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[INLINE:1] Spinal muscular atrophy (SMA) is a rare hereditary neuromuscular disease with a high lethality rate in infants. Variants in the homologous genes survival of motor neuron (SMN)1 and SMN2 have been reported to be SMA pathogenic factors. Previous studies showed that a high inclusion rate of SMN2 exon 7 increased SMN expression, which in turn reduced the severity of SMA. The inclusion rate of SMN2 exon 7 was higher in neural tissues than in non-neural tissues. Neuro-oncological ventral antigen (NOVA) is a splicing factor that is specifically and highly expressed in neurons. It plays a key role in nervous system development and in the induction of nervous system diseases. However, it remains unclear whether this splicing factor affects SMA. In this study, we analyzed the inclusion of SMN2 exon 7 in different tissues in a mouse model of SMA (genotype smn–/–SMN22tg/0) and littermate controls (genotype smn+/–SMN22tg/0). We found that inclusion level of SMN2 exon 7 was high in the brain and spinal cord tissue, and that NOVA1 was also highly expressed in nervous system tissues. In addition, SMN2 exon 7 and NOVA1 were expressed synchronously in the central nervous system. We further investigated the effects of NOVA1 on disease and found that the number of neurons in the anterior horn of spinal cord decreased in the mouse model of SMA during postnatal days 1–7, and that NOVA1 expression levels in motor neurons decreased simultaneously as spinal muscular atrophy developed. We also found that in vitro expression of NOVA1 increased the inclusion of SMN2 exon 7 and expression of the SMN2 protein in the U87MG cell line, whereas the opposite was observed when NOVA1 was knocked down. Finally, point mutation and RNA pull-down showed that the UCAC motif in SMN2 exon 7 plays a critical role in NOVA1 binding and promoting the inclusion of exon 7. Moreover, CA was more essential for the inclusion of exon 7 than the order of Y residues in the motif. Collectively, these findings indicate that NOVA1 interacts with the UCAC motif in exon 7 of SMN2, thereby enhancing inclusion of exon 7 in SMN2, which in turn increases expression of the SMN protein.

Spinal muscular atrophy (SMA) is a genetic disease resulting in the loss of α-motoneurons followed by muscle atrophy. It is caused by knock-out mutations in the survival of motor neuron 1 (SMN1) gene, which has an unaffected, but due to preferential exon 7 skipping, only partially functional human-specific SMN2 copy. We previously described a Drosophila-based screening of FDA-approved drugs that led us to discover moxifloxacin. We showed its positive effect on the SMN2 exon 7 splicing in SMA patient-derived skin cells and its ability to increase the SMN protein level. Here, we focus on moxifloxacin's therapeutic potential in additional SMA cellular and animal models. We demonstrate that moxifloxacin rescues the SMA-related molecular and phenotypical defects in muscle cells and motoneurons by improving the SMN2 splicing. The consequent increase of SMN levels was higher than in case of risdiplam, a potent exon 7 splicing modifier, and exceeded the threshold necessary for a survival improvement. We also demonstrate that daily subcutaneous injections of moxifloxacin in a severe SMA murine model reduces its characteristic neuroinflammation and increases the SMN levels in various tissues, leading to improved motor skills and extended lifespan. We show that moxifloxacin, originally used as an antibiotic, can be potentially repositioned for the SMA treatment. [ABSTRACT FROM AUTHOR]

Spinal muscular atrophy (SMA) is a motor neuron disease caused by loss of function mutations in the Survival Motor Neuron 1 (SMN1) gene and reduced expression of the SMN protein, leading to spinal motor neuron death, muscle weakness and atrophy. Although humans harbour the highly homologous SMN2 gene, its defective splicing regulation yields a truncated and unstable SMN protein. The first therapy for SMA was recently approved by the Food and Drug Administration and consists of an antisense oligonucleotide (Nusinersen) rendering SMN2 functional and thus improving patients' motor activity and quality of life. Nevertheless, not all patients equally respond to this therapy and the long‐term tolerability and safety of Nusinersen are still unknown. Herein, in vivo splicing assays indicated that the HDAC inhibitor LBH589 is particularly efficient in rescuing the SMN2 splicing defect in SMA fibroblasts and SMA type‐I mice‐derived neural stem cells. Western blot analyses showed that LBH589 also causes a significant increase in SMN protein expression in SMA cells. Moreover chromatin immunoprecipitation analyses revealed that LBH589 treatment induces widespread H4 acetylation of the entire SMN2 locus and selectively favors the inclusion of the disease‐linked exon 7 in SMN2 mature mRNA. The combined treatment of SMA cells with sub‐optimal doses of LBH589 and of an antisense oligonucleotide that mimic Nusinersen (ASO_ISSN1) elicits additive effects on SMN2 splicing and SMN protein expression. These findings suggest that HDAC inhibitors can potentiate the activity of Nusinersen and support the notion that 'SMN‐plus' combinatorial therapeutic approaches might represent an enhanced opportunity in the scenario of SMA therapy. [ABSTRACT FROM AUTHOR]