This Week in Science

Science  06 Nov 2015:
Vol. 350, Issue 6261, pp. 646
  1. Ophthalmology

    A visionary approach to transparency

    1. Paula A. Kiberstis

    The clouding of the lens observed in cataracts may be amenable to a nonsurgical fix

    PHOTO: PAUL WHITTEN/SCIENCE SOURCE

    Cataracts are the most common cause of vision loss, especially in our ever-increasing elderly population. Cataracts arise when crystallin, a major protein component of the eye lens, begins to aggregate, which causes the lens to become cloudy. Makley et al. explored whether small molecules that reverse this aggregation might have therapeutic potential for treating cataracts, which normally require surgery (see the Perspective by Quinlan). They used a screening method that monitors the effect of ligands on temperature-dependent protein unfolding and identified several compounds that bind and stabilize the soluble form of crystallin. In proof-of-concept studies, one of these compounds improved lens transparency in mice.

    Science, this issue p. 674; see also p. 636

  2. Plant Science

    Protecting against too much of a good thing

    1. Pamela J. Hines

    The slimy pink rot of potatoes is caused by the bacterium Clostridium puniceum, which cannot grow in the presence of oxygen. These bacteria produce a polyphenolic metabolite known as clostrubin that functions as an antibiotic. Shabuer et al. now show that the bacteria also use clostrubin to protect themselves from the aerobic environment of the potato tuber.

    Science, this issue p. 670

  3. Movement Control

    Generating complex movement patterns

    1. Peter Stern

    What exactly does neuronal activity in the brain's motor cortex encode? In monkeys, Griffin et al. simultaneously recorded from a large number of muscles and from motor cortex cells that project directly to the motor neurons of the spinal cord. Even though the cortical cells had conventional directional tuning curves, different cortical cells were functionally connected to spinal cells with different muscle actions.

    Science, this issue p. 667

  4. Actinide Chemistry

    High fives and sixes for Americium ions

    1. Jake Yeston

    You've probably heard of uranium and plutonium. Americium (Am) is less widely discussed outside chemistry circles, but the separation of this heavier radioactive element from nuclear waste streams is a major goal of fuel reprocessing research. The trouble is that trivalent Am ions are hard to tease apart from similarly charged lanthanide ions. Dares et al. now show that terpyridyl ligands appended to an electrode can promote the oxidation of trivalent Am ions to the pentavalent and hexavalent states (see the Perspective by Soderquist). These more highly charged ions should be easier to isolate for the subsequent use of the Am in next-generation nuclear reactors.

    Science, this issue p. 652; see also p. 635

  5. Climate Change

    Historical perspectives on Old World drought

    1. Kip Hodges

    To understand the significance of climate prediction models of future drought, it is important to establish regional patterns of drought in the past. Cook et al. developed a drought atlas for the “Old World” (north Africa, the Mediterranean Basin, and Europe) based on tree-ring reconstructions. The data confirm that the Northern Hemisphere experienced unusually severe and extensive drought before the 20th century for reasons that are, as yet, not clear.

    Sci. Adv. 10.1126.sciadv.15-00561 (2015).

  6. Quantum Simulation

    Filling a molecular lattice of light

    1. Jelena Stajic

    Cold atoms in optical lattices normally interact only when two of them occupy the same lattice site. More-complex interactions would expand the potential of the system for quantum simulation. A promising approach is to use polar molecules instead of atoms, which interact at much longer length scales. However, “packing” the lattice with molecules is tricky. Moses et al. introduced bosonic 87Rb atoms and fermionic 40K atoms into an optical lattice, combined them into molecules, and brought the molecules into their ground state, achieving a considerable lattice filling of 25%.

    Science, this issue p. 659

  7. Plant Genetics

    How flowers separate males and females

    1. Laura M. Zahn

    Most flowering plant families have bisexual flowers with both male and female function. However, most members of the Cucurbiticeae family, which includes melons, cucumbers, and gourds, have unisexual flowers. To understand this difference in sex expression, Boualem et al. identified a cucumber gene expressed in the female flowers. Mutations in this gene were associated with solely male flowers. By integrating this finding into a sex determination model, the authors explain how unisexual flowers can coexist in the same plant.

