This holiday season, we breathed in lots of good smells—the scent of pine trees, the aroma of pumpkin pie, and the unmistakable smoky smell of a roaring fire. Now, researchers say they’ve caught chromatin in the act of “breathing” in human embryonic stem cells (hESCs) before they differentiate.
The team from California and Italy developed a new method for watching chromatin movements in real time in vivo.
The new tracking method rapidly scans in a line across fluorescently labeled chromatin. The researchers do this over and over to get a time series of chromatin intensity. They then do various mathematical tricks. Here’s what they found out:
- In hESCs, chromatin moved back and forth (which they call “breathing”) at frequencies of 10 to 100 Hz. In HELA cells—which are differentiated but unregulated—the chromatin vibrated a whole lot less. However, the chromatin in regulated and differentiated NIH3T3 cells was very different—there were no peaks of movement.
- From other experiments, it was clear that the movements were not due to whole cell movement or mechanical vibration—they really came from the chromatin.
- The oscillations of chromatin movement in hESCs were energy-dependent.
- As differentiation progressed in hESCs, the peaks of chromatin movement got smaller and smaller.
“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,” they conclude.
So, does chromatin breathe? Read the paper at Epigenetics & Chromatin, December 2012.