How nucleus size affects chromatin motion? - Experimental measurements and a polymer physics theory

Chromatin moves dynamically inside the cell nucleus, and its motion is often correlated with gene functions such as DNA recombination and transcription. A recent study has shown that during early embryogenesis of the nematode, Caenorhabditis elegans, the chromatin motion markedly decreases with the cell stage. However, the underlying mechanism for this transition has yet to be elucidated. Here we systematically investigate the impact of nuclear size to demonstrate that it is indeed a decisive factor in chromatin mobility. We show that a simple theoretical description, which takes into account the length and time scales of chromatin polymer solution, can quantitatively describe the relationship between the nucleus size and the chromatin motion in vivo. Our results emphasize a regulatory role of nuclear size in restricting chromatin motion, and a generic polymer physics model plays a guiding role in capturing this essential feature.

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