This Week in Science

Science  10 Feb 2017:
Vol. 355, Issue 6325, pp. 591
  1. Solar System Formation

    Meteorite magnetism in the early solar system

    1. Keith T. Smith

    Artist's impression of the solar nebula dispersing

    CREDIT: HERNAN CANELLAS

    The young solar system contained a disc of gas and dust within which planet formation occurred. The disc eventually dissipated after the Sun ignited and the planets formed, but exactly when that happened has been difficult to determine. Wang et al. measured tiny magnetic fields preserved in angrites, an ancient type of meteorite. They interpret a drop in magnetic field strength about 4 million years after the solar system formed as a sign that the gas had cleared—along with the magnetic field that it carried. The results will enhance our understanding of planet formation, both in our solar system and around other Sun-like stars.

    Science, this issue p. 623

  2. Evolution

    What drives divergence?

    1. Sacha Vignieri

    Horse evolution has long been held as a classic example of adaptive radiation. It has been thought that an increase in the height of cheek teeth opened up new grass resources, leading to divergence. Cantalapiedra et al., however, found that although the Equinae have experienced high levels of divergence, these splits do not appear to have been related initially to specific phenotypic changes. Instead, it seems that external environmental drivers and patterns of migration and isolation initiated population divergence, with phenotypic changes emerging once lineages had begun to divide.

    Science, this issue p. 627

  3. Geophysics

    Double trouble for the Deccan Traps

    1. Brent Grocholski

    The continental flood basalts in India known as the Deccan Traps formed from a massive outpouring of lava around the time that dinosaurs went extinct. The event dramatically reshaped the landscape and altered the climate. Glišović and Forte used time-reversed convection modeling to reconstruct the origin of this giant magmatic event. They found that two different deep mantle hotspots joined forces about 65 million years ago to produce one of the largest volcanic features on Earth.

    Science, this issue p. 613

  4. Gene Evolution

    Robustness of protein networks

    1. Laura M. Zahn

    It is thought that gene duplication helps cells maintain genetic robustness, but this seems not to be the whole story. Diss et al. investigated the fate of protein-protein interactions among duplicated genes in yeast. Some interacting duplicates evolved mutual dependence, resulting in a more fragile system. This finding helps us understand the evolutionary trajectories of gene duplications and how seemingly redundant genes can increase the complexity of protein interaction networks.

    Science, this issue p. 630

  5. Neuroscience

    Intraneuronal control of protein expression

    1. Stella M. Hurtley

    In cells and tissues, mRNA copy numbers far exceed the number of micro RNAs (miRNAs). How then can a miRNA effectively regulate translation of a particular target mRNA? Sambandan et al. used high-resolution in situ hybridization to detect precursor miRNA in rat neuronal dendrites. They introduced a fluorescent miRNA maturation reporter into hippocampal neurons and detected activity-dependent maturation of the probe in both the soma and dendrites. This local maturation of the miRNA was indeed associated with a local reduction in protein synthesis. Thus, localized miRNA maturation can modulate target gene expression with local and temporal precision.

    Science, this issue p. 634

  6. Vascular Biology

    A target for intracranial aneurysms

    1. Wei Wong

    Surgery is the only therapeutic option currently available for intracranial aneurysms. Aoki et al. delineated a selfamplifying signaling pathway in macrophages that could be pharmacologically targeted to limit the inflammation that initiates intracranial aneurysms and causes them to enlarge. Stimulation of EP2 (prostaglandin E receptor subtype 2) in macrophages increased the levels of COX-2, the enzyme that synthesizes the ligand for EP2, and MCP-1, an attractant for macrophages. Administering an EP2 antagonist to rats prevented the formation and progression of intracranial aneurysms.

    Sci. Signal. 10, eaah6037 (2017).

  7. Infectious Disease

    Starving the pathogen

    1. Anand Balasubramani

    Actively killing pathogens is an important function of the immune response; equally important is limiting nutrient availability to the pathogen, a process known as nutritional immunity. Interleukin-22 (IL-22) plays an essential role in the resolution of infections at epithelial barrier sites, including the skin, lungs, and intestines. Using a systemic model of Citrobacter rodentium infection, Sakamoto et al. uncovered an unexpected role for IL-22 in limiting availability of iron to the pathogen by promoting increased production of heme scavengers from the liver. Thus, beyond barrier immunity, IL-22 plays an additional role in regulating nutritional immunity in systemic bacterial infections.

