This Week in Science

Science  09 Sep 2016:
Vol. 353, Issue 6304, pp. 1109
  1. Geophysics

    Filling in the aftershock gap

    1. Brent Grocholski

    Data from large aftershocks help with regional hazard assessment.


    The aftershocks after an earthquake provide important data for future hazard assessments in seismically active regions. Fan and Shearer tackle the challenge of identifying aftershocks that occur within seconds of the main earthquake. It turns out that large dynamically triggered aftershocks—earthquakes caused by the mainshock—are more common than previously recognized.

    Science, this issue p. 1133

  2. Memory

    Assessing the brain's memory storage capacity

    1. Peter Stern

    A hallmark property of the neuronal network in the hippocampus of the brain is its ability to retrieve patterns from partial or noisy cues. This process is called pattern completion. Despite the importance of pattern completion for memory retrieval, its underlying synaptic mechanisms are poorly understood. By simultaneously recording from up to eight neurons, Guzman et al. found sparse connections between CA3 pyramidal cells in the hippocampus and few synaptic contacts. Computational modeling revealed that such concise macroscopic and microscopic connectivity combine to ensure efficient memory storage and retrieval in this brain region.

    Science, this issue p. 1117

  3. Animal Behavior

    Counting up or eyeing the sky?

    1. Sacha Vignieri

    Ants have remarkable navigation abilities. The accurate measurement of distance by ants is thought to be based on counting strides. Previous work indicates that ants can also measure distance by the movement of the landscape past the eyes (optic flow). Pfeffer and Wittlinger capitalized on the distinctive behavior of Cataglyphis ants, which carry their nest mates, to distinguish the relative importance of these strategies. They found that both approaches are used but operate independently, and that carried ants exclusively use optic flow.

    Cataglyphis bicolor with blindfolded eyes


    Science, this issue p. 1155

  4. Inhibitory Synapses

    Identifying synapse-specific proteins

    1. Peter Stern

    Recently, we have seen enormous progress in our understanding of the protein complexes at excitatory synapses. Much less is known about the molecules at inhibitory synapses. Uezu et al. have discovered that many molecules cluster at postsynaptic inhibitory structures to form a network of proteins with, as yet, mostly unknown functions. However, one novel component, called InSyn1, has been found to colocalize with key scaffolding proteins and regulate inhibitory synaptic transmission in hippocampal neurons.

    Science, this issue p. 1123

  5. Organic Chemistry

    A rhodium route from C-H to C-N bonds

    1. Jake Yeston

    Linking nitrogen to the carbons in aryl rings is a common need in pharmaceutical chemistry. To do so, the carbon usually has to be adorned ahead of time with a reactive group, such as bromide. Paudyal et al. report a rhodium-catalyzed reaction that substitutes aryl C-H bonds with nitrogen groups directly to produce a wide variety of aromatic amines. Cleavage of a N-O bond in the nitrogen-bearing precursor drives the reaction with no need for an external oxidant. All of this can be done for both intermolecular and intramolecular couplings.

    Science, this issue p. 1144

  6. Materials Science

    Flexible and lightweight shielding

    1. Marc S. Lavine

    Electromagnetic shielding can be used to isolate devices from outside interference or to protect people from the radiation generated by a device. Shielding usually takes the form of metal sheets, screens, or foams, but often a flexible and lightweight material is preferable. To fulfill this goal, Shahzad et al. have constructed a shielding material from flakes of transition metal carbides embedded in a polymer matrix. A multilayered material improves shielding effectiveness owing to the greater absorption resulting from multiple internal reflections of the electromagnetic waves.

    Science, this issue p. 1137

  7. Internet Access

    Persistent political bias in Internet allocation

    1. Barbara R. Jasny

    Many groups are using the Internet as a way to share information, organize, and increase their influence. However, there is a digital divide that impedes such efforts that cannot be explained by socioeconomic or geographic factors. Weidmann et al. show that ethnic groups who are excluded from political power within countries also have less access to the Internet.

