Ataxia telangiectasia–like disorder (ATLD) features cerebellar degeneration leading to ataxia, as well as genomic instability and hypersensitivity to agents that cause DSBs. This syndrome results from inherited recessive hypomorphic alleles of Mre11 (ref. 30). Mre11 ATLD1 is a nonsense mutation that truncates 78 amino acids from the C terminus and causes very low levels of all three MRN components. Given the relationship between MRN and CtIP, we determined if CtIP levels are affected in this disorder. Indeed, CtIP levels are depleted in cells derived from a person with ATLD or from a mouse model expressing only Mre11 ATLD1 (Fig. 1a). Ataxia telangiectasia is a disorder similar to ATLD and results from inherited mutation in the ATM gene.
Despite similar clinical outcomes and cellular phenotypes of the disorders, we find that ATM deficiency does not affect CtIP levels (Fig. 1a).