Chromosomes articles within Nature

Featured

  • Letter |

    The ends of eukaryotic chromosomes are composed of repeat sequences known as telomeres. Various proteins bind telomeres to protect them from degradation or inappropriate DNA repair responses, and their length is maintained by a specialized reverse transcriptase, telomerase. These authors show that in the absence of telomerase, telomeres can be maintained by amplifying and recombining heterochromatin sequences there. This process requires histone methylation and two telomere-binding proteins, Pot1 and Ccq1.

    • Devanshi Jain
    • , Anna K. Hebden
    •  & Julia Promisel Cooper

  • Letter |

    The centromeres of chromosomes are specified epigenetically, and the histone H3 variant CENP-A is assembled into the chromatin of all active centromeres. Here, the crystal structure of CENP-A in a tetrameric complex with histone H4 reveals the physical features of centromeric chromatin. CENP-A seems to mark the centromere by altering nucleosome structure from within its folded histone core.

    • Nikolina Sekulic
    • , Emily A. Bassett
    •  & Ben E. Black

  • Letter |

    Birds and mammals have distinct sex chromosomes: in birds, males are ZZ and females ZW; in mammals, males are XY and females XX. By sequencing the chicken Z chromosome and comparing it with the human X chromosome, these authors overturn the currently held view that these chromosomes have diverged little from their autosomal progenitors. The Z and X chromosomes seem to have followed convergent evolutionary trajectories, despite evolving with opposite systems of heterogamety.

    • Daniel W. Bellott
    • , Helen Skaletsky
    •  & David C. Page

  • Letter |

    The topologies of, and spatial relationships between, chromosomes are important but poorly understood. Here, a high-throughput method is used to study intra- and inter-chromosomal interactions in Saccharomyces cerevisiae. A map of the haploid genome is generated at kilobase resolution, and is used to construct a three-dimensional model of the yeast genome. The findings provide a glimpse of the interface between the form and function of a eukaryotic genome.

    • Zhijun Duan
    • , Mirela Andronescu
    •  & William S. Noble

  • Letter |

    Making haploid plants — which inherit chromosomes from only one parent — is useful for genetic research and also, crucially, for plant breeding. A new method for generating haploid Arabidopsis plants is now described, involving the manipulation of a single centromeric protein, CENH3. When cenh3 null plants are crossed with wild-type plants, the mutant chromosomes are eliminated, producing haploid progeny.

    • Maruthachalam Ravi
    •  & Simon W. L. Chan

  • Article |

    Zscan4 is shown to be involved in maintaining telomeres in embryonic stem (ES) cells. Only 5% of ES cells express Zscan4 at a given time, but nearly all ES cells activate Zscan4 at least once within nine passages. The transient Zscan4-positive state is associated with rapid telomere extension by telomere recombination and upregulation of meiosis–specific homologous recombination genes. Knocking down Zscan4 shortens telomeres, increases karyotype abnormalities and spontaneous sister chromatid exchange, and slows down cell proliferation until reaching crisis by eight passages.

    • Michal Zalzman
    • , Geppino Falco
    •  & Minoru S. H. Ko

  • News & Views |

    Hormones are not all-powerful in determining whether birds develop with male or female features. Chickens that are genetic sexual mosaics reveal that individual cells also have a say in the matter.

    • Lindsey A. Barske
    •  & Blanche Capel

  • Letter |

    Here, iPS cell technology is used to study the mechanisms underlying dyskeratosis congenita in humans. Reprogramming restores telomere elongation in dyskeratosis congenita cells despite genetic lesions affecting telomerase. The reprogrammed cells were able to overcome a critical limitation in telomerase RNA component (TERC) levels to restore telomere maintenance and self-renewal, and multiple telomerase components are targeted by pluripotency-associated transcription factors.

    • Suneet Agarwal
    • , Yuin-Han Loh
    •  & George Q. Daley

  • Letter |

    Little is known about the recent evolution of the Y chromosome because only the human Y chromosome has been fully sequenced. The sequencing of the male-specific region of the Y chromosome (MSY) in the chimpanzee and comparison between the MSYs of the two species now reveals that they differ radically in sequence structure and gene content, indicating rapid evolution over the past 6 million years.

    • Jennifer F. Hughes
    • , Helen Skaletsky
    •  & David C. Page

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