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See detailA role for Rhesus factor Rhcg in renal ammonium excretion and male fertility
Biver, Sophie ULg; Belge, Hendrica; Bourgeois, Soline et al

in Nature (2008), 456(7220), 339-343

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See detailFlares from a candidate Galactic magnetar suggest a missing link to dim isolated neutron stars
Castro-Tirado, A. J.; de Ugarte Postigo, A.; Gorosabel, J. et al

in Nature (2008), 455

Magnetars are young neutron stars with very strong magnetic fields of the order of 10[SUP]14[/SUP]-10[SUP]15[/SUP]G. They are detected in our Galaxy either as soft γ-ray repeaters or anomalous X-ray ... [more ▼]

Magnetars are young neutron stars with very strong magnetic fields of the order of 10[SUP]14[/SUP]-10[SUP]15[/SUP]G. They are detected in our Galaxy either as soft γ-ray repeaters or anomalous X-ray pulsars. Soft γ-ray repeaters are a rare type of γ-ray transient sources that are occasionally detected as bursters in the high-energy sky. No optical counterpart to the γ-ray flares or the quiescent source has yet been identified. Here we report multi-wavelength observations of a puzzling source, SWIFT J195509+261406. We detected more than 40 flaring episodes in the optical band over a time span of three days, and a faint infrared flare 11days later, after which the source returned to quiescence. Our radio observations confirm a Galactic nature and establish a lower distance limit of ~3.7kpc. We suggest that SWIFT J195509+261406 could be an isolated magnetar whose bursting activity has been detected at optical wavelengths, and for which the long-term X-ray emission is short-lived. In this case, a new manifestation of magnetar activity has been recorded and we can consider SWIFT J195509+261406 to be a link between the `persistent' soft γ-ray repeaters/anomalous X-ray pulsars and dim isolated neutron stars. [less ▲]

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See detailNeurogenin 2 controls cortical neuron migration through regulation of Rnd2.
Heng, Julian Ik-Tsen; Nguyen, Laurent ULg; Castro, Diogo S et al

in Nature (2008), 455(7209), 114-8

Motility is a universal property of newly generated neurons. How cell migration is coordinately regulated with other aspects of neuron production is not well understood. Here we show that the proneural ... [more ▼]

Motility is a universal property of newly generated neurons. How cell migration is coordinately regulated with other aspects of neuron production is not well understood. Here we show that the proneural protein neurogenin 2 (Neurog2), which controls neurogenesis in the embryonic cerebral cortex, directly induces the expression of the small GTP-binding protein Rnd2 (ref. 3) in newly generated mouse cortical neurons before they initiate migration. Rnd2 silencing leads to a defect in radial migration of cortical neurons similar to that observed when the Neurog2 gene is deleted. Remarkably, restoring Rnd2 expression in Neurog2-mutant neurons is sufficient to rescue their ability to migrate. Our results identify Rnd2 as a novel essential regulator of neuronal migration in the cerebral cortex and demonstrate that Rnd2 is a major effector of Neurog2 function in the promotion of migration. Thus, a proneural protein controls the complex cellular behaviour of cell migration through a remarkably direct pathway involving the transcriptional activation of a small GTP-binding protein. [less ▲]

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See detailStrain accommodation by slow slip and dyking in a youthful continental rift, East Africa
Calais, E.; d'Oreye, N.; Albaric, J. et al

in Nature (2008), 456

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See detailEvolution of metal hyperaccumulation required cis-regulatory changes and triplication of HMA4
Hanikenne, Marc ULg; Talke, Ina N.; Haydon, Michael J. et al

in Nature (2008), 453

Little is known about the types of mutations underlying the evolution of species-specific traits. The metal hyperaccumulator Arabidopsis halleri has the rare ability to colonize heavy-metal-polluted soils ... [more ▼]

