title: Postsymptomatic restoration of SMN rescues the disease phenotype in a mouse model of severe spinal muscular atrophy.
abstract: Spinal muscular atrophy (SMA) is a common neuromuscular disorder in humans. In fact, it is the most frequently inherited cause of infant mortality, being the result of mutations in the survival of motor neuron 1 (SMN1) gene that reduce levels of SMN protein. Restoring levels of SMN protein in individuals with SMA is perceived to be a viable therapeutic option, but the efficacy of such a strategy once symptoms are apparent has not been determined. We have generated mice harboring an inducible Smn rescue allele and used them in a model of SMA to investigate the effects of turning on SMN expression at different time points during the course of the disease. Restoring SMN protein even after disease onset was sufficient to reverse neuromuscular pathology and effect robust rescue of the SMA phenotype. Importantly, our findings also indicated that there was a therapeutic window of opportunity from P4 through P8 defined by the extent of neuromuscular synapse pathology and the ability of motor neurons to respond to SMN induction, following which restoration of the protein to the organism failed to produce therapeutic benefit. Nevertheless, our results suggest that even in severe SMA, timely reinstatement of the SMN protein may halt the progression of the disease and serve as an effective postsymptomatic treatment.
authors.affiliation: The Jackson Laboratory, Bar Harbor, Maine 04609, USA. cat.lutz@jax.org
authors.forename: Cathleen M
authors.initials: CM
authors.lastname: Lutz
authors.forename: Shingo
authors.initials: S
authors.lastname: Kariya
authors.forename: Sunita
authors.initials: S
authors.lastname: Patruni
authors.forename: Melissa A
authors.initials: MA
authors.lastname: Osborne
authors.forename: Don
authors.initials: D
authors.lastname: Liu
authors.forename: Christopher E
authors.initials: CE
authors.lastname: Henderson
authors.forename: Darrick K
authors.initials: DK
authors.lastname: Li
authors.forename: Livio
authors.initials: L
authors.lastname: Pellizzoni
authors.forename: José
authors.initials: J
authors.lastname: Rojas
authors.forename: David M
authors.initials: DM
authors.lastname: Valenzuela
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Murphy
authors.forename: Margaret L
authors.initials: ML
authors.lastname: Winberg
authors.forename: Umrao R
authors.initials: UR
authors.lastname: Monani
mesh_terms: D000483:Alleles; D000818:Animals; D003001:Cloning, Molecular; D003433:Crosses, Genetic; D004195:Disease Models, Animal; D005121:Extremities / Q000473:pathology; D006801:Humans; D051379:Mice; D009046:Motor Neurons / Q000502:physiology*; D009134:Muscular Atrophy, Spinal / Q000503:physiopathology*; D010641:Phenotype; D012018:Reflex; D055533:Survival of Motor Neuron 1 Protein / Q000235:genetics* / Q000378:metabolism / Q000502:physiology*; D013569:Synapses; D016896:Treatment Outcome
chemical_list: C526471:SMN1 protein, human; C526472:Smn1 protein, mouse; D055533:Survival of Motor Neuron 1 Protein