This Week in Science

Science  10 Oct 2014:
Vol. 346, Issue 6206, pp. 204
  1. Neuroprosthetics

    Restoring sensation to amputated limbs

    1. Orla M. Smith

    Prosthetic hand holds cherry tomato

    CREDITS: (TOP TO BOTTOM) V. ALTOUNIAN/SCIENCE; RUSSELL LEE/RUSSELL LEE PHOTO

    A major challenge for amputees—even those who wear prosthetic limbs—is the loss of sensation from the missing limb. Tan et al. placed a simple electronic cuff around nerves in the upper arm of two amputees to activate the neural pathways responsible for hand sensations. The amputees could then perceive multiple natural sensations in their prosthetic hands and perform fine motor tasks such as picking up soft fruit and pulling the stalks out of cherries.

    Sci. Transl. Med. 6, 257ra138 (2014).

  2. Quantum Processing

    A sound proposition for quantum communication

    1. Ian S. Osborne

    Quantum computers exploit the quantum-mechanical properties of materials to store and manipulate information stored in the quantum states of atoms or artificial atoms. Although there are a number of quantum platforms under investigation already, Gustafsson et al. present another, based on the propagation of sound waves on the surface of a crystal (see the Perspective by Ruskov and Tahan). The ability to tune the system and the slow propagation speeds of the acoustic waves offer new opportunities to control and process quantum information.

    Science, this issue p. 207; see also p. 165

  3. Animal Motion

    What's that coming over the hill—is it a robot?

    1. Marc S. Lavine

    Crossing a slope can be difficult, particularly if it is made of sand. Sidewinder rattlesnakes manage to climb sandy hills by adjusting the length of their body in contact with the sand. Marvi et al. designed robots based on this idea to determine what affects climbing ability on sandy slopes (see the Perspective by Socha). Based on the behavior of the robots, the authors performed further animal studies, and used an iterative approach to improve the robots' capabilities and to better understand animal motion.

    Science, this issue p. 224; see also p. 160

  4. Lung Cancer Evolution

    Space, time, and the lung cancer genome

    1. Paula A. Kiberstis

    Lung cancer poses a formidable challenge to clinical oncologists. It is often detected at a late stage, and most therapies work for only a short time before the tumors resume their relentless growth. Two independent analyses of the human lung cancer genome may help explain why this disease is so resilient (see the Perspective by Govindan). Rather than take a single “snapshot” of the cancer genome, de Bruin et al. and Zhang et al. identified genomic alterations in spatially distinct regions of single lung tumors and used this information to infer the tumor's evolutionary history. Each tumor showed tremendous spatial and temporal diversity in its mutational profiles. Thus, the efficacy of drugs may be short-lived because they destroy only a portion of the tumor.

    Science, this issue p. 251, p. 256; see also p. 169

  5. Planetary Dynamics

    Close planet friends get out of line

    1. Margaret M. Moerchen

    Some “warm” giant exoplanets orbit much closer to their star than do similar planets in our solar system. Dawson and Chiang argue that understanding how such orbits have evolved can answer an outstanding question: How do “hot” giant planets (which are more common than these “warm” ones) get so close to their host star? These planets frequently have giant companions. Numerical simulations revealed that planets with an eccentric giant companion may have just the right mutual inclination for the inner planet to be pushed slowly toward the star. This process could then produce systems with “warm” rather than “hot” Jupiters.

    Science, this issue p. 212

  6. Cell-Free Assays

    Reconstituting the right stuff for division

    1. Stella M. Hurtley

    Cytokinesis, when two daughter cells are physically separated from one another, is the final stage of cell division. How dividing cells assemble a cleavage furrow ready for cytokinesis has long interested cell biologists. A major stumbling block to probing the underlying mechanisms has been the lack of a cell-free and fully controllable experimental system. Now, Nguyen et al. have reconstituted cytokinesis organization outside living cells, using a system derived from frog eggs. In the cell-free system, the cell cycle state is “frozen,” and the spatial scale is unusually large. The authors examined the biophysics involved in signaling during cytokinesis over many minutes and many micrometers using powerful imaging techniques.

    Microtubule asters assembled in vitro

    PHOTO: PHUONG ANH NGUYEN

    Science, this issue p. 244

  7. ADULT NEUROGENESIS

    Astrocytes' hidden ability to generate neurons

    1. Pamela J. Hines

    New neurons could be useful in the brain to respond to damage done by disease, trauma, or just plain age. But the adult brain does not produce many new neurons. Working in mice, Magnusson et al. hunted for intrinsic genetic programs that can help adult brains produce replacement neurons. They found that astrocytes, spidery cells that are interspersed between neurons, carry a latent neurogenic program. The ability to entice astrocytes to replace neurons could obviate the need for neuronal replacement strategies.