    Science, this issue p. 688

  8. Nonhuman Genomics

    Symbionts are adapted to work with corals

    1. Laura M. Zahn

    Many corals have formed mutualistic associations with dinoflagellate symbionts, which are thought to provide nutrients and other benefits. To examine the underlying genetics of this association, S. Lin et al. sequenced the genome of the endosymbiont dinoflagellate Symbiodinium kawagutii. The genome includes gene number expansions and encodes microRNAs that show complementarity to genes within the coral genome. Such microRNAs may be involved in regulating coral genes. Furthermore, coral and S. kawagutii appear to share homologs of genes encoding specific nutrient transporters. The findings shed light on how symbiosis is established and maintained between dinoflagellates and corals.

    The genome-sequenced coral Acropora digitifera harbors the Symbiodinium kawagutii endosymbiont

    PHOTO: MDC SEAMARC MALDIVES/WIKICOMMONS

    Science, this issue p. 691

  9. Infectious Disease

    Outflanking RSV

    1. Angela Colmone

    Respiratory syncytial virus (RSV) infection can cause a severe respiratory illness in young children. Researchers are working to fashion a live attenuated vaccine, which would mimic the natural course of infection, but blocking viral replication also stems the immune response. Now Karron et al. report on a version of RSV that induced a protective immune response with decreased viral shedding in humans. Children who received the vaccine produced antibodies to RSV without symptoms in the subsequent RSV season.

    Sci. Transl. Med. 7, 312ra175 (2015).

  10. Microbiome

    Function in the tree of life

    1. Caroline Ash

    How does the composition of microbial communities integrate functionally with the wider environment? Martiny et al. review how patterns of microbial species abundances in different environments and disease states can have strong evolutionary signals. Some environmental changes select the survival of organisms with conserved metabolisms requiring complex configurations of proteins and cofactors that have long evolutionary histories, such as methane producers. In contrast, surviving antibiotic exposure may only require a single gene that can be traded promiscuously among many unrelated organisms. So, depending on the key ingredient (whether it is temperature, light, nutrient, or a dose of antibiotic) and the evolutionary history of its complementary metabolism, shifting environmental conditions will have predictable effects at different levels within the microbial tree of life.

    Science, this issue p. 10.1126/science.aac9323

  11. Metabolic Health

    The clockwork of insulin release

    1. Paula A. Kiberstis

    In healthy people, blood glucose levels are maintained within a narrow range by several physiological mechanisms. Key among them is the release of the hormone insulin by pancreatic β cells, which occurs when glucose levels rise after a meal. In response to insulin, blood glucose is taken up by tissues that need fuel, such as muscle. β cells can anticipate the body's varying demand for insulin throughout the 24-hour day because they have their own circadian clock. How this clock controls insulin release has been unclear. Perelis et al. now show that the activity of transcriptional enhancers specific to β cells regulates the rhythmic expression of genes involved in the assembly and trafficking of insulin secretory vesicles (see the Perspective by Dibner and Schibler).

    Science, this issue p. 10.1126/science.aac4250; see also p. 628

  12. Epigenetics

    Generations affected by histone changes

    1. Beverly A. Purnell

    Parent and even grandparent environmental exposure can transmit adverse health effects to offspring. The mechanism of transmission is unclear, but some studies have implicated variations in DNA methylation. In a mouse model, Siklenka et al. found that alterations in histone methylation during sperm formation in one generation leads to reduced survival and developmental abnormalities in three subsequent generations (see the Perspective by McCarrey). Although changes in DNA methylation were not observed, altered sperm RNA content and abnormal gene expression in offspring were measured. Thus, chromatin may act as a mediator of molecular memory in transgenerational inheritance.

    Science, this issue p. 10.1126/science.aab2006; see also p. 634

  13. Frustrated Magnetism

    Peeking into an exotic magnetic structure

    1. Jelena Stajic

    Cooling materials that contain magnetic interactions generally leads to an ordered magnetic state. In materials known as quantum spin liquids (QSLs), the geometry of the crystal lattice may prevent this ordered state from forming, even at absolute zero. The material herbertsmithite is thought to be a strong candidate for a QSL, but the nature of its ground state is still a mystery. Fu et al. measured shifts in the nuclear magnetic resonance signals of herbertsmithite to conclude that its ground state has a zero spin and is separated from the first excited state by an energy gap (see the Perspective by Furukawa). The results suggest that herbertsmithite is indeed a QSL.

