This Week in Science

Science  09 Feb 2018:
Vol. 359, Issue 6376, pp. 648
  1. Neurodevelopment

    A window on hippocampal neurogenesis

    1. Pamela J. Hines

    Watching the birth and growth of new neurons in the living brain


    Addition of new neurons to the adult brain is key to the hippocampal functions of learning and memory. Pilz et al. labeled individual progenitor cells in the mouse hippocampus and watched them in situ for the next 2 months (see the Perspective by Götz). The results revealed the developmental progression as progenitor cells gave rise to mature cells of the dentate gyrus.

    Science, this issue p. 658; see also p. 639

  2. Psychiatric Genomics

    Genes overlap across psychiatric disease

    1. Laura M. Zahn

    Many genome-wide studies have examined genes associated with a range of neuropsychiatric disorders. However, the degree to which the genetic underpinnings of these diseases differ or overlap is unknown. Gandal et al. performed meta-analyses of transcriptomic studies covering five major psychiatric disorders and compared cases and controls to identify coexpressed gene modules. From this, they found that some psychiatric disorders share global gene expression patterns. This overlap in polygenic traits in neuropsychiatric disorders may allow for better diagnosis and treatment.

    Science, this issue p. 693

  3. Protein Biochemistry

    Interactions of LARKS protein domains

    1. Stella M. Hurtley

    More than 1500 human proteins contain long, disordered stretches of “low complexity”—strings of just a few of the 20 common amino acids. The functions of these low-complexity domains have been unclear. Hughes et al. present atomic-resolution structures that suggest that short segments of two such domains can bind weakly to each other by forming a pair of kinked β-sheets. Because aromatic amino acid side chains stabilize these interactions, the interacting motifs are termed LARKS, for low-complexity, aromatic-rich, kinked segments. Numerous proteins associated with membraneless organelles of biological cells contain low-complexity domains housing multiple LARKS.

    Science, this issue p. 698

  4. Cancer

    Safer without PUMA

    1. Yevgeniya Nusinovich

    Gastrointestinal toxicity is a major cause of side effects from chemotherapy and radiation that can decrease quality of life and limit the dosing of cancer treatments. Tumor suppressor p53 plays a major role in chemotherapy-induced intestinal cell death, but inhibiting p53 is not safe because its loss would worsen cancer growth. Leibowitz et al. blocked only the detrimental function of p53 by inhibiting its downstream effector, PUMA. A small-molecule inhibitor of PUMA protected intestinal cells in mice and in human colon organoids but did not protect cancer cells. The approach may thus provide a viable strategy for intestinal protection in cancer patients.

    Sci. Transl. Med. 10, eaam7610 (2018).

  5. Quantum Optics

    Building up to superradiance, one by one

    1. Ian S. Osborne

    Superradiance is a quantum phenomenon that occurs when emitters are sufficiently close to change spontaneous emission. Controlling the position and state of emitters within an atomic ensemble, however, is technically challenging. Kim et al. show that spatial correlations can be replaced by temporal correlations to achieve superradiance (see the Perspective by Meschede). They dropped prepared atoms into a high-quality optical cavity and found that the number of photons within the cavity built up superradiantly as the atoms dropped through one by one. The method provides a versatile platform for generating nonclassical states of light.

    Science, this issue p. 662; see also p. 641

  6. Cardiovascular Biology

    Protecting the heart by destabilizing mRNA

    1. Wei Wong

    The CCR4-NOT complex removes polyadenylate tails from mRNAs that then undergo degradation. Yamaguchi et al. found that this complex was required to prevent cardiomyocyte death (see the Focus by Das). Mice deficient in a component of this complex had cardiac dysfunction and died of heart failure. Cardiomyocytes from these mice had less deadenylated Atg7 mRNA, which resulted in the activation of cell death–associated genes. These results raise the possibility of cardiovascular side effects for autophagy-promoting drugs, which have been explored for the treatment of various diseases.

    Sci. Signal. 11, eaan3638; see also eaar6364 (2018).

