Notably, the chromosome breakage phenotype observed in the 2 RECQL1-mutant LCLs was comparable to that seen in a LCL derived from a patient with ataxia telangiectasia–like disorder (ATLD) carrying a hypomorphic homozygous truncating mutation in MRE11A (22), following exposure to CPT, but was significantly lower than that seen in the ATLD cell line following exposure to ETOP (Figure 4C). The gene discussed is RECQL; the disease is ataxia-telangiectasia-like disorder.