Transients in the sky: Stellar puzzle
In 2004, astronomers observed an incredibly bright stellar flare. Then two years later, they spotted a type 1b supernova in the same vicinity. Researchers now confirm that the two events occurred in the same place, making it an unlikely coincidence and something of a puzzle.
Andrea Pastorello and colleagues offer a few explanations. The initial flare could have come from a Wolf–Rayet star — a very hot, massive, dying star that throws out a lot of gas. Or it could have come from a binary system, containing the supernova and a luminous blue variable — a bright, hypergiant, variable star that flares periodically. The authors’ conclusions support another publication by an independent group in the journal Astrophysics (R. J. Foley et al. Astrophys. J. 657, L105–L108; 2007).
CONTACT
Andrea Pastorello (Queen's University Belfast, UK)
Tel: +44 28 9097 3509; E-mail: a.pastorello@qub.ac.uk

Planetary science: Saturn’s magnetosphere gets the Cassini treatment

Saturn’s magnetosphere overturns in a way similar to that of Jupiter.
It’s known that cold, dense plasma from Jupiter’s inner magnetosphere is flung outward and replaced by hotter plasma from the outer magnetosphere — a little like convection in a pot of liquid. But whether the same is true for Saturn’s magnetosphere has been a matter of debate, given that Saturn’s magnetosphere shares other features with that of Earth. William Lewis and colleagues now study the cold plasma next to hot, inward-moving plasma in its magnetosphere to show that this cold plasma is outward bound, so Saturn’s magnetosphere does indeed have similar overturning to Jupiter’s — a discovery made possible by Cassini’s plasma spectrometer.
CONTACTWilliam Lewis (Southwest Research Institute, San Antonio, TX, USA)
Tel: +1 210 522 5651; E-mail: wlewis@swri.edu

Genetics: DNA ‘instruction manual’ deciphered

After sequencing the human genome, the next logical step is to figure out how cells make use of this instruction manual. With the results of a huge project that identifies and analyses functional elements taken from part of the human genome.
Thirty-five groups provided over 200 data sets, comprising around 1% of the human genome, for the pilot of the Encyclopedia of DNA Elements (ENCODE) Project. Ewan Birney and an international consortium then described which parts of the selected DNA are transcribed into RNA, where specific proteins are bound to the DNA, how the sequence compares to that of other organisms, and what form the structure of chromatin (the complex of DNA and proteins that make up chromosomes) takes in the selected regions.
From this, the consortium derived a number of exciting new insights into both the nature and evolution of DNA sequences important for biological function. For example, most of the DNA studied appears to be transcribed into RNA, and these DNA transcripts overlap extensively. This is at odds with the view that the human genome contains a relatively small set of discrete genes alongside a mass of biologically inactive 'junk DNA'.
The team also found that around one-half of the genome's functional elements appears to be able to change sequence more freely than expected across mammalian evolution. This suggests the existence of a large pool of neutral elements that are biochemically active but provide no specific benefit to the organism, which may serve as a 'warehouse' for natural selection.
CONTACT
Ewan Birney (EMBL-European Bioinformatics Institute, Cambridge, UK)
Tel: +44 1223 494 420; E-mail: birney@ebi.ac.uk

Anna-Lynn Wegener (EMBL Press Officer, Heidelberg, Germany)
Tel: +49 6221 387 452; E-mail: wegener@embl.de

Zhiping Wang (Boston University, MA, USA) Co-author
Tel: +1 617 353 3509; E-mail: zhiping@bu.edu

John M. Greally (Albert Einstein College of Medicine, Bronx, NY, USA) N&V author
Tel: +1 718 430 2875; E-mail: jgreally@aecom.yu.edu

