# Investigations into multiple fission yeast chromosome size determinants

## TL;DR

This study explores what determines the size of chromosomes in fission yeast, finding that condensin levels, not cell or nuclear size, control chromosome dimensions.

## Contribution

The study identifies chromosomal condensin levels as a key determinant of chromosome size in fission yeast.

## Key findings

- Cell and nuclear volume in interphase have little influence on chromosome size.
- Time spent in mitosis does not significantly affect chromosome dimensions.
- Higher condensin levels lead to more compact chromosomes.

## Abstract

Mitotic chromosome dimensions differ between species, and they differ between developmental stages within an organism. 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 and nuclear volume in interphase, and 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 (thinner and shorter) chromosomes. Our observations inform the 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.

Summary: During cell divisions, chromosome dimensions are matched to the size of the cells that contain them. Here, we explore what defines chromosome size using the tractable fission yeast as a model, including cell size and nuclear volume in interphase, time spent in mitosis and the levels of the chromosomal condensin complex.