Satellite DNA sequence dictates pericentromere heterochromatin formation and function

Pericentromeres are heterochromatic regions adjacent to centromeres that ensure accurate chromosome segregation. Despite their conserved function, they are composed of rapidly evolving A/T-rich satellite DNA. To test the functional consequences of this rapid sequence evolution, we establish hybrid mouse embryos as a model system to compare divergent satellite arrays from distinct species in a common cytoplasm. We show that variation in satellite sequence impacts heterochromatin formation, recruitment of the Chromosome Passenger Complex (CPC), and interactions with the mitotic spindle. Differences in satellite DNA sequence alter pericentromere packaging by Polycomb Repressive Complex 1 (PRC1), as satellite arrays that recruit PRC1 are enriched for specific A/T sequences that the PRC1 AT-hook preferentially binds. Furthermore, PRC1 heterochromatin modifies pericentromere function by inhibiting recruitment of the CPC, increasing microtubule forces on kinetochores during mitosis. Our results provide a direct link between satellite DNA composition and mitotic chromosome behavior and highlight early embryogenesis as a critical point in development that is sensitive to satellite DNA evolution.