This Week in Science

Science  28 Apr 2017:
Vol. 356, Issue 6336, pp. 392
  1. Economics

    Aspiring to do better than one's parents

    1. Gilbert Chin

    Success in achieving the American dream may have been easier then than now.

    CREDIT: H. ARMSTRONG ROBERTS/CLASSICSTOCK

    The American dream promises that hard work and opportunity will lead to a better life. Although the specifics of what constitutes a better life vary from generation to generation, one constant is that children expect to do better—or at least to have a good chance at doing better—than their parents. Chetty et al. show that this dream did come true for children born in the middle of the 20th century, but only for half of children born in 1984 (see the Policy Forum by Katz and Krueger). A more even distribution of economic growth, rather than more growth, would allow more children to fulfill their dreams.

    Science, this issue p. 398; see also p. 382

  2. Neurodevelopment

    Pattern formation in the brain

    1. Pamela J. Hines

    Neurons in the developing brain cooperate to build circuits. Mountoufaris et al. found that ∼50 variable protocadherin genes support a combinatorial identity code that allows millions of olfactory neuron axons to sort into ∼2000 glomeruli. Sharing olfactory receptors drives axons to one glomerulus, and protocadherin diversity allows the multiple axons to touch each other as they converge. On the other hand, Chen et al. found that a single C-type protocadherin underlies the tiled distribution of serotonergic neurons throughout the central nervous system. These neurons, which share protocadherin identity, enervate broad swaths evenly without touching neighboring neurons.

    Science, this issue p. 411, p. 406

  3. Organic Chemistry

    Getting phosphorus into healthy shape

    1. Jake Yeston

    ProTide therapeutics play a trick on the body, getting nucleoside analogs where they need to be by decorating them with unnatural phosphoramidates in place of ordinary phosphates. These compounds pose an unusual synthetic challenge because their configuration must be controlled at phosphorus; most methods have been refined to manipulate the geometry of carbon. DiRocco et al. report a metal-free, small-molecule catalyst that attains high selectivity for nucleoside phosphoramidation by activating both reaction partners. Kinetic studies with an early prototype revealed a double role for the catalyst that inspired the rational design of a more active and selective dimeric structure.

    Science, this issue p. 426

  4. Biochemistry

    Taking a look at fungal bioluminescence

    1. Philip Yeagle

    Glowing fungus, Neonothopanus gardneri

    CREDIT: DAVID LIITTSCHWAGER/NATIONAL GEOGRAPHIC CREATIVE

    Certain mushrooms can emit their own light. Addressing an Aristotelian question unanswered for more than two millennia, Kaskova et al. found the source of mushroom bioluminescence. The mushrooms use the substrate oxyluciferin and the enzyme luciferase in a previously uncharacterized catalytic pathway that emits photons. The luciferase has a broader substrate specificity than expected, which may widen possibilities for using bioluminescence in analytical and imaging technologies.

    Sci. Adv. 10.1126/sciadv.1602847 (2017).

  5. Atomic Gases

    Imaging an atomic soliton train

    1. Jelena Stajic

    Solitons—waveforms that keep their shape as they travel—can form in various environments where waves propagate, such as optical media. In a one-dimensional tube of bosonic atoms, solitons are formed when the interaction between the atoms is suddenly switched from repulsive to attractive. This causes the atoms to clump together into a “train” of solitons. Nguyen et al. used a nearly nondestructive imaging technique to follow the dynamics of this train. The solitons repulsed each other and underwent collective oscillations known as breathing modes.

    Science, this issue p. 422

  6. Batteries

    Zinc can compete with lithium

    1. Marc S. Lavine

    Although lithium-based batteries are ubiquitous, there are still challenges related to their longevity and safety, as well as concerns about material availability. Aqueous rechargeable batteries based on zinc might provide an alternative, but they have been plagued by the formation of dendrites during cycling. Parker et al. show that when zinc is formed into three-dimensional sponges, it can be used with nickel to form primary batteries that allow for deep discharge. Alternatively, the sponges can be used to produce secondary batteries that can be cycled thousands of times and can compete with lithium ion cells.

