title: Tracking the mechanical dynamics of human embryonic stem cell chromatin.
abstract: BACKGROUND
  A plastic chromatin structure has emerged as fundamental to the self-renewal and pluripotent capacity of embryonic stem (ES) cells. Direct measurement of chromatin dynamics in vivo is, however, challenging as high spatiotemporal resolution is required. Here, we present a new tracking-based method which can detect high frequency chromatin movement and quantify the mechanical dynamics of chromatin in live cells.
  
  
  RESULTS
  We use this method to study how the mechanical properties of chromatin movement in human embryonic stem cells (hESCs) are modulated spatiotemporally during differentiation into cardiomyocytes (CM). Notably, we find that pluripotency is associated with a highly discrete, energy-dependent frequency of chromatin movement that we refer to as a 'breathing' state. We find that this 'breathing' state is strictly dependent on the metabolic state of the cell and is progressively silenced during differentiation.
  
  
  CONCLUSIONS
  We thus propose that the measured chromatin high frequency movements in hESCs may represent a hallmark of pluripotency and serve as a mechanism to maintain the genome in a transcriptionally accessible state. This is a result that could not have been observed without the high spatial and temporal resolution provided by this novel tracking method.
authors.affiliation: Laboratory for Fluorescence Dynamics, Department of Biomedical Engineering, University of California, Irvine, CA 92697, USA. egratton22@yahoo.com.
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Hinde
authors.forename: Francesco
authors.initials: F
authors.lastname: Cardarelli
authors.forename: Aaron
authors.initials: A
authors.lastname: Chen
authors.forename: Michelle
authors.initials: M
authors.lastname: Khine
authors.forename: Enrico
authors.initials: E
authors.lastname: Gratton