Volume 509 Issue 7501, 22 May 2014

A conjugating pair of Paramecium cells visualized by confocal microscopy: the mating-type O cell was transformed to express fluorescent-labelled ciliary protein (shown in yellow), and both O and E cells are decorated with the TAP952 anti-monoglycylated tubulin antibody (shown in red). The protozoan Paramecium, widely studied as a typical ciliate, multiplies asexually by binary fission much of the time, but under certain conditions will reproduce sexually. Two mating types, E and O, were discovered in 1937 but only now has the molecular basis for maternal inheritance of mating type been elucidated. Eric Meyer and colleagues show in Paramecium tetraurelia that mating type E depends on expression of the transmembrane protein mtA, and the default type O is determined during development by excision of the mtA promoter by scnRNAs, a class of small ‘scan� RNA that reprograms the Paramecium genome during sexual reproduction by recognizing and excising transposable elements. A similar switch mechanism, involving a different gene, mtB, has evolved independently in a sibling species P. septaurelia, implying that exaptation of the scnRNA pathway may be a general mechanism for transgenerational epigenetic inheritance of differentiated states in Paramecium. Cover: Anne Aubusson-Fleury /Centre de Génétique Moléculaire Gif-sur-Yvette.


World View

Research Highlights

Seven Days



News Feature



Books & Arts

  • Books & Arts |

    Sarah S. Richardson relishes a study of how nineteenth-century US feminists used the biologist's ideas.

    • Sarah S. Richardson



News & Views

  • News & Views |

    Progeny of the protist Paramecium tetraurelia always retain the parental mating type. This inheritance is revealed to result from an RNA-guided DNA-deletion pathway that protects the genome from foreign DNA sequences. See Article p.447

    • Douglas L. Chalker
  • News & Views |

    The probable signature of an ageing massive star's stellar wind has been detected shortly after the star underwent a supernova explosion. The finding suggests that such windy stars can have bright, observable deaths. See Letter p.471

    • John J. Eldridge
  • News & Views |

    Two aspects of the blood–brain barrier — the transport of lipids to the brain and the transport of molecules across cells lining blood vessels — have been shown to be regulated by the same protein, Mfsd2a. See Letters p.503 & p.507

    • Christer Betsholtz
  • News & Views |

    Porous materials called metal–organic frameworks hold promise for many applications, including molecular separations. One such material has been discovered that shape-shifts to amplify its selectivity for a target molecule.

    • Ryotaro Matsuda
  • News & Views |

    Competition for access to a survival factor has been found to explain why incoming cells from the bone marrow replace resident cells in the thymus. Reducing this competition can cause tumours to form. See Article p.465

    • Eduardo Moreno
  • News & Views |

    An analysis of crustal uplift around California's San Joaquin Valley, caused by groundwater extraction, reveals that such removal leads to both seasonal and long-term unclamping of the nearby San Andreas Fault system. See Letter p.483

    • Paul Lundgren

Review Article

  • Review Article |

    Cellular senescence has recently been shown to have roles in complex biological processes other than protection against cancer, and to represent a series of progressive and diverse cellular states after initial growth arrest; better understanding of mechanisms underlying its progression and of acute and chronic senescent cells may lead to new therapeutic strategies for age-related pathologies.

    • Jan M. van Deursen


  • Article |

    The molecular basis for mating-type determination in the ciliate Paramecium has been elucidated, revealing a novel function for a class of small RNAs — these scnRNAs are typically involved in reprogramming the Paramecium genome during sexual reproduction by recognizing and excising transposable elements, but they are now found to be co-opted to switch off expression of the newly identified mating-type gene mtA by excising its promoter, and to mediate epigenetic inheritance of mating types across sexual generations.