Evolution: A gigantic bird-like dinosaur

The remains of a gigantic, surprisingly bird-like dinosaur have been uncovered in Inner Mongolia, China. The animal — which lived in the Late Cretaceous (about 70 million years ago) — is thought to have had a body mass of about 1,400 kilograms, which is surprising as most theories suggest that carnivorous dinosaurs got smaller as they got more bird-like. The dinosaur has been classed as a new species and genus.
Xing Xu and colleagues carried out a phylogenetic analysis of the skeleton and have grouped the fossil with a family that included the beaked, bird-like Oviraptor because of its similarly avian features. What is most striking, however, is that at 1,400 kilograms the fossil is about 35-times heavier than other similar feathered dinosaurs, which rarely exceeded a body mass of 40 kilograms.
The authors estimate that the new dinosaur would have been about eight metres long and would have stood, at the shoulder, twice the height of a man. They suggest that a growth rate considerably faster than large North American tyrannosaurs contributed to this. The team also noticed lines of arrested growth on the fossil, indicating that it was still a young adult when it died, so the full-sized dinosaur may have been even larger than this. But, despite its great size, many features of its anatomy were more bird-like, rather than less, as would have been expected.
CONTACT
Xing Xu (Chinese Academy of Sciences, Beijing, China)
Tel: +86 10 8836 9196; E-mail: xu.xing@ivpp.ac.cn or xingxu@vip.sina.com

Physical Activity May Reduce Risk of Gestational Diabetes Mellitus
SEATTLE - Gestational diabetes mellitus (GDM) complicates 4 percent to 7 percent of all pregnancies in the United States and poses a risk to both infant and mother. However, results of a new study conducted by researchers from Swedish Medical Center's Perinatal Studies program suggests physical activity may reduce risk of GDM.
Babies born to mothers with GDM may be large at birth and suffer complications such as jaundice. These children are more likely to become obese and develop diabetes in early adulthood. Women with GDM are at increased risk of developing other complications during pregnancy, such as preeclampsia, and they are more likely to develop type 2 diabetes after pregnancy.
The results of this new study suggest that women who are physically active during the year before and/or during early pregnancy may be less likely to develop GDM.
The study, which was funded by The National Institute of Child Health and Human Development at National Institutes of Health, suggests that current efforts to encourage Americans to engage in more frequent physical activity may also benefit pregnant women and result in substantial reductions in the incidence of GDM.
Lead author Jennifer Dempsey and colleagues report that women who participated in recreational physical activity during the year before pregnancy reduced their risk of GDM by 56 percent. During this time period, women who exercised for about four hours per week were 76 percent less likely to develop GDM when compared with women who did not exercise. In addition, women who participated in recreational physical activity both before and during early pregnancy enjoyed a 69 percent reduction in risk.
The study, which is ongoing at Swedish Medical Center in Seattle and led by Drs. Michelle Williams, Tanya Sorensen and David Luthy, was presented at the 24th annual meeting of the Society for Maternal-Fetal Medicine in New Orleans.
The investigators are currently conducting additional analyses to determine which metabolic or physiological changes associated with exercise may contribute to this reduced risk of GDM. They are also conducting studies to help identify which specific types, intensities and duration of exercise are associated with optimal pregnancy outcomes.

Biology : Skin barrier formation and caspase-14



A protein known as caspase-14 has been identified as the enzyme involved in the protection of the skin against UVB damage and water loss, according to a study.
The involvement of caspase-family members in programmed cell death and inflammation is well understood but, a function for caspase-14 had previously not been identified. Using caspase-14 knockout mice, Wim Declercq and colleagues show that caspase-14 is responsible for the initial processing of profillagrin to fillagrin. Fillagrin is responsible for aggregating keratin and other proteins in the upper layers of the epidermis to form the stratum corneum – a layer of flattened dead-cell remnants that creates a protective barrier for the skin. The controlled processing of profillagrin to produce fillagrin ultimately maintains the integrity of the epidermis. In mice lacking caspase-14, their skin exhibits a defective stratum corneum and is more sensitive to water loss and UVB photodamage.
The identification of caspase-14 and its role in skin-barrier formation opens avenues for the pharmaceutical manipulation of this process to prevent the damage induced by UVB, the primary agent responsible for sunburn and skin ageing.
Author contact:
Wim Declercq (Ghent University, Belgium)
Tel: +32 9 33 13 660; E-mail: wim.declercq@dmbr.ugent.be


