Differences between CASA/Rk and CAST/Ei
JAX® NOTES Issue 456, Winter 1994
CASA/Rk and CAST/Ei are inbred strains derived from a wild population of the subspecies Mus musculus castaneus. The strains are related but not sublines of the same strain simply maintained by two different holders. M.m. castaneus mice trapped in Thailand by Dr. Joe Marshall were sent to Dr. Verne Chapman at Roswell Park Memorial Institute and then to Drs. E. M. Eicher and T. H. Roderick at The Jackson Laboratory in 1971. CASA/Rk and CAST/Ei were inbred independently by Roderick (Rk) and Eicher (Ei) from this small, imported founder population. Because the mice imported were not inbred, they were segregating for more than one allele at many different loci. Either allele at each locus could have been fixed in either strain during inbreeding. Therefore, we can expect that CASA and CAST may differ at many loci. An allele typed in one strain should not be assumed to be the same in the other. At some loci, especially biochemical polymorphic loci, CASA or CAST may have the same allele as common inbred strains. Information on the loci typed for each strain and at which loci they are known to differ or be the same is available from the on-line electronic database GBASE.
We are encouraging the use of CAST/Ei because the mice in this strain breed better than in CASA/Rk. We maintain a larger colony of CAST/Ei, making it possible to maintain the colony more efficiently and fill requests rapidly. We plan to remove the small colony of CASA/Rk from the breeding colony if the strain can be successfully preserved as frozen embryos.
