Altered Levels of MicroRNA-9, -206, and -132 in Spinal Muscular Atrophy and Their Response to Antisense Oligonucleotide Therapy

The identification of noninvasive biomarkers to monitor the disease progression in spinal muscular atrophy (SMA) is becoming increasingly important. MicroRNAs (miRNAs) regulate gene expression and are implicated in the pathogenesis of neuromuscular diseases, including motor neuron degeneration. In this study, we selectively characterized the expression of miR-9, miR-206, and miR-132 in spinal cord, skeletal muscle, and serum from SMA transgenic mice, and in serum from SMA patients. A systematic analysis of miRNA expression was conducted in SMA mice with different disease severities (severe type I-like and mild type III-like) at different disease stages (pre-, mid-, and late-symptomatic stages), and in morpholino antisense oligonucleotide-treated mice. There was differential expression of all three miRNAs in spinal cord, skeletal muscle and serum samples in SMA mice. Serum miRNAs were altered prior to the changes in spinal cord and skeletal muscle at the presymptomatic stage. The altered miR-132 levels in spinal cord, muscle, and serum transiently reversed to normal level after a single-dose morpholino antisense oligomer PMO25 treatment in SMA mice. We also confirmed a significant alteration of miR-9 and miR-132 level in serum samples from SMA patients. Our study indicates the potential of developing miRNAs as noninvasive biomarkers in SMA.