This Week in Science

Science  30 Sep 2016:
Vol. 353, Issue 6307, pp. 1509
  1. Galactic Structure

    Mapping the local Milky Way

    1. Kip Hodges

    Detailed imaging of the local Milky Way suggests that it may resemble far-away spiral galaxies.

    PHOTOS: (TOP TO BOTTOM) FASLOOFF/ISTOCKPHOTO; NASA/ESA/THE HUBBLE HERITAGE TEAM (STSCI/AURA)

    The spiral structures of far-away galaxies are among the most familiar celestial features. Viewed from within, the structure of our own Milky Way galaxy is harder to appreciate. Interstellar dust also makes it difficult to measure distances between stars in our galaxy with optical astronomy. Using radio astronomy, Xu et al. mapped the nearest spiral arm of the Milky Way in unprecedented detail. This approach helps constrain its size and orientation, as well as the rate of star formation within our galaxy.

    Sci. Adv. 10.1126.sciadv.1600878 (2016).

  2. Signaling

    Organ cross-talk for insulin secretion

    1. Beverly A. Purnell

    Organisms must adapt their growth to changing environmental conditions, such as variations in nutrient access. In Drosophila, dietary amino acids promote the release of insulin-like peptides from the brain, which activate organismic growth. Delanoue et al. show that the peptide Stunted (Sun) is produced by fat cells upon amino acid and TOR signaling. Sun binds to the G protein—coupled receptor Methuselah (Mth) to promote the release of insulin from cells in the brain in response to dietary amino acids. This work demonstrates that cross-talk between organs can modulate insulin levels and ultimately control body size.

    Science, this issue p. 1553

  3. HIV-1 Vaccines

    On the path toward a vaccine

    1. Kristen L. Mueller

    A major goal in combating HIV-1 is the development of a vaccine that can elicit broadly neutralizing antibodies (bNAbs). As bNAbs develop, however, they acquire many somatic mutations, so that they differ substantially in sequence and antigen-binding capability from their germline precursors. To circumvent this challenge, Sok et al. used mice engineered to express the human immunoglobulin locus. Despite the extremely rare frequency of germline precursor antibodies (less than one per mouse), nearly 30% of mice immunized with their germline-targeting immunogen developed a bNAb precursor response. This suggests feasibility in humans, where precursor frequencies are higher.

    Science, this issue p. 1557

  4. Graphene

    Recreating optics in graphene

    1. Jelena Stajic

    Light usually takes the shortest path to propagate between two points. In contrast, electrons in solids experience collisions. To get into a regime that resembles the propagation of light, researchers need very clean materials. Having achieved this regime in graphene, Chen et al. used the bending of electron trajectories in magnetic fields to show that, at a boundary between regions of different carrier densities, electrons “refract” in analogy to the refraction of light. In a related experiment, Lee et al. probed the transport of these ballistic electrons in a superlattice band structure.

    Science, this issue pp. 1522 and 1526

  5. Gene Regulation

    Repairing the breaks you make

    1. Guy Riddihough

    Cyclin A2 is a mammalian cell cycle protein that plays a critical role in DNA replication and mitotic entry. It has been associated with poor clinical outcomes in human tumors. Kanakkanthara et al. show that cyclin A2 binds to the 3′ end of a specific mRNA molecule that codes for the critical DNA repair enzyme Mre11. This binding stimulates the expression of the Mre11 mRNA, thereby coordinating the replication of DNA with the presence of the machinery that repairs DNA lesions caused by replication errors.

    Science, this issue p. 1549

  6. Geophysics

    Rock deformation goes magnetic

    1. Brent Grocholski

    The topography in regions such as the western United States depends on the strength of the crust and lithosphere. To better understand regional tectonic–scale topographic evolution, Liu et al. incorporated magnetotelluric imaging, which relies on electromagnetic fields to investigate subsurface properties, into lithospheric evolution models (see the Perspective by Kaus). This approach constrains the strength and viscosity of Earth's near-surface layer, highlighting how a new data source can shed light on the response of subsurface rock to stress.

    Science, this issue p. 1515; see also p. 1495

  7. Additive Manufacture

    More function with 3D printing

    1. Phil Szuromi

    3D periodic spiral antenna produced through hybrid manufacturing

    PHOTO: DRAPER LABS/MACDONALD ET AL.

    The creation of parts by the guided layer-by-layer deposition of materials, better known as three-dimensional (3D) printing, is often confined to a single material. This can limit the functionality of the fabricated structures. MacDonald and Wicker review methods in 3D printing for integrating dissimilar materials and also for interconnecting active components, such as adding wires to power embedded sensors and motors. Multifunctional capabilities can be enhanced with electronic, mechanical, electromagnetic, and biological components.

    Science, this issue p. 1512

  8. Enhancer Function

    CRISPR editing illuminates function

    1. Laura M. Zahn

    The noncoding regions around a gene tend to control the transcription of protein-coding genes, but the specific elements involved are difficult to determine. Leveraging the editing ability of the CRISPR-Cas9 system, Sanjana et al. tiled guide RNAs across three genes associated with vemurafenib-resistant cancers. This allowed for the coverage of both coding and noncoding sequences in order to identify functional noncoding regions. CRISPR-Cas9 mutagenesis can therefore functionally evaluate noncoding mutations in an unbiased way.

    Science, this issue p. 1545

  9. Cancer Immunology

    Engineering antitumor activity

    1. Leslie K. Ferrarelli

    Dendritic cells present antigens, including those from tumor cells, to T cells to stimulate immune responses. Antitumor vaccines based on injecting dendritic cells, however, have not been effective. Li et al. found that melanoma cells released cytokines that activated a transcriptional pathway that suppressed the antitumor responses of dendritic cells infiltrating the tumors. Vaccination experiments in tumor-bearing mice suggested that injecting dendritic cells engineered to overcome or prevent the response to tumor-derived cytokines might prove to be an effective immunotherapy strategy in cancer patients.

