的一种体内平衡调控因子的作用，这个作用在对新的发育提示信号做出反应当中可能具有重要性。（Letter p. 546）
----------------------
NEWS AND VIEWS
----------------------
Archaeology: Maya, Khmer and Inca pp479-480
Past societies have struggled against environmental problems similar to
those that beset us today. Three publications illuminate the outcomes for
three different tropical civilizations during the period AD 700-1600.
Jared Diamond
doi:10.1038/461479a
http://www.nature.com/nature/journal/v461/n7263/full/461479a.html
Developmental biology: Rise of the source-sink model pp480-481
Gradients of signalling molecules dictate where specific cell types form in
developing tissues, but how these gradients are set up is much debated. A
model proposed 40 years ago by Francis Crick may provide an answer.
Alexander F. Schier and Daniel Needleman
doi:10.1038/461480a
http://www.nature.com/nature/journal/v461/n7263/full/461480a.html
Climate change: The El Nino with a difference pp481-484
Patterns of sea-surface warming and cooling in the tropical Pacific seem
to be changing, as do the associated atmospheric effects. Increased global
warming is implicated in these shifts in El Nino phenomena.
Karumuri Ashok and Toshio Yamagata
doi:10.1038/461481a
http://www.nature.com/nature/journal/v461/n7263/full/461481a.html
Chemical biology: Caught in the activation pp484-485
A crystal structure reveals how a protein kinase is activated by the binding
of a small molecule at a pocket far from the catalytic site. This opens the
door to the design of modulators of protein phosphorylation.
Yi Liu
doi:10.1038/461484a
http://www.nature.com/nature/journal/v461/n7263/full/461484a.html
Astrophysics: Inner workings of a star pp485-486
By borrowing a technique used by seismologists to investigate Earth's interior,
astronomers have probed the hitherto-unknown interior rotation profile of a
white-dwarf star.
Sung-Chul Yoon
doi:10.1038/461485a
http://www.nature.com/nature/journal/v461/n7263/full/461485a.html
Developmental biology: A bad boy comes good pp486-487
Reactive oxygen species are often blamed for the development of cancer and
other diseases. Contrary to their 'bad boy' reputation, these species seem to
be essential for the development of immune cells, at least in the fly.
Ulrich Theopold
doi:10.1038/461486a
http://www.nature.com/nature/journal/v461/n7263/full/461486a.html
Human genetics: Tracing India's invisible threads pp487-488
One measure of the extraordinary level of human diversity found in India is
the use of 15 languages on its banknotes. The genetic underpinnings of that
population diversity are yielding to whole-genome analysis.
Aravinda Chakravarti
doi:10.1038/461487a
http://www.nature.com/nature/journal/v461/n7263/full/461487a.html
----------------------
ARTICLES
----------------------
Reconstructing Indian population history pp489-494
Genome-wide analysis of human variation in 25 diverse groups from India
reveals two ancient populations, genetically divergent, that are ancestral
to most Indians today. Traditionally upper caste and Indo-European speakers
tend to be descended from a group that is genetically close to Middle Easterners,
Central Asians and Europeans. The other group, the 'Ancestral South Indians',
does not appear to be close to any group outside the subcontinent.
David Reich et al.
doi:10.1038/nature08365
Abstract: http://www.nature.com/nature/journal/v461/n7263/abs/nature08365.html
Article: http://www.nature.com/nature/journal/v461/n7263/full/nature08365.html
A luminal epithelial stem cell that is a cell of origin for prostate cancer
pp495-500
A known regulator of prostate epithelial differentiation, Nkx3-1, is shown here
to mark a stem cell population that functions during prostate regeneration.
Furthermore, in mice in which the Pten tumour suppressor gene is deleted in a
group of rare cells that express Nkx3-1 in the absence of testicular androgens,
termed CARN cells, there is rapid carcinoma formation after andogen-mediated
regeneration. These observations indicate that prostate cancer can originate in CARN cells.
Xi Wang et al.
doi:10.1038/nature08361
Abstract: http://www.nature.com/nature/journal/v461/n7263/abs/nature08361.html
Article: http://www.nature.com/nature/journal/v461/n7263/full/nature08361.html
----------------------
LETTERS
----------------------
Seismic evidence for the loss of stellar angular momentum before the
white-dwarf stage pp501-503
The majority of all stars finish their evolution as white dwarf stars. If
white dwarf stars kept the angular momentum of their progenitors, they should
rotate relatively rapidly, with typical periods of the order of a few seconds.
