The oxidation–reduction cycle of the highly conserved protein, peroxiredoxin, constitutes a universal non-transcription-based circadian clock. This marker, conserved throughout all three phylogenetic domains suggests that this type of cellular timekeeping may have co-evolved across organisms since about 2.5 billion years ago.
This press release contains:
--- Summaries of newsworthy papers:
Astrophysics: Superflares on solar-type stars
Comment: Catch the transit of Venus while you can!
Neuroscience: Breaking down the blood–brain barrier
Diabetes: Regulating regulatory cells
Comment: Beyond the great and good
Evolution: One clock to rule them all
Cancer: Variation in mutated breast cancer genes
Quantum physics: Clocking tunnelling times
And finally... Genome sequence reveals butterflies’ true colours
---Geographical listing of authors
 Astrophysics: Superflares on solar-type stars (AOP; N&V)
An analysis of very strong events known as 'superflares' observed on stars with masses and temperatures similar to the Sun is presented in Nature this week. Superflares are large releases of (probably magnetic) energy that can be up to 10,000 times more energetic than those seen on our Sun; there is no historical record of superflares on our Sun in the past 2,000 years, and a strong case that there has not been one in the past billion years. The latest findings provide estimates of the occurrence frequency of superflares on different solar-type stars.
Detailed study of superflares is hampered by the rareness of these events, but the Kepler satellite provides useful data for analysis as it can watch many stars at once. Using these data, Hiroyuki Maehara and colleagues report observations of 365 superflares, including 101 from slowly rotating solar-type stars, from around 83,000 stars observed over 120 days. The data indicate that slowly rotating stars (like the Sun) have superflares much less often than rapidly rotating ones. Superflares are thought to be caused by magnetic interactions with so-called hot Jupiters (a class of exoplanets with masses similar to that of Jupiter). However, no such hot Jupiters have been discovered around solar-type stars, which indicates that hot Jupiters associated with superflares are rare, the authors suggest. One characteristic shared by the superflare stars is that they have large starspots (much larger than those on the Sun).
Bradley Schaefer discusses this work in an accompanying News & Views article, and suggests that it is unlikely that our Sun has such events.
Hiroyuki Maehara (Kyoto University, Japan)
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Bradley Schaefer (Louisiana State University, Baton Rouge, LA, USA) N&V author
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Comment: Catch the transit of Venus while you can! (pp 303-304)
On 5–6 June, the skies will host an extremely rare astronomical event. Venus will cross in front of the Sun for only the second time in the twenty-first century, and the eighth time since anyone has been able to watch the event with a telescope. Scientists have a moral obligation to collect as much data about this event as possible, argues Jay Pasachoff in a Comment in Nature this week, because it provides a crucial opportunity to calibrate or improve our methods for finding and studying far-off planets around distant stars.
This year is particularly exciting because the Sun is going through an active sunspot phase. This makes the transit of Venus across the Sun very similar to what exoplanets might look like passing in front of other, 'spotty' stars. Researchers such as Pasachoff are keen to see what can be determined about a planet's size, or the nature of its atmosphere, from transit data.
The transit could also help us to understand Venus better. The Venus Express probe has been orbiting Venus since 2006. But it has only a limited view: it can take atmospheric measures only at sunrise and sunset each day over a different spot of the planet, making it impossible to tell if the differences seen are due to changes in space or time. Only from a transit can an entire slice of the planet's atmosphere be seen all at once.
Jay Pasachoff (Williams College, Williamstown, MA, USA)
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 Neuroscience: Breaking down the blood–brain barrier (AOP)
Research that explains how a protein associated with Alzheimer’s disease risk can cause vascular defects in the brain is reported in Nature this week. The work describes how expression of the protein, APOE4, leads to degradation of brain tissue and altered blood flow, which in turn can lead to neurodegenerative changes in mice. In addition, a target for treating APOE4-mediated damage is uncovered.
The APOE4 gene has been connected to defects in vascular integrity in the brain, such as dysfunction of the blood–brain barrier (BBB), but the underlying mechanisms have remained unclear. Berislav Zlokovic and co-workers find that APOE4 activates a pathway in mouse pericytes — cells crucial for the maintenance of the BBB —that causes the barrier, which normally prevents toxic elements entering brain tissue, to break down. Subsequently, neuronal uptake of blood-derived neurotoxic proteins increases and blood flow is reduced. The authors show that the vascular defects associated with APOE4 precede neuronal dysfunction and can initiate neurodegenerative changes.
