• Letter |

    In synthetic biology, the use of regulatory proteins that bind either DNA or RNA to reprogram mammalian cellular functions allows a variety of computational ‘logic circuits’ to be built in a plug-and-play manner, which may pave the way for precise and robust control of future gene-based and cell-based therapies.

    • Simon Ausländer
    • , David Ausländer
    •  & Martin Fussenegger
  • Letter |

    Progesterone stimulates an increase in Ca2+ levels in human sperm, but the underlying signalling mechanism is poorly understood. Two studies now show that progesterone activates the sperm-specific, pH-sensitive CatSper calcium channel, leading to a rapid influx of Ca2+ ions into the spermatozoa. These results should help to define the physiological role of progesterone and CatSper in sperm, and could lead to the development of new classes of non-hormonal contraceptives.

    • Polina V. Lishko
    • , Inna L. Botchkina
    •  & Yuriy Kirichok
  • Letter |

    Cell death by apoptosis is crucial for tissue development and function, and occurs throughout life. Apoptotic cells must be cleared by phagocytic cells, but the mechanisms that regulate cell clearance in vivo remain unclear. Here, a conserved engulfment protein, ELMO1, is shown to be required for the phagocytic clearance of apoptotic germ cells by Sertoli cells in mouse testes. The findings make a compelling case for the relationship between engulfment and tissue homeostasis in vivo.

    • Michael R. Elliott
    • , Shuqiu Zheng
    •  & Kodi S. Ravichandran
  • 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