title: A large animal model of spinal muscular atrophy and correction of phenotype.
abstract: OBJECTIVE
  Spinal muscular atrophy (SMA) is caused by reduced levels of survival motor neuron (SMN) protein, which results in motoneuron loss. Therapeutic strategies to increase SMN levels including drug compounds, antisense oligonucleotides, and scAAV9 gene therapy have proved effective in mice. We wished to determine whether reduction of SMN in postnatal motoneurons resulted in SMA in a large animal model, whether SMA could be corrected after development of muscle weakness, and the response of clinically relevant biomarkers.
  
  
  METHODS
  Using intrathecal delivery of scAAV9 expressing an shRNA targeting pig SMN1, SMN was knocked down in motoneurons postnatally to SMA levels. This resulted in an SMA phenotype representing the first large animal model of SMA. Restoration of SMN was performed at different time points with scAAV9 expressing human SMN (scAAV9-SMN), and electrophysiology measurements and pathology were performed.
  
  
  RESULTS
  Knockdown of SMN in postnatal motoneurons results in overt proximal weakness, fibrillations on electromyography indicating active denervation, and reduced compound muscle action potential (CMAP) and motor unit number estimation (MUNE), as in human SMA. Neuropathology showed loss of motoneurons and motor axons. Presymptomatic delivery of scAAV9-SMN prevented SMA symptoms, indicating that all changes are SMN dependent. Delivery of scAAV9-SMN after symptom onset had a marked impact on phenotype, electrophysiological measures, and pathology.
  
  
  CONCLUSIONS
  High SMN levels are critical in postnatal motoneurons, and reduction of SMN results in an SMA phenotype that is SMN dependent. Importantly, clinically relevant biomarkers including CMAP and MUNE are responsive to SMN restoration, and abrogation of phenotype can be achieved even after symptom onset.
authors.affiliation: Department of Molecular and Cellular Biochemistry, Ohio State University Wexner Medical Center, Columbus, OH.
authors.forename: Sandra I
authors.initials: SI
authors.lastname: Duque
authors.forename: W David
authors.initials: WD
authors.lastname: Arnold
authors.forename: Philipp
authors.initials: P
authors.lastname: Odermatt
authors.forename: Xiaohui
authors.initials: X
authors.lastname: Li
authors.forename: Paul N
authors.initials: PN
authors.lastname: Porensky
authors.forename: Leah
authors.initials: L
authors.lastname: Schmelzer
authors.forename: Kathrin
authors.initials: K
authors.lastname: Meyer
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Kolb
authors.forename: Daniel
authors.initials: D
authors.lastname: Schümperli
authors.forename: Brian K
authors.initials: BK
authors.lastname: Kaspar
authors.forename: Arthur H M
authors.initials: AH
authors.lastname: Burghes
mesh_terms: D000818:Animals; D015415:Biomarkers; D000229:Dependovirus / Q000235:genetics; D004195:Disease Models, Animal; D004576:Electromyography; D015316:Genetic Therapy / Q000379:methods*; D005822:Genetic Vectors / Q000627:therapeutic use; D006801:Humans; D009046:Motor Neurons / Q000378:metabolism* / Q000473:pathology; D009134:Muscular Atrophy, Spinal / Q000209:etiology / Q000473:pathology / Q000503:physiopathology / Q000628:therapy*; D010641:Phenotype; D034741:RNA, Small Interfering / Q000627:therapeutic use; D055532:SMN Complex Proteins / Q000235:genetics / Q000378:metabolism*; D013552:Swine
chemical_list: D015415:Biomarkers; D034741:RNA, Small Interfering; D055532:SMN Complex Proteins