    Sci. Immunol. 2, eaai8371 (2017).

  8. Quantum Entanglement

    Transitional approach to entanglement

    1. Jelena Stajic

    In an entangled many-particle system, changing the state of one constituent affects the rest of the system. This property can be used as a resource in quantum information processing, but getting many particles to participate in entanglement is tricky. Luo et al. used another collective phenomenon, a quantum phase transition, to entangle more than 900 atoms in a Bose-Einstein condensate. The size of the entangled ensemble remained stable, making the approach practical for precision measurements.

    Science, this issue p. 620

  9. Telomeres

    A protein to trim too-long telomeres

    1. Guy Riddihough,
    2. Stella M. Hurtley

    Telomeres cap the ends of linear eukaryotic chromosomes. They consist of multiple copies of short DNA repeats. The length of telomeres is important to genome stability; if they become too short, individuals can become prone to cancer and premature aging. Li et al. discovered a protein, TZAP (telomeric zinc finger-associated protein), which instead prevents telomeres from becoming too long (see the Perspective by Lossaint and Lingner). TZAP binds directly to the telomeric DNA repeats, competing with the shelterin complex. It stimulates telomere trimming, preventing aberrantly long telomeres.

    Science, this issue p. 638; see also p. 578

  10. Cardiovascular Disease

    A radical idea for blood pressure control

    1. Yevgeniya Nusinovich

    Hypertension (high blood pressure) is very common, especially in older adults, and it contributes to a number of other cardiovascular disorders. Although a variety of therapeutic interventions are available for this condition, none of them are specific or long-lasting, and they can all cause side effects, which decrease adherence to treatment. Hilgers et al. discovered that increased expression of thioredoxin, a protein that scavenges free radicals and restores proteins damaged by oxidation, reduced hypertension in mice. Injection of recombinant human thioredoxin also reduced hypertension in mouse models, and its protective effects lasted for weeks, suggesting that it may be possible to adapt this approach for long-term treatment of human patients.

    Sci. Transl. Med. 9, eaaf6094 (2017).

  11. Autophagy

    Change for good

    1. Stella M. Hurtley

    In the immune system, autophagy has been implicated in the maintenance and survival of plasma and memory cells, but its role in B cells during early viral infection remains unclear. Martinez-Martin et al. investigated the role of autophagy in B cells by using a combination of innovative imaging, pharmacological agents, and genetic models. B cell activation triggered an increase in the rate of autophagy and also switched the mechanism from canonical autophagy to noncanonical pathways involving the regulator WIPI2. Genetic ablation of WIPI2 in B cells promoted noncanonical autophagy. WIPI2 restrains noncanonical autophagy upon B cell activation through a mechanism involving mitochondrial status. Thus, the switch from canonical to noncanonical autophagy regulates B cell differentiation and fate during viral infection.

    Science, this issue p. 641

  12. Conservation

    Looking back to move forward

    1. Sacha Vignieri

    The current impacts of humanity on nature are rapid and destructive, but species turnover and change have occurred throughout the history of life. Although there is much debate about the best approaches to take in conservation, ultimately, we need to permit or enhance the resilience of natural systems so that they can continue to adapt and function into the future. In a Review, Barnosky et al. argue that the best way to do this is to look back at paleontological history as a way to understand how ecological resilience is maintained, even in the face of change.

    Science, this issue p. eaah4787

  13. Biophysics

    Superresolution imaging in sharper focus

    1. Valda Vinson

    An optical microscope cannot distinguish objects separated by less than half the wavelength of light. Superresolution techniques have broken this “diffraction limit” and provided exciting new insights into cell biology. Still, such techniques hit a limit at a resolution of about 10 nm. Balzarotti et al. describe another way of localizing single molecules called MINFLUX (see the Perspective by Xiao and Ha). As in photoactivated localization microscopy and stochastic optical reconstruction microscopy, fluorophores are stochastically switched on and off, but the emitter is located using an excitation beam that is doughnut-shaped, as in stimulated emission depletion. Finding the point where emission is minimal reduces the number of photons needed to localize an emitter. MINFLUX attained ∼1 nm precision, and, in single-particle tracking, achieved a 100-fold enhancement in temporal resolution.

