DNA Content Contributes to Nuclear Size Control in Xenopus

Cells adapt to drastic changes in genome quantity during evolution and cell division by adjusting the nuclear size to exert genomic functions. However, the mechanism by which DNA content within the nucleus contributes to controlling the nuclear size, remains unclear. Here, we experimentally evaluated the effects of DNA content by utilizing cell-free Xenopus egg extracts and imaging of in vivo embryos. Upon manipulation of DNA content while maintaining cytoplasmic effects as constant, both plateau size and expansion speed of the nucleus correlated highly with DNA content. We also found an increase in the amount of membranes on the nuclear surface when DNA content was low and alterations in the nuclear expansion dynamics after converting the chromatin structures. These results demonstrate a novel model in which the physical properties of the chromatin, rather than the coding sequences themselves, contribute to nuclear expansion by generating forces that expand the nucleus outwardly.