This Week in Science

Science  19 Aug 2016:
Vol. 353, Issue 6301, pp. 786
  1. Geomorphology

    Unlinking erosion from uplift in Tibet

    1. Brent Grocholski

    The Parlung River in Eastern Tibet

    PHOTO(FROM TOP): MATCOVITCH-NATAN ET AL.; ZHANGZHUGANG/WIKICOMMONS

    Conventional wisdom suggests that the locations of gorges or “knickpoints” along the edges of large plateaus remain fixed because erosion drives tectonic uplift. Nowhere should this be more evident than the rapidly uplifting and eroding Tibetan plateau. However, King et al. found evidence for slow migration of a major knickpoint along the Parlung River in eastern Tibet. They used a new method with exceptional time resolution for determining regional cooling rates called multi–OSL (optically stimulated luminescence) thermochronology. It appears that the Parlung knickpoint is steadily moving upstream as a response to tectonic uplift that is unrelated to the local erosion rates.

    Science, this issue p. 800

  2. Crystallography

    Stop wiggling and hold that pose

    1. Phil Szuromi

    X-ray crystallography can be the definitive method for determining the structure and chirality of small organic molecules, but orientational disorder in the crystal can limit its resolution. Lee et al. used a chiral metal-organic framework containing formate ligands that can bind and align molecules covalently to reduce this motion (see the Perspective by Öhrström). The structure and absolute configuration—i.e., which spatial arrangement of atoms is the R or S isomer—of several organic molecules can thus be measured. These range from small molecules, such as methanol, to complex plant hormones, such as gibberellins that have eight stereocenters or jasmonic acid, whose absolute configuration had not previously been directly established.

    Science, this issue p. 808; see also p. 754

  3. Separation Membranes

    Carbon sieving to separate the similar

    1. Marc S. Lavine

    Separating organic molecules, particularly those with almost equal sizes and similar physical properties, can be challenging and may require energy-intensive techniques such as freeze fractionation. Taking inspiration from reverse osmosis of aqueous fluids, Koh et al. describe the synthesis, characterization, and mass transport performance of carbon molecular sieve membranes for the separation of liquid-phase organic molecules at room temperature. This technique is capable of separating very similar isomers, such as ortho- and para-xylene, on an industrial scale.

    Science, this issue p. 804

  4. Human Genetics

    Genetic variation and cardiovascular disease

    1. Laura M. Zahn

    In the past decade, genome-wide association studies have identified thousands of markers in DNA that increase risk for common diseases, but their downstream disease-causing effects are not well understood. Franzén et al. examined gene expression in tissues affected by cardiovascular diseases (CVDs), allowing them to assign disease-causal genes with tissue-specific effects to more than half of these markers, particularly those increasing risk for CVDs. Dissecting the inherited risk of CVDs is promising for predisposed individuals because this knowledge can aid in earlier and more precise diagnosis and therapy.

    Science, this issue p. 827

  5. Synthetic Genomics

    Recoding and repurposing genetic codons

    1. Laura M. Zahn

    By recoding bacterial genomes, it is possible to create organisms that can potentially synthesize products not commonly found in nature. By systematic replacement of seven codons with synonymous alternatives for all protein-coding genes, Ostrov et al. recoded the Escherichia coli genome. The number of codons in the E. coli genetic code was reduced from 64 to 57 by removing instances of the UAG stop codon and excising two arginine codons, two leucine codons, and two serine codons. Over 90% functionality was successfully retained. In 10 cases, reconstructed bacteria were not viable, but these few failures offered interesting insights into genome-design challenges and what is needed for a viable genome.

    Science, this issue p. 819

  6. Behavioral Ecology

    Born prepared to be hot

    1. Sacha Vignieri

    Embryonic birds are sensitive to external sounds while in the egg, and information can be transmitted from parent to offspring acoustically. Mariette et al. show that zebra finch parents call to their eggs when temperatures rise. These calls influence how chicks grow after hatching and their tolerance of and preferences for higher temperatures. Thus, parents are able to prepare their offspring for the warming environment in which they must grow and reproduce. Such mechanisms, if more widely distributed, may help some species adapt to our warming world.

    Zebra finch calls can help their unhatched chicks adapt to hotter temperatures.

    PHOTO: GOLDEN-COLT/ISTOCK.COM

    Science, this issue p. 812

  7. Physiology

    Sleeping with lower blood pressure

    1. Wei Wong

    Individuals with sleep apnea periodically stop breathing or breathe more shallowly while sleeping. The resulting intermittent decreases in blood oxygen concentrations (hypoxia) activate an organ called the carotid body, which sends out signals to increase breathing but also increases blood pressure and can lead to hypertension. Using a rodent model of sleep apnea, Yuan et al. found that the carotid bodies of the rodents produced reactive oxygen species that stimulate the generation of hydrogen sulfide, a gasotransmitter that in turn stimulates carotid body activity. Inhibiting the enzyme that generates hydrogen sulfide prevented the rodents from developing high blood pressure.

