Loss of heterozygosity on chromosome 5 in vicinity of the telomere in gamma-radiation-induced thymic lymphomas in mice

Analysis of the loss of heterozygosity at the D5Mit143 locus was done for t hymic lymphomas induced by gamma-irradiation of mice from two reciprocal ba ckcrosses (BALB/c x CcS-13)F1 x BALB/c and (BALB/c x CcS-13)FI x CcS-13. BA LB/c mice are susceptible to gamma-ray induction of lymphomas. The CcS-13 s train is one of 20 CcS/Dem (CcS) series of recombinant congenic strains, an d the CcS-13 mice are resistant to gamma-radiation-induced lymphomas [1, 8] . Our preliminary tests show 50% (6/12) frequency of allelic loss at the D5Mi t143 locus in thymic lymphomas induced by gamma-irradiation of the mice fro m (BALB/c x CcS-13)F1 x BALB/c backcross. Yet, in gamma-radiation-induced l ymphomas from the backcross made in opposite direction, namely, (BALB/c x C cS-13)FI x CcS-13, the analysis with the D5Mit143 marker revealed low incid ence of the loss of heterozygosity, 6.7% (1/15). The DSMit143 locus resides in the distal part of chromosome 5, close to the telomere. Allelic loss of heterozygosity at the D5Mit143 locus showed strain specific ity. In each case, the lost allele derived from the CcS-13 resistant strain . Our current results and previously done linkage analysis [8] let us to susp ect existence of a putative tumor suppressor gene for gamma-radiation-induc ed lymphoma at the region of murine chromosome 5.