This Week in Science

Science  05 Jun 2015:
Vol. 348, Issue 6239, pp. 1102
  1. Social Evolution

    For bees, many roads lead to social harmony

    1. Sacha Vignieri

    Honey bees (Apis mellifera) form complex societies

    CREDITS: (TOP TO BOTTOM) BARTESAGHI ET AL.; © PHIL DEGGINGER/ALAMY

    Eusociality, where workers sacrifice their reproductive rights to support the colony, has evolved repeatedly and represents the most evolved form of social evolution in insects. Kapheim et al. looked across the genomes of 10 bee species with varying degrees of sociality to determine the underlying genomic contributions. No one genomic path led to eusociality, but similarities across genomes were seen in features such as increases in gene regulation and methylation. It also seems that selection pressures relaxed after the emergence of complex sociality.

    Science, this issue p. 1139

  2. Human Oocytes

    Earliest stages of human development revealed

    1. Stella M. Hurtley

    Most of our knowledge about meiosis in mammalian oocytes stems from studies of mouse oocytes. However, chromosome segregation in mouse oocytes is much more reliable than in human oocytes. Working with the clinic that first pioneered IVF, Holubcové et al. studied freshly harvested human oocytes. They used high-resolution fluorescence microscopy to watch more than 100 human oocytes as they went through each step of meiosis.

    Human meiosis in living color

    CREDIT: ZUZANA HOLUBCOVA AND MELINA SCHUH/MRC LABORATORY OF MOLECULAR BIOLOGY

    Science, this issue p. 1143

  3. Nitrogen Cycling

    More N2O is no laughing matter

    1. Nicholas S. Wigginton

    Because N2O is a potent greenhouse gas, tracking its sources and sinks—including those from natural processes—is imperative. Babbin et al. developed an isotopic tracer method to measure biological N2O reduction rates directly in the Eastern Tropical North Pacific Ocean. Incomplete denitrification results in the rapid cycling and net accumulation of N2O. As oxygen minimum zones expand in the global ocean, more N2O may enter the atmosphere than previously expected.

    Science, this issue p. 1127

  4. Friction

    A frigid simulator for friction

    1. Jelena Stajic

    Friction can be a friend or a foe, depending on whether we are trying to brake on a slippery road or to protect moving parts in industrial equipment. It results from the forces between atoms on the two surfaces in contact, but the details of the process are not well understood. Bylinskii et al. constructed a tunable friction simulator out of a handful of cold trapped ions that move in the potential of an optical lattice (see the Perspective by Meyer). They could vary the friction force experienced by the ions from maximal to nearly zero simply by changing the spatial arrangement of the ion array with respect to the optical lattice.

    Science, this issue p. 1115; see also p. 1089

  5. Political Science

    Not getting all sides of the news?

    1. Barbara R. Jasny

    People are increasingly turning away from mass media to social media as a way of learning news and civic information. Bakshy et al. examined the news that millions of Facebook users' peers shared, what information these users were presented with, and what they ultimately consumed (see the Perspective by Lazer). Friends shared substantially less cross-cutting news from sources aligned with an opposing ideology. People encountered roughly 15% less cross-cutting content in news feeds due to algorithmic ranking and clicked through to 70% less of this cross-cutting content. Within the domain of political news encountered in social media, selective exposure appears to drive attention.

    Science, this issue p. 1130; see also p. 1090

  6. Ecophysiology

    Double trouble

    1. Sacha Vignieri

    It is well known that climate change will warm ocean waters, but dissolved oxygen levels also decrease as water warms. Deutsch et al. combined data on metabolism, temperature, and demographics to determine the impact of marine deoxygenation on a variety of fish and crustacean species (see the Perspective by Kleypas). Predicted climate and oxygen conditions can be expected to contract the distribution of marine fish poleward, as equatorward waters become too low in oxygen to support their energy needs. Furthermore, even the more-poleward waters will have reduced oxygen levels.

