This Week in Science

Science  16 Mar 2018:
Vol. 359, Issue 6381, pp. 1227
  1. Fisheries

    Healthy fisheries can reduce bycatch

    1. Sacha Vignieri

    Fishing may accidentally capture endangered species such as this green sea turtle.


    Bycatch of marine mammals, turtles, and birds during commercial fishing is a considerable threat. Activities intended to reduce bycatch are often thought to conflict with commercial fishing. However, Burgess et al. show that in the majority of cases, managing fishery stocks to best promote long-term sustainability would also reduce bycatch. Rebuilding fish stocks will naturally promote lower bycatch, and these factors together will facilitate sustainable profit generation from fish harvest.

    Science, this issue p. 1255

  2. Induced Seismicity

    Injection depth matters for induced earthquakes

    1. Brent Grocholski

    Wastewater injection has induced earthquakes in Oklahoma, but the relative importance of operational and geologic parameters in triggering such earthquakes is unclear. Hincks et al. developed an advanced Bayesian network to determine the interplay between these parameters in Oklahoma. The injection depth above the crystalline basement was the most important parameter when considering the potential for release of seismic energy. This modeling strategy may provide a way to improve forecasts of the impact of proposed regulatory changes on induced seismicity.

    Science, this issue p. 1251

  3. Surface Chemistry

    Watching graphene grow

    1. Phil Szuromi

    The growth of graphene on metal surfaces can be catalyzed by mobile surface metal atoms. Patera et al. used a high-speed scanning tunneling microscope to image the growth of graphene islands on a nickel surface. High temperatures caused carbon to diffuse to the surface, where mobile nickel atoms catalyzed graphene growth on the edges of islands. Molecular dynamics and density functional theory calculations provide mechanistic insights into the reaction steps.

    Science, this issue p. 1243

  4. Polymers

    Mimicking the designs found in proteins

    1. Marc S. Lavine

    Natural proteins combine a range of useful features, including chemical diversity, the ability to rapidly switch between preprogrammed shapes, and a hierarchy of structures. Panganiban et al. designed random copolymers with polar and nonpolar groups, using many of the features found in proteins (see the Perspective by Alexander-Katz and Van Lehn). Their structures could serve as “broad spectrum” surfactants, able to promote the solubilization of proteins in organic solvents and help preserve the functionality of proteins in aqueous environments.

    Science, this issue p. 1239; see also p. 1216

  5. Cognitive Science

    The infant as philosopher

    1. Gilbert Chin,
    2. Andrew M. Sugden

    Visual behaviors, such as a shift in one's gaze or a prolonged stare, can be diagnostic of internal thoughts. Cesana-Arlotti et al. used these measures to demonstrate that preverbal infants can formulate a logical structure called a disjunctive syllogism (see the Perspective by Halberda). That is, if A or B is true, and A is false, then B must be true. Presenting infants with scenes where the outcome revealed B to be false evoked looks of surprise.

    Science, this issue p. 1263; see also p. 1214

  6. Neurodevelopment

    Call to action

    1. Pamela J. Hines

    The developing brain initially makes more synapses than it needs. With further development, excess synapses are pruned away, leaving mature circuits. Synapses can be eliminated by microglia, which engulf and destroy them. Vainchtein et al. found that the microglia are called into action by astrocytes, supportive cells on which neurons rely. Astrocytes near a redundant synapse release the cytokine interleukin-33 (IL-33), which recruits microglia to the site. In mice, disruptions in this process, as caused by deficiency in IL-33, led to too many excitatory synapses and overactive brain circuitry.

    Science, this issue p. 1269

  7. Soft Robots

    Robots reach out

    1. Rachel Kline

    Flying robot with folded (left) and extended (right) arm


    Unmanned aerial vehicles (UAVs) sometimes need to reach into confined spaces. Previous foldable robotic arms have been too flexible to be practical. Kim et al. created a modular, origami-inspired robotic arm with a locking mechanism based on the idea that when two folds intersect at a right angle, only one can be folded at a time. This allowed tendon-based actuation by a single electric motor and enabled a UAV to grasp objects in a narrow space and insert a camera among tree branches.

    Sci. Robot. 3, eaar2915 (2018).

  8. Aging

    Lysosomes keep neuronal stem cells young

    1. L. Bryan Ray

    An important consequence of aging is loss of regenerative capacity in stem cells, particularly those of the nervous system. Leeman et al. isolated quiescent and activated stem cells from mice and compared their transcriptomes. The findings emphasize the role of large lysosomes in quiescent neuronal stem cells in which aggregated proteins accumulate. Treatments that stimulated lysosomal function allowed aged quiescent stem cells to clear protein aggregates and restored the cells' ability to be activated. Such restoration of stem cell function might alleviate compromised proteostasis in aging.

