Editors' Choice

Science  03 Mar 2017:
Vol. 355, Issue 6328, pp. 921
  1. Development

    Heal our breaking hearts

    1. Megan Eldred

    New evidence sheds light on regeneration in human heart tissue.

    PHOTO: ROGER J. BICK & BRIAN J. POINDEXTER/UT-HOUSTON MEDICAL SCHOOL/SCIENCE SOURCE

    Myocardial infarction (heart attack) causes irreversible damage to the heart, leaving the survivor with reduced cardiac output and lowering their quality of life. Some animals, such as the zebrafish and the neonatal mouse, have a regenerative capacity, but until now, we have not been able to elucidate any regenerative capability in the adult human heart. Voges et al. have grown immature human cardiac organoids that display an innate ability to regenerate after injury. Unlike in adult tissue, these organoids do not form fibrotic scars and can recover functionally. The organoids provide the first insight into human cardiac regeneration and are a step toward finding a source for cellular therapy after cardiac damage.

    Development 10.1242/dev.143966 (2017).

  2. Cancer

    The search for cancer cell vulnerabilities

    1. L. Bryan Ray

    Efficient screening of gene essentiality in mammalian cells, enabled by CRISPR-mediated gene editing, offers the opportunity to search for genes that are particularly required for proliferation and survival of tumor cells. Wang et al. used such screens to search for genes that are essential for growth in cancer cells driven by RAS mutations commonly found in human cancers. Such screens can help reveal functionally important interactions. The authors identified PREX1 as a key activator of MAP kinase signaling in the studied cancer cells. PREX is a guanine nucleotide exchange factor for the small guanosine triphosphatase Rac1, best known for its roles in controlling cell motility. The strategy holds promise for the development of cancer therapies directed at specific vulnerabilities of cancer cells.

    Cell 10.1016/j.cell.2017.01.013 (2017).

  3. Clean Energy

    The PACE of clean energy development

    1. H. Jesse Smith

    Residential solar photovoltaic installations can be encouraged with funding mechanisms that cost taxpayers nothing.

    PHOTO: ASHLEY COOPER/GETTY IMAGES

    The Property Assessed Clean Energy (PACE) program is a national initiative designed to promote investment in solar photovoltaics by commercial, nonprofit, and residential property owners. Its central feature is to provide low-cost, long-term funding, which is repaid as an assessment on the property's regular tax bill, as is done for sidewalks and sewers, for example. Spurring such investment clearly is a good goal, but is the program effective? Ameli et al. used a natural experiment in northern California to test the capacity of PACE, finding that it has been a great success, more than doubling residential photovoltaic installations in the region at no cost to the taxpayers.

    Appl. Energy 10.1016/j.apenergy.2017.01.037 (2017).

  4. Cancer

    Immunotherapy—the forest and the trees

    1. Paula A. Kiberstis

    The clinical success of cancer immunotherapy has been both gratifying and perplexing to immunologists. One unsolved mystery is why fewer than 20% of cancer patients respond to this treatment. Spitzer et al. hypothesized that immune cells influencing the efficacy of immunotherapy reside outside the tumor microenvironment, the focus of most previous research. They used mass cytometry to assess system-wide immune responses that contribute to antitumor immunity in mice treated with immunotherapy. They found that CD4 T cells in peripheral tissues continued to proliferate after tumor rejection and were required for protection against new tumors. These results raise the possibility that therapies exploiting the antitumor activity of CD4 T cells may benefit cancer patients who do not respond to existing immunotherapies.

    Cell 168, 487 (2017).

  5. Vertebrate Paleontology

    Live birth in a new lineage

    1. Sacha Vignieri

    Live birth has evolved multiple times among vertebrates, most notably in mammals. Although live birth also occurs in some reptiles, including several extinct marine reptiles, it has appeared convincingly to be absent in the Archosauromorphs, the lineage leading to dinosaurs, birds, and crocodiles. Liu et al. describe a previously unknown marine Archosauromorph from the middle Triassic in China, Dinocephalosaurus, which shows evidence of an embryo within the body cavity. Viviparity in marine animals has clear functional advantages, but the lack of evidence for live birth across millions of years in this large group has caused some to question whether its evolution was impossible because of some genetic or developmental constraint. This new evidence suggests that, at least initially, this was not the case.

    Nat. Commun. 1038/ncomms14445 (2017).

  6. Physics

    Signatures of chiral anomaly multiply

    1. Jelena Stajic

    Chiral anomaly is one of the most striking phenomena predicted to occur in Dirac and Weyl semimetals. One of its consequences, the decrease in electrical resistance with applied magnetic field, has been observed in several of these materials, but disentangling it from other, less exotic effects is tricky. Working with nanoplates of the Dirac semimetal Cd3As2, Zhang et al. observed two additional signatures of the chiral anomaly in nonlocal transport and optical response. The unusual nonlocal transport was caused partly by the diffusion of valley polarization, which in turn was a consequence of the chiral anomaly. These complementary signatures will make it possible to study the phenomenon more closely.

    Nat. Commun. 10.1038/ncomms13741 (2017).

  7. Organic Chemistry

    Lighting the way to fluorine placement

    1. Jake Yeston

    Fluorination is a powerful strategy to fine-tune molecular properties in pharmaceutical research, but it is often difficult to place the F atoms exactly where you want them. Pitts et al. report a photochemical reaction applied to polycyclic terpenoid frameworks that reliably fluorinates C–H bonds three or four carbons away from the oxygen in an enone group. The site selectivity in one case distinguished among 65 different aliphatic C–H bonds. The authors postulate a radical mechanism involving H-atom abstraction by the enone in a triplet excited state.

    J. Am. Chem. Soc. 10.1021/jacs.7b00335 (2017).