Editors' Choice

Science  26 Jun 2015:
Vol. 348, Issue 6242, pp. 1441
  1. Human Genetics

    Cultural imprints on the human genome

    1. Laura M. Zahn

    Animal domestication altered the human diet and may have done the same to our genome

    PHOTO: BORSEV/ISTOCKPHOTO

    As modern humans and society evolved, animal husbandry and farming changed the way humans eat. Valente et al. investigated how differences in diet may have played a role in human evolution. Examining the genetics of African populations with different modes of subsistence, as compared to Europeans, the authors identify selection on gene variants postulated to be adaptive for different diets. However, the degree to which these signals are associated with diet, rather than other environmental factors and evolutionary forces, requires further study. This highlights the difficultly of identifying how human culture has affected our genome.

    BMC Genet. 10.1186/s12863-015-0212-1 (2015).

  2. DNA Binding

    A sex-determining interaction

    1. Valda Vinson

    Across much of the animal kingdom, DMRT proteins are involved in regulating sexual development. In humans, DMRT1 both activates a male sex-determining gene and deactivates female sex-determining genes. Murphy et al. report a crystal structure showing three DNA binding DM domains, each comprising a zinc binding module followed by a recognition helix, bound to target DNA. Recognition helices from two domains lie antiparallel in a widened major groove. They find that DMRT1 can bind as a dimer, trimer, or tetramer in vitro and in vivo, with DNA sequence and shape dictating the binding mode. A mutation that causes male-to female sex reversal in humans reduces binding affinity and interferes with the binding stoichiometry of wild-type DMRT1.

    Nat. Struct. Mol. Biol. 22, 442 (2015).

  3. Neuroscience

    A new way to reduce drug seeking

    1. Peter Stern

    A methyl donor can reduce an addict's urge for ever more cocaine

    PHOTO: GBRUNDIN /ISTOCKPHOTO

    Relapse is a serious problem for many individuals trying to recover from addiction. Because DNA methylation regulates neural functions associated with synaptic plasticity, learning, and memory, Wright et al. investigated its role in sensitization to cocaine and reinstatement to cocaine and associated cues. A methyl donor, l-methionine, reduced behavioral sensitization to the locomotor-activating and drug-seeking effects of chronic cocaine use. l-methionine also blocked a cocaine-induced marker of neuronal activation after reinstatement in the nucleus accumbens and the medial prefrontal cortex, two brain regions responsible for drug seeking and relapse.

    J. Neurosci., 35, 8948 (2015).

  4. Microbiology

    How bladder cells kick out unwelcome intruders

    1. Stella M. Hurtley

    The bladder epithelium acts as the front line of the urinary defense system against microbial infection. Miao et al. examined urine samples from humans and mice and the extracellular medium of cultured bladder epithelial cells after infection by uropathogenic Escherichia coli. Remarkably, they found numerous viable bacteria encased in host-derived membrane-bound vesicles. Intracellular bacteria were initially taken up by autophagosomes and targeted to lysosomes. The bacteria raised the normally low lysosomal pH, which might be expected to protect them from lysosomal degradation. However, the bladder cells sensed the neutralized lysosomes and exocytosed them, expelling the membrane-encased bacteria. The bacteria were thus incapable of reinfection, and the bladder cells defended against their unwelcome visitors.

    Cell 161, 1306 (2015).

  5. Physics

    Seeing single fermions in optical lattices

    1. Jelena Stajic

    Peeking directly into quantum matter as it undergoes phase transitions at low temperature has long been a goal of condensed-matter physicists. This intimate view was made possible by atomic physicists, who visualized individual atoms of 87Rb in optical analogs of solid-state systems: optical lattices. But the relevant particle in solid-state systems is an electron—a fermion—whereas an atom of 87Rb is a boson. Visualizing single fermionic atoms in optical lattices presented considerable technical challenges; now, Cheuk et al., Parsons et al., and Haller et al. have achieved this goal using two different atomic species (fermionic 40K and 6Li) and two different cooling techniques. It is expected that these works will enable insight into the many-body behavior of fermions.

    Phys. Rev. Lett. 114, 193001; 213002 (2015); arXiv:1503.02005.

  6. Analytical Chemistry

    A faster way to weigh electrode products

    1. Jake Yeston

    Fermonic 40K atoms on a densely filled optical lattice

    PHOTO: LAWRENCE CHEUK/MIT

    It's becoming increasingly convenient to measure the mass of chemical compounds. Whereas mass spectrometry used to require intricate preparation, several current implementations can weigh molecules straight from a sample in open air. Brown et al. have now adapted one such technique to study the short-lived initial products of electrochemical oxidation reactions. Their apparatus incorporates a spinning platinum electrode that accumulates a thin film of the reaction medium on its surface. Application of voltage then generates charged products in that film that can be swept into the mass spectrometer within tens of milliseconds. The authors apply the technique to identify diimine intermediates in both uric acid and xanthine oxidations.

    J. Am. Chem. Soc. 10.1021/jacs.5b03862 (2015).

  7. Education

    A PORTAAL to active learning

    1. Melissa McCartney

    The shift from traditional lectures to active learning continues in science education. Eddy et al. report on the Practical Observation Rubric To Assess Active Learning (PORTAAL), a new assessment tool designed to help teachers implement active learning activities. A thorough review of the discipline-based education research literature led to the identification of 21 readily implemented elements shown to increase relevant learning goals with undergraduate students, which are now easily evaluated using PORTAAL. After only 5 hours of training, teachers can use PORTALL to measure how their teaching practices and classrooms align with research-supported best practices for active learning. Additionally, PORTAAL provides feedback and guidance to instructors, allowing them to improve their pedagogy.

    CBE Life Sci. Educ. 14, ar23; 10.1187/cbe.14-06-0095 (2015).

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