Little is known about the types of mutations underlying the evolution of species-specific traits. The metal hyperaccumulator Arabidopsis halleri has the rare ability to colonize heavy-metal-polluted soils, and, as an extremophile sister species of Arabidopsis thaliana, it is a powerful model for research on adaptation. A. halleri naturally accumulates and tolerates leaf concentrations as high as 2.2% zinc and 0.28% cadmium in dry biomass. On the basis of transcriptomics studies, metal hyperaccumulation in A. halleri has been associated with more than 30 candidate genes that are expressed at higher levels in A. halleri than in A. thaliana. Some of these genes have been genetically mapped to broad chromosomal segments of between 4 and 24 cM co-segregating with Zn and Cd hypertolerance. However, the in planta loss-of-function approaches required to demonstrate the contribution of a given candidate gene to metal hyperaccumulation or hypertolerance have not been pursued to date. Using RNA interference to downregulate HMA4 (HEAVY METAL ATPASE 4) expression, we show here that Zn hyperaccumulation and full hypertolerance to Cd and Zn in A. halleri depend on the metal pump HMA4. Contrary to a postulated global trans regulatory factor governing high expression of numerous metal hyperaccumulation genes, we demonstrate that enhanced expression of HMA4 in A. halleri is attributable to a combination of modified cis-regulatory sequences and copy number expansion, in comparison to A. thaliana. Transfer of an A. halleri HMA4 gene to A. thaliana recapitulates Zn partitioning into xylem vessels and the constitutive transcriptional upregulation of Zn deficiency response genes characteristic of Zn hyperaccumulators. Our results demonstrate the importance of cis-regulatory mutations and gene copy number expansion in the evolution of a complex naturally selected extreme trait. The elucidation of a natural strategy for metal hyperaccumulation enables the rational design of technologies for the clean-up of metal-contaminated soils and for bio-fortification. [less ▲]

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See detailImproper ferroelectricity in perovskite oxide artificial superlattices
Bousquet, Eric ULg; Dawber, Matthew; Stucki, Nicolas et al

in Nature (2008), 452(7188), 732-736

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See detailA warm layer in Venus' cryosphere and high-altitude measurements of HF, HCl, H[SUB]2[/SUB]O and HDO
Bertaux, Jean-Loup; Vandaele, Ann-Carine; Korablev, Oleg et al

in Nature (2007), 450

Venus has thick clouds of H[SUB]2[/SUB]SO[SUB]4[/SUB] aerosol particles extending from altitudes of 40 to 60km. The 60-100km region (the mesosphere) is a transition region between the 4day retrograde ... [more ▼]

Venus has thick clouds of H[SUB]2[/SUB]SO[SUB]4[/SUB] aerosol particles extending from altitudes of 40 to 60km. The 60-100km region (the mesosphere) is a transition region between the 4day retrograde superrotation at the top of the thick clouds and the solar-antisolar circulation in the thermosphere (above 100km), which has upwelling over the subsolar point and transport to the nightside. The mesosphere has a light haze of variable optical thickness, with CO, SO[SUB]2[/SUB], HCl, HF, H[SUB]2[/SUB]O and HDO as the most important minor gaseous constituents, but the vertical distribution of the haze and molecules is poorly known because previous descent probes began their measurements at or below 60km. Here we report the detection of an extensive layer of warm air at altitudes 90-120km on the night side that we interpret as the result of adiabatic heating during air subsidence. Such a strong temperature inversion was not expected, because the night side of Venus was otherwise so cold that it was named the `cryosphere' above 100km. We also measured the mesospheric distributions of HF, HCl, H[SUB]2[/SUB]O and HDO. HCl is less abundant than reported 40years ago. HDO/H[SUB]2[/SUB]O is enhanced by a factor of ~2.5 with respect to the lower atmosphere, and there is a general depletion of H[SUB]2[/SUB]O around 80-90km for which we have no explanation. [less ▲]

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See detailA dynamic upper atmosphere of Venus as revealed by VIRTIS on Venus Express
Drossart, P.; Piccioni, G.; Gérard, Jean-Claude ULg et al

in Nature (2007), 450

The upper atmosphere of a planet is a transition region in which energy is transferred between the deeper atmosphere and outer space. Molecular emissions from the upper atmosphere (90-120 km altitude) of ... [more ▼]

The upper atmosphere of a planet is a transition region in which energy is transferred between the deeper atmosphere and outer space. Molecular emissions from the upper atmosphere (90-120 km altitude) of Venus can be used to investigate the energetics and to trace the circulation of this hitherto little-studied region. Previous spacecraft(1) and ground-based(2-4) observations of infrared emission from CO2, O-2 and NO have established that photochemical and dynamic activity controls the structure of the upper atmosphere of Venus. These data, however, have left unresolved the precise altitude of the emission(1) owing to a lack of data and of an adequate observing geometry(5,6). Here we report measurements of day-side CO2 non-local thermodynamic equilibrium emission at 4.3 mu m, extending from 90 to 120 km altitude, and of night-side O-2 emission extending from 95 to 100 km. The CO2 emission peak occurs at similar to 115 km and varies with solar zenith angle over a range of similar to 10 km. This confirms previous modelling(7), and permits the beginning of a systematic study of the variability of the emission. The O-2 peak emission happens at 96 km +/- 1 km, which is consistent with three-body recombination of oxygen atoms transported from the day side by a global thermospheric sub-solar to anti-solar circulation, as previously predicted(8). [less ▲]