    Science, this issue p. 415

  7. Paleogenomics

    Ancient genomics of horse domestication

    1. Laura M. Zahn

    The domestication of the horse was a seminal event in human cultural evolution. Librado et al. obtained genome sequences from 14 horses from the Bronze and Iron Ages, about 2000 to 4000 years ago, soon after domestication. They identified variants determining coat color and genes selected during the domestication process. They could also see evidence of admixture with archaic horses and the demography of the domestication process, which included the accumulation of deleterious variants. The horse appears to have undergone a different type of domestication process than animals that were domesticated simply for food.

    Science, this issue p. 442

  8. CRISPR Technology

    Sensitive and specific CRISPR diagnostics

    1. Laura M. Zahn

    Methods are needed that can easily detect nucleic acids that signal the presence of pathogens, even at very low levels. Gootenberg et al. combined the allele-specific sensing ability of CRISPR-Cas13a with recombinase polymerase amplification methods to detect specific RNA and DNA sequences. The method successfully detected attomolar levels of Zika virus, as well as the presence of pathogenic bacteria. It could also be used to perform human genotyping from cell-free DNA.

    Science, this issue p. 438

  9. Robotics Architecture

    Thinking local about building

    1. Marc S. Lavine

    Custom manufacturing is commonly associated with small, specialized parts and designs. However, a growing branch of tools is being developed for making much larger buildings and objects. Keating et al. successfully built a 15-m open dome structure with a solar-powered array of robotic arms that used sand, compressed earth, ice, recycled plastic, and chains as building materials. The robot used real-time data to adjust its processing, making it adaptable to the local conditions.

    Sci. Robot. 2, eaam8986 (2017).

  10. Neurodevelopment

    Single-cell diversity in the brain

    1. Pamela J. Hines

    The cells that make up an organism may all start from one genome, but somatic mutations mean that somewhere along the line of development, an organism's individual cellular genomes diverge. McConnell et al. review the implications and causes of single-cell genomic diversity for brain function. Somatic mutations caused by mobile genetic elements or errors in DNA repair may underlie certain neuropsychiatric disorders.

    Science, this issue p. eaal1641

  11. Plant Biology

    Germ cells on demand

    1. Pamela J. Hines

    Unlike animals, plants do not set aside a germline. Instead, germ cells are developed on demand from somatic lineages. Zhao et al. examined the regulatory pathways that manage the transition from somatic to germ cell development in the small plant Arabidopsis (see the Perspective by Vielle-Calzada). The transcription factor WUSCHEL (WUS) was needed early on for development of ovules. Soon after, a trio of inhibitors that work through a cyclin-dependent kinase allowed a transcriptional repressor to down-regulate WUS. This opened the door to meiosis, while restricting the number of reproductive units per seed to one.

    Science, this issue p. eaaf6532; see also p. 378

  12. Cancer Therapy

    An old cancer drug's degrading new look

    1. Paula A. Kiberstis

    Typically, cancer drugs that help only a small number of patients in clinical trials are not pursued. This might change in a future world of precision medicine, where biomarkers will match specific drugs to the patients most likely to respond. Han et al. identified the mechanism of action of a cancer drug called indisulam, a sulfonamide tested previously in patients with solid tumors. Indisulam and related sulfonamides killed cells by disrupting precursor mRNA splicing. The drugs targeted a specific RNA splicing factor for degradation by “gluing” it to the CUL4-DCAF15 ubiquitin ligase. Experiments with cancer cell lines suggest that future clinical trials of these drugs should focus on leukemias and lymphomas with high DCAF15 expression levels.

    Science, this issue p. eaal3755

  13. Renewable Resources

    Solar heat helps harvest humidity

    1. Phil Szuromi

    Atmospheric humidity and droplets constitute a huge freshwater resource, especially at the low relative humidity (RH) levels typical of arid environments. Water can be adsorbed by microporous materials such as zeolites, but often, making these materials release the water requires too much energy to be practical. Kim et al. used a metal-organic framework (MOF) material that has a steep increase in water uptake over a narrow RH range to harvest water, using only ambient sunlight to heat the material. They obtained 2.8 liters of water per kilogram of MOF daily at 20% RH.

