Murine segmental duplications are hot spots for chromosome and gene evolution.

Mouse and rat genomic sequences permit us to obtain a global view of evolutionary rearrangements that have occurred between the two species and to define hallmarks that might underlie these events. We present a comparative study of the sequence assemblies of mouse and rat genomes and report an enrichment of rodent-specific segmental duplications in regions where synteny is not preserved. We show that segmental duplications present higher rates of molecular evolution and that genes in rearranged regions have evolved faster than those located elsewhere. Previous studies have shown that synteny breakpoints between the mouse and the human genomes are enriched in human segmental duplications, suggesting a causative connection between such structures and evolutionary rearrangements. Our work provides further evidence to support the role of segmental duplications in chromosomal rearrangements in the evolution of the architecture of mammalian chromosomes and in the speciation processes that separate the mouse and the rat.