Shaban, H. A. et al. Genome Biol. 21, 95 (2020).
Studying genome organization and dynamics is crucial for understanding the regulation of gene expression. Although genome movement has been explored, a method for studying bulk chromatin dynamics at high resolution was not available. Shaban et al. have developed high-resolution diffusion mapping (Hi-D) to quantitatively map the dynamics of chromatin and abundant nuclear proteins. In Hi-D, labeled DNA or nuclear proteins are imaged over time, and then dense optical flow reconstruction is used to quantify the local motion at sub-pixel accuracy. Next, a Bayesian interference approach is employed to classify local types of diffusion, and biophysical properties such as diffusion constants are used to create two-dimensional maps of dynamics. With Hi-D the researchers were able to map the dynamics of chromatin under multiple conditions as well as the dynamics of RNA polymerase II. A key observation of the study is that chromatin dynamics are dictated by DNA–DNA contacts and protein binding rather than chromatin density and compaction.