Observations show that they rotate much more slowly, but it is not known whether
a white dwarf could 'hide' some of its original angular momentum below its
superficial layers. Here, a determination of the internal rotation profile of
a white dwarf shows that it rotates as a solid body and with a relatively long period.
S. Charpinet, G. Fontaine and P. Brassard
doi:10.1038/nature08307
Abstract: http://www.nature.com/nature/journal/v461/n7263/abs/nature08307.html
Article: http://www.nature.com/nature/journal/v461/n7263/full/nature08307.html
Violation of Bell's inequality in Josephson phase qubits pp504-506
Bell inequalities are a quantitative measure that can distinguish classically
determined correlations from stronger quantum correlations, and their measurement
provides strong experimental evidence that quantum mechanics provides a complete
description. The violation of a Bell inequality is now demonstrated in a solid-state
system; the experiment provides further strong evidence that a macroscopic
electrical circuit is really a quantum system.
Markus Ansmann et al.
doi:10.1038/nature08363
Abstract: http://www.nature.com/nature/journal/v461/n7263/abs/nature08363.html
Article: http://www.nature.com/nature/journal/v461/n7263/full/nature08363.html
Stable isotope constraints on Holocene carbon cycle changes from an Antarctic
ice core pp507-510
Antarctic ice cores can be used to reconstruct atmospheric CO2 concentrations,
revealing significant changes during the Holocene epoch which started 11,000
years ago. Here, a highly resolved [delta]13C record is presented for the past
11,000 years from measurements on atmospheric CO2 trapped in an Antarctic ice core.
These data are combined with a simplified carbon cycle model to shed light on the
processes responsible for the changes in CO2 concentrations.
Joachim Elsig et al.
doi:10.1038/nature08393
Abstract: http://www.nature.com/nature/journal/v461/n7263/abs/nature08393.html
Article: http://www.nature.com/nature/journal/v461/n7263/full/nature08393.html
El Nino in a changing climate pp511-514
A distinctly different type of El Nino event, causing global climate effects
dramatically different from those caused by the canonical El Nino, was observed
in the late twentieth century. Using data from projected global warming scenarios
it is now demonstrated that this new type of El Nino event is likely to become
progressively more common in the future as a result of anthropogenic climate change.
Sang-Wook Yeh et al.
doi:10.1038/nature08316
Abstract: http://www.nature.com/nature/journal/v461/n7263/abs/nature08316.html
Article: http://www.nature.com/nature/journal/v461/n7263/full/nature08316.html
An epistatic ratchet constrains the direction of glucocorticoid receptor evolution
pp515-519
Whether evolution can go back to an ancestral structure by reversing the selection
pressure on function has long fascinated biologists. Here, the evolution of hormone
specificity in the vertebrate glucocorticoid receptor is used as a case-study to
investigate this issue; the mutations that optimized the new specificity of the
glucocorticoid receptor are found to have destabilized elements of the protein
structure that were required to support the ancestral conformation.
Jamie T. Bridgham, Eric A. Ortlund and Joseph W. Thornton
doi:10.1038/nature08249
Abstract: http://www.nature.com/nature/journal/v461/n7263/abs/nature08249.html
Article: http://www.nature.com/nature/journal/v461/n7263/full/nature08249.html
Population context determines cell-to-cell variability in endocytosis and virus
infection pp520-523
Susceptibility to drug treatment or viral infection can vary greatly from one cell
to another even in a population of genetically identical cells cultured together,
but until now the causes of this heterogeneity had not been investigated. Here,
deterministic links are revealed between fundamental cellular features and a cell's
population context - for example, whether a cell is localized at the centre or
at the periphery of an island of adhering cells.
Berend Snijder et al.
doi:10.1038/nature08282
Abstract: http://www.nature.com/nature/journal/v461/n7263/abs/nature08282.html
Article: http://www.nature.com/nature/journal/v461/n7263/full/nature08282.html
Integration of neuronal clones in the radial cortical columns by EphA and ephrin-A
signalling pp524-528
During development of the cerebral cortex, excitatory projection neurons migrate
to form a cellular infrastructure of radial columns. However, some of these
clonally related neurons undergo a lateral shift to intermix with neurons
originating from neighbouring proliferative units. This process is now shown
to be dependent on Eph receptor A and ephrin A signalling, a so far unrecognized
mechanism for lateral neuronal dispersion that seems to be essential for the
proper intermixing of neuronal types in the cortical columns.
