3D-CLEM reveals that a major portion of mitotic chromosomes is not Chromatin

Daniel Booth, Alison J Beckett, Oscar Molina, Itaru Samejima, Hiroshi Masumoto, Natalay Kouprina, Vladimir Larionov, Ian A Prior, William Earnshaw

Research output: Contribution to journalArticlepeer-review

Abstract

Recent studies have revealed the importance of Ki-67 and the chromosome periphery in chromosome structure and segregation, but little is known about this elusive chromosome compartment. Here we used correlative light and serial block face scanning electron microscopy, which we term 3D-CLEM, to model the entire mitotic chromosome complement at ultra-structural resolution. Prophase chromosomes exhibit a highly irregular surface appearance with a volume smaller than metaphase chromosomes. This may be due to the absence of the periphery, which associates with chromosomes only after nucleolar disassembly later in prophase. Indeed, the nucleolar volume almost entirely accounts for the extra volume found in metaphase chromosomes. Analysis of wild-type and Ki-67-depleted chromosomes reveals that the periphery comprises 30-47% of the entire chromosome volume and over 33% of the protein mass of isolated mitotic chromosomes determined by quantitative proteomics. Thus, chromatin makes up a surprisingly small percentage of the total mass of metaphase chromosomes.
Original languageEnglish
Pages (from-to)790-802
Number of pages13
JournalMolecular Cell
Volume64
Issue number4
Early online date10 Nov 2016
DOIs
Publication statusPublished - 17 Nov 2016

Keywords

  • 3D-CLEM
  • chromosome periphery
  • Ki-67
  • electron microscopy
  • CLEM

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