This Week in Science

Science  15 Mar 2019:
Vol. 363, Issue 6432, pp. 1187
  1. Forest Ecology

    Herbivores shape tropical forests

    1. Andrew M. Sugden

    Letis mycerina larva feeding on Inga thibaudiana leaves.

    PHOTO: MARIA-JOSE ENDARA

    In tropical forests, high local tree diversity is driven by negative density dependence, a process whereby plant performance is inhibited by closely related neighbors. Negative density dependence could be caused by competition for resources among neighbors or result from shared herbivores and pathogens. Using data from forest plots in Panama, Forrister et al. compared the contributions of these mechanisms. They found no effect of competition, but strong effects of plant chemistry and shared herbivores on coexisting Inga tree species.

    Science, this issue p. 1213

  2. Climate Change

    The state of ocean CO2 uptake

    1. H. Jesse Smith

    The ocean is an important sink for anthropogenic CO2 and has absorbed roughly 30% of our emissions between the beginning of the industrial revolution and the mid-1990s. This effect is an important moderator of climate change, but can we count on it to remain as strong in the future? Gruber et al. calculated the ocean uptake of anthropogenic CO2 for the interval from 1994 to 2007, which continued as expected. They also observed clear regional deviations from this pattern, suggesting that there is no guarantee that uptake will remain as robust with time.

    Science, this issue p. 1193

  3. Piezoelectrics

    A flexible strategy for piezoelectrics

    1. Brent Grocholski

    Piezoelectric materials produce charge when they are deformed, making them ideal for various types of sensors. However, virtually all piezoelectric materials are ceramics, which are far from ideal for applications requiring flexible sensors. Liao et al. now describe a molecular material with piezoelectric properties comparable to the industry-standard ceramic lead zirconate titanate. The exceptional properties come from finding a molecular solid-solution series that allows for compositional optimization of the piezoelectric properties.

    Science, this issue p. 1206

  4. Signal Transduction

    Defective degradation as disease mechanism

    1. L. Bryan Ray

    Ubiquitination often targets proteins for destruction. Castel et al. describe a mechanism by which mutations in the small guanine triphosphatase RIT1 may act to cause certain developmental disorders and cancers. They detected a protein, LZTR1, that interacted with wild-type RIT1 but not with oncogenic mutant forms of RIT1. LZTR1 acts as a substrate-specific adaptor for a ubiquitin ligase. Altered forms of RIT1 that are not subject to ubiquitin-mediated degradation thus accumulate. Because RIT1 functions in growth factor signaling and excessive signaling, these findings may explain the malignancies associated with RIT1 mutations.

    Science, this issue p. 1226

  5. Population Genetics

    Genomics of the Iberian Peninsula

    1. Laura M. Zahn

    Ancient DNA studies have begun to help us understand the genetic history and movements of people across the globe. Focusing on the Iberian Peninsula, Olalde et al. report genome-wide data from 271 ancient individuals from Iberia (see the Perspective by Vander Linden). The findings provide a comprehensive genetic time transect of the region. Linguistics analysis and genetic analysis of archaeological human remains dating from about 7000 years ago to the present elucidate the genetic impact of prehistoric and historic migrations from Europe and North Africa.

    Science, this issue p. 1230; see also p. 1153

  6. Transplantation

    Transplanted memories

    1. Anand Balasubramani

    Parabiosis experiments in mice have shaped our understanding of the tissue-retention properties of tissue-resident memory T cells (TRM). Snyder et al. studied donor and recipient T cells in human lung transplant patients. Their results provide a rare glimpse into the generation and maintenance of human TRM. Whereas donor T cells were barely detectable in blood within 10 weeks after transplantation, donor TRM were abundant and persisted in transplanted lungs for more than a year. Recipient T cells infiltrating the lung gradually acquired TRM profiles over time. In this 20-patient cohort, persistence of donor lung TRM correlated with improved clinical outcome.

    Sci. Immunol. 4, eaav5581 (2019).

  7. Neurodegeneration

    Manganese spreads neurodegeneration

    1. Leslie K. Ferrarelli

    Chronic exposure to high amounts of manganese, such as that experienced by welders, is associated with symptoms of Parkinson's disease. A hallmark of the disease is aggregation of the protein α-synuclein, which is toxic to neurons. Harischandra et al. found that exosomes isolated from serum collected from welders contained misfolded α-synuclein. In cultured cells and mouse models, exposure to manganese or isolated manganese-induced exosomes promoted the transfer of α-synuclein between neurons and microglia, which induced inflammation and neuronal cell death.

    Sci. Signal. 12, eaau4543 (2019).

  8. Quantum Dots

    Superefficient light emission

    1. Marc S. Lavine

    A challenge to improving synthesis methods for superefficient light-emitting semiconductor nanoparticles is that current analytical methods cannot measure efficiencies above 99%. Hanifi et al. used photothermal deflection spectroscopy to measure very small nonradiative decay components in quantum dot photoluminescence. The method allowed them to tune the synthesis of CdSe/CdS quantum dots so that the external luminescent efficiencies exceeded 99.5%. This is important for applications that require an absolute minimum amount of photon energy to be lost as heat, such as photovoltaic luminescent concentrators.

    Science, this issue p. 1199

  9. Reproductive Biology

    Mysterious males

    1. Sacha Vignieri

    In parthenogenetic species, females produce female offspring, generally without the input of males. Given this, the production of males would seem to be a waste of resources. Grosmaire et al. report that in a particular soil nematode, males are regularly produced at a rate of about 9%. They found that the male sperm was required for egg activation, yet the sperm DNA never transmitted on to the subsequent female generation. Male DNA was only passed on through sibling mating, which allows for male production to be evolutionarily stable.