    Science, this issue p. 655; see also p. 631

  14. Microbiome

    What makes the gut microbiome stable?

    1. Caroline Ash

    Classically, we think of our microbiome as stable, benign, and cooperative. Recent experimental work is beginning to unpick essential functions that can be attributed to the stable microbiota of humans. To be able to manipulate the microbiome to improve health, we need to understand community structure and composition and we need models to quantify and predict stability. Coyte et al. applied concepts and tools from community ecology to gut microbiome assembly. Independently developed models converged on a surprising answer: A high diversity of species is likely to coexist stably when the system is dominated by competitive, rather than cooperative, interactions.

    Science, this issue p. 663

  15. Protein Synthesis

    Proximity best for building protein complexes

    1. Guy Riddihough

    The synthesis of protein subunits and their assembly into a fully functional complex are generally thought to be two distinct processes. Shieh et al. studied the synthesis and assembly of the luciferase complex in Escherichia coli. Organization of the luciferase subunits LuxA and LuxB side by side into an operon promotes their colocalized synthesis and assembly into an active enzyme complex. Indeed, the association between the subunits occurs as they are being synthesized on ribosomes, which helps order the sequence of subunit interactions.

    Science, this issue p. 678

  16. Structural Biology

    Getting rid of carbon dioxide

    1. Valda Vinson

    In mammals, red blood cells deliver oxygen to tissues and remove carbon dioxide. Key to this essential process is a membrane protein called anion exchanger 1 (AE1) which transports bicarbonate (formed from carbon dioxide) out of red blood cells in exchange for chloride. This decreases the pH inside the blood cells, so that oxygen is released from hemoglobin and can diffuse into tissues. Arakawa et al. report the crystal structure of the transmembrane anion exchanger domain of AE1, which includes 14 transmembrane helices. The structure provides a basis for understanding the effects of mutations that lead to red blood cell diseases and also gives insight into the mechanism of ion transport.

    Science, this issue p. 680

  17. Plant Evolution

    Distant relatives can share gene function

    1. Laura M. Zahn

    The plants Arabidopsis thaliana and Papaver rhoeas (poppy) shared a common ancestor approximately 140 million years ago. Because of this evolutionary distance, although many of their genes share function, the mechanisms that allow these genes to function are expected to have diverged. However, Z. Lin et al. found that a pair of genes that prevent self-fertilization in poppy can confer the same trait when expressed in Arabidopsis. This incompatibility was much more like that of poppy than that of incompatible close relatives of Arabidopsis. Thus, similar long-distance transfer of incompatibility, a trait of interest for plant breeding, may be useful between other distantly related species.

    Science, this issue p. 684

  18. Public Health

    Hope for dengue control?

    1. Julia Fahrenkamp-Uppenbrink

    Each year, almost 400 million people around the world, many of them children, are infected with dengue virus. Most experience no or mild symptoms, but those that develop severe dengue may die. A recently developed vaccine offers hope but has modest efficacy. In a Perspective, Wilder-Smith and Gubler argue that the use of this vaccine can nevertheless have major public health benefits. The vaccine shows promise for reducing hospitalizations and appears to be safe for children between 9 and 16 years old. Licensing and using the vaccine now is likely to reduce the public health burden from dengue. It would also provide an opportunity to learn from its use while research toward more effective vaccines continues.

    Science, this issue p. 626

  19. GPCR Signaling

    Agonist control of voltage sensitivity

    1. John F. Foley

    Some G protein–coupled receptors (GPCRs) are affected by changes in plasma membrane potential. Rinne et al. found that depolarization enhanced signaling by the M3 muscarinic acetylcholine receptor when the agonists choline or pilocarpine were bound. In contrast, depolarization attenuated M3 receptor signaling when the agonists carbachol or acetylcholine were bound. Mutation of a critical residue in the binding pocket for agonists switched the response of the carbachol-bound receptor so that signaling was enhanced by membrane depolarization. These results may help to explain why drugs that are agonists of the same GPCR can have distinct effects.

    Sci. Signal. 8, ra110 (2015).