    Science, this issue p. 1132; see also p. 1086

  7. Cell Biology

    Giving an old organelle the old heave-ho

    1. Paula A. Kiberstis

    Centrioles are ancient cellular organelles that build centrosomes, the major microtubule-organizing centers in animal cells. Duplication of centrioles is tightly controlled to ensure that each dividing cell has precisely two centrosomes. Human cancer cells often have extra centrosomes, which has been hypothesized to confer a proliferative advantage. Wong et al. developed small molecules (centrinones) that allowed them to reversibly “delete” centrioles from cells (see the Perspective by Stearns). Surprisingly, cancer cells continued to divide in the absence of centrosomes, whereas normal cells stopped dividing.

    Science, this issue p. 1155; see also p. 1091

  8. Dinosaur Dentition

    Was triceratops in need of a good dentist?

    1. Barry Pogson

    Reptiles and mammalian herbivores tend to differ in the way their teeth align. Ericksson et al. combined nanomechanics and paleontology to study the dental structure of herbivorous dinosaurs. Triceratops and duckbilled dinosaur teeth evolved for efficient chewing of plant matter, resulting in a dental complexity and tooth wear patterns similar to those seen in mammals.

    Sci. Adv. 10.1126/sciadv.1500055 (2015).

  9. Preeclampsia

    Drugs play a PPARt against preeclampsia

    1. Yevgeniya Nusinovich

    Preeclampsia is a life-threatening complication of pregnancy, with symptoms including high blood pressure and protein in the urine. The underlying causes of preeclampsia are not yet understood. The only effective treatment for preeclampsia is preterm delivery, which poses risks for the child. Holobotovskyy et al. show that a vascular protein called RGS5 plays an important role in the regulation of blood pressure during pregnancy. The absence of this protein caused a preeclampsia-like syndrome in mouse models. The mice were treated effectively with drugs called PPAR agonists, some of which are already approved for use in humans with diabetes.

    Sci. Transl. Med. 7, 290ra8 8 (2015).

  10. Viral Immunology

    Viral exposure—the complete history

    1. Paula A. Kiberstis

    In addition to causing illness, viruses leave indelible footprints behind, because infection permanently alters the immune system. Blood tests that detect antiviral antibodies can provide information about both past and present viral exposures. Typically, such tests measure only one virus at a time. Using a synthetic representation of all human viral peptides, Xu et al. developed a blood test that identifies antibodies against all known human viruses. They studied blood samples from nearly 600 people of differing ages and geographic locations and found that most had been exposed to about 10 viral species over their lifetime. Despite differences in the rates of exposure to specific viruses, the antibody responses in most individuals targeted the same viral epitopes.

    Science, this issue 10.1126/science.aaa0698

  11. Neurodegeneration

    A mouse model for ALS

    1. Stella M. Hurtley

    A G4C2 repeat expansion in C9ORF72 is known to be the major genetic cause of frontotemporal dementia and amyotrophic lateral sclerosis (c9FTD/ALS). However, a lack of animal models recapitulating key disease features has hindered efforts to understand and prevent c9FTD/ALS-related neurodegeneration. Until now. Chew et al. describe a mouse model that mimics both neuropathological and clinical phenotypes of c9FTD/ALS.

    Science, this issue p. 1151

  12. Antibiotics

    New for old—TB drug development

    1. Caroline Ash

    Tuberculosis (TB) is a global health threat for which there is only lengthy drug treatment. Patients need to consume multiple tablets over several months and frequently fail to complete their treatment. Consequently, drug-resistant strains of the pathogen have emerged, which add to the threat. Kling et al. revisited a natural product called griselimycin, extracted from the same organism that produced the prototype anti-TB drug, streptomycin. Unmodified griselimycin has poor pharmacological properties. However, one synthetic derivative had improved oral uptake and penetrated cells of the immune system that harbor the TB mycobacterium. In combination with other drugs, the griselimycin derivative showed high potency in mice with TB.

