This Week in Science

Science  12 Jun 2015:
Vol. 348, Issue 6240, pp. 1218
  1. Biogeography

    Emerging patterns in species distribution

    1. Andrew M. Sugden

    Human trade in produce promotes the spread of invasive mollusk species

    CREDIT: © ALENA DUDAEVA /DREAMSTIME

    Human influences are leading to a shift in the geographical distribution of animal species. Capinha et al. compared the distributions of native mollusk species with those introduced to new areas by human activities. The ranges of native species are still broadly constrained by limitations on their capacity for dispersal, whereas those of the introduced aliens are affected more by climate and patterns of human movement. As humans continue to break down barriers to dispersal, more species' distributions will come to be limited by their environmental tolerances.

    Science, this issue p. 1248

  2. Cell Division Cycle

    How cells sense connected chromosomes

    1. L. Bryan Ray

    Cells have a “checkpoint” that pauses cell division until all chromosomes are properly arranged on the mitotic spindle to allow precise distribution of one copy of each chromosome to each daughter cell. Hiruma et al. and Ji et al. explain the molecular mechanism by which cells sense that they are ready to divide. The protein kinase MPS1 associates with a protein complex at the kinetochore of the chromosome. Its activity produces signals that pause the cell cycle. When the chromosome becomes properly attached to the mitotic spindle, microtubules of the spindle physically compete for binding to the same site on the kinetochore where MPS1 is bound. Thus, once the kinetochore is properly attached, MPS1 dissociates, the inhibitory signal is lost, and cell division is allowed to proceed.

    Science, this issue pp. 1264 and 1260

  3. Climate Change

    Change was in the air

    1. H. Jesse Smith

    Atmospheric oxygen concentration variations have affected climate over the past 500 million years

    CREDIT: INTERNATIONAL SPACE STATION/NASA

    The atmospheric fraction of molecular oxygen gas, O2, currently at 21%, is thought to have varied between around 35 and 15% over the past 500 million years. Because O2 is not a greenhouse gas, often this variability has not been considered in studies of climate change. Poulson and Wright show that indirect effects of oxygen abundance, caused by contributions to atmospheric pressure and mean molecular weight, can affect precipitation and atmospheric humidity (see the Perspective by Peppe and Royer). These effects may thus have produced significant changes in the strength of greenhouse forcing by water vapor, surface air temperatures, and the hydrological cycle in the geological past.

    Science, this issue p. 1238; see also p. 1210

  4. Nanomedicine

    Nanoformulation keeps vein grafts healthy

    1. Megan Frisk

    The MK2i peptide is now in clinical trials aimed at halting inflammation and fibrosis after vein grafting. However, low bioavailability and rapid degradation have slowed MK2i's clinical translation. Evans et al. formulated the MK2i peptide in electrostatically complexed nanoparticles. The resulting MK2i-nanopolyplexes entered both vascular smooth muscle and endothelial cells in human veins. Their delivery reduced proinflammatory cytokine levels, vascular smooth muscle cell migration, and neointima formation (i.e., vessel thickening). In rabbit vein grafts, treatment with MK2i-nanopolyplexes, but not free MK2i, prevented intimal hyperplasia for 1 month after transplant. Thus, nanopolyplexes might improve the utility of vein grafts in the longer term.

    Sci. Transl. Med. 7, 291ra95 (2015).

  5. Bioengineering

    Reconstruction of circadian oscillations

    1. Philip Yeagle

    Circadian rhythms are found widely in the tree of life. However, circadian clocks are often difficult to study reductively in their natural organism, in part because of high redundancy within these systems. Silver et al. transplanted a circadian clock from a cyanobacterium into a noncircadian organism, Escherichia coli. Enabling study in a noncircadian organism opens the opportunity to molecularly dissect the clock and suggests ways to engineer time-dependent biological circuits.

    Sci. Adv. 10.1126.sciadv.1500358 (2015).

