Abstract

Toward the end of mitosis, neighboring chromosomes gather closely to form a compact cluster before nuclear envelope reassembly begins. This is important for reassembling the nuclear envelope around the entire chromosome mass, but not individual chromosomes. By analyzing mice and cultured cells lacking expression of chromokinesin Kid/kinesin-10, we showed that Kid localizes to the boundaries of anaphase and telophase chromosomes and helps to hold individual chromosomes together to form a compact chromosome mass at telophase. In mice, loss of the Kid-mediated anaphase chromosome compaction often causes the formation of multinucleated cells, specifically at oocyte meiosis II and the first couple of mitoses, leading to embryonic death. In contrast, neither male meiosis nor somatic mitosis after the morula-stage is fatally affected by Kid-deficiency. These data suggest that Kid-mediated anaphase chromosome compaction is specifically essential for mammalian early-stage embryos, which are under the strong influence of the ooplasm, to encapsulate chromosomes into one nucleus.

Cell 132: 771-782 (2008)