    Sci. Signal. 9, ra94 (2016).

  10. Neurodegeneration

    Receptor propagates protein aggregation

    1. Pamela J. Hines

    The protein α-synuclein, which is abundant in brain neurons, functions as a soluble monomer. Abnormal oligomerization of this protein into insoluble aggregates correlates with Parkinson's disease (PD). The progression of PD may depend on the spread of aggregation from neuron to neuron. Mao et al. show that the neuronal surface protein LAG3 (encoded by lymphocyte-activation gene 3) binds preferentially to multimeric rather than monomeric α-synuclein (see the Perspective by Jucker). Subsequent endocytosis internalizes the multimeric α-synuclein, seeding the aggregation phenomenon in new cells.

    Science, this issue p. 1513; see also p. 1498

  11. Cancer

    A histone brake on tumor growth

    1. Guy Riddihough

    Individual tumors consist of a diverse collection of cells with different propensities to grow uncontrollably. This heterogeneity is often associated with the degree of differentiation of the subpopulations of tumor cells. Morales Torres et al. show that the level of a chromatin protein, linker histone H1.0, underlies the variable differentiation and therefore the growth potential of cancer cell populations. Silencing the H1.0-encoding gene allows tumor cells to self-renew, whereas inducing its high expression promotes differentiation and limits tumor maintenance. These findings suggest how modulating epigenetic states might control tumor growth.

    Science, this issue p. 1514

  12. Protoplanetary Disks

    Spiral arms in a disk around a young star

    1. Keith T. Smith

    A disk of gas and dust orbits around young stars as they form. Eventually, planets can form in such disks. Perez et al. used submillimeter interferometry to observe the protoplanetary disk around the young star Elias 2-27 (see the Perspective by Rice). Emission from the dust shows a spiral pattern within the body of the disk. Studying the structure of protoplanetary disks will help astronomers understand how young stars accrete material and how planets form.

    Science, this issue p. 1519; see also p. 1492

  13. Biodiversity

    Patterns of global genetic diversity

    1. Andrew M. Sugden

    Mapping of global biodiversity has been focused mainly at the species level; the distribution of underlying genetic diversity is less well documented. Miraldo et al. attach geographic coordinates to publicly available mitochondrial DNA sequence data for 4500 species of mammals and amphibians (see the Perspective by Pereira). Genetic diversity is generally higher in the tropics than at higher latitudes and also shows patterns relating to the intensity of human activity. Specifically, amphibians have decreased genetic diversity in heavily affected regions, and mammals have the highest genetic diversity in regions with intermediate human impact. These findings pave the way for a deeper understanding of the impacts of humans on underlying patterns of fundamental biotic diversity.

    Science, this issue p. 1532; see also p. 1494

  14. HIV-1 Infection

    Progression at a standstill

    1. Lindsey Pujanandez

    Although most people that become infected with HIV-1 develop AIDS, rare individuals maintain immune function in the presence of virus. This phenomenon is also seen in natural hosts of the closely related simian immunodeficiency virus (SIV). Muenchhoff et al. describe a cohort of pediatric HIV-1 patients that have normal CD4 T cell counts, despite high viremia and lack of antiviral treatment. These children have low immune activation, including lower expression of chemokine receptor CCR5 on central memory CD4 T cells, similar to sooty mangabeys infected with SIV. The immune mechanisms described in these patients shed light on HIV pathogenesis, which may help in developing treatments.

    Sci. Transl. Med. 8, 358ra125 (2016).

  15. Virology

    Modeling hepatitis A in mice

    1. Kristen L. Mueller

    Although viral hepatitis is a major cause of morbidity worldwide, scientists lack good small-animal models for studying it, especially models that recapitulate virus-caused liver pathology. Hirai-Yuki et al. report a mouse model for infection with hepatitis A virus (HAV). HAV-infected mice lacked type I interferon signaling, causing many symptoms similar to those of acute HAV in humans, including low-grade viremia and cell death and inflammation in the liver. Liver pathology depended on the innate immune signaling protein MAVS and interferon response factors 3 and 7. The use of these mice may provide important insights into the causes of viral hepatitis–dependent pathology in humans.

    Science, this issue p. 1541

  16. Social Memory

    Sites and circuits to recognize friends

    1. Peter Stern

    The ability to recognize and memorize familiar conspecifics is crucial for all social animals. Okuyama et al. found that the ventral hippocampus and its projections to a brain region called the nucleus accumbens are necessary and sufficient for a specific social memory (see the Perspective by Saxena and Morris). Both the number of activated ventral hippocampal neurons and the strength and stability of the responding cells were greater in response to a familiar than to a novel animal. Engram cell identification and manipulation technologies provided strong evidence that a specific population of pyramidal neurons in the ventral hippocampus holds the memory of a familiar animal.

    Science, this issue p. 1536; see also p. 1496

  17. Cognition

    Bees have good moods, too

    1. Sacha Vignieri

    Mood can influence our impression of ambiguous stimuli. Perry et al. show that such emotional-state biases are present in bumblebees, a finding that greatly increases the breadth of taxa in which such emotional influences are found (see the Perspective by Mendl and Paul). Specifically, bees that were given a reward of sugar water before a choice between two neutral cues responded as though the cues were positive stimuli. Further, bees given sugar water were more resilient in the face of a simulated predator attack. The application of a dopamine antagonist eliminated these positive predispositions, suggesting that the mechanism is similar to that found in vertebrates.

    Science, this issue p. 1529; see also p. 1499