    Science, this issue p. 1151

  8. Cell Migration

    Dissecting collective cell migration

    1. Stella M. Hurtley

    During development or wound healing, cells frequently move in concert. Sunyer et al. describe a mechanism by which clusters of cells respond to a gradient in the stiffness of the extracellular matrix. The same machinery that senses stiffness, the actomyosin cytoskeleton, is responsible for propulsion toward it. This so-called collective durotaxis appears to be a simple and primitive, but nonetheless efficient, mechanism by which clusters of cells migrate.

    Science, this issue p. 1157

  9. Alzheimer's Disease

    Losing memory by protein cleavage

    1. Wei Wong

    Learning and remembering changes the shape of neurons. In mouse models of Alzheimer's disease, neurons do not undergo the morphological changes induced by learning and remembering and they also have defects in calcium signaling. Tong et al. found that forms of presenilin-1 (PS1) with familial Alzheimer's disease-associated mutations excessively cleaved and inactivated the calcium sensor STIM1. The cleavage of STIM1 by PS1 may contribute to the memory loss that is characteristic of Alzheimer's disease.

    Sci. Signal. 9, ra89 (2016).

  10. Cancer

    Standardizing the CAR assembly line

    1. Yevgeniya Nusinovich

    Chimeric antigen receptor-modified T (CAR-T) cells are engineered to recognize specific tumor antigens. They have shown promising results in clinical trials for leukemia, but it has been difficult to predict therapeutic efficacy and toxicity for individual patients. To address this issue, Turtle et al. treated non-Hodgkin's lymphoma patients with CAR-T cells prepared from strictly defined subsets. By carefully controlling the ratio of CD4 to CD8 T cells, treatment conditions can be characterized that correlate with therapeutic response and toxicity, including the drug regimen before CAR-T treatment.

    Sci. Transl. Med. 8, 355ra116 (2016).

  11. Social Sciences

    The many human impacts of climate

    1. Gilbert Chin

    It is now possible to link specific human outcomes to weather events that are drawn from the probability distribution of climate, thanks to high-dimensional data sets and longitudinal analysis. Carleton and Hsiang review recent findings in the areas of human health, economics, social conflict, and demographics, all of which show marks of changes in climate.

    Science, this issue p. 1112

  12. Climate Change

    Improving predictions

    1. Sacha Vignieri

    Climate change is here, and understanding how we might mitigate its effects is a priority. Despite the urgency, attaining an understanding of the responses of complex natural systems to climate is an incredibly challenging venture. In a Review, Urban et al. find that the biggest obstacle to making accurate predictions is a lack of basic data across species. Improved acquisition of such data, in conjunction with improved theoretical models, is vital to understand what may happen to ecosystems under changing climate conditions.

    Science, this issue p. 1113

  13. Macrophages

    How tissue macrophages differentiate

    1. Kristen L. Mueller

    Immune cells called macrophages reside in nearly every organ of the body, where they play roles in pathogen resistance and tissue homeostasis and repair. Although the tissue microenvironment strongly shapes macrophage phenotype and function, all tissue macrophages arise during embryonic development and originate, at least in part, from a common progenitor. Using a variety of techniques, including population-level and single-cell RNA sequencing, Mass et al. find that tissue macrophages in mice stem from a common precursor called a premacrophage, which colonizes the whole embryo 9 to 10 days after conception. Once seeded in tissues, macrophages acquire diverse gene expression profiles.

    Science, this issue p. 1114

  14. Bioengineering

    Building better cellular memories

    1. L. Bryan Ray

    A challenge for bioengineering is to build cellular recording devices that can monitor and store information about the timing and magnitude of events in a living organism. Perli et al. describe an ingenious strategy to adapt CRISPR-Cas-mediated genome editing for this task. They modified the editing mechanism so that small guide RNAs act on the same locus in DNA from which the guide RNAs themselves were transcribed. This causes mutagenesis that increases over time and in proportion to the intensity of a signal and leaves a molecular record of the activity of a specific promoter. Such a system could, for example, provide better insight into the location and timing of events that regulate tumor cells as they grow in vivo.

