Browsing by Author "Lin, Hua"

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    DNA damage reduces heterogeneity and coherence of chromatin motions
    (National Academy of Science, 2022) Locatelli, Maëlle; Lawrimore, Josh; Lin, Hua; Sanaullah, Sarvath; Seitz, Clayton; Segall, Dave; Kefer, Paul; Moreno, Naike Salvador; Lietz, Benton; Anderson, Rebecca; Holmes, Julia; Yuan, Chongli; Holzwarth, George; Bloom, Kerry S.; Liu, Jing; Bonin, Keith; Vidi, Pierre-Alexandre; Physics, School of Science
    Chromatin motions depend on and may regulate genome functions, in particular the DNA damage response. In yeast, DNA double-strand breaks (DSBs) globally increase chromatin diffusion, whereas in higher eukaryotes the impact of DSBs on chromatin dynamics is more nuanced. We mapped the motions of chromatin microdomains in mammalian cells using diffractive optics and photoactivatable chromatin probes and found a high level of spatial heterogeneity. DNA damage reduces heterogeneity and imposes spatially defined shifts in motions: Distal to DNA breaks, chromatin motions are globally reduced, whereas chromatin retains higher mobility at break sites. These effects are driven by context-dependent changes in chromatin compaction. Photoactivated lattices of chromatin microdomains are ideal to quantify microscale coupling of chromatin motion. We measured correlation distances up to 2 µm in the cell nucleus, spanning chromosome territories, and speculate that this correlation distance between chromatin microdomains corresponds to the physical separation of A and B compartments identified in chromosome conformation capture experiments. After DNA damage, chromatin motions become less correlated, a phenomenon driven by phase separation at DSBs. Our data indicate tight spatial control of chromatin motions after genomic insults, which may facilitate repair at the break sites and prevent deleterious contacts of DSBs, thereby reducing the risk of genomic rearrangements.
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    A guide for single-particle chromatin tracking in live cell nuclei
    (Wiley, 2022) Zhang, Mengdi; Seitz, Clayton; Chang, Garrick; Iqbal, Fadil; Lin, Hua; Liu, Jing; Physics, School of Science
    The emergence of labeling strategies and live cell imaging methods enables the imaging of chromatin in living cells at single digit nanometer resolution as well as milliseconds temporal resolution. These technical breakthroughs revolutionize our understanding of chromatin structure, dynamics and functions. Single molecule tracking algorithms are usually preferred to quantify the movement of these intranucleus elements to interpret the spatiotemporal evolution of the chromatin. In this review, we will first summarize the fluorescent labeling strategy of chromatin in live cells which will be followed by a systematic comparison of live cell imaging instrumentation. With the proper microscope, we will discuss the image analysis pipelines to extract the biophysical properties of the chromatin. Finally, we expect to give practical suggestions to broad biologists on how to select methods and link to the model properly according to different investigation purposes. This article is protected by copyright. All rights reserved.