Interspecific backcrosses provide an important new tool for centromere mapping of mouse chromosomes.

Centromere mapping of mouse chromosomes has been problematic due to a paucity of appropriate markers. As a result, the mapping of centromeres has most often relied on the use of Robertsonian chromosomes to mark chromosome ends. Many Robertsonian translocations have been shown to suppress recombination in pericentric regions; therefore, centromere mapping data generated by using Robertsonian chromosomes must be interpreted with caution. We have utilized a new tool for centromere mapping that is applicable to all mouse chromosomes (except the Y chromosome) and that potentially overcomes the inherent limitations of using Robertsonian translocations. Briefly, an interspecific backcross mapping panel was constructed from crosses of C57BL/6Ros and Mus spretus mice. The centromere of each chromosome was subsequently typed by in situ hybridization, using a major satellite probe that uniformly labels C57BL/6Ros centromeres but hybridizes only weakly to M. spretus centromeres. Genetic markers that were already known to map in the proximal region of each of the mouse chromosomes were then typed by segregation analyses of restriction fragment length polymorphisms. These studies have made it possible to align the interspecific genetic map of each of the mouse autosomes and the X chromosome with respect to the centromere. They also provide a basis for comparison with centromere mapping data generated previously by other means.