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

Abstract

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.

Ataluren‐driven restoration of Shwachman‐Bodian‐Diamond syndrome protein function in Shwachman‐Diamond syndrome bone marrow cells

“…Ataluren is a small molecule already approved by EMA for the treatment of DMD able to sustain PTC suppression by promoting insertion of near‐cognate tRNAs at the nonsense codon site . However, cell type‐dependent variations in ataluren therapeutic efficacy are known to hamper the ability of this drug to correct nonsense mutated protein expression . Thus, to rule out cell type‐specific effects, we first tested the ability of ataluren in restoring SBDS protein expression in both SDS hematological (i.e., LCLs and primary PBMCs) and nonhematological (i.e., MSCs) cells all obtained from patients carrying the c.[183–184TA > TC] mutation.…”

“…In this regard, recent evidence indicates that ataluren promotes nonsense suppression in human cells and yeasts through insertion of near‐cognate tRNAs at the nonsense codon site, resulting in amino acid replacements similar to those observed in endogenous read‐through . However, the efficacy of ataluren in promoting PTC read‐trough activity appears to be weaker in certain cell types . Thus, to rule out any bias due to the cell type being analyzed, we sought to determine the effect of ataluren treatment on SBDS protein expression in a panel of BM‐derived hematological and non hematological SDS cell lines consisting of a series of LCLs, PBMCs, BM‐MSCs, and BM‐MNCs freshly isolated from multiple SDS patients.…”

Nonsense Suppression as an Approach to Treat Lysosomal Storage Diseases

“…Among LSDs, PTC124 has been shown to restore enzyme activity in cultured fibroblasts and lymphoblasts derived from patients with infantile neuronal ceroid lipofuscinosis [64] and in cultured fibroblasts derived from MPS VI patients [68] (Table 1). Short-term, two-day administration of PTC124 to Cln1-R151X mice, a model of nonsense infantile neuronal ceroid lipofuscinosis, revealed an increase in palmitoyl-protein thioesterase activity in the liver and muscle of PTC124-treated mice relative to controls [71]. However, no increase in enzyme activity was observed in other tissues.…”

Homozygous PPT1 Splice Donor Mutation in a Cane Corso Dog With Neuronal Ceroid Lipofuscinosis

“…At least 4 different transgenic mouse models carrying nullifying Ppt1 mutations have been created and shown to exhibit CLN1‐like disease characteristics . These models are the subjects of ongoing and planned evaluations of therapeutic interventions intended for human CLN1 patients . Due to differences in longevity, size, and the complexities of neuroanatomy and behavior, canine NCL models have some advantages over rodent models for optimizing therapeutic interventions or establishing their efficacy.…”

“…[15][16][17][18] These models are the subjects of ongoing and planned evaluations of therapeutic interventions intended for human CLN1 patients. [19][20][21][22][23][24] Due to differences in longevity, size, and the complexities of neuroanatomy and behavior, canine NCL models have some advantages over rodent models for optimizing therapeutic interventions or establishing their efficacy. Indeed, a TPP1-deficient canine model for the CLN2 form of NCL has been used to develop enzyme replacement treatment 25 and paved the way for ongoing human trials (https://clinical trials.gov/ct2/show/NCT02678689).…”