A novel, ataxic mouse model of Ataxia Telangiectasia caused by a clinically relevant nonsense mutation

Ataxia Telangiectasia (A-T) is caused by null mutations in the genome stability gene, ATM (A-T mutated). In mice, similar null mutations do not replicate A-T9s characteristic severe ataxia with associated cerebellar dysfunction and atrophy. By increasing genotoxic stress, through the insertion of null mutations in the Atm (nonsense) and related Aptx (knockout) genes, we have generated a novel A-T mouse that first develops mild ataxia, associated with abnormal Purkinje neuron (PN) activity and decreased size, progressing to severe ataxia correlated with further reduced PN activity as well as PN loss and overall cerebellar atrophy. These mice also exhibit high incidences of cancer and immune abnormalities that are all hallmarks of the human disorder. Enabled by the insertion of a clinically relevant nonsense mutation in Atm, we demonstrate that small molecule readthrough (SMRT) compounds can restore ATM production, indicating their potential as a future A-T therapeutic.