Masaaki Torii, Kazue Hashimoto-Torii, Pat Levitt and Pasko Rakic
doi:10.1038/nature08362
Abstract: http://www.nature.com/nature/journal/v461/n7263/abs/nature08362.html
Article: http://www.nature.com/nature/journal/v461/n7263/full/nature08362.html
Asymptomatic deer excrete infectious prions in faeces pp529-532
Infectious prion diseases are transmitted naturally within affected host
populations, for example of sheep and deer. Once an animal is symptomatic its
excretions may contain contagious prions, but the biological importance of these
sources in sustaining epidemics remains unclear. Here it is shown that asymptomatic
mule deer infected with chronic wasting disease excrete infectious prions in their
faeces long before they develop clinical signs of prion disease.
Gultekin Tamguney et al.
doi:10.1038/nature08289
Abstract: http://www.nature.com/nature/journal/v461/n7263/abs/nature08289.html
Article: http://www.nature.com/nature/journal/v461/n7263/full/nature08289.html
Fgf8 morphogen gradient forms by a source-sink mechanism with freely diffusing
molecules pp533-536
Concentration gradients of certain molecules termed 'morphogens' are known to
control tissue development during embryogenesis, but how exactly these gradients
are formed remains unclear. Using the technique of fluorescence correlation
spectroscopy, Fgf8 morphogen gradients are now shown to be established and
maintained in living zebrafish by two essential factors: free diffusion of
single molecules away from the source and a sink function of the receiving cells.
Shuizi Rachel Yu et al.
doi:10.1038/nature08391
Abstract: http://www.nature.com/nature/journal/v461/n7263/abs/nature08391.html
Article: http://www.nature.com/nature/journal/v461/n7263/full/nature08391.html
Reactive oxygen species prime Drosophila haematopoietic progenitors for
differentiation pp537-541
Reactive oxygen species (ROS) are generally considered to be deleterious to
cells. Despite the fact that, in mammals, haematopoietic stem cells contain
low levels of ROS, common myeloid progenitors (CMPs) unexpectedly produce
relatively high levels of ROS. Here it is shown that the equivalent class of
cells to CMPs in Drosophila display increased levels of ROS in vivo, apparently
priming them for differentiation.
Edward Owusu-Ansah and Utpal Banerjee
doi:10.1038/nature08313
Abstract: http://www.nature.com/nature/journal/v461/n7263/abs/nature08313.html
Article: http://www.nature.com/nature/journal/v461/n7263/full/nature08313.html
A dimerization-dependent mechanism drives RAF catalytic activation pp542-545
Activation of the kinase RAF, a member of the ERK (extracellular signal-regulated kinase)
pathway, is triggered by the binding of growth factors to receptor tyrosine kinases.
Activating mutations in RAF can lead to unbridled signalling through the ERK pathway
and have been linked to several human cancers. Here, the activation mechanism of RAF
is shown to involve a specific mode of dimerization of its kinase domain, which is
relevant for the action of the RAF activator KSR and certain oncogenic mutations.
Thanashan Rajakulendran et al.
doi:10.1038/nature08314
Abstract: http://www.nature.com/nature/journal/v461/n7263/abs/nature08314.html
Article: http://www.nature.com/nature/journal/v461/n7263/full/nature08314.html
Active turnover modulates mature microRNA activity in Caenorhabditis elegans pp546-549
MicroRNAs have important roles in shaping gene expression profiles during development,
repressing target messenger RNAs to control various biological processes. The
degradation of mature microRNAs in the nematode Caenorhabditis elegans, mediated
by the 5[prime][rarr]3[prime] exoribonuclease XRN-2, is now found to affect
functional microRNA homeostasis in vivo.
Saibal Chatterjee and Helge Groszhans
doi:10.1038/nature08349
Abstract: http://www.nature.com/nature/journal/v461/n7263/abs/nature08349.html
Article: http://www.nature.com/nature/journal/v461/n7263/full/nature08349.html
| 《Nature》目录要览 — 2011-04-28出版 |
| 《Nature》目录要览：2011-01-20出版 |
| 《Nature》目录要览：2010-12-23出版 |
| 《Nature》目录要览：2010-12-16出版 |
| 《Nature》目录要览：2010-12-09出版 |
| 《Nature》目录要览：2010-12-02出版 |
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