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See detailElectronic and structural transitions in dense liquid sodium
Raty, Jean-Yves ULg; Schwegler, E.; Bonev, S. A.

in Nature (2007), 449(7161), 448-451451

At ambient conditions, the light alkali metals are free-electron-like crystals with a highly symmetric structure. However, they were found recently to exhibit unexpected complexity under pressure 1-6. It ... [more ▼]

At ambient conditions, the light alkali metals are free-electron-like crystals with a highly symmetric structure. However, they were found recently to exhibit unexpected complexity under pressure 1-6. It was predicted from theory 1.2 - and later confirmed by experiment 3-5 - that lithium and sodium undergo a sequence of symmetry-breaking transitions, driven by a Peierls mechanism, at high pressures. Measurements of the sodium melting curve 6 have subsequently revealed an unprecedented (and still unexplained) pressure-induced drop in melting temperature from 1,000 K at 30 GPa down to room temperature at 120 GPa. Here we report results from ab initio calculations that explain the unusual melting behaviour in dense sodium. We show that molten sodium undergoes a series of pressure-induced structural and electronic transitions, analogous to those observed in solid sodium but commencing at much lower pressure in the presence of liquid disorder. As pressure is increased, liquid sodium initially evolves by assuming a more compact local structure. However, a transition to a lower-coordinated liquid takes place at a pressure of around 65 GPa, accompanied by a threefold drop in electrical conductivity. This transition is driven by the opening of a pseudogap, at the Fermi level, in the electronic density of states - an effect that has not hitherto been observed in a liquid metal. The lower-coordinated liquid emerges at high temperatures and above the stability region of a close-packed free-electron-like metal. We predict that similar exotic behaviour is possible in other materials as well. [less ▲]

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See detailDiscovery of a bright quasar without a massive host galaxy
Magain, Pierre ULg; Letawe, Géraldine ULg; Courbin, F. et al

in Nature (2005), 437(7057), 381-384

A quasar is thought to be powered by the infall of matter onto a supermassive black hole at the centre of a massive galaxy(1,2). Because the optical luminosity of quasars exceeds that of their host galaxy ... [more ▼]

A quasar is thought to be powered by the infall of matter onto a supermassive black hole at the centre of a massive galaxy(1,2). Because the optical luminosity of quasars exceeds that of their host galaxy, disentangling the two components can be difficult. This led in the 1990s to the controversial claim of the discovery of 'naked' quasars(3-7). Since then, the connection between quasars and galaxies has been well established(8). Here we report the discovery of a quasar lying at the edge of a gas cloud, whose size is comparable to that of a small galaxy, but whose spectrum shows no evidence for stars. The gas in the cloud is excited by the quasar itself. If a host galaxy is present, it is at least six times fainter than would normally be expected(8,9) for such a bright quasar. The quasar is interacting dynamically with a neighbouring galaxy, whose gas might be feeding the black hole. [less ▲]

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See detailMorphological differences between Saturn's ultraviolet aurorae and those of Earth and Jupiter
Clarke, J. T.; Gérard, Jean-Claude ULg; Grodent, Denis ULg et al

in Nature (2005), 433(7027), 717-719

It has often been stated that Saturn's magnetosphere and aurorae are intermediate between those of Earth, where the dominant processes are solar wind driven(1), and those of Jupiter, where processes are ... [more ▼]