    Science, this issue p. 1210

  10. Immunology

    Tissue macrophages have a split personality

    1. Seth Thomas Scanlon

    Resident tissue macrophages (RTMs) reside in various tissue-specific niches during development. They evince microenvironment-directed phenotypes that support host defense and tissue homeostasis. Chakarov et al. used single-cell RNA sequencing and fate-mapping of murine lung RTMs to interrogate RTM-subset heterogeneity, interrelationships, and ontogeny (see the Perspective by Mildner and Yona). In addition to alveolar macrophages, they identified two different interstitial macrophage populations. One population mostly abutted nerve fibers; the other population preferentially localized near blood vessels and appeared to support vessel integrity and inhibit inflammatory cell infiltration into tissues.

    Science, this issue p. eaau0964; see also p. 1154

  11. Anthropology

    The first fricatives

    1. Andrew M. Sugden

    In 1985, the linguist Charles Hockett proposed that the use of teeth and jaws as tools in hunter-gatherer populations makes consonants produced with lower lip and upper teeth (“f” and “v” sounds) hard to produce. He thus conjectured that these sounds were a recent innovation in human language. Blasi et al. combined paleoanthropology, speech sciences, historical linguistics, and methods from evolutionary biology to provide evidence for a Neolithic global change in the sound systems of the world's languages. Spoken languages have thus been shaped by changes in the human bite configuration owing to changes in dietary and behavioral practices since the Neolithic.

    Science, this issue p. eaav3218

  12. Regeneration

    Acoel-regeneration regulatory landscapes

    1. Laura M. Zahn

    Some animals, including some types of worms, can undergo whole-body regeneration and replace virtually any missing cell type. Gehrke et al. sequenced and assembled the genome of Hofstenia miamia, a regenerative acoel worm species (see the Perspective by Alonge and Schatz). They identified a variable motif corresponding to regulation of the early growth response (egr) gene that was involved in regeneration. RNA interference experiments and validation in a second species showed that the protein Egr is a pioneer factor that stimulates regeneration.

    Science, this issue p. eaau6173; see also p. 1152

  13. Inorganic Chemistry

    Iron's new Best Friend

    1. Jake Yeston

    Carbon monoxide (CO) is one of the most widely studied ligands in the chemistry of transition metals. One of its distinguishing features is a two-way bonding motif, in which CO donates electrons to the metal while the metal simultaneously engages in “back bonding” in the other direction. Theory has suggested that the isoelectronic boron fluoride diatomic, BF, would be even more effective at both types of bonding. However, it has been challenging to prepare the requisite compounds for comparison. Drance et al. now report synthesis of a terminal iron-BF complex, with donor and acceptor characteristics that compare favorably to analogous CO and N2 complexes.

    Science, this issue p. 1203

  14. Cancer

    Tissue specificity in cancer drivers

    1. Gemma Alderton

    Why are cancer genes associated with certain types of cancer that affect specific organs, rather than causing cancer in all tissues? This fascinating conundrum raises questions about the process of tumorigenesis and how tissue specificity can determine susceptibility, as well as resistance, to developing cancer. In a Perspective, Haigis et al. discuss why this tissue specificity exists. They suggest that tissue-specific epigenetic changes that determine cell fate likely affect the signaling networks within cells that can be permissive or resistant to cancer gene mutations. Improved understanding of this question may reveal new therapeutic strategies to prevent and treat cancer.

    Science, this issue p. 1150

  15. Molecular Biology

    Oxygen sensing revisited

    1. Paula A. Kiberstis

    The cellular response to hypoxia (oxygen deficiency) is a contributing factor in many human diseases. Previous studies examining the way in which hypoxia alters gene expression have focused on oxygen-sensing enzymes that regulate the activity of a transcription factor called hypoxia-inducible factor (see the Perspective by Gallipoli and Huntly). Chakraborty et al. and Batie et al. now show that hypoxia can also affect gene expression through direct effects on chromatin regulators. Certain histone demethylases, such as KDM6A and KDM5A, were found to be direct sensors of oxygen. In cell-culture models, hypoxia diminished the activity of these enzymes and caused changes in the expression of genes that govern cell fate.

    Science, this issue p. 1217, p. 1222; see also p. 1148

  16. Decision-Making

    The neuroscience of trust

    1. Kollen Post

    Negative emotional states have a powerful effect on decision-making. In an effort to map the interaction of the two within the human brain, Engelmann et al. set up 41 participants in an investment simulation. The participants had to decide how much money they would give to anonymous human “trustees” versus “banks”—computers programmed for the task. These two scenarios were further subdivided by pain: Subjects faced strong electric shocks in some blocks and mild electric stimuli in others. The participants gave less money, in general, when faced with the threat of shock. Furthermore, activity in areas of the brain associated with trust and empathy was suppressed in trustee-dependent decisions during threat of shock.

    Sci. Adv. 10.1126/sciadv.aau3413 (2019).

  17. Parasitic Diseases

    Worms go A-WOL

    1. Orla M. Smith

    New drugs are urgently needed for treating the neglected tropical diseases onchocerciasis and lymphatic filariasis. As part of the anti-Wolbachia (A-WOL) consortium, Taylor et al. launched a drug discovery program that identified macrolide antibiotic tylosin A as capable of eliminating the bacterial endosymbiont Wolbachia, which is necessary for the viability and fertility of filarial worms. Tylosin A analogs were developed, and analog A-1574083 had superior efficacy compared with tetracycline antibiotics for clearing Wolbachia from filarial nematodes in mouse and gerbil models of filarial infection. The safety and pharmacology profiles of A-1574083 (now called ABBV-4083) have allowed it to enter clinical testing.

    Sci. Transl. Med. 11, eaau2086 (2019).

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