    Sci. Signal. 9, ra80 (2016).

  8. Cancer

    Photobombing Tregs during cancer

    1. Yevgeniya Nusinovich

    Regulatory T cells (Tregs) are immunosuppressive cells that reduce inflammation. But reducing inflammation interferes with cancer defenses. Sato et al. have found a way to selectively deplete Tregs in tumors to promote antitumor effects while minimizing the risk of excess inflammation and autoimmunity. Such selectivity can be achieved by deploying a method called near-infrared photoimmunotherapy. In this technique, part of an antibody that recognizes Tregs is fused to a light-sensitive dye. Shining near-infrared light on the tumor activates the antibody and triggers killing of the Tregs. In mice, this treatment not only killed the targeted tumor but also destroyed untreated tumors of the same type that were located in other parts of the body, indicating its potential for the treatment of metastatic disease.

    Sci. Transl. Med. 8, 352ra110 (2016).

  9. Immunogenomics

    Microglia development follows a stepwise program

    1. Laura M. Zahn

    Microglia are cells that defend the central nervous system. However, because they migrate into the brain during development, the changes that they undergo, including those that affect gene expression, have been difficult to document. Matcovitch-Natan et al. transcriptionally profiled gene expression and analyzed epigenetic signatures of microglia at the single-cell level in the early postnatal life of mice. They identified three stages of microglia development, which are characterized by gene expression and linked with chromatin changes, occurring in sync with the developing brain. Furthermore, they showed that the proper development of microglia is affected by the microbiome.

    Science, this issue p. 789

  10. Economics

    Measuring consumption and wealth remotely

    1. Gilbert Chin

    Nighttime lighting is a rough proxy for economic wealth, and nighttime maps of the world show that many developing countries are sparsely illuminated. Jean et al. combined nighttime maps with high-resolution daytime satellite images (see the Perspective by Blumenstock). With a bit of machine-learning wizardry, the combined images can be converted into accurate estimates of household consumption and assets, both of which are hard to measure in poorer countries. Furthermore, the night- and day-time data are publicly available and nonproprietary.

    Science, this issue p. 790; see also p. 753

  11. Statistical Physics

    To thermalize, or not to thermalize?

    1. Jelena Stajic

    Intuition tells us that an isolated physical system subjected to a sudden change (i.e., quenching) will evolve in a way that maximizes its entropy. If the system is in a pure, zero-entropy quantum state, it is expected to remain so even after quenching. How do we then reconcile statistical mechanics with quantum laws? To address this question, Kaufman et al. used their quantum microscope to study strings of six rubidium atoms confined in the wells of an optical lattice (see the Perspective by Polkovnikov and Sels). When tunneling along the strings was suddenly switched on, the strings as a whole remained in a pure state, but smaller subsets of two or three atoms conformed to a thermal distribution. The force driving the thermalization was quantum entanglement.

    Science, this issue p. 794; see also p. 752

  12. Gene Regulation

    Patterns of development regulation within tissues

    1. Barbara R. Jasny

    Expression of a given gene at the RNA level does not always correlate with expression at the protein level for many organisms. Walley et al. have built an integrated atlas of gene expression and regulatory networks in developing maize, using the same tissue samples to measure the transcriptome, proteome, and phosphoproteome. Coexpression networks from the transcriptome and proteome showed little overlap with each other, even though they showed enrichment of similar pathways. Integration of mRNA, protein, and phosphoprotein data sets improved the predictive power of the gene regulatory networks.

    Science, this issue p. 814

  13. Zika Virus

    Characterizing the Zika virus antibody response

    1. Kristen L. Mueller

    Given the public health emergency that Zika virus poses, scientists are seeking to understand the Zika-specific immune response. Stettler et al. analyzed 119 monoclonal antibodies isolated from four donors that were infected with Zika virus during the present epidemic, including two individuals that had previously been infected with dengue virus, another member of the flavivirus family. Neutralizing antibodies primarily recognized the envelope protein domain III (EDIII) or quaternary epitopes on the intact virus, and an EDIII-targeted antibody protected mice against lethal infection. Some EDI/II-targeting antibodies cross-reacted with dengue virus in vitro and could enhance disease in dengue-infected mice. Whether dengue and Zika virus antibodies cross-react in humans remains to be tested.

    Science, this issue p. 823