Story ideas from the Proceedings of the National Academy of Sciences

PNAS tipsheet for Oct. 6-10

ARTICLE HIGHLIGHTS

• Noninvasive test for fetal Down syndrome
• Evolution of a personality
• Adaptation to future climate change
• Combination therapy for diabetic kidney disease

ALSO OF INTEREST

• Atomic-level insight into nanostructures
• Support for treatment of early aging
• Blind rats' compensation

Down syndrome occurs in a fetus when there are three copies of chromosome 21 instead of two. Tests for the abnormal chromosome count, called "fetal aneuploidy," are currently carried out by invasive procedures that can harm the developing fetus. Stephen Quake and colleagues have now developed a prototype noninvasive procedure for identifying fetal aneuploidy. Using samples of maternal blood, the researchers were able to pinpoint cases of aneuploidy in a cohort of 18 pregnant women. Maternal blood contains free-floating DNA, 10 percent of which comes from the fetus. If a particular chromosome is over-represented in this DNA mixture, the fetus is likely the source, implying an excess chromosome number. The authors employed a gene sequencing method that amplified short fragments of DNA and mapped its chromosomes. They report that of the most common aneuploidies, those on chromosome 21 (Down syndrome), were clearly identifiable from the fetal DNA. With the dropping cost of gene sequencing, this method could soon become a cheap and safer alternative to current invasive tests, according to the researchers.

ARTICLE #08-08319: "Noninvasive diagnosis of fetal aneuploidy by shotgun sequencing DNA from maternal blood," by H. Christina Fan, Yair J. Blumenfeld, Usha Chitkara, Louanne Hudgins, and Stephen R. Quake

MEDIA CONTACT: Stephen Quake, Department of Bioengineering, Stanford University, Stanford, CA; tel: 650-736-7890; e-mail: quake@stanford.edu

Nearly all animals have a "personality," which helps them respond to their environment, but the degree to which they respond to their surroundings and others is highly variable. Franz Weissing and colleagues provide an evolutionary explanation for how these personalities developed over time and why being highly responsive isn't always the best strategy. Their results explain how different personalities can emerge amongst animals, from fish to birds and mice, and even people. With a simple mathematical model representing the range of possible choices in different situations and the payoff for each, the researchers show that being responsive is most advantageous when the trait is rare, but disadvantageous when common. The result explains why responsive and unresponsive individuals can coexist in a population. The authors also found that being responsive often feeds on itself, and becomes less costly with time, leading to individuals who are consistently more responsive than others. Natural selection thus results in two groups within a population, one of which responds to environmental stimuli in all kinds of contexts, while another is largely unresponsive to them. The researchers suggest that these patterns of responsiveness can induce correlations among other traits, like boldness and aggression, which provides an explanation for why such correlations are often found in animal populations.

ARTICLE #08-05473: "Evolutionary emergence of responsive and unresponsive personalities," by Max Wolf, G. Sander van Doorn and Franz J. Weissing

MEDIA CONTACT: Franz Weissing, Theoretical Biology Group, University of Groningen, Haren, THE NETHERLANDS; tel: +31-50-363-2131 (day), +31-50-534-3097 (evening); e-mail: F.J.Weissing@rug.nl

Even the most stringent of climate policies will not be able to prevent global warming entirely, according to a new analysis. In addition to efforts to reduce anthropogenic greenhouse gas emissions, D.P. van Vuuren and colleagues assert that societies should also consider strategies to adapt to higher global temperatures. The researchers' analysis examines a wide range of climate policy scenarios from different emission models and shows that, in all of these scenarios, the average surface temperature rise will be reduced, but not avoided. The ranges of 21st century climate change published so far by the Intergovernmental Panel on Climate Change did not take into account efforts to reduce climate change. In this study, the researchers projected the effects of multiple mitigation strategies using two climate models and taking into account uncertainties in the climate system and carbon cycle. The analysis reports an average minimum warming by the year 2100 of 1.4 degrees Celsius from baseline levels in 1990 for the most stringent emission reduction scenarios. While the minimum temperature rise is significantly less than that projected without emission mitigation policies, it is higher than previous reports that focused on climate inertia alone.

