title: A novel morpholino oligomer targeting ISS-N1 improves rescue of severe spinal muscular atrophy transgenic mice.
abstract: In the search for the most efficacious antisense oligonucleotides (AOs) aimed at inducing SMN2 exon 7 inclusion, we systematically assessed three AOs, PMO25 (-10, -34), PMO18 (-10, -27), and PMO20 (-10, -29), complementary to the SMN2 intron 7 splicing silencer (ISS-N1). PMO25 was the most efficacious in augmenting exon 7 inclusion in vitro in spinal muscular atrophy (SMA) patient fibroblasts and in vitro splicing assays. PMO25 and PMO18 were compared further in a mouse model of severe SMA. After a single intracerebroventricular (ICV) injection in neonatal mice, PMO25 increased the life span of severe SMA mice up to 30-fold, with average survival greater by 3-fold compared with PMO18 at a dose of 20 μg/g and 2-fold at 40 μg/g. Exon 7 inclusion was increased in the CNS but not in peripheral tissues. Systemic delivery of PMO25 at birth achieved a similar outcome and produced increased exon 7 inclusion both in the CNS and peripherally. Systemic administration of a 10-μg/g concentration of PMO25 conjugated to an octaguanidine dendrimer (VMO25) increased the life span only 2-fold in neonatal type I SMA mice, although it prevented tail necrosis in mild SMA mice. Higher doses and ICV injection of VMO25 were associated with toxicity. We conclude that (1) the 25-mer AO is more efficient than the 18-mer and 20-mer in modifying SMN2 splicing in vitro; (2) it is more efficient in prolonging survival in SMA mice; and (3) naked Morpholino oligomers are more efficient and safer than the Vivo-Morpholino and have potential for future SMA clinical applications.
authors: Dubowitz Neuromuscular Centre, Institute of Child Health, University College London, United Kingdom. haiyan.zhou@ucl.ac.uk
authors: Haiyan
authors: H
authors: Zhou
authors: Narinder
authors: N
authors: Janghra
authors: Chalermchai
authors: C
authors: Mitrpant
authors: Rachel L
authors: RL
authors: Dickinson
authors: Karen
authors: K
authors: Anthony
authors: Loren
authors: L
authors: Price
authors: Ian C
authors: IC
authors: Eperon
authors: Stephen D
authors: SD
authors: Wilton
authors: Jennifer
authors: J
authors: Morgan
authors: Francesco
authors: F
authors: Muntoni
mesh_terms: D017398:Alternative Splicing; D000818:Animals; D020029:Base Pairing; D001483:Base Sequence; D004195:Disease Models, Animal; D005091:Exons; D023061:Gene Order; D006801:Humans; D007438:Introns; D051379:Mice; D008822:Mice, Transgenic; D060172:Morpholinos / Q000008:administration & dosage / Q000737:chemistry / Q000378:metabolism*; D009134:Muscular Atrophy, Spinal / Q000235:genetics* / Q000378:metabolism* / Q000401:mortality / Q000628:therapy; D012045:Regulatory Sequences, Nucleic Acid; D055540:Survival of Motor Neuron 2 Protein / Q000235:genetics* / Q000378:metabolism*
chemical_list: D060172:Morpholinos; D055540:Survival of Motor Neuron 2 Protein