...And Control of all fates
Cell Biology investigates how pluripotency, the ability of a stem cell to differentiate into every cell type of the adult organism, is regulated.
Understanding how stem cells maintain their pluripotent state has involved the characterisation of a multitude of transcription factors – the proteins that determine whether a specific gene is expressed or not. Pluripotency in embryonic stem cells was thought to be controlled primarily by the transcription factors Oct3/4 and Sox2, as these proteins were believed to activate Oct-Sox enhancers – regulatory regions that determine the expression of pluripotent stem cell-specific genes. Shinji Masui and colleagues used mutant mice lacking the Sox2 gene to show that although Sox2 is needed for stem cell pluripotency, it is not required for the enhancers to function and in fact governs the expression of Oct3/4. The authors went on to show that this regulation is indirect, as Sox2 controls the expression of a number of transcription factors that in turn regulate Oct3/4 expression.
This study illustrates the precise regulation of pluripotency by key proteins, and reorders the hierarchy of these factors with Sox2 as the master regulator — another small step towards a complete understanding of stem cell biology.
Author contact:
Shinji Masui (International Medical Centre of Japan, Tokyo, Japan)
Tel: +81 3 3202 7181; E-mail: masui@ri.imcj.go.jp

The dual role of BRCA2 in DNA repair
The dual role of the gene BRCA2 in DNA repair is described in two independent studies. The studies from Stephen West’s and Luca Pellegrini’s groups shed light on the role of the gene, mutations of which result in predisposition to breast cancer and other malignancies.
The protein encoded by BRCA2 is involved in homologous recombination, a process whereby damaged DNA is repaired using an intact copy of DNA as a template. This process also includes the protein RAD51, which interacts directly with two different regions of BRCA2, called BRC and TR2. The BRC region had been previously suggested to be involved in terminating homologous recombination. Data from the two present studies indicate that the TR2 region can oppose the activity of BRC, suggesting that BRCA2 contains regions that both favor and disrupt homologous recombination. These activities might operate at different stages of DNA repair.
Both reports also provide insight into how the opposing activities of BRCA2 can be regulated – a phosphorylation event at TR2 results in the loss of its interaction with RAD51, acting as a turn-off switch. These findings advance our knowledge of BRCA2’s role in genetic stability, and contribute to our understanding of why mutations in BRCA2 increase the likelihood of cancer.
Author contacts:
Stephen West (Cancer Research UK, London, UK) Author paper [16]
Tel: +44 1707 625 868; E-mail: stephen.west@cancer.org.uk

Luca Pellegrini (University of Cambridge, UK) Author paper [17]
Tel: +44 1223 333 662; E-mail: luca@cryst.bioc.cam.ac.uk


Deciphering the histone code
A method to identify all modifications on histones, the proteins around which DNA is packed, is presented online. This study should allow researchers a better understanding of how genes are regulated by alterations to these proteins.
DNA holds all the information for the building blocks of life, but how a cell reads this genetic information depends on histones, and in particular on modifications to these histones. For example, the attachment of methyl groups to histones usually signals that a gene is silent, whereas the attachment of acetyl groups corresponds to gene activation. Scientists have dubbed the combinatorial use of histone modifications the ‘histone code’, but the extent to which different modifications are combined in the histone code is still unknown.
To help crack the code, Neil Kelleher and colleagues devised a method to identify all the possible modifications that occur on histones in a cell. First they separated different histone variants, depending on their degree of acetylation and methylation, by hydrophilic interaction chromatography, then they applied high-resolution tandem mass spectroscopy to identify all modifications on each variant and the exact residues carrying them. By using a mass spectrometry technique known as ‘top down,’ in which intact proteins are fragmented inside the mass spectrometer, they observed better preservation of modifications than traditional mass spectrometry methods looking at pre-digested proteins. For one particular histone alone, they found over 150 different patterns of modification.
This method helps to decipher the elements that make up the histone code and will allow researchers to relate the pattern of these modifications to the regulation of gene activity.
Author contact:
Neil Kelleher (University of Illinois at Urbana-Champaign, IL, USA)
Tel: +1 217 333 5071; E-mail: kelleher@scs.uiuc.edu