Zlokovic and colleagues suggest that cyclophilin A (CypA), a component of the pathway activated by APOE4, is a key target for treating APOE4-mediated neurovascular defects and the resulting neuronal dysfunction. They show that in mice treated with cyclosporine A, a drug that binds intracellular CypA and inhibits its effects, BBB disruption is eliminated.
Berislav Zlokovic (University of Southern California, Los Angeles, CA, USA)
Tel: +1 323 442 2566; E-mail: Berislav.Zlokovic@med.usc.edu
 Diabetes: Regulating regulatory cells (AOP)
A unique population of immune cells known as regulatory T (Treg) cells in fat tissue have been shown to control inflammation and, thereby, metabolic disorders associated with type-2 diabetes. A potential mechanism for this action is provided in Nature this week, and a major regulator of Treg cells that reside in fat tissue is identified. This regulator is shown to have a role in the action of the leading class of type-2 diabetes drugs.
Diane Mathis and colleagues previously found a unique population of Treg cells in the adipose tissue of lean mice that disappears when obesity sets in. Enrichment of these Treg cells in the visceral fat is associated with reduced inflammation and insulin resistance, two risk factors for type-2 diabetes. In the present study the authors suggest that the function of these Treg cells is controlled by the peroxisome proliferator activated receptor g (PPAR-g), a key regulator of fat cell production and metabolism. They show that expression of PPAR-g in visceral fat Treg cells contributes to the insulin-sensitizing activity of the type-2 diabetes drug pioglitazone.
These results provide proof-of-principle that it is possible to target a designated population of Treg cells for a particular therapeutic goal.
Diane Mathis (Harvard Medical School, Boston, MA, USA)
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Comment: Beyond the great and good (pp 301-302)
The government chief science adviser role, established in the United Kingdom, is being rolled out worldwide ― from New Zealand and Japan to the European Union and the United Nations. As a successor is sought for John Beddington, the current holder of the UK post who steps down at the end of this year, science-policy experts Robert Doubleday and James Wilsdon assess how the model is working in a Comment piece in this week’s Nature.
Challenging a recent UK House of Lords report that highlights the qualities that make a successful science adviser, the authors argue that too much emphasis is being placed on the personal character and reputation of the individual expert ― an approach that is typical in Britain. For such posts to succeed internationally, more should be done to shore up the science-advice system across government departments and to share best practice and ideas worldwide.
James Wilsdon (University of Sussex, Falmer, UK)
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 Evolution: One clock to rule them all (AOP)
The oxidation–reduction cycle of the highly conserved protein, peroxiredoxin, constitutes a universal non-transcription-based circadian clock, reports a study published in Nature. This marker, conserved throughout all three phylogenetic domains ― Archaea, Bacteria and Eukaryota ― suggests that this type of cellular timekeeping may have co-evolved across organisms since about 2.5 billion years ago.
Most organisms possess an endogenous circadian clock that tunes metabolism, physiology and behaviour to external conditions, namely a 24-hour period. Although most cellular clocks rely on networks of transcription feedback loops, a common ‘clock’ mechanism between various organisms has not been found. Previous findings have reported that the protein peroxiredoxin is important for non-transcriptional mechanisms in cellular timekeeping, but the reasons behind this were unclear.
Because peroxiredoxin is a highly conserved metabolic protein across all domains of life, Akhilesh Reddy and colleagues characterized the circadian oscillations of its oxidation state in mice, fungus, Drosophila and bacteria. They found that these redox cycles are conserved among all these organisms, which span Archaea, Bacteria and Eukaryota.
Akhilesh Reddy (University of Cambridge, UK)
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 Cancer: Variation in mutated breast cancer genes (AOP)
An analysis of mutated genes associated with breast cancer reveals that there is wide variation in the number of mutations between individual cases. So-called driver mutations, which are causally implicated in the development of cancer, are identified in several new cancer genes. The study is published in Nature this week and highlights substantial genetic diversity underlying this disease.
To explore the mutated cancer genes and mutational processes underlying breast cancer, Michael Stratton and co-workers examined the genomes of 100 breast cancer samples. Multiple mutational signatures were uncovered; the authors observed 73 different combinations of mutated cancer genes, and driver mutations in at least 40 cancer genes, although the number of drivers seems to vary substantially between cases. Mutation number is found to correlate with age at diagnosis and cancer histological grade.
This genome analysis provides a direct survey of the landscape of driver mutations in breast cancer, which the authors hope will influence strategies to seek new modes of prevention and treatment.