    • Deepankar Pratap Singh
    • , Baptiste Saudemont
    • , Gérard Guglielmi
    • , Olivier Arnaiz
    • , Jean-François Goût
    • , Malgorzata Prajer
    • , Alexey Potekhin
    • , Ewa Przybòs
    • , Anne Aubusson-Fleury
    • , Simran Bhullar
    • , Khaled Bouhouche
    • , Maoussi Lhuillier-Akakpo
    • , Véronique Tanty
    • , Corinne Blugeon
    • , Adriana Alberti
    • , Karine Labadie
    • , Jean-Marc Aury
    • , Linda Sperling
    • , Sandra Duharcourt
    •  & Eric Meyer
  • Article |

    Plasticity within neuronal microcircuits is believed to be the substrate of learning, and this study identifies two distinct disinhibitory mechanisms involving interactions between PV+ and SOM+ interneurons that dynamically regulate principal neuron activity in the amygdala and thereby control auditory fear learning.

    • Steffen B. E. Wolff
    • , Jan Gründemann
    • , Philip Tovote
    • , Sabine Krabbe
    • , Gilad A. Jacobson
    • , Christian Müller
    • , Cyril Herry
    • , Ingrid Ehrlich
    • , Rainer W. Friedrich
    • , Johannes J. Letzkus
    •  & Andreas Lüthi
  • Article |

    T cells develop from thymic precursor cells that are constantly replaced with newly arriving bone marrow progenitor cells, and the ‘old’ and ‘new’ cells are shown here to compete; in the absence of cell competition, when the influx of new bone marrow progenitor cells is blocked, the old cells acquire the ability to self-renew and eventually become transformed, leading to the development of a form of leukaemia.

    • Vera C. Martins
    • , Katrin Busch
    • , Dilafruz Juraeva
    • , Carmen Blum
    • , Carolin Ludwig
    • , Volker Rasche
    • , Felix Lasitschka
    • , Sergey E. Mastitsky
    • , Benedikt Brors
    • , Thomas Hielscher
    • , Hans Joerg Fehling
    •  & Hans-Reimer Rodewald


  • Letter |

    The detection of strong emission lines in an early-time spectrum of type IIb supernova SN 2013cu reveals Wolf–Rayet-like wind signatures, suggesting that the supernova’s progenitor may have been a Wolf–Rayet star with a wind dominated by helium and nitrogen, with traces of hydrogen.

    • Avishay Gal-Yam
    • , I. Arcavi
    • , E. O. Ofek
    • , S. Ben-Ami
    • , S. B. Cenko
    • , M. M. Kasliwal
    • , Y. Cao
    • , O. Yaron
    • , D. Tal
    • , J. M. Silverman
    • , A. Horesh
    • , A. De Cia
    • , F. Taddia
    • , J. Sollerman
    • , D. Perley
    • , P. M. Vreeswijk
    • , S. R. Kulkarni
    • , P. E. Nugent
    • , A. V. Filippenko
    •  & J. C. Wheeler
  • Letter |

    Conventional quantum cryptography relies on monitoring signal disturbance to make sure that information leakage is negligible; here a new quantum method of achieving security is described, in which little information is leaked to the eavesdropper regardless of the signal disturbance.

    • Toshihiko Sasaki
    • , Yoshihisa Yamamoto
    •  & Masato Koashi
  • Letter |

    Human-caused groundwater depletion in California’s San Joaquin Valley contributes to uplift of the surrounding mountains and may affect the stability of the San Andreas Fault.

    • Colin B. Amos
    • , Pascal Audet
    • , William C. Hammond
    • , Roland Bürgmann
    • , Ingrid A. Johanson
    •  & Geoffrey Blewitt
  • Letter |

    This study describes the construction of a focused CRISPR/Cas-based lentiviral library in human cells and a method of gene identification based on functional screening and high-throughput sequencing analysis.

    • Yuexin Zhou
    • , Shiyou Zhu
    • , Changzu Cai
    • , Pengfei Yuan
    • , Chunmei Li
    • , Yanyi Huang
    •  & Wensheng Wei
  • Letter |

    Tumorigenesis driven by the oncogene BRAFV600E is shown both to depend on the BRAF substrates MEK1/2 associating with copper, and to be sensitive to copper-chelating drugs, suggesting merit in testing such drugs for the treatment of BRAF mutation-positive cancers.

