Skin pigmentation: The fake tan that protects against cancer

Summaries of newsworthy papers from Nature including Obesity drug development in double bind, Atlantic waters influence El Niño impact, ‘Atomic clock’ gets designer label, Accelerated Greenland ice sheet melting confirmed, Creating a 'shadow person' illusion


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This press release contains:

* Summaries of newsworthy papers:

Skin pigmentation: The fake tan that protects against cancer

Weight control: Obesity drug development in double bind

Climate change: Atlantic waters influence El Niño impact

Quantum physics: ‘Atomic clock’ gets designer label

Climate change: Accelerated Greenland ice sheet melting confirmed

And finally… Creating a 'shadow person' illusion

* Mention of papers to be published at the same time with the same embargo
* Geographical listing of authors

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[1] Skin pigmentation: The fake tan that protects against cancer (pp 340-344)

Researchers studying pigmentation in mice have come up with a skin treatment that not only causes sunless tanning in skin, but could also mimic the ability of dark skin to counter the effects of ultraviolet rays and protect against cancer.

Skin cancer is a particular danger for fair-skinned people, many of whom have a defect in a hormonal pathway that leads to production of the skin pigment melanin. David Fisher and his colleagues report, in a paper to be published in Nature this week, that the defective pigmentation pathway can be restored in genetically engineered, fair-skinned mice by direct application of the plant-derived compound forskolin to the skin.

What is more, the resulting skin pigmentation helped to ward off the DNA damage expected by subsequent exposure to ultraviolet radiation, which can lead to cancer. If the findings can be reproduced in humans, the treatment could give fair-skinned people the chance to avoid sun damage without having to avoid the sunshine.


David E Fisher (Dana-Farber Cancer Institute, Boston, MA, USA)
Tel: +1 617 632 4916; E-mail: [email protected]

[2] Weight control: Obesity drug development in double bind (pp 289-295)

Developing drugs to combat obesity is a real ‘Catch 22’ situation. The most effective treatments, according to an article in this week’s Nature, are likely to be combinations of drugs that show little effect when taken alone. But drug combinations cannot be approved by the US Food and Drug Administration (FDA) unless the individual drugs are proven safe and effective.

M. W. Schwartz and colleagues review the neural mechanisms that regulate food intake. Weight loss causes changes in the neural systems that control food-seeking behaviour and feelings of being full up. So, both the motivation to find food and size of meals tend to increase until energy stores are replenished. Mutations in any of several key molecules involved in this process can cause severe obesity in animal models and in humans.

These molecules offer targets for drug design, but the hoped-for breakthroughs have yet to emerge. Treatments that target specific brain regions or signalling pathways are unlikely to work because other parts of the brain are likely to compensate. Combined therapies may be the answer, but unless the FDA changes its stance on approving drug combinations, pharmaceutical companies have little incentive to pursue them.

And a news feature in this week's Nature explores the emerging links between sleep and obesity. Sleeping and eating are two of our most elementary drives, but in Western society both are veering out of control: we starve ourselves of sleep and gorge ourselves on food. Researchers have found that people who sleep less tend to be more overweight and that only two nights of sleep deprivation sends appetite control hormones dramatically askew in healthy young people. There are emerging overlaps between the brain mechanisms that control sleep and those that control appetite - mechanisms that may, in our evolutionary past, have been essential to fend off starvation.


Michael W Schwartz (Harborview Medical Center and University of Washington, Seattle, WA, USA)
Tel: +1 206 341 5288; E-mail: [email protected]

Media contact for this paper:

Susan Gregg-Hanson (Media Relations Manager, Harborview Medical Center, Seattle, WA, USA)
Tel: +1 206 731 4097; E-mail: [email protected]

[3] Climate change: Atlantic waters influence El Niño impact (pp 324-328)

The surface temperature of equatorial Atlantic waters can directly influence the impact of El Niño, scientists report in this week’s Nature. The finding should help us understand seasonal climate variations in African countries bordering the Atlantic, and lead to better climate-prediction models.

El Niño events happen about once every three to seven years, when the sea surface on the South American side of the tropical Pacific warms dramatically, altering the cycle of heat and moisture fluctuations throughout the ocean and atmosphere. Warm air from the Pacific drifts east, where it raises the temperature of tropical Atlantic waters.

But sometimes, El Niño is followed by cooling in the tropical Atlantic. Ping Chang and colleagues think they know why: the equatorial Atlantic is not a passive recipient of the El Niño weather system, as many had thought, but interferes with the far-reaching effects of El Niño. The key factor determining the influence of El Niño, they say, is an interaction between the Atlantic ocean and Atlantic atmosphere at the time when El Niño is happening in the Pacific, and so they recommend positioning a monitoring system in the tropical Atlantic.


Ping Chang (Texas A&M University, College Station, Texas, USA)
Tel: +1 979 845 8196; E-mail: [email protected]

[4] Quantum physics: ‘Atomic clock’ gets designer label (pp 316-319)

In Nature this week, scientists use the phenomenon of quantum entanglement to make particularly precise measurements on the transition between two atomic states - the basis of an ‘atomic clock’. Two entangled, intimately linked states in separate ions are designed to create a system resistant to the measurement ‘noise’ created by the buffetings of the environment.

Previous transition measurements were made on atomic states in one ion; entangling states in separate ions has already been shown to improve the signal-to-noise ratio of such measurements. But the new approach also improves these measurements’ quality, cancelling technical noise from the laser and magnetic fields required for the experiment.

C.F. Roos and colleagues use a pair of trapped entangled calcium ions, a few micrometres apart in space. This non-locality means the ions experience slightly different magnetic field values. Taking account of this effect allows impressively precise measurement of the electric quadrupole moment between two states. The approach, the scientists suggest, paves the way for precision measurement in other atomic systems.


