Tissue‐specific variation in nonsense mutant transcript level and drug‐induced read‐through efficiency in the Cln1 (R151X) mouse model of INCL

About 10% of inherited diseases are caused by nonsense mutations [Trends Mol Med 18 (2012) 688], and nonsense suppression drug therapy promoting translation through premature stop codons is an emerging therapeutic approach. Infantile neuronal ceroid lipofuscinosis (INCL), a childhood neurodegenerative disease, results from mutations in the CLN1 gene encoding the lysosomal enzyme, palmitoyl‐protein thioesterase 1 (PPT1) [Biochim Biophys Acta 1832 (2013) 1806, Hum Mutat (2012) 63, Biochim Biophys Acta 1832 (2013) 1881]. The nonsense mutation p.R151X is the most common disease‐causing CLN1 mutation Hum Mutat (2012) 63. In the novel Cln1 (R151X) mouse model of INCL, we found large, tissue‐specific variations in Cln1 (R151X) mRNA level and PPT1 residual enzyme activity. These tissue‐specific differences strongly influenced the read‐through efficiency of ataluren (PTC124), a well‐known nonsense suppression drug. A two‐day treatment with ataluren (10 mg/kg) increased PPT1 enzyme activity in the liver and muscle, but not in any other tissue examined. Our study identifies a new challenge/hurdle for read‐through drug therapy: variable efficiency of read‐through therapy in the different tissues/organs because of tissue‐specific variations in nonsense mutant transcript levels.