This Week in Science

Science  20 Apr 2018:
Vol. 360, Issue 6386, pp. 280
  1. Extinction

    Megafaunal loss

    1. Sacha Vignieri

    Megafauna, such as these rhinos, have been under threat from humans for millennia.

    CREDIT: RYAN RIGGS

    Today, it is well known that human activities put larger animals at greater risk of extinction. Such targeting of the largest species is not new, however. Smith et al. show that biased loss of large-bodied mammal species from ecosystems is a signature of human impacts that has been following hominin migrations since the Pleistocene. If the current trend continues, terrestrial mammal body sizes will become smaller than they have been over the past 45 million years. Megafaunal mammals have a major impact on the structure of ecosystems, so their loss could be particularly damaging.

    Science, this issue p. 310

  2. Early Earth

    A strongly oxidizing Paleoproterozoic era

    1. H. Jesse Smith

    Two billion years ago, marine sulfate concentrations were around one-third as high as modern ones, constituting an oxidizing capacity equivalent to more than 20% of that of the modern ocean-atmosphere system. Blättler et al. found this by analyzing a remarkable evaporite succession more than 1 billion years older than the oldest comparable deposit discovered to date. These quantitative results, for a time when only more qualitative information was previously available, provide a constraint on the magnitude and timing of early Earth's response to the Great Oxidation Event 2.3 billion years ago.

    Science, this issue p. 320

  3. Neurodevelopment

    Transient instruction changes migration

    1. Pamela J. Hines

    The brain neocortex is built by waves of neurons migrating from deep within the brain to the surface layers. Ohtaka-Maruyama et al. found that a layer of neurons that multipolar neurons encounter on their travels instructs the migrating neurons to change phenotype and direction (see the Perspective by Schinder and Lanuza). These subplate neurons form transient glutamatergic synapses with the immature migrants. This results in the migrating multipolar neurons becoming bipolar, more directed, and faster in their final migrations.

    Science, this issue p. 313; see also p. 265

  4. Autism Genomics

    Inherited variation contributes to autism

    1. Laura M. Zahn

    About one-quarter of genetic variants that are associated with autism spectrum disorder (ASD) are due to de novo mutations in protein-coding genes. Brandler et al. wanted to determine whether changes in noncoding regions of the genome are associated with autism. They applied whole-genome sequencing to ∼2600 families with at least one affected child. Children with ASD had inherited structural variants in noncoding regions from their father. Regulatory regions of some specific genes were disrupted among multiple families, supporting the idea that a component of autism risk involves inherited noncoding variation.

    Science, this issue p. 327

  5. Drug Development

    An innovative approach for a rare disease

    1. Priscilla N. Kelly

    Charcot-Marie-Tooth disease type 2A (CMT2A) is a rare, inherited neurodegenerative condition. Affected individuals develop severe progressive muscle weakness, motor deficits, and peripheral neuropathy. Although defects in the gene encoding mitofusin 2 (MFN2) are known to cause CMT2A, the disease remains incurable. Rocha et al. identified specific MFN2 residues contributing to the disease and developed a class of MFN2-agonist drugs. The small molecules restored mitochondrial fusion and activity in the sciatic nerves of mice; they may also help in other diseases linked to mitochondrial trafficking.

    Science, this issue p. 336

  6. HIV

    Taking an active interest in HIV latency

    1. Lindsey Pujanandez

    HIV cure efforts have been thwarted by an inability to target the latent reservoir, which is thought to be largely composed of resting CD4 T cells. A recent report suggested that the Fcγ receptor CD32 might be a marker of latently infected CD4 T cells. Abdel-Mohsen et al. meticulously examined T cells from treated HIV patients across the world. CD32+ HIV-infected T cells had an activated phenotype and HIV RNA, indicating active HIV transcription. In contrast, the majority of HIV DNA resided in CD32 cells. Thus, targeting CD32+ cells is unlikely to hit the latent HIV reservoir.

    Sci. Transl. Med. 10, eaar6759 (2018).

  7. Materials Science

    Reserving the right to stretch

    1. Marc S. Lavine

    Retractable antennae or certain spider silks can stretch well beyond their apparent length because they have a reserve of material that lets them expand and contract over much longer distances. Grandgeorge et al. made nonwoven fibrous membranes by electrospinning a block copolymer with varying ratios of two components. They infused these membranes with a liquid that let the fibers buckle and fold without changing the apparent surface area. When the membranes were stretched, this material could unbuckle and slide along the membrane surface, allowing it to extend without breakage.

    A designed polymer can stretch like a spring.

    PHOTO: SORBONNE UNIVERSITÉ/CNRS

    Science, this issue p. 296

  8. Cancer

    Earlier detection of ovarian cancer

    1. Philippa J. Benson

    Ovarian cancer is the fifth leading cause of cancer-related deaths among females in the United States, owing in part to the late stage at which it is often diagnosed. Survival rates increase dramatically when it is detected early, and new methods for advanced detection are greatly needed. Williams et al. developed a carbon nanotube–based sensor that optically detects the U.S. Food and Drug Administration–approved ovarian cancer biomarker HE4. When implanted into live cancer-bearing mice, distinct wavelength responses from individual nanotubes in the device rapidly and repeatedly differentiated mice with ovarian cancer from controls. The same was true in tests using samples from ovarian cancer patients.

