This Week in Science

Science  08 Nov 2019:
Vol. 366, Issue 6466, pp. 702
  1. Bioengineering

    Improving access to contraception

    1. Nicholas A. Peppas

    A microneedle array, as seen by scanning electron microscopy

    CREDIT: WEI LI, GEORGIA TECH

    Current long-acting contraceptive methods can be invasive and cumbersome, often restricting patient access to basic, yet critical, health care. Li et al. developed a microneedle patch that simplifies drug delivery and addresses limitations in current contraceptive methods. The patch has an effervescent backing that rapidly separates microneedles from the patch with little to no skin irritation. The patch requires no special intervention by the user, thus potentially providing a more accessible method of contraception.

    Sci. Adv. 10.1126/sciadv.aaw8145 (2019).

  2. Metrology

    Trapped atoms to probe gravity

    1. Ian S. Osborne

    Exploiting the wave nature of atoms in an interferometer setup can be used to provide a precise measure of gravity. The precision is limited to the time scale of the interferometric measurement, which in turn is limited to the distance that the atoms drop, typically just over a couple of seconds for a 10-meter drop tower. Xu et al. describe a trapped atom interferometer in which the interrogation time of the interferometric measurements can be extended to 20 seconds. The new interferometer design and subsequent improved precision can be used to make fundamental tests of general relativity as well as precision measurements of other potentials.

    Science, this issue p. 745

  3. Stem Cells

    Skeletal muscle during homeostasis

    1. Beverly A. Purnell

    Scanning electron microscopy image of developing muscle cells

    CREDIT: DENNIS KUNKEL MICROSCOPY/SCIENCE SOURCE

    Muscle stem cells function in the regeneration of skeletal muscle after injury, but their role in homeostasis is unclear. De Morree et al. show that, in the absence of injury, stem cells in different muscles have different rates of spontaneous activation and fusion, which depend on the level of Pax3 protein (see the Perspective by Xi and Pyle). Regulation of Pax3 protein occurs posttranscriptionally through the small nucleolar RNA U1 and microRNA miR206. This work explains how muscle stem cells are maintained under normal conditions and shows that homeostatic muscle stem cell activation varies in different muscle groups.

    Science, this issue p. 734; see also p. 684

  4. Polymer Chemistry

    Toward less brittle degradable plastic

    1. Jake Yeston

    Bacteria produce a class of polyesters, termed polyhydroxyalkanoates, that are particularly appealing on account of how easily they undergo biodegradation. Unfortunately, these polymers also tend to be overly brittle for many applications. Tang et al. report that a molecular lanthanide catalyst can sequentially polymerize chiral and then achiral diastereomers to form polyhydroxyalkanoate varieties that are substantially more ductile. The catalyst selectively produces these copolymers directly from diastereomeric mixtures of monomers, obviating the need for a wasteful separation process ahead of time.

    Science, this issue p. 754

  5. Air Pollution

    A shifting lifetime for NOx

    1. H. Jesse Smith

    Nitrogen oxides (NOx) have a central role in controlling air quality, so designing effective strategies to combat air pollution, especially by ozone and particulate matter, depends on knowing their atmospheric abundances. Those abundances depend not only on NOx production rates but also on their lifetimes. Laughner and Cohen report that NOx lifetimes can be measured directly from satellite observations of nitrogen dioxide. They used data on 49 North American cities to show how NOx lifetimes there changed between 2005 and 2014. Accounting for this change in lifetime should help to reconcile conflicting trends between bottom-up and top-down emissions estimates.

    Science, this issue p. 723

  6. Galaxies

    Ionizing photons escape a lensed galaxy

    1. Keith T. Smith

    Young, hot stars emit ultraviolet radiation, which can ionize a neutral gas. The first generation of stars converted most of the intergalactic gas in the Universe from neutral to ionized form during the epoch of reionization less than a billion years after the Big Bang. Rivera-Thorsen et al. took advantage of a gravitational lensing system to observe 12 images of the same star-forming region in a distant galaxy and determined the fraction of ultraviolet photons that escape into the intergalactic medium. Although this galaxy is younger than the epoch of reionization, the results provide clues about how ultraviolet photons escape their host galaxies and contribute to the reionization process.