A red-letter day for brain connectivity

Insights into grapheme-colour synesthesia are presented in a paper of Neuroscience. People with this condition – who see a cascade of colours associated with individual letters when looking at a page of text – appear to have more neural connections in areas of the brain involved in word processing and binding perceptions together.
Romke Rouw and Steven Scholte used a technique called diffusion tensor imaging (DTI) to look at brain differences between grapheme-colour synesthetes and healthy controls without this condition. DTI allows non-invasive visualisation of the white matter tracts, or axons, connecting neural cell bodies. The researchers found that synesthetes had more axons connecting three brain areas: the right fusiform gyrus, near regions involved in word and colour processing, and the left intraparietal sulcus and frontal cortex, both part of a network of regions involved in binding and consciousness.
The study also found differences among the synesthetes, according to how they perceived the association between words and colours. Some synesthetes, known as projectors, report stronger experiences that are projected into the external world, while others, known as associators, report weaker experiences that appear in their ‘mind’s eye’. The degree of structural connectivity in a region known as the right temporal cortex was correlated with the strength of the synesthetic experience. These results suggest a two-stage model of synesthesia, with increased connectivity in some areas being important for generating perceptual binding, and connectivity in other areas determining the intensity of the resultant perceptions.
Author contact:
Romke Rouw (University of Amsterdam, The Netherlands)
Tel: +31 20 525 6742; E-mail: R.Rouw@uva.nl

Gene copy number and risk of autoimmunity

Individuals with fewer than two copies of the gene FCGR3B are more susceptible to a variety of autoimmune disorders, including lupus, according to a study.
Evidence is accumulating that, in addition to gene mutations, variation in the actual number of copies of individual genes can influence susceptibility to common diseases. It was previously shown that variation in the copy number of FCGR3B, a cell-surface receptor that contributes to the protective functions of the immune system, is associated with susceptibility to a kidney disease called glomerulonephritis. Timothy Aitman and colleagues now report that FCGR3B copy number variation is associated more broadly with autoimmune disorders, including lupus, microscopic polyangiitis, and Wegener’s granulomatosis. The small group of individuals who have no copies of FCGR3B have a dramatically elevated risk of autoimmune disease. This is among the first demonstrations that common naturally occurring variation in gene copy number can influence human susceptibility to disease.
Author contact:
Timothy Aitman (Imperial College, London, UK)
Tel: +44 208 383 4253; E-mail: t.aitman@csc.mrc.ac.uk

Glitter of gold traps microparticles


A simple technique for trapping suspended microparticles with a laser-illuminated array of gold microdots is demonstrated by Romain Quidant and colleagues online. The technique could prove useful for manipulating living cells in ‘lab-on-a-chip’ microfluidic systems.
Until now, the most promising approach to controlling cells and other micrometre-sized particles suspended in a liquid has been with so-called optical tweezers. These devices exploit the fact that such particles are attracted to and can be trapped by a focused light field. But one of their drawbacks is that they are bulky and complex devices to set up.
The technique demonstrated by Quidant and colleagues is much simpler. It relies on the fact that when a gold microdot or other metallic microstructure is illuminated with light, it will concentrate the optical field in its vicinity, similar in effect to the focusing power of a lens. By setting out an array of gold microdots on a glass slide and illuminating it with a laser, the authors effectively create an array of optical tweezers, which they use to trap microparticles suspended in a fluid droplet placed on the slide. Moreover, they show that they can use the array to selectively trap particles of a specific size from a collection of two different sizes, by controlling the size of the gold dots.
Author contact:
Romain Quidant (Institut de Ciencies Fotoniques, Barcelona, Spain)
Tel: +34 93 55 34 076; E-mail: romain.quidant@icfo.es