    Science, this issue p. 1106

  13. Multiferroics

    Visualizing ferroelectric domains

    1. Jelena Stajic

    Multiferroic materials support intertwined ferromagnetic and ferroelectric orders, with the magnetic field capable of controlling the electric order and vice versa. Matsubara et al. used second harmonic generation microscopy to visualize what happens to the ferroelectric domains in the multiferroic TbMnO3 when an externally applied magnetic field changes the direction of electric polarization by 90°. Unexpectedly, the domain walls, initially parallel to the polarization vector, did not change their shape or position. The resulting transition from neutral to charged domain walls may help in the development of future ferroelectric devices.

    Science, this issue p. 1112

  14. Friction

    Slip sliding away

    1. Marc S. Lavine

    Many applications would benefit from ultralow friction conditions to minimize wear on the moving parts such as in hard drives or engines. On the very small scale, ultralow friction has been observed with graphite as a lubricant. Berman et al. achieved superlubricity using graphene in combination with crystalline diamond nanoparticles and diamondlike carbon (see the Perspective by Hone and Carpick). Simulations showed that sliding of the graphene patches around the tiny nanodiamond particles led to nanoscrolls with reduced contact area that slide easily against the amorphous diamondlike carbon surface.

    Science, this issue p. 1118; see also p. 1087

  15. Organic Thin Films

    Standing at order

    1. Phil Szuromi

    Thin films of organic molecules on solid substrates tend to nucleate at many sites and grow multiple domains. However, one large uniform film would be much more desirable in device applications. Seiki et al. designed organic molecules that filled space in a hexagonal tiling; a propeller-like triptycene base adhered to crystalline surfaces and alkyl tails extended away from it. The authors could make well-ordered multilayer films up to centimeter length scales.

    Science, this issue p. 1122

  16. Coral Reefs

    Not as deep

    1. Sacha Vignieri

    As our climate warms, many species ranges are predicted to shift toward the warmer poles. Focusing solely on temperatures, however, ignores many factors that change across latitudes, such as the intensity of solar radiation. Muir et al. looked at global distributions of two groups of reef-building corals (see the Perspective by Kleypas). Most reef-building corals occur deep enough to be protected from surge. However, corals require sunlight to sustain their symbiotic photosynthetic algae. Because solar radiation is more limited farther away from the equator, future populations might be limited to more turbulent shallow waters.

    Science, this issue p. 1135; see also p. 1086

  17. Electron Microscopy

    Pushing the limits of electron microscopy

    1. Valda Vinson

    Recent advances in cryo–electron microscopy (cryo-EM) allow structures of large macromolecules to be determined at near-atomic resolution. So far, though, resolutions approaching 2 Å, where features key to drug design are revealed, remain the province of x-ray crystallography. Bartesaghi et al. achieved a resolution of 2.2 Å for a 465-kD ligand-bound protein complex using cryo-EM. The density map is detailed enough to show close to 800 water molecules, magnesium and sodium ions, and precise side-chain conformations. These results bring routine use of cryo-EM in rational drug design a step closer.

    Science, this issue p. 1147

  18. Aging Stem Cells

    Heterochromatin in aging stem cells

    1. Beverly A. Purnell

    Analysis of human aging syndromes, such as Werner syndrome (WS), may lead to greater understanding of both premature and normal aging. Zhang et al. generated isogenic WS-specific human embryonic stem cell lines (see the Perspective by Brunauer and Kennedy). WS-mesenchymal stem cells displayed features characteristic of premature aging, including heterochromatin disorganization. WRN protein thus functions in the maintenance of heterochromatin, and heterochromatin alterations may represent a driving force of human aging.

    Science, this issue p. 1160; see also p. 1093

  19. Bone Biology

    A scaffold for directing bone breakdown

    1. John F. Foley

    Too much bone breakdown by osteoclasts and not enough bone formation by osteoblasts can lead to osteoporosis. The cytokine RANKL and the kinase p38 stimulate precursor cells in the bone to become osteoclasts. Lin et al. found that the binding of RANKL to its receptor complex recruited the scaffold protein RACK1, leading to the activation of p38. RANKL was less effective at stimulating osteoclast formation and bone loss in those portions of mouse skulls treated to reduce RACK1 levels than in untreated parts. These results provide a potential therapeutic target for osteoporosis.

    Sci. Signal. 8, ra54 (2015).