ARTICLE #07-01129: "Temperature increase of 21st century mitigation scenarios," by D. P. Van Vuuren, M. Meinshausen, G. K. Plattner. F. Joos, K.M. Strassmann, S.J. Smith, T.M.L. Wigley, S.C.B. Raper, K. Riahi, F. de la Chesnaye, et al.

MEDIA CONTACT: D.P. van Vuuren, Netherlands Environmental Assessment Agency, Bilthoven, THE NETHERLANDS; tel: +31-30-274-2046; e-mail: detlef.vanvuuren@pbl.nl

Researchers have developed a combination therapy that can help prevent and may even reverse diabetic nephropathy in mice, a kidney condition that, in humans, can lead to end-stage kidney disease and death. Yan Chun Li and colleagues developed a multidrug treatment that blocks the effects of the renin-angiotensin system--a hormone system whose overactivity can lead to high blood pressure--and prevents the kidney from compensating for the blockage. The combination consists of losartan, a hypertension drug that blocks the angiotensin type 1 receptor, and paricalcitol, a form of Vitamin D that prevents kidney cells from increasing production of the hormone renin. In diabetic mice, the researchers found that either drug helped improve kidney injury, but treatment with both drugs worked markedly better. The combination prevented most forms of kidney damage associated with diabetic nephropathy and allowed the kidney to almost entirely recover. The authors suggest that if further animal testing is equally effective, the treatment could be useful for humans.

ARTICLE #08-03751: "Combination therapy with AT1 receptor blocker and vitamin D analog markedly ameliorates diabetic nephropathy: Blockade of compensatory renin increase," by Zhongyi Zhang, Yan Zhang, Gang Ning, Dilip K. Deb, Juan Kong, and Yan Chun Li

MEDIA CONTACT: Yan Chun Li, Department of Medicine, University of Chicago, Chicago, IL; tel: 773-702-2477 (day), 773-493-2886 (evening), 773-474-3605 (mobile); e-mail: cyan@medicine.bsd.uchicago.edu

Atomic-level insight into nanostructures

Researchers combine theoretical calculations with electron microscopy techniques to characterize nanoparticles and nanotubes.

ARTICLE #08-05407: "Atom by atom: HRTEM insights into inorganic nanotubes and fullerene-like structures," by Maya Bar Sadan, Lothar Houben, Andrey N. Enyashin, Gotthard Seifert, and Reshef Tenne

MEDIA CONTACT: Reshef Tenne, Materials and Interfaces Department, Weizmann Institute of Science, Rehovot, ISRAEL; tel: +972-8-934-2394; e-mail: reshef.tenne@weizmann.ac.il

MEDIA CONTACT: Lothar Houben, Institute of Solid State Research, Forschungszentrum Jülich, Jülich, GERMANY; tel: +49-2461-618-037; e-mail: l.houben@fz-juelich.de

A drug treatment in a mouse model of premature aging syndrome shows promise in the treatment of cardiovascular disease in the animals.

ARTICLE #08-07840: "A farnesyltransferase inhibitor prevents both the onset and late progression of cardiovascular disease in a progeria mouse model," by Brian C. Capell, Michelle Olive, Michael R. Erdos, Kan Cao, Dina A. Faddah, Urraca L. Tavarez, Karen N. Conneely, Xuan Qu, Hong San, Santhi K. Ganesh, et al.

MEDIA CONTACT: Francis Collins, National Human Genome Research Institute, National Institutes of Health, Bethesda, MD; tel: 301-496-5382; e-mail: 4rancis@mail.nih.gov

Rats blinded after birth grow stronger, more responsive whisker muscles as pups to compensate for a lack of eyesight.

ARTICLE #08-08431: "Late onset muscle plasticity in the whisker pad of enucleated rats," Brenda Toscano-Márquez, Eduardo Martínez-Martínez, Elías Manjarrez, Lourdes Martínez, Julieta Mendoza-Torreblanca, and Gabriel Gutiérrez-Ospina

MEDIA CONTACT: Gabriel Gutiérrez Ospina, Universidad Nacional Autónoma de Mexico, Departamento de Biología Celular y Fisiología, Mexico City, MEXICO; tel: +52-555-5622-8959; e-mail: gabo@correo.biomedicas.unam.mx