Christian F Roos (Oesterreichische Akademie der Wissenschaften, Innsbruck, Austria)
Tel: +43 512 507 4728; E-mail: [email protected]

[5] Astronomy: Bright supernova does not act as a standard candle (pp 308-311; N&V)

Astronomers have observed a peculiar supernova that does not fit the standard model for these enormous thermonuclear explosions. In Nature this week Andrew Howell and colleagues reveal the offender, which does not obey the relationships allowing type Ia supernovae to be calibrated as ‘standard candles’ or indicators of distance.

Type-Ia supernovae are all thought to be explosions of carbon-oxygen white dwarf stars that have grown to near 1.4-times the mass of the Sun - a mass they should not reach, known as the ‘Chandrasekhar mass’ - by accreting matter from a companion star. Their peak luminosities can be determined from the way their brightness changes as a function of time. This means they can be calibrated to be used as standard candles - an astronomical reference object. Using supernovae we first found the accelerating expansion of the Universe, and inferred the need for dark energy.

But one type-Ia supernova - coming from a pack of young stars - seems to break the rules. Apart from having an exceptionally high luminosity, it also has a low kinetic energy: both imply that it originated from a white dwarf larger than the Chandrasekhar mass. So it cannot be used as a standard candle, as its lightcurve does not fit the usual shape. Such extreme supernovae may have to be screened out in cosmological studies, to avoid contamination of the results, the authors suggest.


Andrew Howell (University of Toronto, Ontario, Canada)
Tel: +1 416 946 5432; E-mail [email protected]

David Branch (University of Oklahoma, Norman, OK, USA)
Tel: +1 405 325 3961; E-mail: [email protected]

[6] Climate change: Accelerated Greenland ice sheet melting confirmed (pp 329-331; N&V)

Greenland’s ice sheet is melting faster, according to satellite observations analysed in this week’s Nature. Isabella Velicogna and John Wahr suggest that the rate of ice loss increased by 250% during May 2004-April 2006, relative to April 2002-April 2004. Ice is now being lost at around 248 cubic kilometres per year, equivalent to a global sea level rise of 0.5 millimetres per year.

The results represent a parallel and independent analysis of data also examined by Jinanli Chen and colleagues, published in Science (10 August 2006; doi:10.1126/science.1129007). Both studies use data from the Gravity Recovery and Climate Experiment (GRACE) satellite, launched by NASA in 2002, which measures monthly changes in the Earth’s gravitational field. The two studies agree very closely on the increased numerical rate of ice sheet melting.

The present analysis differs from the earlier results in two regards: it extends the analysis period to April 2006 - compared with November 2005; and it finds the accelerated rate of ice loss to occur almost entirely in southern Greenland.


Isabella Velicogna (Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA)
Tel: +1 818 393 0497; E-mail: [email protected]

Tavi Murray (University of Wales Swansea, UK)
Tel: +44 1792 602269; E-mail: [email protected]

[7] And finally… Creating a 'shadow person' illusion (pp 287)

Electrical stimulation of the brain can create the sensation of a 'shadow person' mimicking your bodily movements, according to studies of a patient who was being evaluated for epilepsy treatment. The discovery may help to shed light on brain processes that contribute to the symptoms of schizophrenia, which can include the sensation that one's own actions are being performed by someone else.

Doctors evaluating a 22-year-old woman with no history of psychiatric problems found that stimulation of an area of her brain called the left temporoparietal junction caused her to feel that a person was standing behind her. The patient reported that this figure adopted the same bodily positions as her, although she did not recognize the effect as an illusion of her own body. At one point in the investigation, the patient was asked to lean forward and clasp her knees: this led to a sensation that the shadow figure was embracing her, which she described as unpleasant.

The finding could be a step towards understanding psychiatric effects such as feelings of paranoia, persecution and alien control, say neuroscientists, led by Olaf Blanke, who report the discovery in a Brief Communication in this week's Nature.


Olaf Blanke (Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland)
Tel: +41 21 693 96 21; E-mail: [email protected]


[8] Spontaneous symmetry breaking in a quenched ferromagnetic spinor Bose-Einstein condensate (pp 312-315)

[9] A guest-free germanium clathrate (320-323)

[10] A common progenitor for haematopoietic and endothelial lineages in the zebrafish gastrula (pp 337-339)

[11] Calcineurin/NFAT signalling regulates pancreatic B-cell growth and function (pp 345-349)


***This paper will be published electronically on Nature's website on 20 September at 1800 London time / 1300 US Eastern time (which is also when the embargo lifts) as part of our AOP (ahead of print) programme. Although we have included it on this release to avoid multiple mailings it will not appear in print on 21 September, but at a later date.***

[12] Direct observation of individual RecA filaments assembling on single DNA molecules

DOI: 10.1038/nature05197


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.

Innsbruck: 4


Toronto: 5

Victoria: 5


Gif-sur-Yvette : 5

Marseille: 5

Paris: 5


Dresden: 9


Takaramachi: 1

Yanagido: 1


Geneva: 7

Lausanne: 7


London: 11

Oxford: 5


Berkeley: 5, 8

Davis: 12

Pasadena: 5, 6

San Francisco: 10

Stanford: 2, 11

Boulder: 6
Lexington: 1

Boston: 1

New Hampshire

Dartmouth: 1

North Carolina

Chapel Hill: 10


College Station: 3

Houston: 9


Seattle: 2


For North America and Canada

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For Japan, Korea, China, Singapore and Taiwan

Itsumi Kitahara, Nature Tokyo

Tel: +81 3 3267 8751; E-mail: [email protected]

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Published: 20 Sep 2006

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