DBA/2N.pUR288 (N7)

BALB/c.pUR288 (N6)

DBA/2N.pUR288 (N7)

Fig. 1. Development of a genetic system that is conducive for correlating the genetics of oxidative B cell mutagenesis with the susceptibility to PCT development. The system is based on PCT-hypersusceptible C.D2-Idhl-Pep3, PCT-susceptible B/c, and PCT-resistant D2 mice congenie for shuttle vector /.LIZ or pUR288. The congenie mice were generated by facilitated backcrossing of ALIZ or pUR288 from B6 donor mice to the indicated recipients. All congenies are homozygous, ALIZ+/+ or placZ+/+. However, the pUR288 congenies contain only 20 copies of the transgene instead of the 40 copies in B6-pUR288 parental mice. This loss was caused by limiting the backcross of pUR288 to the 10-copy transgene on chromosome 3. The second 10-copy transgene on chromosome 4 was eliminated during breeding because this chromosome contains as many as three R and S genes for PCTG. The presence of these genes in the neighborhood of pUR288 would have complicated the backcross in a major way and possibly interfered with the desired R/S phenotype of the congenies.

to anyone who contemplates a similar backcross, because we did observe several mice with severe reductions in rescue efficiency. The reasons for that remained unclear; however, deletions in the transgenic concatemer during pairing of homologous chromosomes in meiosis are a possible candidate. Summarizing 3 years of breeding, genotyping, and testing for shuttle vector rescue efficiency, Fig. 1 illustrates the congenic strains currently available.

XLIZ (Big Blue) Assay

Shuttle Vector and Principle of Assay

The principal utility of the XLIZ shuttle vector (Fig. 2A) lies in its ability to transfer a suitable target and reporter gene for mutagenesis (lacl and alacZ, respectively) from the mouse genome to an Escherichia coli detection system.7

7 G. S. Provost, P. L. Kretz, R. T. Hamner, C. D. Matthews, B. J. Rogers, K. S. Lundberg, M. J. Dycaico, and J. M. Short, Mutat. Res. 288, 133 (1993).

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