Dr. Thomas Roderick, The Jackson Laboratory
The In(13)43Rk mutation was radiation induced by exposing a male that likely derived from a Mus poschiavinus to 1000 rads from a cesium irradiator. This male was subsequently bred to a C57BL/6J female. This large inversion, which encompasses Ap3b1, was maintained through a breeding scheme that made use of the pearl mutation, Ap3b1pe. By breeding to a pearl homozygote this inversion was captured in repulsion with the recessive pearl mutation as a marker. By intercrossing these repulsion heterozygotes the offspring can be: homozygous for the pearl coat color mutation and thus lack the inversion; homozygous for the inversion; or heterozygous for both pearl and the inversion carried in repulsion. Any non-pearl pups can be intercrossed for a progeny test to identify those carrying the pearl mutation, and therefore repulsion heterozygotes, from those not carrying pearl and therefore homozygous for the inversion. Embryos were cryopreserved from this line from repulsion heterozygotes either intercrossed or bred to mice homozygous for the inversion. Thus, the cryorecovered pups will either be homozygous for the inversion or heterozygous for the inversion and pearl in repulsion.