Cancer genomics: Modelling instability


A mouse model that for the first time mimics the levels of genomic instability in human cancers is presented online. The authors show that mouse and human tumours show similar genetic alterations, and suggest that future research should use this mouse model to understand the genetics of human cancer better.
Ronald DePinho and colleagues engineered lymphoma-prone mice with chromosomal instability to assess the usefulness of mouse models in cancer gene discovery. Using a comparative genomics approach they identified mutated genes in the model that are also altered in human T-cell acute lymphoblastic lymphomas and/or in a diverse range of other tumours. The researchers demonstrate a complexity and comparability in the human and mouse oncogenes that they believe means mouse models of tumours with a high degree of genomic instability will be a valuable resource for investigating complex human cancer genomes.
Author contact:
Ronald A DePinho (Dana Farber Cancer Institute, Boston, MA, USA)
Tel: +1 617 632 6085; E-mail: ron_depinho@dfci.harvard.edu

Evolution: Paddlefish clues to limb development
The limbs of tetrapods — land-living vertebrates — are usually thought to have been evolutionary innovations unique to that group. However, traces of limbs can be found in the development of primitive ray-finned fishes, according to a report.
The perceived uniqueness of the tetrapod limb may be a reflection of comparisons with fishes, notably the zebrafish (Danio rerio), which is often used as a model organism in embryological studies. However, the zebrafish is rather highly evolved, meaning that rather than lacking vestiges of limbs to begin with, it could have lost them during its ancestry. This latter possibility seems most likely following Neil Shubin and colleagues' study of Hox-gene expression in the development of the fins of a 'living fossil', the paddlefish Polyodon spathula.
Polyodon is one of the few relics of a type of bony fish common in the seas in the Palaeozoic era, more than 250 million years ago. Hox-gene expression in the developing fins of Polyodon shows patterns long considered to be tetrapod hallmarks. This finding demonstrates that some aspects of limb development are primitive and held in common by all bony fish — but have been lost in highly evolved fishes such as the zebrafish.
CONTACT
Neil Shubin (University of Chicago, IL, USA)
Tel: +1 773 834 7472; E-mail: nshubin@uchicago.edu

Optical materials: Semiconducting nanocrystals light up the way

A new type of nanocrystal that can be used as a laser material is reported in Nature magazine. 'Soft' optical materials like this can easily be processed in solution, offering flexibility for laser design, and the devices may find use in applications including lab-on-a-chip technologies and quantum information processing devices.
Semiconductor nanocrystals have excellent light-emitting properties, making them good candidates for use in laser applications. But achieving the crucial condition for lasing — optical amplification — has proved problematic: normally the nanocrystals need to contain at least two excitons (electron–hole pairs, which are the precursors for light emission in semiconductors), but owing to the nanocrystal’s tiny size, the excitons annihilate each other before optical amplification can occur.
Victor I. Klimov and colleagues circumvent this problem by designing nanocrystals with cores and shells made from different semiconductor materials, in such a way that electrons and holes are physically isolated from each other. In such engineered nanocrystals, only one exciton per nanocrystal is required for optical amplification, as has here been experimentally demonstrated by Klimov and colleagues. This opens the door to practical use in laser applications.
CONTACT
Victor I. Klimov (Los Alamos National Laboratory, NM, USA)
Tel: +1 505 665 8284; E-mail: klimov@lanl.gov

Todd D. Krauss (University of Rochester, NY, USA) N&V author
Tel: +1 585 275 5093; E-mail: krauss@chem.rochester.edu