    Science, this issue p. 237

  8. Economic Demography

    Adjusting to fewer kids and more elderly

    1. Gilbert Chin

    In many countries, populations are aging as retirees live longer, and the rates of population growth have declined as fewer babies are born. These demographic changes have evoked alarmist predictions that future retirement pensions will need to be curtailed, constraining future generations' purchasing power. Lee et al. point out that compensatory factors, such as more women working more years, along with a better educated workforce, may mitigate these demographic impacts (see the Perspective by Smeeding).

    Science, this issue p. 229; see also p. 163

  9. Conservation

    Needed: Better metrics, rigorously tested

    1. Julia Fahrenkamp-Uppenbrink

    News of species and ecosystems in peril abound around the world. Many governments have made commitments to protect biodiversity. But how well do we understand the changes in our natural environment? Different metrics, such as species abundance and extinction risk, can give very different impressions of conservation success. Collen and Nicholson argue that to be successful, conservation efforts require an agreed set of metrics of biodiversity change. These metrics may include existing as well as new ones and must undergo rigorous testing to ensure that they are suitable for the conservation target that they are used for.

    Science, this issue p. 166

  10. Organic Synthesis

    Sceptrin goes through the looking glass

    1. Jake Yeston

    Marine sponges produce a trio of compounds—sceptrin, massadine, and ageliferin—that have intrigued chemists because they seemed to result from ring-forming reactions outside the standard repertoire of enzyme catalysis. Ma et al. now report laboratory syntheses of the first two compounds that uncover a surprising twist: It turns out the real structure of sceptrin is the mirror image of the originally reported structure. The work partially bolsters the prevailing biosynthetic hypothesis, though its revelation of enantiodivergence (the emergence of distinct mirror-image motifs in one compound class) is a rare event in natural product chemistry.

    Science, this issue p. 219

  11. World Population

    Global population growth continuing

    1. Barbara R. Jasny

    The United Nations released new population projections for all countries in July 2014. Gerland et al. analyzed the data and describe the probabilistic population projections for the entire world as well as individual regions and countries (see the Perspective by Smeeding). World population is likely to continue growing for the rest of the century, with at least a 3.5-fold increase in the population of Africa. Furthermore, the ratio of working-age people to older people is almost certain to decline substantially in all countries, not just currently developed ones.

    Science, this issue p. 234; see also p. 163

  12. Early Universe

    A light leak to transform the universe

    1. Margaret M. Moerchen

    After the universe had cooled into an expanse of neutral gas after the Big Bang, how did the first starlight emerge from the dark? Borthakur et al. found a local starburst galaxy that leaks continuum radiation, which may provide some clues. Wind-generated gaps in the neutral gas enable large fractions of ionizing radiation to escape, possibly mimicking processes in the early universe.

    Science, this issue p. 216

  13. Conservation Targets

    Indicators of progress and decline

    1. Andrew M. Sugden

    The targets set by the Convention on Biological Diversity in 2010 focused international efforts to alleviate global biodiversity decline. However, many of the consequences of these efforts will not be evident by the 2020 deadline agreed to by governments of 150 countries. Tittensor et al. analyzed data on 55 different biodiversity indicators to predict progress toward the 2020 targets—indicators such as protected area coverage, land-use trends, and endangered species status. The analysis pinpoints the problems and areas that will need the most attention in the next few years.

    Science, this issue p. 241

  14. Yeast Meiosis

    Monopolin masterfully manages meiosis

    1. Stella M. Hurtley

    Biologists have wondered for decades how replicated sister chromatids, which normally separate during mitotic cell division, instead comigrate during the first meiotic division, meiosis I. This process segregates chromosomal homologs and is needed to produce haploid gametes after the second, more mitosis-like, meiotic division. One hypothesis for sister chromatid comigration suggests that meiosis I–specific factors directly cross-link the sister kinetochores that attach each sister chromatid to dynamic microtubule tips. Yeast possesses a putative kinetochore cross-linker, known as monopolin, but monopolin's precise role during meiosis I is unknown. Sarangapani et al. isolated functional meiotic kinetochores from yeast cells. They reconstituted kinetochore activity in vitro and found that monopolin causes kinetochore fusion and underlies the sister chromatid comigration seen in meiosis I.

    Science, this issue p. 248

  15. Neuroscience

    Enhancing pain with a growth factor

    1. Leslie K. Ferrarelli

    Muscle injury is associated with inflammation and pain and requires muscle growth to restore damaged tissue. Insulin-like growth factor 1 (IGF-1) stimulates muscle growth. Zhang et al. report that IGF-1 makes sensory neurons more sensitive to painful stimuli. IGF-1 increased the activation of a voltage-gated calcium channel through a G protein–dependent pathway in mouse sensory neurons, which increased neuronal activity. Blocking the G protein–dependent pathway or the calcium channel in sensory neurons prevented increased sensitivity to touch or heat in mice with chronic inflammation. Thus, targeting this pathway may be a therapeutic option for patients with chronic pain.

    Sci. Signal. 7, ra94 (2014).