    Science, this issue p. 738

  7. Drug Testing

    Spotting species-specific toxicity

    1. Caitlin Czajka

    Candidate drug testing using standard preclinical models cannot accurately predict which compounds are likely to cause drug-induced liver injury in humans. To improve selection of promising drug candidates, Jang et al. developed Liver-Chips, which consist of rat, dog, or human hepatocytes, endothelial cells, Kupffer cells, and stellate cells. Using the microfluidic chips, the authors confirmed the mechanism of action of several known hepatotoxic drugs and an experimental compound. A second experimental compound that induced fibrosis in rat Liver-Chips did not alter hepatocyte function in human chips, whereas a third compound demonstrated increased toxicity in dog Liver-Chips. Multispecies chips could help identify species-specific differences in drug metabolism and toxicity.

    Sci. Transl. Med. 11, eaax5516 (2019).

  8. Ancient Genomics

    A 10,000-year transect of Roman populations

    1. Laura M. Zahn

    Rome wasn't built (or settled) in a day. Antonio et al. performed an ancestral DNA analysis to investigate the genetic changes that occurred in Rome and central Italy from the Mesolithic into modern times. By examining 127 Roman genomes and their archaeological context, the authors demonstrate a major ancestry shift in the Neolithic between hunter gatherers and farmers. A second ancestry shift is observed in the Bronze Age, likely coinciding with trade and an increased movement of populations. Genetic changes track the historical changes occurring in Rome and reflect gene flow from across the Mediterranean, Europe, and North Africa over time.

    Science, this issue p. 708

  9. Plant Science

    Growing more and better food

    1. Pamela J. Hines

    Increasing human populations demand more productive agriculture, which in turn relies on crop plants adjusted for high-yield systems. Eshed and Lippman review how genetic tuning of the signaling systems that regulate flowering and plant architecture can be applied to crops. Crops that flower sooner might be adaptable to regions with shorter growing seasons, and compact plant shapes might facilitate agricultural management. The universality of these plant hormone systems facilitates application to a range of crops, from the orphan crop teff to the well-known wheat.

    Science, this issue p. eaax0025

  10. Biosynthetic Enzymes

    Moving modules drive biosynthesis

    1. Michael A. Funk

    Modular biosynthesis of small molecules—where enzyme units can be swapped in and out of assembly line complexes to produce desired products—is a distant goal in the lab despite a huge diversity of modular systems in nature. Part of the challenge is in understanding how modules interact and hand off intermediates. Reimer et al. determined crystal structures of portions of a nonribosomal peptide synthetase, including a full dimodule. Module positioning differed between these structures even when the same intermediate was attached to the enzyme. The authors used small-angle x-ray scattering to confirm that large conformational changes are possible during biosynthesis and handoff between modules.

    Science, this issue p. eaaw4388

  11. Ancient Sociology

    Ancient DNA informs on past cultures

    1. Laura M. Zahn

    Archaeology has used analysis of the artifacts and remains of people to uncover their past behaviors and to infer their cultural practices. However, establishing genetic relationships has only recently become possible. Mittnik et al. examined the kinship and inheritance of the remains of people from the German Lech River Valley over a time period spanning the Late Neolithic Corded Ware Culture, the Bell Beaker Complex, the Early Bronze Age, and the Middle Bronze Age (see the Perspective by Feinman and Neitzel). From genetic and archaeological analyses, it was revealed that the Early Bronze Age household's burials over multiple generations consisted of a high-status core family and unrelated low-status individuals. Furthermore, women were not related to the men within the household, suggesting that men stayed within their birth communities in this society, but women did not.

    Science, this issue p. 731; see also p. 682

  12. Geochemistry

    Bound to rock

    1. H. Jesse Smith

    Organic matter binds to phyllosilicates, a process which affects both its transport and chemical stability. How does that affect the fate of terrestrial organic carbon that enters the ocean? Blattmann et al. show that organic carbon derived from soils is stripped from mineral surfaces upon discharge and dispersal into the ocean, whereas organic matter derived from ancient rocks is preserved there. Their results show that preservation of continentally derived organic matter in marine sediments is controlled largely by phyllosilicate mineralogy.

    Science, this issue p. 742

  13. Topological Optics

    Inducing optical spin-orbit coupling

    1. Ian S. Osborne

    The coupling of the spin-orbit interactions in solid-state systems can give rise to a wide range of exotic electronic transport effects. But solid-state systems tend to be somewhat limited in their flexibility because the spin-orbit coupling is fixed. By contrast, optical systems have recently been shown to mimic complex solid-state systems, with flexibility in design providing the ability to control and manipulate the system properties. Using a liquid crystal–filled photonic cavity, Rechcińska et al. emulated an artificial Rashba-Dresselhaus spin-orbit coupling in a photonic system and showed control of an artificial Zeeman splitting. The results illustrate a powerful approach of engineering synthetic Hamiltonians with photons for the simulation of nontrivial condensed matter and quantum phenomena.