    Science, this issue p. 1115

  15. Biophysics

    How base pairs stack up

    1. Phil Szuromi

    The interactions between nucleic acid bases include not only the hydrogen bonding between bases but also the π-orbital interactions between base pairs. To probe these interactions, Kilchherr et al. constructed an ensemble of DNA origami structures of blunt-end DNA strands. The forces in the structures between two particles held together only by stacking interactions were determined with optical tweezers. The derived free energy for stacking interactions varied from −0.7 to −3 kcal/mol, depending on base sequences.

    Science, this issue p. 1116

  16. Vaccines

    Zika vaccines protect monkeys

    1. Kristen L. Mueller

    The best way to halt the current Zika virus epidemic would be a protective vaccine. Abbink et al. tested the immunogenicity and protective efficacy of inactivated virus, gene-based, and vector-based vaccines in rhesus monkeys. All three platforms completely protected the animals from infectious Zika virus challenge (see the Perspective by Lipsitch and Cowling). Antibodies isolated from vaccinated animals conferred protection when passively transferred into unvaccinated mice or monkeys, demonstrating the important role that antibodies play in mediating protection. These studies set the stage for the development and testing of Zika virus vaccines for humans.

    Science, this issue p. 1129; see also p. 1094

  17. Geochemistry

    Iron sulfide sails through the Grand Tack

    1. Brent Grocholski

    A long-standing problem in geochemistry is the sequestration of iron-loving elements into the core of early Earth. Rather than causing the observed depletion of these elements in the mantle, Rubie et al. contend that metal segregation during the formation of Earth's core should have increased mantle concentrations. This is because of the high-pressure conditions of core formation that prevailed for Earth when Jupiter was executing its “Grand Tack” through the solar system. The sulfur concentrations in the magma oceans of early Earth became very high during accretion and, as Earth cooled, liquid iron sulfide stripped the mantle of the iron-loving elements, explaining the observed depletion.

    Science, this issue p. 1141

  18. Antibiotic Resistance

    Visualizing evolution in real time

    1. Caroline Ash

    Microbial antibiotic resistance arises in large, complex natural environments over time. Baym et al. developed a large culturing device in which they studied the emergence of resistance over space, time, and increasing antibiotic concentrations (see the Perspective by McNally and Brown). Diverse patterns of mutations always resulted in resistance. Sometimes resistance came with a cost to growth, requiring compensatory mutations to regain fitness. Sometimes mutator phenotypes arose. Unexpectedly, the most fit mutants were not necessarily the lineages that emerged to invade regions with higher antibiotic concentrations. Often, outgrowths trapped even more resistant lineages behind them. This observatory allows regular sampling to monitor rates and sequences of mutation and can be modified for a range of model organisms and evolutionary questions.

    Science, this issue p. 1147; see also p. 1096

  19. Tumor Metabolism

    Putting precision medicine in tissue context

    1. Paula A. Kiberstis

    Cancer patients are often matched to targeted therapies on the basis of the specific driver mutations present in their tumors. For an emerging group of therapies, Mayers et al. find that the metabolism of a target tumor may be a key determinant of its response and may be determined by the tumor's tissue of origin, not mutation status alone (see the Perspective by Vousden and Yang). They traced the fate of branched-chain amino acids (BCAAs) in mouse models of lung and pancreatic cancer that were initiated with identical driver mutations. Lung tumors showed increased uptake and utilization of BCAA nitrogen for amino acid and nucleotide biosynthesis. In contrast, pancreatic tumors showed decreased uptake of free BCAAs. These differences indicate that the tissue of origin shapes tumor metabolism and should be considered when matching patients with therapies.

    Science, this issue p. 1161; see also p. 1095

  20. Ecology

    Reducing the ecosystem impacts of dams

    1. Julia Fahrenkamp-Uppenbrink

    Around the world, tens of thousands of dams regulate river flow and provide electrical power. By altering water and sediment flows, dams influence downstream ecosystems. In a Perspective, Poff and Schmidt explain that negative downstream effects can be ameliorated at low cost by managing either daily or seasonal water releases to make allowances for local ecosystem requirements. For example, avoiding water releases from a dam on the Colorado River for a few weekends each year could help large insects to recover, thereby also providing food for local fishes.

    Science, this issue p. 1099