TP53 and B-cell chronic lymphocytic leukemia: To generate models that faithfully mimic genomic aberrations that are recurrently observed in high-risk human CLL, we generated animals in which B cell-specific expression of Cre recombinase leads to the conditional deletion of Trp53 or Atm. We employed the Eμ:TCL1 background and crossed in a Cd19Cre allele15, to allow B cell-specific deletion of LoxP-flanked Trp53 or Atm alleles16, 17 (Fig. 1a).