Biophysics: Clustering key to membrane remodelling
A sophisticated simulation study reveals a trick that many membrane-bound proteins could use to vastly amplify their own effect on the shape of the membranes they are interacting with.
Biological membranes are much more than passive physical barriers: changes in their shape are linked to important cellular tasks such as endocytosis and protein sorting. It’s known that specialized proteins can sense and create membrane curvature, but the energy needed to accomplish complex membrane remodelling — large changes in membrane shape or topology — is only available when several proteins act together. But how do they coordinate their action?
Kurt Kremer and colleagues now show that a single protein interacting with a membrane causes local changes in membrane shape. Importantly, this attracts other proteins in the vicinity, which then cluster together yielding enough energy for the membrane to be remodelled, allowing, for example, vesicles to be formed.
CONTACT
Kurt Kremer (Max-Planck-Institut fur Polymerforschung, Mainz, Germany)
Tel: +49 6131 379 140; E-mail: kremer@mpip-mainz.mpg.de

Michael M. Kozlov (Tel Aviv University, Israel) N&V author
Tel: +972 3 640 7863; E-mail: michk@post.tau.ac.il

Extreme weather: A look from the lagoon
Changes in the El Niño/Southern Oscillation and the strength of the West African monsoon have played an important part in controlling the frequency of intense hurricanes in the tropical North Atlantic over the past 5,000 years, a study suggests.
Jeffrey P. Donnelly and Jonathan D. Woodruff constructed a long-term record of intense hurricane activity in the western tropical North Atlantic Ocean. Storms associated with intense hurricanes that strike the island of Vieques in Puerto Rico deposit layers of coarse, sandy material in a lagoon, so the authors used sediment cores from the lagoon to reconstruct the frequency of intense hurricanes in this area over the last 5,000 years.
Their record shows striking similarities to records of El Niño events and rainfall in tropical Africa, suggesting that changes in the El Niño/Southern Oscillation and the strength of the West African monsoon had an important role in controlling the frequency of intense hurricanes in the tropical North Atlantic over this interval.
The lengthy time-interval studied helps to clarify the factors that control hurricane activity, because instrumental records only cover the past few decades. Furthermore, the results suggest that it is important to understand how the El Niño/Southern Oscillation and the West African monsoon will respond to future climate change to accurately predict changes in intense hurricane activity.
CONTACT
Jeffrey P. Donnelly (Woods Hole Oceanographic Institution, MA, USA)
Tel: +1 508 294 2994; E-mail: jdonnelly@whoi.edu

Crows are smart! Research group at Keio University succeeds in drawing up the world’s first stereotaxic atlas of a crow
Prof. Shigeru Watanabe and Associate Prof. Eiichi Izawa of Keio University and his group became the first in the world to succeed in drawing up a stereotaxic atlas of a crow. Crows are known to be smart, and the findings proved that the pallium of the crow brain, which is related to intellectual activities, is well developed.

