UTILITY OF C57BL 6J X 129/SV(JAE) EMBRYONIC STEM-CELLS FOR GENERATINGCHROMOSOMAL DELETIONS - TOLERANCE TO GAMMA-RADIATION AND MICROSATELLITE POLYMORPHISM/

We have previously reported a method for making nested deletion comple xes in mice by irradiation of ES cells. The kev to this technology is that F-1 hybrid ES cells (called v17.2) of the genotype (BALB/cTa x 12 9/Sv(Jae)) retain germline colonizing ability after exposure to levels of ionizing radiation that induce chromosomal deletions. In an effort to identify other genotypes of ES cells that are suitable for this te chnology, the radiation sensitivity of the cell line v6.4, which is of the genotype (C57BL/6J x radiation exposures, the developmental poten tial of these cells was assayed by injecting them into blastocysts to generate chimeric mice. These experiments showed that while cell letha lity increased as the level of radiation increased, the surviving ES c ells retained full totipotency at all exposure levels, up to 400 Rads. Because polymorphism between parental microsatellite alleles in the F -1 hyrbrid ES cells is important for ascertaining the sizes of induced deletions, the 129/SvJ and 129/Sv(Jae) allele sizes of 38 microsatell ite loci on chromosome (Chr) 17 were determined. This revealed a highe r level of polymorphism between 129 and C57BL/6J on Chr 17. The radiat ion tolerance, high polymorphism between parental strains, and presenc e of the widely used C57BL/6J strain component make v6.3 ES cells an a ttractive cell line for generating radiation-induced chromosomal delet ions.