    Science, this issue p. 430

  14. Intergalactic Medium

    Using quasar pairs to measure smoothness

    1. Keith T. Smith

    Space between galaxies is filled with a tenuous gas known as the intergalactic medium (IGM). The presence of hydrogen atoms in the IGM at different redshifts imprints a series of absorption lines in the spectra of background quasars. Rorai et al. studied pairs of closely spaced quasars and quantified how similar their absorption lines are as a function of transverse separation and redshift. They thus assessed the smoothness of the IGM on relatively small scales—several times the size of a galaxy. The results constrain interactions between galaxies and the IGM, such as heating by ultraviolet photons.

    Science, this issue p. 418

  15. Materials Science

    When forces depend on orientation

    1. Marc S. Lavine

    In oriented attachment, small nuclei or crystals come together to make a larger crystal, but only when complementary facets approach each other. Does this mean that there is an orientational dependence of the force between two nanocrystals? Zhang et al. report a delicate method to measure the van der Waals attraction between rutile TiO2 nanocrystals. They imaged the contact point in situ with environmental transmission electron microscopy, which allowed the interparticle distances to be measured accurately. This elucidated the relationship between the nanocrystals' orientations, surface hydrations, and interactions. The results suggest that there is enough force to generate a torque between the crystals to ensure a complementary interaction.

    Science, this issue p. 434

  16. Ecology

    Plant the right tree

    1. Julia Fahrenkamp-Uppenbrink

    City trees can perform important functions, such as removing harmful particulates from the air and increasing the physical and mental well-being of city dwellers. In a Perspective, Willis and Petrokofsky explain, however, that not all trees are equally beneficial. Particulate uptake differs widely from one species to another. Tree size and shape also matter, because large trees may trap air pollution. And pollen from certain tree species can cause severe allergic reactions. Tree-planting efforts in cities should move beyond simple considerations of beauty to consider the distinct advantages and disadvantages of individual tree species for improving urban living.

    Science, this issue p. 374

  17. Immunology

    Interferon-independent antiviral defense

    1. John F. Foley

    Antiviral responses are normally initiated by interferon production, which stimulates the phosphorylation and activation of STAT1 and STAT2. These transcription factors, in complex with the transcriptional regulator IRF9, mediate antiviral gene expression. Wang et al. report that interferon-stimulated gene expression can be mediated by unphosphorylated STAT1 and STAT2 with IRF9 in the absence of interferon production or signaling. This complex protected cells from viral infection and, thus, mediates homeostatic, interferon-independent antiviral responses.

    Sci. Signal. 10, eaah4248 (2017).

  18. Metabolic Disease

    Liver T cells in obesity-associated diabetes

    1. Anand Balasubramani

    Obesity is associated with increased risk of developing a range of disorders, including cardiovascular diseases and type 2 diabetes. In obese individuals, accumulation of fat in the liver, termed nonalcoholic fatty liver disease (NAFLD), has been linked to the development of insulin resistance. Ghazarian et al. found that type I interferon-driven activation of CD8+ T cells in the liver correlated with insulin resistance in patients with NAFLD and in mouse models of obesity. Furthermore, the gut microbiome played an important role in driving inflammation in the livers of obese mice. These findings add to the growing recognition of the immune axis in metabolic disorders associated with obesity.

    Sci. Immunol. 2, eaai7616 (2017).

  19. Malaria

    An antimalarial to add to the armamentarium

    1. Orla M. Smith

    Malaria continues to be a scourge in much of Africa. Paquet et al. screened a small-molecule library against the human malaria parasite, Plasmodium falciparum, and identified the 2-aminopyridine chemical class as having potent activity. An optimized compound, MMV390048, was active against multiple parasite life cycle stages, both in the mammalian host and the mosquito vector, and also killed drug-resistant parasites. MMV390048 killed the malaria parasite by blocking the parasite's phosphatidylinositol 4-kinase and protected monkeys from malaria infection. MMV390048 has potential as a new antimalarial drug that may contribute to global malaria eradication efforts.

    Sci. Transl. Med. 9, eaad9735 (2017).

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