  6. Induced Seismicity

    How to observe fault injections in real time

    1. Brent Grocholski

    Faults in the ground are known to deform in response to procedures such as wastewater injection that change the pore pressure. Guglielmi et al. took a crack at monitoring this process in real time with a controlled fluid injection into an inactive fault (see the Perspective by Cornet). Reactivating the dead fault induced aseismic slip, which triggered small earthquakes. These observations can inform models of how friction is related to slip rate. The technique can also be applied to field-scale monitoring of seismicity-inducing wastewater injections.

    Science, this issue p. 1224; see also p. 1204

  7. Physiology

    Receptor in the brain controls breathing

    1. L. Bryan Ray

    Control of breathing in mammals depends primarily not on sensing oxygen, but rather on detecting concentrations of carbon dioxide in the blood. Failure of this system can cause potentially deadly sleep apnias. Taking a hint from insects, which use a heterotrimeric guanine nucleotide–binding protein-coupled receptor (GPCR) to sense carbon dioxide, Kumar et al. demonstrate that the GPCR GPR4 is essential to control breathing in mice. GPR4 senses protons generated by the formation of carbonic acid in the blood and works with a pH-sensitive potassium channel called TASK-2 in a set of brain cells that control breathing.

    Science, this issue p. 1255

  8. Solar Cells

    Taking in more sun

    1. Phil Szuromi

    Most efforts to grow superior films of organic-inorganic perovskites for solar cells have focused on methylammonium lead iodide (MAPbI3). However, formamidinium lead iodide (FAPbI3) has a broader solar absorption spectrum that could ultimately lead to better performance. Yang et al. grew high-quality FAPbI3 films by starting with a film of lead iodide and dimethylsulfoxide (DMSO) and then exchanging the DMSO with formamidinium iodide. Their best devices achieved power conversion efficiencies exceeding 20%.

    Science, this issue p. 1234

  9. Electrochemistry

    Molybdenum doping drives high activity

    1. Phil Szuromi

    Platinum (Pt) is an effective catalyst of the oxygen reduction reaction in fuel cells but is scarce. One approach to extend Pt availability is to alloy it with more abundant metals such as nickel (Ni). Although these catalysts can be highly active, they are often not durable because of Ni loss. Huang et al. show that doping the surface of octahedral Pt3Ni nanocrystals with molybdenum not only leads to high activity (∼80 times that of a commercial catalyst) but enhances their stability.

    Science, this issue p. 1230

  10. Nanomaterials

    Quality manufacture beats quality control

    1. Marc S. Lavine

    For semiconductor nanocrystals, tight control over particle size is needed to obtain particles with uniform properties. However, post-synthesis purification methods can be difficult and costly. Hendricks et al. present a family of substituted thioureas as a class of chalcogen precursors (see the Perspective by Hens). The rate of reactivity is connected to the specific chemistry of the precursor, making it possible to synthesize metal chalcogenide nanocrystals, such as PbS, with a specific size, narrow size distribution, and full conversion of the reactants.

    Science, this issue p. 1226; see also p. 1211

  11. Insect Flight

    Not too fast and not too slow

    1. Sacha Vignieri

    Moths are typically active during dawn and dusk when light levels are low and vision is challenging. Slower visual response times can allow for greater light sensitivity, but flying insects are both moving and tracking moving targets, making such tradeoffs potentially problematic. Using a combination of modeling and experiments, Sponberg et al. show that moths are able to avoid this potential decrease in visual acuity (see the Perspective by Warrant). This is because the point at which their perception of movement would be compromised is just above the natural frequency at which flowers sway. Thus, insect vision is precisely adapted to the light and movement conditions of their environment.