  7. Materials Science

    Crystallography of sensitive materials

    1. Marc S. Lavine

    High-resolution transmission electron microscopy is an invaluable tool for looking at the crystalline structures of many materials. However, the need for high beam doses, especially as a sample is rotated to find the crystal axes, can lead to damage, particularly in fragile materials. Zhang et al. combined a state-of-the-art direct-detection electron-counting camera with ways to limit the overall electron dose to analyze delicate materials such as metal organic frameworks. With this approach, they could see the benzene rings in a UiO-66 linker and the coexistence of ligand-free (metal-exposing) and ligand-capped surfaces in UiO-66 crystals.

    Science, this issue p. 675

  8. Biomechanics

    Making quick turns

    1. Sacha Vignieri

    Hummingbirds are well known for their impressive maneuvering during flight. Dakin et al. used a computer vision approach to characterize the details of flight in >200 hummingbirds from 25 species (see the Perspective by Wainwright). Larger species had enhanced agility owing to increased muscle mass. In all species, muscles dictated transitional movement, whereas wing shape facilitated sharp turns and rapid rotations. Species, and individuals within species, played on their strengths by combining inherent traits and learned skills.

    Science, this issue p. 653; see also p. 636

  9. Quantum Optics

    Connecting quantum emitters

    1. Ian S. Osborne

    Exploiting topological properties of a system allows certain properties to be protected against the disorder and scattering caused by defects. Barik et al. demonstrate a strong light-matter interaction in a topological photonic structure (see the Perspective by Amo). They created topological edge states at the interface between two photonic, topologically distinct regions and coupled them to a single quantum emitter. The chiral nature of single-photon emission was used to inject single photons of opposite polarization into counterpropagating topological edge states. Such a topological quantum optics interface may provide a powerful platform for developing robust integrated quantum optical circuits.

    Science, this issue p. 666; see also p. 638

  10. Synthetic Biology

    Toward programmed therapeutics

    1. Valda Vinson

    Advances in synthetic biology are enabling the development of new gene and cell therapies. Kitada et al. review recent successes in areas such as cancer immunotherapy and stem cell therapy, point out the limitations of current approaches, and describe prospects for using synthetic biology to overcome these challenges. Broader adoption of these therapies requires precise, context-specific control over cellular behavior. Gene circuits can be built to give sophisticated control over cellular behaviors so that therapeutic functions can, for example, be programmed to activate in response to disease biomarkers.

    Science, this issue p. eaad1067

  11. Tissue Regeneration

    Keeping cholesterol at bay

    1. Stella M. Hurtley

    A decline in tissue repair is a universal hallmark of aging. The failure to regenerate myelin sheaths in multiple sclerosis lesions contributes to chronic progressive disease and disability. Understanding the cause and preventing this failure is a key goal in regenerative medicine. Cantuti-Castelvetri et al. report that the self-limiting inflammatory response, which is necessary for remyelination to occur, is maladaptive in the central nervous system (CNS) of old mice (see the Perspective by Chen and Popko). Cholesterol-rich myelin debris overwhelmed the efflux capacity of phagocytes, resulting in a transition of free cholesterol into crystals, thereby inducing lysosomal rupture and inflammasome stimulation. Thus, drugs being developed to promote cholesterol clearance in human atherosclerosis lesions may also be good candidates for regenerative medicine in the CNS.

    Science, this issue p. 684; see also p. 635

  12. Molecular Biology

    Tracking mitotic chromosome formation

    1. Steve Mao

    How cells pack DNA into fully compact, rod-shaped chromosomes during mitosis has fascinated cell biologists for more than a century. Gibcus et al. delineated the conformational transition trajectory from interphase chromatin to mitotic chromosomes minute by minute during the cell cycle. The mitotic chromosome is organized in a spiral staircase architecture in which chromatin loops emanate radially from a centrally located helical scaffold. The molecular machines condensin I and II play distinct roles in these processes: Condensin II is essential for helical winding, whereas condensin I modulates the organization within each helical turn.

    Science, this issue p. eaao6135

  13. Neuroscience

    Stimulating deep inside the brain

    1. Peter Stern

    Noninvasive deep brain stimulation is an important goal in neuroscience and neuroengineering. Optogenetics normally requires the use of a blue laser inserted into the brain. Chen et al. used specialized nanoparticles that can upconvert near-infrared light from outside the brain into the local emission of blue light (see the Perspective by Feliu et al.). They injected these nanoparticles into the ventral tegmental area of the mouse brain and activated channelrhodopsin expressed in dopaminergic neurons with near-infrared light generated outside the skull at a distance of several millimeters. This technique allowed distant near-infrared light to evoke fast increases in dopamine release. The method was also used successfully to evoke fear memories in the dentate gyrus during fear conditioning.