It has often been stated that Saturn's magnetosphere and aurorae are intermediate between those of Earth, where the dominant processes are solar wind driven(1), and those of Jupiter, where processes are driven by a large source of internal plasma(2-4). But this view is based on information about Saturn that is far inferior to what is now available. Here we report ultraviolet images of Saturn, which, when combined with simultaneous Cassini measurements of the solar wind(5) and Saturn kilometric radio emission(6), demonstrate that its aurorae differ morphologically from those of both Earth and Jupiter. Saturn's auroral emissions vary slowly; some features appear in partial corotation whereas others are fixed to the solar wind direction; the auroral oval shifts quickly in latitude; and the aurora is often not centred on the magnetic pole nor closed on itself. In response to a large increase in solar wind dynamic pressure(5) Saturn's aurora brightened dramatically, the brightest auroral emissions moved to higher latitudes, and the dawn side polar regions were filled with intense emissions. The brightening is reminiscent of terrestrial aurorae, but the other two variations are not. Rather than being intermediate between the Earth and Jupiter, Saturn's auroral emissions behave fundamentally differently from those at the other planets. [less ▲]

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See detailSolar wind dynamic pressure and electric field as the main factors controlling Saturn's aurorae
Crary, Frank J.; Clarke, John T.; Dougherty, Michele K. et al

in Nature (2005), 433(7027), 720-722

The interaction of the solar wind with Earth's magnetosphere gives rise to the bright polar aurorae and to geomagnetic storms(1), but the relation between the solar wind and the dynamics of the outer ... [more ▼]

The interaction of the solar wind with Earth's magnetosphere gives rise to the bright polar aurorae and to geomagnetic storms(1), but the relation between the solar wind and the dynamics of the outer planets' magnetospheres is poorly understood. Jupiter's magnetospheric dynamics and aurorae are dominated by processes internal to the jovian system(2), whereas Saturn's magnetosphere has generally been considered to have both internal and solar-wind-driven processes. This hypothesis, however, is tentative because of limited simultaneous solar wind and magnetospheric measurements. Here we report solar wind measurements, immediately upstream of Saturn, over a one-month period. When combined with simultaneous ultraviolet imaging(3) we find that, unlike Jupiter, Saturn's aurorae respond strongly to solar wind conditions. But in contrast to Earth, the main controlling factor appears to be solar wind dynamic pressure and electric field, with the orientation of the interplanetary magnetic field playing a much more limited role. Saturn's magnetosphere is, therefore, strongly driven by the solar wind, but the solar wind conditions that drive it differ from those that drive the Earth's magnetosphere. [less ▲]

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See detailAn Earth-like correspondence between Saturn's auroral features and radio emission
Kurth, William S.; Gurnett, Donald A.; Clarke, John T. et al

in Nature (2005), 433(7027), 722-725

Saturn is a source of intense kilometre-wavelength radio emissions that are believed to be associated with its polar aurorae(1,2), and which provide an important remote diagnostic of its magnetospheric ... [more ▼]

Saturn is a source of intense kilometre-wavelength radio emissions that are believed to be associated with its polar aurorae(1,2), and which provide an important remote diagnostic of its magnetospheric activity. Previous observations implied that the radio emission originated in the polar regions, and indicated a strong correlation with solar wind dynamic pressure(1,3-7). The radio source also appeared to be fixed near local noon and at the latitude of the ultraviolet aurora(1,2). There have, however, been no observations relating the radio emissions to detailed auroral structures. Here we report measurements of the radio emissions, which, along with high-resolution images of Saturn's ultraviolet auroral emissions(8), suggest that although there are differences in the global morphology of the aurorae, Saturn's radio emissions exhibit an Earth-like correspondence between bright auroral features and the radio emissions. This demonstrates the universality of the mechanism that results in emissions near the electron cyclotron frequency narrowly beamed at large angles to the magnetic field(9,10). [less ▲]

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See detailEurope-Wide Reduction In Primary Productivity Caused By The Heat And Drought In 2003
Ciais, P.; Reichstein, M.; Viovy, N. et al

in Nature (2005), 437(7058),

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See detailAnthropogenic ocean acidification over the twenty-first century and its impact on calcifying organisms
Orr, James C.; Fabry, Victoria J.; Aumont, Olivier et al

in Nature (2005), 437(7059), 681-686

Today's surface ocean is saturated with respect to calcium carbonate, but increasing atmospheric carbon dioxide concentrations are reducing ocean pH and carbonate ion concentrations, and thus the level of ... [more ▼]