It has been known that the brain of a crow weighs 10-13g, very large compared to its total body weight. However, the details, such as which part of the brain is largely developed, were not clear. Prof. Shigeru Watanabe and Associate Prof. Eiichi Izawa of the Faculty of Letters and their group became the first in the world to succeed in drawing up a stereotaxic atlas of a crow. Recent observations had shown that crows have intelligence comparable to primates and have skills of tool-making and deceiving others. Prof. Watanabe and Associate Prof. Izawa clarified the total picture of the crow brain in detail to prove these observations, and the research can be applied in neuroscientific experiments in the future. These findings can be a breakthrough to finding out the brain evolution of animals including human beings.
1. About the stereotaxic atlas
The stereotaxic atlas is indispensable for studies of the brain. This is similar to a 3-dimensional map of a cross-section of the brain of fixed coordinates. By using this method, it is possible to identify the exact placements inside the brain. This stereotaxic atlas of the jungle crow was released on 14 May at http://www.cirm.keio.ac.jp/db/bird_brain, and will appear in “Integration of comparative neuroanatomy and comparative cognition” (Keio Univ. Press) to be published in the near future.
2. Characteristics of the crow brain
The crow is known to have a large brain compared to its body weight, and to have outstanding cognitive abilities. The stereotaxic atlas of the crow shows that brain areas called ‘pallium’ corresponding to the mammalian cortex, which controls thinking, learning and feeling, makes up a large portion of the brain, and within the ‘pallium’, the dorsal part which is related to intellectual activities, is large and well developed. This area is thought to be relevant to the association area (where multiple information such as visual or auditory signals are integrated) of the cerebral cortex in mammal brains including humans, and enables the crow to process complicated information. Crows are known to be smart, and the new completion of the stereotaxic atlas of the crow proved this.
3. Methods for drawing up the stereotaxic atlas
The research started with developing a stereotaxic holder to keep the crow brain in a fixed position. Stereotaxic holders for mice/rats and pigeons are commercially available, but for crows, it had to be custom-made. The brain was frozen under -20℃ and sliced into thin plates. The plates were then stained with cresyl violet for Nissle substance and luxol fast blue for myelinated fibers. The plates were examined under a microscope to separate the nerve cells according to density. At the same time, imaging of the plates were done to create an atlas and to name each group of nerve cells. The same process was repeated for all the plates of the crow brain from the front to the back, sliced in the thickness of 1mm. The atlas was completed by combining these data.
This research is part of the 21st Century COE Program Keio University Graduate School Toward an Integrated Methodology for the Study of the Mind. The Center of Excellence was selected by the 21st Century COE (Center of Excellence) Program of the Ministry of Education, Culture, Sports, Science and Technology toward an integrated methodology for the study of the mind. The newest findings in neuroscience, behavioral genetics are combined with philosophy, linguistics, information science and representational theories.
Inquiries: Mr. Ogawa or Ms. Kawagoe, Office of Communications and Public Relations, Keio University
TEL: ＋81-3-5427-1541 FAX: ＋81-3-5441-7640
E-mail: m-koho@adst.keio.ac.jp http://www.keio.ac.jp/

IMMUNOLOGY : Another immune evasion strategy by HIV

Interaction of the human immunodeficiency virus (HIV) with dendritic cells—a specialized type of immune cell—circumvents immune activation and greatly enhances infection of T lymphocytes, reports a study to be published in the June issue of Nature Immunology.
Dendritic cells are required to initiate immune responses, and as targets of HIV infection, these cells are important contributors to HIV pathogenesis. Alison Simmons and colleagues evaluated the effect of HIV interaction with DC-SIGN, a protein receptor found largely on the surface of dendritic cells. HIV binding to DC-SIGN elicited a signalling pathway that prevented dendritic cells from actively stimulating subsequent immune responses. In addition, the authors show that HIV–DC-SIGN interaction can lead to transfer of virus to nearby T lymphocytes that then become infected leading to a burst of HIV production.
These results reveal how HIV can both evade dendritic cell immune activity and amplify its own replication. With nearly 40 million people world-wide currently living with HIV-AIDS, understanding the myriad ways that HIV can modulate immune responses is of paramount importance.
Author contact:
Alison Simmons (Weatherall Institute of Molecular Medicine, Oxford, UK)
Tel: +44 1865 222 616; E-mail: asimmons@hammer.imm.ox.ac.uk

Additional contact for comment:
Anthony Cunningham (Westmead Millennium Institute, Australia)
Tel: +61 2 9845 9005; E-mail: tony_cunningham@wmi.usyd.edu.au

Gene combinations influence AIDS progression

Different combinations of genetic variants of two modulators of the innate human immune system strongly influence AIDS progression in HIV-positive individuals, according to a study.
Natural killer cells are part of the antiviral immune response, and their activity is controlled by receptors called KIRs that are present on the cell surface. The KIR receptors that inhibit natural killer cell activity (KIR3DL1) are triggered by HLA-B molecules, which are presented by other cells of the immune system. Mary Carrington and colleagues examined variation in the genes encoding KIR3DL1 and HLA-B in more than 1,500 HIV-positive individuals, and found that particular combinations of variants conferred protection against AIDS progression.
These results may explain at least part of the variability in progression of the disease in infected individuals. The authors also note that the observed rapid evolution of these genes may be driven by pathogens such as HIV.
Author contact:
Mary Carrington (National Cancer Institute, Frederick, MD, USA)
Tel: +1 301 846 1390; E-mail: carringt@ncifcrf.gov