    Science, this issue p. 1245; see also p. 1212

  12. Ecology

    A brave new world with a wider view

    1. Sacha Vignieri

    Researchers have long attempted to follow animals as they move through their environment. Until relatively recently, however, such efforts were limited to short distances and times in species large enough to carry large batteries and transmitters. New technologies have opened up new frontiers in animal tracking remote data collection. Hussey et al. review the unique directions such efforts have taken for marine systems, while Kays et al. review recent advances for terrestrial species. We have entered a new era of animal ecology, where animals act as both subjects and samplers of their environments.

    Science, this issue 10.1126/science.1255642, 10.1126/science.aaa2478

  13. Tissue Regeneration

    A shot in the arm for damaged tissue

    1. Paula A. Kiberstis

    Tissue damage can be caused by injury, disease, and even certain medical treatments. There is great interest in identifying drugs that accelerate tissue regeneration and recovery, especially drugs that might benefit multiple organ systems. Zhang et al. describe a compound with this desired activity, at least in mice (see the Perspective by FitzGerald). SW033291 promotes recovery of the hematopoietic system after bone marrow transplantation, prevents the development of ulcerative colitis in the intestine, and accelerates liver regeneration after hepatic surgery. It acts by inhibiting an enzyme that degrades prostaglandins, lipid signaling molecules that have been implicated in tissue stem cell maintenance.

    Science, this issue 10.1126/science.aaa2340; see also p. 1208

  14. Brain Networks

    Cooperating brain regions express similar genes

    1. Peter Stern

    When the brain is at rest, a number of distinct areas are functionally connected. They tend to be organized in networks. Richiardi et al. compared brain imaging and gene expression data to build computational models of these networks. These functional networks are underpinned by the correlated expression of a core set of 161 genes. In this set, genes coding for ion channels and other synaptic functions such as neurotransmitter release dominate.

    Science, this issue p. 1241

  15. Innate Immunity

    Detecting Gram-negative bacteria

    1. Kristen L. Mueller

    Invariant molecules specific to different classes of microbes, but not expressed by eukaryotic cells, alert the immune system to a potential invader. Gaudet et al. identified one such molecule expressed by a variety of Gram-negative bacteria: the monosaccharide heptose-1,7-bisphosphate (HBP) (see the Perspective by Brubaker and Monack). HBP is an intermediate in the synthesis of lipopolysaccharide, a major component of bacterial cell walls. Rather than alerting the immune system through traditional pathogen detection pathways, such as Toll-like receptors, HBP signals through the host protein TIFA (TRAF-interacting protein with forkhead-associated domain), which activates both innate and adaptive immune responses to control the infection.

    Science, this issue p. 1251; see also p. 1207

  16. Sex Determination

    Manipulating M factor alters mosquito sex

    1. Beverly A. Purnell

    Female mosquitoes feed on blood and in so doing transmit pathogens to millions annually. Although the molecular mechanism for determining sex in many animals is known, the specific factors in mosquitoes have been elusive. This is because sex determination in insects involves a section of the genome that is highly repetitive. Hall et al. now identify a male-determining factor (M factor) in Aedes aegypti. Manipulation of the M factor produced sex-change phenotypes. Knocking out the gene Nix resulted in feminized males, and ectopic expression gave masculinized females. These findings should help to advance strategies for converting female mosquitoes into nonbiting males.

    Science, this issue p. 1268

  17. Biochemistry

    SUMO switching for degradation

    1. Wei Wong

    Acute promyelocytic leukemia is caused by a fusion protein, a portion of which is the nuclear protein PML. Arsenic trioxide chemotherapy triggers the degradation of this fusion protein through modification of the PML portion. Fasci et al. found that under basal conditions, SUMO2 was constantly added to and removed from a specific lysine residue in PML. In cells exposed to arsenic trioxide, SUMO1, rather than SUMO2, was conjugated to this residue (which the authors called the “switch” residue), leading to the formation of SUMO2 chains on a different lysine residue (the “chain” residue) and the ubiquitylation and breakdown of PML.

    Sci. Signal. 8, ra56 (2015).