Cell-cycle and Age-Related Modulations of Mouse Chromosome Stiffness

Abstract Chromosome structure is complex, and many aspects of its organization remain poorly understood. Measuring chromosome stiffness offers valuable insight into their structural properties. In this study, we analyzed the stiffness of chromosomes from metaphase I (MI) and metaphase II (MII) oocytes. Our results revealed a ten-fold increase in stiffness (Young’s modulus) of MI chromosomes compared to somatic chromosomes. Furthermore, the stiffness of MII chromosomes was lower than that of MI chromosomes. We examined the role of meiosis-specific cohesin complexes in regulating chromosome stiffness. Surprisingly, chromosomes from three meiosis-specific cohesin mutants exhibited stiffness comparable to that of wild-type chromosomes, indicating that these cohesins are not the primary determinants of chromosome stiffness. Additionally, our findings revealed an age-related increase in chromosome stiffness in MI oocytes. Since aging is associated with elevated levels of DNA damage, we investigated the impact of etoposide-induced DNA damage on oocyte chromosome stiffness and found that it led to a reduction in MI chromosome stiffness. Overall, our study underscores the dynamic and cyclical nature of chromosome stiffness, modulated by both the cell cycle and age-related factors.