Instability of the D4Mit12 microsatellite marker in C57BL/6J x BALB/cJF1 hybrid mice is independent of the tumor phenotype.

We examined the stability of different types of DNA microsatellite markers in gamma-radiation-induced thymic lymphomas as well as normal, nontumorous tissues of F1 hybrid mice derived from the parental strains C57BL/6J, RF/J, and BALB/cJ. Surprisingly, the D4Mit12 microsatellite showed genomic instability in a significant fraction of DNAs of the (C57BL/6J x BALB/cJ) F1 hybrids with independence of the tumor phenotype. This instability was not found in the reciprocal F1 DNAs, in DNAs of the parental strains, or in DNAs of (C57BL/6J x RF/J) F1 hybrid mice. These results suggest that the instability of the D4Mit 12 microsatellite is dependent on its repeat length, the genetic background of F1 hybrids, and the maternal origin of the C57BL/6J allele.