Michael Stratton (Wellcome Trust Sanger Institute, Hinxton, UK)
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 Quantum physics: Clocking tunnelling times (pp 343-346; N&V)
One of the most fundamental quantum processes ― tunnelling of a particle through a barrier ― is probed in this week’s Nature. In the experiment, the dynamics of the particle outside the barrier are manipulated, allowing the timing of the tunnelling event to be determined. Such information provides a stringent test for theoretical descriptions of the process.
Tunnelling of an electron is a ubiquitous quantum mechanical phenomenon that affects physical, chemical and biological processes. Nirit Dudovich and colleagues explore the link between tunnelling and the dynamics of the particle outside the barrier by using laser pulses to induce electrons to tunnel from helium atoms and carbon dioxide molecules, and later return and recombine with their parent atom or molecule. A second laser pulse changes the dynamics of the electron after tunnelling, which influences the light bursts emitted during recombination.
The authors demonstrate that their technique can uncover subtle differences in the dynamics of electrons that originate from different orbitals within a carbon dioxide molecule. This opens the door to studying tunnelling in more complex systems, and more generally to time-resolving multi-electron rearrangements in atoms and molecules.
Nirit Dudovich (Weizmann Institute of Science, Rehovot, Israel)
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Manfred Lein (Leibniz Universität Hannover, Germany) N&V author
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 And finally... Genome sequence reveals butterflies’ true colours (AOP)
The genome of the postman butterfly (Heliconius melpomene) has been sequenced and is reported in Nature this week. The findings provide insights into butterfly biology and the evolution of diversity within the Heliconius genus.
Heliconius butterflies have been used to study ecology, behaviour, mimicry and speciation. The genus comprises 43 species whose wings exhibit a wide range of different colour patterns; many are brightly coloured so as to appear unpalatable to potential predators. James Mallet and colleagues from the Heliconius Genome Consortium sequenced the genome of Heliconius melpomene. Using comparative resequencing they show that closely related Heliconius species exchange protective colour-pattern genes promiscuously, indicating that hybridization may have a key role in adaptive radiation — in other words, this gene exchange may enable species to share the evolutionary cost of warding off would-be predators. The authors also found that these butterflies have an expanded repertoire of Hox genes, which control body plan, and of olfactory receptor genes. This is unexpected given that Heliconius have excellent colour vision and are thought to rely primarily on this sense.
The sequence offers new opportunities for comparative genomics within this economically significant insect order, which includes many pest species and the silkmoth (Bombyx mori), the only domesticated insect.
James Mallet (Harvard University, Cambridge, MA, USA)
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ALSO IN THIS ISSUE…
 Light-induced liquid crystallinity (pp 347-349)
 Recent Northern Hemisphere tropical expansion primarily driven by black carbon and tropospheric ozone (pp 350-354)
 KCTD13 is a major driver of mirrored neuroanatomical phenotypes of the 16p11.2 copy number variant (pp 363-367; N&V)
 Structure of the nociceptin/orphanin FQ receptor in complex with a peptide mimetic (pp 395-399; N&V)
 Structure of the delta opioid receptor bound to naltrindole (pp 400-404; N&V)
 NPR3 and NPR4 are receptors for the immune signal salicylic acid in plants
GEOGRAPHICAL LISTING OF AUTHORS:
The following list of places refers to the whereabouts of authors on the papers numbered in this release. For example, London: 4 - this means that on paper number four, there will be at least one author affiliated to an institute or company in London. The listing may be for an author's main affiliation, or for a place where they are working temporarily. Please see the PDF of the paper for full details.
Paris: 5, 7
Rio Piedras: 7
Cambridge: 4, 5, 7
Edinburgh: 4, 7, 13
Hinxton: 5, 7
London: 5, 6, 7
Norwich: 5, 7
UNITED STATES OF AMERICA
Irvine: 7, 9
La Jolla: 11
Los Angeles: 2
San Diego: 9
San Francisco: 7
New Haven: 7
Baltimore: 7, 10
College Park: 7
Boston: 3, 5, 7, 10
Mississippi State: 7
Saint Louis: 2
Chapel Hill: 11
Durham: 10, 13
Wright Patterson Air Force Base: 8
Seattle: 4, 13
From North America and Canada
Neda Afsarmanesh, Nature New York
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From Japan, Korea, China, Singapore and Taiwan
Eiji Matsuda, Nature Tokyo
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From the UK
Rebecca Walton, Nature London
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