• Letter |

    In multicellular organisms, apoptotic cells are removed from tissues by phagocytes, which recognize and engulf the dying cells. The molecular mechanisms underlying the subsequent degradation of the cells have been unclear. Here, two evolutionarily conserved genes have been identified that are required for such processing in Caenorhabditis elegans and mammals. An understanding of these events could lead to new treatments for diseases associated with poor engulfment and destruction of dying cells.

    • Jason M. Kinchen
    •  & Kodi S. Ravichandran
  • Letter |

    A genome-wide RNA interference screen to systematically test the genetic basis for formation and function of the Drosophila muscle is described. A role in muscle for 2,785 genes is identified; many of these genes are phylogenetically conserved.

    • Frank Schnorrer
    • , Cornelia Schönbauer
    •  & Barry J. Dickson
  • Article |

    In mammals, embryos are considered to be sexually indifferent until the action of a sex-determining gene initiates gonadal differentiation. Here it is demonstrated that this situation is different for birds. Using rare, naturally occurring chimaeric chickens where one side of the animal appears male and the other female, it is shown that avian somatic cells possess an inherent sex identity and that, in birds, sexual differentiation is cell autonomous.

    • D. Zhao
    • , D. McBride
    •  & M. Clinton
  • Letter |

    The brain's capacity to respond to instructive capacity underlies behavioural learning, but how instructive experience acts on the juvenile brain, a period in which learning is often enhanced, remains unknown. Here, two-photon in vivo imaging is used to study the brains of zebra finches as they learn to sing. The results indicate that behavioural learning results when instructive experience is able to rapidly stabilize and strengthen synapses on the sensorimotor neurons that control the learned behaviour.

    • Todd F. Roberts
    • , Katherine A. Tschida
    •  & Richard Mooney
  • Article |

    Pancreatic β-cells release insulin, which controls energy homeostasis in vertebrates, and its lack causes diabetes mellitus. The transcription factor neurogenin 3 (Neurog3) initiates differentiation of β-cells and other islet cell types from pancreatic endoderm; here, the transcription factor Rfx6 is shown to direct islet cell differentiation downstream of Neurog3 in mice and humans. This may be useful in efforts to generate β-cells for patients with diabetes.

    • Stuart B. Smith
    • , Hui-Qi Qu
    •  & Michael S. German
  • Letter |

    Animals use the Earth's magnetic field for orientation but the biophysical basis of this is unclear. The light-dependent magnetic sense of Drosophila melanogaster was recently shown to be mediated by the cryptochrome (Cry) photoreceptor; here, using a transgenic approach, the type 1 and 2 Cry of the monarch butterfly are shown to both function in the magnetoreception system of Drosophila, and probably use an unconventional photochemical mechanism.

    • Robert J. Gegear
    • , Lauren E. Foley
    •  & Steven M. Reppert
  • Letter |

    The extent of epigenetic reprogramming in mammalian primordial germ cells (PGCs) and in early embryos, and its molecular mechanisms, are poorly understood. DNA methylation profiling in PGCs now reveals a genome–wide erasure of methylation, with female PGCs being less methylated than male ones. A deficiency of the cytidine deaminase AID interferes with the genome–wide erasure of DNA methylation, indicating that AID has a critical function in epigenetic reprogramming.

    • Christian Popp
    • , Wendy Dean
    •  & Wolf Reik
  • Letter |

    Sperm can increase their swimming velocity and gain a competitive advantage over sperm from another male by forming cooperative groups, such that selection should favour cooperation of the most closely related sperm. Sperm of deer mice are now shown to aggregate more often with conspecific than heterospecific sperm, in accordance with this theory, whereas in a monogamous species lacking sperm competition, sperm indiscriminately group with unrelated conspecific sperm.

    • Heidi S. Fisher
    •  & Hopi E. Hoekstra