    • Donita C. Brady
    • , Matthew S. Crowe
    • , Michelle L. Turski
    • , G. Aaron Hobbs
    • , Xiaojie Yao
    • , Apirat Chaikuad
    • , Stefan Knapp
    • , Kunhong Xiao
    • , Sharon L. Campbell
    • , Dennis J. Thiele
    •  & Christopher M. Counter
  • Letter |

    Here, the presentation of lipid antigens by CD1d is shown to induce retrograde anti-inflammatory signalling in intestinal epithelial cells, resulting in the production of IL-10.

    • Torsten Olszak
    • , Joana F. Neves
    • , C. Marie Dowds
    • , Kristi Baker
    • , Jonathan Glickman
    • , Nicholas O. Davidson
    • , Chyuan-Sheng Lin
    • , Christian Jobin
    • , Stephan Brand
    • , Karl Sotlar
    • , Koichiro Wada
    • , Kazufumi Katayama
    • , Atsushi Nakajima
    • , Hiroyuki Mizuguchi
    • , Kunito Kawasaki
    • , Kazuhiro Nagata
    • , Werner Müller
    • , Scott B. Snapper
    • , Stefan Schreiber
    • , Arthur Kaser
    • , Sebastian Zeissig
    •  & Richard S. Blumberg
  • Letter |

    Mfsd2a is the major transporter of the omega-3 fatty acid docosahexaenoic acid (DHA) into brain, with Mfsd2a-knockout mice showing reduced DHA in brain, neuronal cell loss in hippocampus and cerebellum, behavioural disorders and reduced brain size; DHA is transported in a sodium-dependent manner, in the form of lysophosphatidylcholines (LPCs) carrying long-chain fatty acids.

    • Long N. Nguyen
    • , Dongliang Ma
    • , Guanghou Shui
    • , Peiyan Wong
    • , Amaury Cazenave-Gassiot
    • , Xiaodong Zhang
    • , Markus R. Wenk
    • , Eyleen L. K. Goh
    •  & David L. Silver
  • Letter |

    Mfsd2a is a key regulator of blood–brain barrier (BBB) formation and function in mice: Mfsd2a is selectively expressed in BBB-containing blood vessels in the CNS; Mfsd2a−/− mice have a leaky BBB and increased vesicular transcytosis in CNS endothelial cells; and Mfsd2a endothelial expression is regulated by pericytes to facilitate BBB integrity.

    • Ayal Ben-Zvi
    • , Baptiste Lacoste
    • , Esther Kur
    • , Benjamin J. Andreone
    • , Yoav Mayshar
    • , Han Yan
    •  & Chenghua Gu
  • Letter |

    Many bacteria are able to survive in the presence of antibiotics in part because they possess pumps that can remove a broad range of small molecules; here, the structure of one such pump, AcrAB–TolC, is determined using X-ray crystallography and cryo-electron microscopy.

    • Dijun Du
    • , Zhao Wang
    • , Nathan R. James
    • , Jarrod E. Voss
    • , Ewa Klimont
    • , Thelma Ohene-Agyei
    • , Henrietta Venter
    • , Wah Chiu
    •  & Ben F. Luisi
  • Letter |

    The crystal structure of the bacterial protein YidC is reported, together with a structure-based functional analysis, providing insight into the role of YidC in inserting single-spanning membrane proteins into the membrane.

    • Kaoru Kumazaki
    • , Shinobu Chiba
    • , Mizuki Takemoto
    • , Arata Furukawa
    • , Ken-ichi Nishiyama
    • , Yasunori Sugano
    • , Takaharu Mori
    • , Naoshi Dohmae
    • , Kunio Hirata
    • , Yoshiko Nakada-Nakura
    • , Andrés D. Maturana
    • , Yoshiki Tanaka
    • , Hiroyuki Mori
    • , Yuji Sugita
    • , Fumio Arisaka
    • , Koreaki Ito
    • , Ryuichiro Ishitani
    • , Tomoya Tsukazaki
    •  & Osamu Nureki


Career Brief

  • Career Brief |

    Administrative tasks gobble scientists' time, says report

  • Career Brief |

    Prize winners invest their money in postdoc endowment

  • Career Brief |

    Scientists will soon need to understand the language of many disciplines and sectors


  • Futures |

    An experimental direction.

    • John Frizell
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