    Sci. Adv. 10.1126/sciadv.aaq1090 (2018)

  9. Quantum Gases

    Recurring coherence

    1. Jelena Stajic

    A finite isolated system should return almost to its initial state if it evolves for long enough. For a large system, “long enough” is often unfeasibly long. Rauer et al. found just the right conditions to observe the recurrence of the initial state in a system of two one-dimensional superfluids with thousands of atoms in each. The superfluids were initially coupled—locking their quantum mechanical phases together—and then allowed to evolve independently. After the uncoupling, the researchers observed their phases regaining coherence two more times.

    Science, this issue p. 307

  10. Yeast Genomics

    Trigenic interactions in yeast link bioprocesses

    1. Laura M. Zahn

    To dissect the genotype-phenotype landscape of a cell, it is necessary to understand interactions between genes. Building on the digenic protein-protein interaction network, Kuzmin et al. created a trigenic landscape of yeast by using a synthetic genetic array (see the Perspective by Walhout). Triple-mutant analyses indicated that the majority of genes with trigenic associations functioned within the same biological processes. These converged on networks identified in the digenic interaction landscape. Although the overall effects were weaker for trigenic than for digenic interactions, trigenic interactions were more likely to bridge biological processes in the cell.

    Science, this issue p. eaao1729; see also p. 269

  11. Advanced Imaging

    Continuing the resolution revolution

    1. Stella M. Hurtley

    The living cell contains dynamic, spatially complex subassemblies that are sensitive to external perturbations. To minimize such perturbations, cells should be imaged in their native multicellular environments, under as gentle illumination as possible. However, achieving the spatiotemporal resolution needed to follow three-dimensional subcellular processes in detail under these conditions is challenging: Sample-induced aberrations degrade resolution and sensitivity, and high resolution usually requires intense excitation. Liu et al. combined noninvasive lattice light-sheet microscopy with aberration-correcting adaptive optics to study a variety of delicate subcellular events in vivo, including organelle remodeling during mitosis and growth cone dynamics during spinal cord development.

    Science, this issue p. eaaq1392

  12. Quantum Optics

    Large-scale integrated quantum optics

    1. Ian S. Osborne

    The ability to pattern optical circuits on-chip, along with coupling in single and entangled photon sources, provides the basis for an integrated quantum optics platform. Wang et al. demonstrate how they can expand on that platform to fabricate very large quantum optical circuitry. They integrated more than 550 quantum optical components and 16 photon sources on a state-of-the-art single silicon chip, enabling universal generation, control, and analysis of multidimensional entanglement. The results illustrate the power of an integrated quantum optics approach for developing quantum technologies.

    Science, this issue p. 285

  13. Nanophotonics

    Light confined to a single atomic layer

    1. Ian S. Osborne

    The development of nanophotonic technology is reliant on the ability to confine light to spatial dimensions much less than the wavelength of the light itself. Typically, however, in metal plasmonic approaches, there is a trade-off between confinement and losses. Alcaraz Iranzo et al. fabricated heterostructures comprising monolayers of graphene and hexagonal boron nitride (hBN) and an array of metallic rods. The light was confined vertically (as propagating plasmons) between the metal and the graphene, even when the insulating hBN spacer was just a single monolayer. Such heterostructures should provide a powerful and versatile platform for nanophotonics.

    Science, this issue p. 291

  14. Materials Science

    Small, smooth, and bendable diamonds

    1. Brent Grocholski

    If you manage to deform a diamond, it usually means you have broken it. Diamonds have very high hardness, but they do not deform elastically. This limits their usefulness for some applications. However, Banerjee et al. discovered that diamond nanoneedles can deform elastically after all (see the Perspective by LLorca). The key was in their small size (300 nm), which allowed for very smooth-surfaced, defect-free diamonds. The deformation was close to the theoretical limit for diamond, which opens up the potential for applications in microelectronics and drug delivery.

    Science, this issue p. 300; see also p. 264

  15. Colloids

    Images frozen in time

    1. Marc S. Lavine

    Freezing processes involving multiple phases are common, as seen in the zone refining used to remove impurities from a crystal through the heating of a narrow region. However, it is difficult to visualize the processes as they happen. Dedovets et al. studied the freezing of an oil-in-water emulsion and the interaction of the oil droplets with the leading edge of the freezing water. In situ visualization of the freezing front was achieved through confocal microscopy of samples on a moving sample holder. The authors tracked the effects of solution concentration on the droplet positions and observed premelting at the interface of the droplets by using fluorescence markers.