    Science, this issue p. 1277

  9. Neurotechnology

    Good vibrations for movement perception

    1. Mattia Maroso

    Because prostheses do not provide physical feedback during movement, amputees may not feel that they are in full control of their bodily action. Marasco et al. developed an automated neural-machine interface that vibrates the muscles used for the control of prosthetic hands. This system instilled kinesthetic sense in amputees, allowing them to control prosthetic hand movements in the absence of visual feedback and increasing their sense of control.

    Sci. Transl. Med. 10, eaao6990 (2018).

  10. Topological Photonics

    Topological protection for lasers

    1. Ian S. Osborne

    Ideas based on topology, initially developed in mathematics to describe the properties of geometric space under deformations, are now finding application in materials, electronics, and optics. The main driver is topological protection, a property that provides stability to a system even in the presence of defects. Harari et al. outline a theoretical proposal that carries such ideas over to geometrically designed laser cavities. The lasing mode is confined to the topological edge state of the cavity structure. Bandres et al. implemented those ideas to fabricate a topological insulator laser with an array of ring resonators. The results demonstrate a powerful platform for developing new laser systems.

    Science, this issue p. eaar4003, p. eaar4005

  11. Circadian Rhythms

    Daily transcription cycling in the baboon

    1. L. Bryan Ray

    Much of our knowledge about the important effects of circadian rhythms in physiology comes from studies of mice, which are nocturnal. Mure et al. report transcriptional profiles from many tissues and brain regions in baboons over a 24-hour period (see the Perspective by Millius and Ueda). The results emphasize how extensive rhythmic expression is, with more than 80% of protein-coding genes involved. They also highlight unanticipated differences between the mouse and baboon in the cycling of transcripts in various tissues. The findings provide a comprehensive analysis of circadian variation in gene expression for a diurnal animal closely related to humans.

    Science, this issue p. eaao0318; see also p. 1210

  12. Human Genomics

    Hidden effects of Mendelian inheritance

    1. Laura M. Zahn

    Identifying the determinate factors of genetic disease has been quite successful for Mendelian inheritance of large-effect pathogenic variants. In these cases, two non- or low-functioning genes contribute to disease. However, Mendelian effects of lesser strength have generally been ignored when looking at genomic consequences in human health. Bastarache et al. used electronic records to identify the phenotypic effects of previously unidentified Mendelian variations. Their analysis suggests that individuals with undiagnosed Mendelian diseases may be more prevalent in the general population than assumed. Because of this, genetic analysis may be able to assist clinicians in arriving at a diagnosis.

    Science, this issue p. 1233

  13. Enzymology

    A quick freeze shows an enzyme's secrets

    1. Michael A. Funk

    Organic radicals are chemically useful in enzymatic reactions but are often hard to observe, owing to their short lifetimes. Dong et al. used rapid freeze-quench methods to trap two intermediates formed by a noncanonical radical S-adenosylmethionine (SAM) enzyme: a fragmented SAM molecule bound to the iron-sulfur cluster through an iron-carbon bond and a product-like radical. The structure of the SAM-bound enzyme reveals a noncolinear arrangement of carbon, sulfur, and iron atoms. The arrangement of bonds suggests that the organometallic intermediate may be created through a two-electron nucleophilic mechanism. A subsequent radical intermediate is formed on the protein substrate and resolves by oxidation to form the amino acid product diphthamide.

    Science, this issue p. 1247

  14. Nitrogen Cycle

    Stream physics set the limits

    1. H. Jesse Smith

    A combination of physical transport processes and biologically mediated reactions in streams and their sediments removes dissolved inorganic nitrogen (DIN) from the water. Although stream chemistry and biology have been considered the dominant controls on how quickly DIN is removed, Grant et al. show that physics is what sets the limits on removal rates of nitrate (a component of DIN). Residence time in the hyporheic zone (the region below the sediment surface where groundwater and surface water mix) determines the maximum rate at which nitrate can be removed from stream water. Nevertheless, at local scales, chemistry and biology modify how closely to that maximum rate removal occurs.

    Science, this issue p. 1266

  15. Malaria

    Sexual development in Plasmodium

    1. Caroline Ash

    Malaria-causing parasites (Plasmodium) have complex life histories in the tissues of humans. For the most part, the parasites focus their efforts on replication within the human host cells. However, occasionally, some replicating cells release gametes into the bloodstream, which are picked up by biting mosquitoes. Filarsky et al. discovered that the Plasmodium parasite keeps the production of gametes under tight epigenetic control using heterochromatin protein 1 (HP1). Plasmodium gametocytogenesis is initiated when HP1 is evicted from upstream of gamete-specific genes by gametocyte development 1 (GDV1) protein. GDV1 is in turn regulated by its antisense RNA. What triggers GDV1 expression remains unclear. Elucidating this pathway could provide a target for interrupting malaria transmission.