    Science, this issue p. 727

  14. Solar Cells

    Maintaining the bandgap

    1. Phil Szuromi

    The bandgap of the black α-phase of formamidinium-based lead triiodide (FAPbI3) is near optimal for creating high-efficiency perovskite solar cells. However, this phase is unstable, and the additives normally used to stabilize this phase at ambient temperature—such as methylammonium, caesium, and bromine—widen its bandgap. Min et al. show that doping of the α-FAPbI3 phase with methylenediammonium dichloride enabled power conversion efficiencies of 23.7%, which were maintained after 600 hours of operation. Unencapsulated devices had high thermal stability and retained >90% efficiency even after annealing for 20 hours at 150°C in air.

    Science, this issue p. 749

  15. Infectious Diseases

    Measles infection prunes B cell memory

    1. Ifor Williams

    Measles virus is a highly infectious lymphotropic virus associated with an extended period of immunosuppression after elimination of the virus. Petrova et al. sequenced the immunoglobulin gene repertoire of naïve and memory B cells in paired pre– and post–measles infection blood samples from unvaccinated children. Memory B cell clones present before infection were depleted in post-measles samples even after lymphocyte counts had recovered, a change not seen in controls that were given a flu vaccination. The naïve B cell repertoire exhibited multiple perturbations after measles infection, including a profound skew toward clones with immature features in ∼10% of the cohort. The B cell repertoire changes documented in this study provide a molecular explanation for the durable “immune amnesia” observed after measles infection in unvaccinated populations.

    Sci. Immunol. 4, eaay6125 (2019).

  16. Immunology

    Fighting fire

    1. Gemma Alderton

    There are numerous cell death pathways. Pyroptosis is a proinflammatory type of cell death that is important in responses to infection as well as to sterile (nonpathogen) insults. In a Perspective, Kayagaki and Dixit discuss recent advances in understanding the pyroptosis pathway and how its prolonged activation can lead to pathogenic inflammation, such as atherosclerotic heart disease. Indeed, preclinical data and clinical observations suggest that inhibiting pyroptosis may have therapeutic potential for inflammatory diseases and some types of cancer.

    Science, this issue p. 688

  17. Metabolism

    Improving metabolism with TFEB

    1. Wei Wong

    TFEB is a transcription factor best known for its role in transcriptionally activating genes encoding autophagy factors. Evans et al. found that mice over-expressing TFEB in adipocytes were protected from the adverse metabolic consequences of a high-fat diet. Adipose tissue browning is a process in which white adipose tissue acquires the energy-burning properties of brown adipose tissue, and TFEB promoted this process through the transcriptional coactivator PGC-1a, rather than the induction of autophagy genes.

    Sci. Signal. 12, eaau2281 (2019).

  18. Psychology

    Cultural evolution

    1. Tage S. Rai

    There is substantial variation in psychological attributes across cultures. Schulz et al. examined whether the spread of Catholicism in Europe generated much of this variation (see the Perspective by Gelfand). In particular, they focus on how the Church broke down extended kin-based institutions and encouraged a nuclear family structure. To do this, the authors developed measures of historical Church exposure and kin-based institutions across populations. These measures accounted for individual differences in 20 psychological outcomes collected in prior studies.

    Science, this issue p. eaau5141; see also p. 686

  19. Cancer

    Seeing double can be a good thing

    1. Paula A. Kiberstis

    Many human breast cancers harbor activating mutations in PIK3CA, the gene coding for the catalytic subunit of phosphoinositide 3-kinase (PI3K). Clinical trials are underway to evaluate the efficacy of PI3K inhibitors in cancer patients. Vasan et al. found unexpectedly that a subset of breast cancers harbor not one—but two—PIK3CA mutations, and the mutations occur on the same allele (see the Perspective by Toker). In model systems, the double mutations hyperactivate PI3K signaling and enhance tumor growth. Preliminary analysis of clinical trial data suggests that breast cancers with double mutations are more responsive to PI3K inhibitors than those with a single mutation. PIK3CA mutational status could help identify the breast cancer patients most likely to benefit from these drugs.

    Science, this issue p. 714; see also p. 685