Spinal muscular atrophy (SMA) is a neuromuscular disease particularly characterised by degeneration of ventral motor neurons. Survival motor neuron (SMN) 1 gene mutations cause SMA, and gene addition strategies to replace the faulty SMN1 copy are a therapeutic option. We have developed a novel, codon-optimised hSMN1 transgene and produced integration-proficient and integration-deficient lentiviral vectors with cytomegalovirus (CMV), human synapsin (hSYN) or human phosphoglycerate kinase (hPGK) promoters to determine the optimal expression cassette configuration. Integrating, CMV-driven and codon-optimised hSMN1 lentiviral vectors resulted in the highest production of functional SMN protein in vitro. Integration-deficient lentiviral vectors also led to significant expression of the optimised transgene and are expected to be safer than integrating vectors. Lentiviral delivery in culture led to activation of the DNA damage response, in particular elevating levels of phosphorylated ataxia telangiectasia mutated (pATM) and γH2AX, but the optimised hSMN1 transgene showed some protective effects. Neonatal delivery of adeno-associated viral vector (AAV9) vector encoding the optimised transgene to the Smn2B/− mouse model of SMA resulted in a significant increase of SMN protein levels in liver and spinal cord. This work shows the potential of a novel codon-optimised hSMN1 transgene as a therapeutic strategy for SMA.
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EMC was partially funded by a scholarship from Royal Holloway University of London. NAMN was partially funded by a scholarship and student stipend, from Royal Holloway University of London and The Spinal Muscular Atrophy Trust. HF acknowledges financial support for SMA research from the Great Ormond Street Hospital Charity (GOSH) which funds SB (Grant No. V5018). RJY-M acknowledges general financial support from SMA UK (formerly The SMA Trust), through the UK SMA Research Consortium, for SMA research in his laboratory. MB acknowledges general financial support from SMA UK, Muscular Dystrophy UK, Action Medical Research, SMA Angels Charity and Academy of Medical Sciences for SMA research in her laboratory.
NAMN, EMC, and RJY-M have filed a patent application on the uses of the novel SMN transgene reported in this manuscript. SB, HRF, and MB report no conflicts of interest.
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Nafchi, N.A.M., Chilcott, E.M., Brown, S. et al. Enhanced expression of the human Survival motor neuron 1 gene from a codon-optimised cDNA transgene in vitro and in vivo. Gene Ther (2023). https://doi.org/10.1038/s41434-023-00406-0