Plastin-3 extends survival and reduces severity in mouse models of spinal muscular atrophy

Abstract

Spinal muscular atrophy (SMA) is a leading genetic cause of infantile death and is caused by the loss of survival motor neuron-1 (<i>SMN1</i>). Importantly, a nearly identical gene is present called <i>SMN2</i>; however, the majority of <i>SMN2</i>-derived transcripts are alternatively spliced and encode a truncated, dysfunctional protein. Recently, several compounds designed to increase SMN protein have entered clinical trials, including antisense oligonucleotides (ASOs), traditional small molecules, and gene therapy. Expanding beyond SMN-centric therapeutics is important, as it is likely that the breadth of the patient spectrum and the inherent complexity of the disease will be difficult to address with a single therapeutic strategy. Several SMN-independent pathways that could impinge upon the SMA phenotype have been examined with varied success. To identify disease-modifying pathways that could serve as stand-alone therapeutic targets or could be used in combination with an SMN-inducing compound, we investigated adeno-associated virus-mediated (AAV-mediated) gene therapy using plastin-3 (<i>PLS3</i>). Here, we report that AAV9-<i>PLS3</i> extends survival in an intermediate model of SMA mice as well as in a pharmacologically induced model of SMA using a splice-switching ASO that increases SMN production. <i>PLS3</i> coadministration improves the phenotype beyond the ASO, demonstrating the potential utility of combinatorial therapeutics in SMA that target SMN-independent and SMN-dependent pathways.