Nanotubes sort out their left and right


Left- and right-handed carbon nanotubes can be separated from one another, according to a paper. Although nanotubes have previously been sorted on the basis of their diameter or length, this method is the first to discriminate between those with opposite helical twists.
Some molecules, which are known as ‘chiral’, can exist as mirror-image forms that cannot be superimposed on each other. Louis Pasteur was, in 1849, the first to separate such molecules, by meticulously sorting asymmetric crystals of tartaric acid by hand, using tweezers and a microscope. Following in his footsteps, Naoki Komatsu and co-workers designed pairs of chemical ‘nano-tweezers’ that can selectively pluck either left- or right-handed nanotubes from a mixture.
The ability to separate carbon nanotubes — one of nanotechnology’s most promising building blocks — in this way will lead to a better understanding of their optical properties, and may offer unique opportunities for photonics and quantum optics.
Author contact:
Naoki Komatsu (Shiga University of Medical Science, Otsu, Japan)
Tel: +81 77 548 2102; E-mail: nkomatsu@belle.shiga-med.ac.jp

CHEMICAL BIOLOGY : A little sugar for the brain

The amount of sugar on proteins inside neural cells changes in response to brain stimulation, which implicates sugar modification as a new player in brain signalling, according to a paper to be published in the June issue of Nature Chemical Biology. Changes in the levels of phosphorylation of serine and threonine residues have a well-known role in cell signalling. Although most glycosylation, or modification of proteins by the attachment of sugars, occurs on proteins outside the cell, one sugar modification, called O-GlcNAc, can be attached to serine or threonine residues of proteins inside cells. Because phosphorylation and O-GlcNAc modifications occur on exactly the same amino acid side chains, O-GlcNAc could be critical in cellular signalling. However, a lack of tools to identify the precise positions of O-GlcNAc modifications in vivo has made it difficult to investigate this hypothesis.
Linda Hsieh-Wilson and colleagues have now developed a proteomic method that uses mass spectrometry to determine in vivo O-GlcNAc levels. When rats were injected with an excitatory stimulus, the authors identified changes in the sugar levels at specific sites of proteins found in the brain. With this information, it will now be possible to investigate the exact role O-GlcNAc plays in brain function.
Author contact:
Linda Hsieh-Wilson (California Institute of Technology, Pasadena, CA, USA)
Tel: +1 626 395 6101; E-mail: lhw@caltech.edu

Unexpected biodiversity springs from the depths
Five-hundred and eighty-five new species of crustacean have been found in the depths of the Southern Ocean, thanks to three sampling expeditions set up as part of the ANDEEP (Antarctic benthic deep-sea biodiversity) project. Unexpected levels of biodiversity were found in this dark and largely unstudied place, challenging assumptions that deep sea diversity is depressed in this area.
On their expeditions, Angelika Brandt and colleagues collected biological specimens and environmental data from different regions 774 to 6,348 metres under the surface of the Weddell Sea and adjacent areas. The Weddell Sea is an important source of deep water for the rest of the ocean and provides a possible route for species to enter the deep water. In line with this, the team found deep-sea faunas that were also found in adjacent shelf communities and in other oceans.
They spotted 674 species of isopod — a diverse order of crustaceans — of which over 80% were new to science. In some regions, groups of slope-dwelling isopods and marine worms included species that had invaded from the Southern Ocean’s deep continental shelf. Species living in the deepest parts of the Weddell Sea tended to have strong links to other oceans, particularly if they were good dispersers, like certain amoeboids. But poor dispersers, such as isopods, nematode worms and seed shrimps, were Southern Ocean-specific species.
CONTACT
Angelika Brandt (University of Hamburg, Germany)
Tel: +49 40 42838 2278; E-mail: abrandt@zoologie.uni-hamburg.de