    Science, this issue p. 1259

  16. Circadian Rhythms

    Chromosome dynamics and cellular clocks

    1. L. Bryan Ray

    Many genes undergo daily or circadian changes in their rate of transcription. Kim et al. explored the mechanism by which the circadian clock is linked to chromosome dynamics (see the Perspective by Diettrich Mallet de Lima and Göndör). They used a chromosome conformation capture technique (Hi-C) to identify the interactions of adjacent DNA fragments and determine how DNA looping that altered such interactions changed over daily cycles. The repressive transcription factor Rev-erbα, which functions as part of the mammalian clock mechanism, appears to bind to chromatin and recruit a protein complex that evicts other proteins that enhance looping, thus favoring enhancer-promoter interactions.

    Science, this issue p. 1274; see also p. 1212

  17. Single-Cell Analysis

    Mutation rates and effects in single cells

    1. Laura M. Zahn

    Understanding the dynamics of mutations and the distribution of fitness effects is critical for most evolutionary models. Robert et al. used a single-cell technology to visualize the accumulation of new mutations. The method identifies DNA sequences with mispaired bases and small insertions or deletions caused by DNA replication errors in living Escherichia coli cells. Following the fates of cells after mutation allowed for a precise quantification of the effects of new mutations. A smaller fraction of mutations were found to be deleterious than predicted previously from indirect observations.

    Science, this issue p. 1283

  18. Cancer Therapy

    A new target induces synthetic lethality

    1. Gemma Alderton

    Identifying mutations that can be targeted to cause tumor cell death selectively in a process known as synthetic lethality has become a paradigm of cancer research. Loss of DNA repair can provide a selective growth advantage to tumor cells by enhancing mutation rates and driving tumor evolution. In a Perspective, Higgins and Boulton discuss how the DNA damage response protein known as DNA polymerase θ is increased in certain tumors, such as those found in breast and ovarian cancers. This pathway represents an exciting anticancer target that could perhaps be combined with radiotherapy to improve therapeutic response.

    Science, this issue p. 1217

  19. Ecology

    How animals navigate infection risk

    1. Julia Fahrenkamp-Uppenbrink

    Ecologists have long recognized how fear of predators affects animal behavior. In a Perspective, Weinstein et al. highlight the importance of another factor: infection risk. Using examples from a range of animals, they show how the disgust triggered by potential sources of infection affects animal behavior. Understanding how animals respond to the overlapping landscapes of predation and infection risk is crucial for predicting how ecosystems respond to changing environments.

    Science, this issue p. 1213

  20. Immunology

    A psoriasis target in Langerhans cells

    1. Erin Williams

    Psoriasis is an autoimmune skin condition that is linked to the proinflammatory cytokine interleukin-17 (IL-17), which is produced by T cells in the skin. Zheng et al. found that p38α signaling in skin-resident dendritic cells (Langerhans cells) was important for the pathogenesis of psoriasis in a mouse model of the disease. p38α signaling in Langerhans cells stimulated the production of IL-23, which is critical for the development of IL-17–producing T cells. Genetic deletion or pharmacological inhibition of p38α reduced skin inflammation in mice with established psoriatic disease.

    Sci. Signal. 11, eaao1685 (2018).

  21. Infectious Disease

    Structural insights into RSV

    1. Christiana N. Fogg

    Respiratory syncytial virus (RSV) causes respiratory infections associated with severe morbidity and mortality in infants, young children, and the elderly. No licensed vaccine against this disease exists. Fedechkin et al. describe cocrystal structures of the RSV G glycoprotein conserved central domain (CCD) bound by two different broadly neutralizing monoclonal antibodies (mAbs). Both mAbs bind to conformational epitopes on this highly conserved region. The RSV G CCD can activate the chemokine receptor CX3CR1, and this activity can be blocked by binding of the mAbs. These findings provide insight into how neutralizing mAbs interact with the RSV G glycoprotein and may advance the development of RSV vaccines and therapeutics.

    Sci. Immunol. 3, eaar3534 (2018).

  22. Neuroscience

    MHCI suppresses relapse

    1. Kevin S. LaBar

    Relapse is a persistent problem in the treatment of drug addiction and carries a great personal and societal cost. Murakami et al. discovered a molecular mechanism that suppresses relapse to cocaine addiction in mice. In a transgenic mouse model, cocaine self-administration reduced major histocompatibility complex class I (MHCI) levels in the brain's reward system, enhanced glutamate signaling, and led to behavioral relapse. Up- or down-regulating genes that influence the function of MHCI in dopamine neurons prevented or promoted this addictive profile.

    Sci. Adv. 10.1126/sciadv.aap7388 (2018).