    Science, this issue p. 303

  16. Plant Ecology

    A short-term trend reversed

    1. Andrew M. Sugden

    Theory and empirical data both support the paradigm that C4 plant species (in which the first product of carbon fixation is a four-carbon molecule) benefit less from rising carbon dioxide (CO2) concentrations than C3 species (in which the first product is a three-carbon molecule). This is because their different photosynthetic physiologies respond differently to atmospheric CO2 concentrations. Reich et al. document a reversal of this pattern in a 20-year CO2 enrichment experiment using grassland plots with each type of plant (see the Perspective by Hovenden and Newton). Over the first 12 years, biomass increased with elevated CO2 in C3 plots but not C4 plots, as expected. But over the next 8 years, the pattern reversed: Biomass increased in C4 plots but not C3 plots. Thus, even the best-supported short-term drivers of plant response to global change might not predict long-term results.

    Science, this issue p. 317; see also p. 263

  17. Cancer Genomics

    The cellular composition of H3K27M gliomas

    1. Laura M. Zahn

    Diffuse midline gliomas with histone H3 lysine27-to-methionine mutations (H3K27M-glioma) are an aggressive type of childhood cancer with few options for treatment. Filbin et al. used a single-cell sequencing approach to study the oncogenic programs, genetics, and cellular hierarchies of H3K27M-glioma. Tumors were mainly composed of cells resembling oligodendrocyte precursor cells, whereas differentiated malignant cells were a smaller fraction. In comparison with other gliomas, these cancers had distinct oncogenic programs and stem cell–like profiles that contributed to their stable tumor-propagating potential. The analysis also identified a lineage-specific marker that may be useful in developing therapies.

    Science, this issue p. 331

  18. Structural Biology

    First steps of translocation elucidated

    1. Stella M. Hurtley

    Ribosomes synthesizing membrane or secretory proteins are targeted to the endoplasmic reticulum (ER) in eukaryotic cells by the signal recognition particle (SRP). Upon reaching the ER, the SRP interacts with its receptor to promote transfer of the signal sequence to the protein-conducting channel or translocon. Kobayashi et al. studied the ribosomal complex that forms on the ER, in which the SRP and its receptor interact to transfer the newly synthesized protein to the translocon. The observed organization of the assembly reveals the roles of multiple eukaryotic-specific protein components present in the SRP and its receptor in stabilizing the conformation that facilitates signal sequence handover.

    Science, this issue p. 323

  19. Neurodegeneration

    Conformation changes or cooperativity?

    1. Gemma Alderton

    Parkin is a commonly mutated protein ubiquitin ligase implicated in Parkinson's disease. Understanding how Parkin functions is important to understanding its pathogenic role. In a Perspective, Arkinson and Walden discuss recent structural insights into the activities of Parkin. These have led to the interesting proposal that Parkin, and other ubiquitin ligases in the same family, may function cooperatively—so that two proteins are needed to carry out its enzymatic functions. Although conformational changes of Parkin are not ruled out, this model may help explain the Parkinson's disease–associated mutation profile that spans the Parkin protein.

    Science, this issue p. 267

  20. Hypothesis

    Restoring blood vessel stability

    1. Lisa D. Chong

    What if a wide array of diseases that afflict blood vessels—from atherosclerosis to transplant vasculopathy and vascular malformations—had a common causal element? In a Perspective, Schwartz et al. propose that fundamental aspects of normal vascular remodeling promote disease if prolonged or exaggerated. They also suggest that unchecked vascular endothelial cell activation and extracellular matrix remodeling are common to multiple pathologies. If this is the case, interventions to restore vascular stability could improve health outcomes in multiple disease states.

    Science, this issue p. 270

  21. Hormones

    Estrogen accentuates autoimmunity

    1. Erin Williams

    More than any other risk factor, being female confers the greatest risk of developing an autoimmune disorder. Mohammad et al. identified a role for estrogen in the development of autoimmune T cell responses. Deletion of estrogen receptor α (ERα) in T cells reduced disease burden in a mouse model of colitis. ERα-expressing T cells were more activated after stimulation and produced more proinflammatory cytokines than T cells lacking this receptor. Conversely, ERα-deficient T cells were more likely to differentiate into regulatory T cells, which suppress the development of autoimmune disorders.

    Sci. Signal. 11, eaap9415 (2018).

  22. Allergy

    Potent platelets

    1. Christiana N. Fogg

    Anaphylaxis results from inappropriate immune responses to allergens. Human platelets express the immunoglobulin G (IgG) receptor FcγRIIA/CD32A and release inflammatory mediators in response to their engagement. However, the contribution of platelets to anaphylaxis is not well understood. To address this, Beutier et al. developed mouse models that express either human FcγRIIA/CD32A alone or the full human IgG receptor complexity. Anaphylaxis induced a marked decrease in platelet levels, but preventive platelet depletion reduced anaphylaxis severity. A clinical study of patients with drug-induced anaphylaxis showed that a severe reaction was likewise associated with fewer circulating platelets. Activated platelets released serotonin, which contributed to anaphylaxis severity. Thus, platelets play a critical role in IgG-mediated anaphylaxis.

    Sci. Immunol. 3, eaan5997 (2018).