    Science, this issue p. 606; see also p. 582

  14. Cell Fate

    Limiting potential for totipotency

    1. Beverly A. Purnell

    Biological roles for microRNAs are not limited to RNA silencing and posttranscriptional regulation; they have now been shown to also regulate cell pluripotency. Choi et al. eliminated miR-34a from mouse embryonic stem cells and found that the cells exhibited a bidirectional cell fate potential, generating both embryonic and extraembryonic lineages (see the Perspective by Hasuwa and Siomi). During miR-34a deficiency, an endogenous retrovirus was induced, at least in part through Gata2-dependent transcriptional activation. Thus, the interplay of protein-coding genes, noncoding RNAs, and endogenous retroviruses can change cell fate plasticity and the developmental potential of pluripotent stem cells.

    Science, this issue p. eaag1927; see also p. 581

  15. Many-Body Physics

    Machine learning and quantum physics

    1. Jelena Stajic

    Elucidating the behavior of quantum interacting systems of many particles remains one of the biggest challenges in physics. Traditional numerical methods often work well, but some of the most interesting problems leave them stumped. Carleo and Troyer harnessed the power of machine learning to develop a variational approach to the quantum many-body problem (see the Perspective by Hush). The method performed at least as well as state-of-the-art approaches, setting a benchmark for a prototypical two-dimensional problem. With further development, it may well prove a valuable piece in the quantum toolbox.

    Science, this issue p. 602; see also p. 580

  16. Microbiota

    Chemically guided functional profiling

    1. Caroline Ash

    The big challenge posed by the microbiota living in or on humans is working out what they do for us. Microorganisms generate large quantities of peptides and proteins that may have profound systemic effects on the host. Levin et al. took microbial metagenome data and used a combination of bioinformatic tools to generate a network that clusters sequences of enzymes sharing similar biological functions (see the Perspective by Glasner). Experiments verified these homology and structuralchemical inferences. The analysis identified enzymes involved in anaerobic short-chain fatty acid production and L-proline biosynthesis, both of which are key mediators of healthy microbiota-host symbioses.

    Science, this issue p. eaai8386; see also p. 577

  17. Chemical Biology

    Targeting proteins at the other sulfur

    1. Jake Yeston

    As the only amino acid with a thiol (SH) group, cysteine is easily targeted for site-selective protein modifications. Hydrophobic methionine also has sulfur in its side chain, but its capping methyl group has hindered analogous targeting efforts. Lin et al. introduce a complementary protocol to tether new substituents exclusively to methionine, even in the presence of cysteine. They used an oxaziridine group as an oxidant to form sulfimide (S=N) linkages. The approach allowed antibody-drug conjugation and chemoproteomic screening for reactive methionine surface residues.

    Science, this issue p. 597

  18. Statistics

    Misconceptions about measurement error

    1. Julia Fahrenkamp-Uppenbrink

    When they get a measurable effect in a noisy study, many researchers assume that the effect would have been even stronger in the absence of noise. But, as Loken and Gelman explain in a Perspective, this assumption only holds true for large-scale, high-information studies. In noisy settings, observed effects can often be larger than they would have been without the influence of measurement error. Measurement error and other uncontrolled variations are thus not always attenuating factors in identifying statistically significant effects.

    Science, this issue p. 584

  19. Optoelectronics

    Multifunctional displays

    1. Ian S. Osborne

    As we head toward the “Internet of things” in which everything is integrated and connected, we need to develop the multifunctional technology that will make this happen. Oh et al. developed a quantum dot-based device that can harvest and generate light and process information. Their design is based on a double-heterojunction nanorod structure that, when appropriately biased, can function as a light-emitting diode or a photodetector. Such a dual-function device should contribute to the development of intelligent displays for networks of autonomous sensors.

    Science, this issue p. 616