Attenuation of Nonsense-Mediated mRNA Decay Enhances In Vivo Nonsense Suppression

Abstract

Nonsense suppression therapy is an approach to treat genetic diseases caused by nonsense mutations. This therapeutic strategy pharmacologically suppresses translation termination at Premature Termination Codons (PTCs) in order to restore expression of functional protein. However, the process of Nonsense-Mediated mRNA Decay (NMD), which reduces the abundance of mRNAs containing PTCs, frequently limits this approach. Here, we used a mouse model of the lysosomal storage disease mucopolysaccharidosis I-Hurler (MPS I-H) that carries a PTC in the Idua locus to test whether NMD attenuation can enhance PTC suppression in vivo. Idua encodes alpha-L-iduronidase, an enzyme required for degradation of the glycosaminoglycans (GAGs) heparan sulfate and dermatan sulfate. We found that the NMD attenuator NMDI-1 increased the abundance of the PTC-containing Idua transcript. Furthermore, co-administration of NMDI-1 with the PTC suppression drug gentamicin enhanced alpha-L-iduronidase activity compared to gentamicin alone, leading to a greater reduction of GAG storage in mouse tissues, including the brain. These results demonstrate that NMD attenuation significantly enhances suppression therapy in vivo.

Synthetic Aminoglycosides Efficiently Suppress Cystic Fibrosis Transmembrane Conductance Regulator Nonsense Mutations and Are Enhanced by Ivacaftor

“…Other approaches to augment rescue of CFTR nonsense mutations, such as the coadministration of polyanions, such as poly-L-aspartic acid, or NMD inhibitors, such as NMDI-1, are other options that could be tested in the future (13,55). Furthermore, time-dependent increases in activity have been observed with prolonged administration of NB84 in a mouse model of Hurler's syndrome (38), a finding also observed in patients with CF administered ataluren in an open label trial (16), suggesting that enhanced readthrough with these agents may be possible with chronic administration in vivo.…”

Effect of Readthrough Treatment in Fibroblasts of Patients Affected by Lysosomal Diseases Caused by Premature Termination Codons

“…In our study, we focused on nonsense or frameshift mutations leading to PTC resulting in an almost complete absence of particular key proteins involved in lysosomal function and cell homeostasis maintenance. Preclinical studies with gentamicin or PTC124 had succeeded by enhancing stop codon readthrough and were able to be used as therapeutic agents for genetic diseases [9][10][11][12][13][14][15][16][17][18][36][37][38][39][40][41][42]. PTC124 has been successfully extended into clinical trials [18,43], although preliminary results are not clear for Duchenne muscular dystrophy [44].…”

“…Glutamine is preferably inserted at nonsense UAG or UAA codons, whereas UGA miscode to tryptophan [36][37][38]. Taking into account these rules, the predicted amino acid changes were analyzed, using an in silico approach, for each patient (Polyphen-2 and SIFT analyses).…”

Nonsense-mediated decay in genetic disease: Friend or foe?

“…In addition, another NMD inhibitor called NMD-I was recently discovered. NMD-I inhibits UPF1 dephosphorylation by blocking the interaction between UPF1 and SMG5, thus preventing the recruitment of PP2A and dephosphorylation of UPF1 [172, 173]. For the treatment of many genetic disorders, the use of any single therapy may not surpass the therapeutic threshold needed to produce enough functional protein to effectively alter disease outcome.…”