A new ultradian rhythm in mammalian cell dry mass observed by holography

We have discovered a new 4 h ultradian rhythm that occurs during the interphase of the cell cycle in a wide range of individual mammalian cells, including both primary and transformed cells. The rhythm was detected by holographic lens-free microscopy that follows the histories of the dry mass of thousands of single live cells simultaneously, each at a resolution of five minutes. It was vital that the rhythm was observed in inherently heterogeneous cell populations, thus eliminating synchronization and labeling bias. The rhythm is independent of circadian rhythm, and is temperature-compensated. We show that the amplitude of the fundamental frequency provides a way to quantify the effects of, chemical reagents on cells, thus shedding light on its mechanism. The rhythm is suppressed by proteostasis disruptors and is detected only in proliferating cells, suggesting that it represents a massive degradation and re-synthesis of protein every 4 h in growing cells.

Automated summary

A new 4-hour ultradian rhythm has been discovered during the interphase of the cell cycle, detected in various individual mammalian cells using holographic lens-free microscopy. This rhythm is independent of the circadian rhythm, and provides a way to quantify the effects of chemical reagents on cells through the amplitude of the fundamental frequency. It represents a massive degradation and re-synthesis of protein every 4 hours in proliferating cells, and is suppressed by proteostasis disruptors.