severe Taiwanese Smn -/-;SMN2 SMA mice ( 22) that could potentially be restored by known and available pharmacological compounds. This strategy uncovered several potential therapeutic candidates, including harmine, which was further evaluated in cell and animal models, showing an ability to restore molecular networks and improve several disease phenotypes, including lifespan and weight. Our study highlights the tremendous potential of intersecting disease multiomics with drug perturbational responses to identify therapeutic compounds capable of modulating dysfunctional cellular and molecular networks to ameliorate SMA phenotypes. ResultsEarly restoration of SMN in SMA mice restores muscle protein and transcript expression. We first set out to determine the effect of early SMN restoration on the proteomic and transcriptomic profiles of SMA skeletal muscle, with the intent to design therapeutic strategies against the genes and proteins that remained unchanged. To do so, the severe Taiwanese Smn -/-;SMN2 SMA mouse model ( 22) received a facial i.v. injection at P0 and P2 of the previously described Pip6a-phosphordiamidate morpholino oligomer (Pip6a-PMO) or Pip6a-scrambled pharmacological compounds (10 μg/g; ref. 23,24). Pip6a is a cell-penetrating peptide (CPP) conjugated either to an SMN2 exon 7 inclusion-promoting ASO (PMO) or a scrambled ASO (23, 24). We have previously reported that administration of Pip6a-PMO to newborn Smn -/-;SMN2 mice led to increased SMN protein levels in numerous tissues, including skeletal muscle, and a concomitant 40-fold increase in survival ( 23). We harvested the tibialis anterior (TA) from P2 (presymptomatic) untreated Smn -/-;SMN2 and WT mice, P7 (symptomatic) untreated Smn -/-;SMN2 and WT mice, and P7 Pip6a-scrambled Smn -/-;SMN2 and Pip6a-PMO-treated Smn -/-;SMN2 mice. TAs were then cut in 2, whereby one half was used for transcriptomics (whole-transcript array assay) and the other for proteomics (liquid chromatography-mass spectrometry; LC-MS). Quantitative PCR (qPCR) analysis of the ratio of FL SMN2 over total SMN2 confirms a significant increase in FL SMN2 expression in P7 Pip6a-PMO-treated Smn -/-;SMN2 mice compared with age-matched untreated and Pip6a-scrambled-treated Smn -/-;SMN2 mice (Figure 1A).Despite differences between the transcriptomic and proteomic methodologies, highlighted by hierarchical clustering and combined Principal Component Analysis (PCA; Supplemental Figure 1; supplemental material available online with this article; https://doi.org/10.1172/jci.insight.149446DS1), we were able to find clear separation of experimental groups and agreement between transcriptomic and proteomic profiles once the variance attributed to the differences in methodologies was removed (Figure 1B). At P7, we observed a clear separation of Smn -/-;SMN2 and WT samples, where only Pip6a-PMO-treated Smn -/-;SMN2 mice clustered with WT (Figure 1B and Supplemental Figure 2). We also found that P2 Smn -/-;SMN2 and WT samples clustered together (Figure 1B and Supplemental Figure 2), suggest...
Spinal muscular atrophy (SMA) is a childhood disorder caused by loss of the SMN gene. Pathological hallmarks are spinal cord motor neuron death, neuromuscular junction dysfunction and muscle atrophy. The first SMN genetic therapy was recently approved and other SMN-dependent treatments are not far behind. However, not all SMA patients will reap their maximal benefit due to limited accessibility, high costs and differential effects depending on timing of administration and disease severity. The repurposing of commercially available drugs is an interesting strategy to ensure more rapid and less expensive access to new treatments. In this mini-review, we will discuss the potential and relevance of repositioning drugs currently used for neurodegenerative, neuromuscular and muscle disorders for SMA.
Spinal muscular atrophy (SMA) is a neuromuscular disorder caused by loss of survival motor neuron (SMN) protein. While SMN restoration therapies are beneficial, they are not a cure. We aimed to identify novel treatments to alleviate muscle pathology combining transcriptomics, proteomics and perturbational datasets. This revealed potential drug candidates for repurposing in SMA. One of the lead candidates, harmine, was further investigated in cell and animal models, improving multiple disease phenotypes, including SMN expression and lifespan. Our work highlights the potential of multiple, parallel data driven approaches for development of novel treatments for use in combination with SMN restoration therapies. RESULTS Early restoration of Smn in SMA mice restores muscle protein and transcript expression.We first set out to determine the effect of early SMN restoration on the proteomic and transcriptomic profiles of SMA skeletal muscle, with the intent to design therapeutic strategies against the genes and proteins that remain unchanged. To do so, the severe Taiwanese Smn-/-;SMN2 SMA mouse model 24 received a facial intravenous (IV) injection at post-natal day (P) 0 and P2 of the previously described Pip6a-PMO or Pip6a-scrambled pharmacological compounds (10 g/g) 25,26. Pip6a is a cell-penetrating peptide (CPP) either conjugated to an SMN2 exon 7 inclusion-promoting ASO (PMO) or a scrambled ASO 25,26. We harvested the tibialis anterior (TA) from P2 (pre-symptomatic) untreated Smn-/-;SMN2 and wild type (WT) mice, P7 (symptomatic) untreated Smn-/-;SMN2 and WT mice and P7 Pip6a-scrambled-and Pip6a-PMO-treated Smn-/-;SMN2 mice. TAs were then cut in two, whereby one half was used for transcriptomics and the other for proteomics. qPCR analysis of the ratio of FL SMN2 over total SMN2 confirms a significant increase in FL SMN2 expression in P7 Pip6a-PMO-treated Smn-/-;SMN2 mice compared to age-matched untreated and Pip6a-scrambled-treated Smn-/-;SMN2 mice ( Fig. 1a).Despite differences between transcriptomic and proteomic methodologies highlighted by hierarchical clustering and combined Principal Component Analysis (PCA) ( Supplementary Fig. 1), we were able to find clear separation of experimental groups and agreement between transcriptomic and proteomic profiles once the variance attributed to the differences in methodologies was removed ( Fig. 1b). At P7, we observed clear separation of Smn-/-;SMN2-and WT samples, where only P7 Pip6a-PMO treated Smn-/-
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