Peripheral SMN restoration is essential for long-term rescue of a severe spinal muscular atrophy mouse model

Spinal muscular atrophy (SMA) is a motor neurone disease caused by a mutation in a gene called SMN1 that is necessary for the survival of motor neurons. Humans have a duplicate gene, SMN2, but that is barely expressed. One promising form of therapy involves increasing SMN2 expression. It has been assumed that it would be necessary to increase the expression of SMN2 in spinal cord motor neurons to achieve a therapeutic effect. Not so. In a mouse model of SMA, subcutaneous, peripheral administration of an antisense oligonucleotide that corrects a splicing defect in SMN2 is shown to provide a much more powerful therapy than direct delivery to the brain. Surprisingly, peripheral rescue is found to be essential for long-term rescue of SMA, and biomarkers suggest that the liver has an important role of the liver in SMA pathogenesis.