    Science, this issue p. 679; see also p. 633

  14. Optics

    Seeding a laser amplifier

    1. Ian S. Osborne

    Amplification of femtosecond laser pulses requires a lasing medium or a nonlinear crystal. The chemical properties of the lasing medium or adherence to momentum conservation rules in the nonlinear crystal constrain the frequency and the bandwidth of the amplified pulses. Vampa et al. seeded modulation instability in a laser crystal pumped with femtosecond near-infrared pulses. This provided a method for the high gain amplification of broadband and short laser pulses up to intensities of 1 terawatt per square centimeter. The method avoids constraints related to doping and phase matching and can be expected to be applied to a wide pool of glasses and crystals.

    Science, this issue p. 673

  15. Protein Targeting

    When do you really need SRP?

    1. Stella M. Hurtley

    Proteins destined for the cell exterior are recruited during synthesis to the surface of the endoplasmic reticulum (ER) by the signal recognition particle (SRP). The classic view suggests that SRP recognizes signal sequences at the beginning of proteins. Working in yeast, Costa et al. found that many proteins with cleavable signal peptides were efficiently targeted during synthesis in the absence of SRP. In contrast, proteins with internal targeting signals universally depended on SRP and were susceptible to aberrant mitochondrial targeting in its absence. These studies establish the full physiological role of SRP in ensuring accurate and efficient protein targeting in the secretory pathway.

    Science, this issue p. 689

  16. Atmospheric Chemistry

    Do we know the air we breathe indoors?

    1. Julia Fahrenkamp-Uppenbrink

    Many people spend most of their lives indoors, yet air pollution studies tend to focus on outdoor air. In a Perspective, Gligorovski and Abbatt highlight recent advances in understanding the reactions that occur in indoor living environments—for example, owing to smoking and the use of cookstoves and cleaning agents. Even the mere presence of humans in a room changes the air chemistry. Because of these reactions, humans are exposed to a bewildering array of chemicals with little-known health impacts.

    Science, this issue p. 632

  17. Autoimmunity

    At home in the pancreas

    1. Christiana N. Fogg

    Type 1 diabetes (T1D) is associated with enrichment of autoreactive CD8+ T cells that target pancreatic islet cells. Culina et al. studied islet-reactive CD8+ T cells reactive to the zinc transporter 8186–194 (ZnT8186–194) and other islet epitopes in healthy individuals and T1D patients. These epitopes showed equivalent functionality and similar frequencies and naive phenotypes in the peripheral circulation across both groups. In contrast, ZnT8186–194-reactive CD8+ T cells were enriched in the pancreases of T1D patients relative to those of healthy controls and showed cross-reactivity to an epitope from the commensal Bacteroides stercoris. Thus, incomplete central tolerance may allow the survival of these islet-reactive CD8+ T cells in the periphery, and proinflammatory conditions in the islets may contribute to T1D progression.

    Sci. Immunol. 3, eaao4013 (2018).

  18. Neuroscience

    A brain rhythm for speech integration

    1. Kevin S. LaBar

    Spoken communication demands coordination between auditory and motor aspects of language processing. Assaneo and Poeppel measured brain oscillations while humans listened to speech produced at different rates. Neural synchrony across auditory and motor speech areas was selectively enhanced at 4.5 Hz, a frequency corresponding to the mean syllable rate generated across human languages. Neural network simulations validated the findings, revealing an oscillatory mechanism for coupling sensory and motor codes of speech patterning.

    Sci. Adv. 10.1126/sciadv.aao3842 (2018).

  19. Nanomaterials

    Programmed nanoparticle stacking

    1. Phil Szuromi

    A polymer pore template can control the order of assembly of nanoparticles into well-defined stacks and create superlattices. Lin et al. used DNA strands on gold nanoparticles to control interparticle distance. The DNA strands contained modified adenines with more rigid ribose groups that formed stronger base pairs. The height of the stacks of three different types of gold nanoparticle could be changed with different solvents, which in turn changed their optical response.

    Science, this issue p. 669