Investigations into fission yeast chromosome size determinants

Mitotic chromosome dimensions differ between organisms, and they differ within a species between developmental stages. The physiological determinants of chromosome size remain poorly understood. Here, we investigate chromosome size determinants in the fission yeast Schizosaccharomyces pombe . Super-resolution microscopy and semi-automated measurements reveal that cell or nuclear volume in interphase, or the time spent in mitosis (both previously proposed chromosome size determinants), have little influence on resultant chromosome dimensions. Instead, levels of the chromosomal condensin complex affect chromosome size, with increasing condensin levels resulting in more compact, shorter and thinner, chromosomes. These observations inform our understanding of how chromosome dimensions are controlled in an organism. They suggest that a chromosome-intrinsic mechanism sets chromosome size, more so than the environment in which chromosomes find themselves in.