Physical properties of the chromosomes and implications for development.

Remarkable progress has been made in understanding chromosome structures inside the cell nucleus. Recent advances in Hi-C technologies enable the detection of genome-wide chromatin interactions, providing insight into three-dimensional (3D) genome organization. Advancements in the spatial and temporal resolutions of imaging as well as in molecular biological techniques allow the tracking of specific chromosomal loci, improving our understanding of chromosome movements. From these data, we are beginning to understand how the intra-nuclear locations of chromatin loci and the 3D genome structure change during development and differentiation. This emerging field of genome structure and dynamics research requires an interdisciplinary approach including efficient collaborations between experimental biologists and physicists, informaticians, or engineers. Quantitative and mathematical analyses based on polymer physics are becoming increasingly important for processing and interpreting experimental data on 3D chromosome structures and dynamics. In this review, we aim to provide an overview of recent research on the physical aspects of chromosome structure and dynamics oriented for biologists. These studies have mainly focused on chromosomes at the cellular level, using unicellular organisms and cultured cells. However, physical parameters that change during development, such as nuclear size, may impact genome structure and dynamics. Here, we discuss how chromatin dynamics and genome structures in early embryos change during development, which we expect will be a hot topic in the field of chromatin dynamics in the near future. We hope this review helps developmental biologists to quantitatively investigate the physical natures of chromosomes in developmental biology research.