Development of therapies for spinal muscular atrophy using gene therapy and nanotechnology

• Main Author: Little, Daniel
• Other Authors: Azzouz, Mimoun ; Giuseppe, Battaglia ; Ning, Ke
• Published: University of Sheffield 2013
• Subjects: 616.7
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.581632

Spinal muscular atrophy (SMA) is a genetic disease which is characterized by muscle weakness and atrophy. The disease arises from mutations in the survival motor neuron 1 (SMN1) gene causing degeneration of spinal cord motor neurons. No effective treatment is currently available for SMA however it may be possible to treat the disease using gene therapy. The aim of this project is to develop potential therapies for SMA by investigating different viral and non-viral gene therapy vectors and assessing the effect of potential disease modifying genes. The data collected are described under four chapters as follows: 1: The aim here was to develop a novel approach based on polymer nanoparticles (polymersomes) for gene delivery. Encapsulation of DNA by polymersomes was optimised and polymersomes were used to restore SMN levels into a fibroblast cell line isolated from a child with severe SMA. 2: The ability of adeno-associated virus serotype 5 (AAV5) vectors expressing GFP to transduce the central nervous system (CNS) following intravenous injection was tested in neonatal wild-type mice. Overall transduction efficiency of AAV5-GFP in the brain was low and very few lumbar spinal cord neurons were found to be transduced, suggesting that AAV5 is not an appropriate vector to treat diseases such as SMA. 3: AAV6 was used to overexpress hnRNP R in an in vivo model of SMA. hnRNP R is a candidate disease modifying gene for SMA due to its interaction with SMN and β-actin. However this strategy had only a very marginal effect on the phenotype and life-span of this SMA mouse model. 4: Finally AAV9 was used to silence phosphatase and tensin homolog (PTEN) in an in vivo model of SMA. PTEN is a negative regulator of growth which acts on the PI3K/Akt pathway. AAV9-mediated PTEN silencing resulted in a significant increase in the lifespan of a SMA mouse model coupled with an improved phenotype. In conclusion this work highlights two major findings: i) polymersomes can be used to deliver SMN plasmid DNA to restore SMN mRNA and protein levels in an in vitro model of SMA; ii) AAV9-mediated silencing of PTEN can improve the phenotype and increase lifespan of a SMA mouse model.