Distinctive nuclear organisation of centromeres and regions involved in pluripotency in human embryonic stem cells.

Nuclear organisation is thought to be important in regulating gene expression. Here we investigate whether human embryonic stem cells (hES) have a particular nuclear organisation, which could be important for maintaining their pluripotent state. We found that whereas the nuclei of hES cells have a general gene-density-related radial organisation of chromosomes, as is seen in differentiated cells, there are also distinctive localisations for chromosome regions and gene loci with a role in pluripotency. Chromosome 12p, a region of the human genome that contains clustered pluripotency genes including NANOG, has a more central nuclear localisation in ES cells than in differentiated cells. On chromosome 6p we find no overall change in nuclear chromosome position, but instead we detect a relocalisation of the OCT4 locus, to a position outside its chromosome territory. There is also a smaller proportion of centromeres located close to the nuclear periphery in hES cells compared to differentiated cells. We conclude that hES cell nuclei have a distinct nuclear architecture, especially at loci involved in maintaining pluripotency. Understanding this level of hES cell biology provides a framework within which other large-scale chromatin changes that may accompany differentiation can be considered.