Today's surface ocean is saturated with respect to calcium carbonate, but increasing atmospheric carbon dioxide concentrations are reducing ocean pH and carbonate ion concentrations, and thus the level of calcium carbonate saturation. Experimental evidence suggests that if these trends continue, key marine organisms - such as corals and some plankton - will have difficulty maintaining their external calcium carbonate skeletons. Here we use 13 models of the ocean - carbon cycle to assess calcium carbonate saturation under the IS92a 'business-as-usual' scenario for future emissions of anthropogenic carbon dioxide. In our projections, Southern Ocean surface waters will begin to become undersaturated with respect to aragonite, a metastable form of calcium carbonate, by the year 2050. By 2100, this undersaturation could extend throughout the entire Southern Ocean and into the subarctic Pacific Ocean. When live pteropods were exposed to our predicted level of undersaturation during a two-day shipboard experiment, their aragonite shells showed notable dissolution. Our findings indicate that conditions detrimental to high-latitude ecosystems could develop within decades, not centuries as suggested previously. [less ▲]

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See detailInsight and the sleep committee
Maquet, Pierre ULg; Ruby, P.

in Nature (2004), 427(6972), 304-305

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See detailStructural basis of protein phosphatase 1 regulation
Terrak, Mohammed ULg; Kerff, Frédéric ULg; Langsetmo, K. et al

in Nature (2004), 429(6993), 780-4

The coordinated and reciprocal action of serine/threonine (Ser/Thr) protein kinases and phosphatases produces transient phosphorylation, a fundamental regulatory mechanism for many biological processes ... [more ▼]

The coordinated and reciprocal action of serine/threonine (Ser/Thr) protein kinases and phosphatases produces transient phosphorylation, a fundamental regulatory mechanism for many biological processes. The human genome encodes a far greater number of Ser/Thr protein kinases than of phosphatases. Protein phosphatase 1 (PP1), in particular, is ubiquitously distributed and regulates a broad range of cellular functions, including glycogen metabolism, cell-cycle progression and muscle relaxation. PP1 has evolved effective catalytic machinery but lacks substrate specificity. Substrate specificity is conferred upon PP1 through interactions with a large number of regulatory subunits. The regulatory subunits are generally unrelated, but most possess the RVxF motif, a canonical PP1-binding sequence. Here we reveal the crystal structure at 2.7 A resolution of the complex between PP1 and a 34-kDa N-terminal domain of the myosin phosphatase targeting subunit MYPT1. MYPT1 is the protein that regulates PP1 function in smooth muscle relaxation. Structural elements amino- and carboxy-terminal to the RVxF motif of MYPT1 are positioned in a way that leads to a pronounced reshaping of the catalytic cleft of PP1, contributing to the increased myosin specificity of this complex. The structure has general implications for the control of PP1 activity by other regulatory subunits. [less ▲]

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See detailInsight and the sleep committee
Maquet, Pierre ULg; Ruby, Perrine

in Nature (2004), 427(6972), 304-305

We all spend about a third of our lives asleep, an essential but seemingly unproductive state. Experimental evidence now emerges to support anecdotal evidence that sleep can stimulate creative thinking.

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See detailCorrigenda: The lipid phosphatase SHIP2 controls insulin sensitivity
Clément, S.; Krause, U.; Desmedt, F. et al

in Nature (2004), 431

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See detailEvolution of the polarization of the optical afterglow of the γ-ray burst GRB030329
Greiner, Jochen; Klose, Sylvio; Reinsch, Klaus et al

in Nature (2003), 426

The association of a supernova with GRB030329 strongly supports the `collapsar' model of γ-ray bursts, where a relativistic jet forms after the progenitor star collapses. Such jets cannot be spatially ... [more ▼]

The association of a supernova with GRB030329 strongly supports the `collapsar' model of γ-ray bursts, where a relativistic jet forms after the progenitor star collapses. Such jets cannot be spatially resolved because γ-ray bursts lie at cosmological distances; their existence is instead inferred from `breaks' in the light curves of the afterglows, and from the theoretical desire to reduce the estimated total energy of the burst by proposing that most of it comes out in narrow beams. Temporal evolution of the polarization of the afterglows may provide independent evidence for the jet structure of the relativistic outflow. Small-level polarization (~1-3 per cent) has been reported for a few bursts, but its temporal evolution has yet to be established. Here we report polarimetric observations of the afterglow of GRB030329. We establish the polarization light curve, detect sustained polarization at the per cent level, and find significant variability. The data imply that the afterglow magnetic field has a small coherence length and is mostly random, probably generated by turbulence, in contrast with the picture arising from the high polarization detected in the prompt γ-rays from GRB021206 (ref. 18). [less ▲]

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