Abstract
The hereditary neurodegenerative disorder spinal muscular atrophy (SMA) is characterized by the loss of spinal cord motor neurons and skeletal muscle atrophy. SMA is caused by mutations of the survival motor neuron (SMN) gene leading to a decrease in SMN protein levels. The SMN deficiency alters nuclear body formation and whether it can contribute to the disease remains unclear. Here we screen a series of small-molecules on SMA patient fibroblasts and identify flunarizine that accumulates SMN into Cajal bodies, the nuclear bodies important for the spliceosomal small nuclear RNA (snRNA)-ribonucleoprotein biogenesis. Using histochemistry, real-time RT-PCR and behavioural analyses in a mouse model of SMA, we show that along with the accumulation of SMN into Cajal bodies of spinal cord motor neurons, flunarizine treatment modulates the relative abundance of specific spliceosomal snRNAs in a tissue-dependent manner and can improve the synaptic connections and survival of spinal cord motor neurons. The treatment also protects skeletal muscles from cell death and atrophy, raises the neuromuscular junction maturation and prolongs life span by as much as 40 percent (p < 0.001). Our findings provide a functional link between flunarizine and SMA pathology, highlighting the potential benefits of flunarizine in a novel therapeutic perspective against neurodegenerative diseases.
Highlights
Protein localization is critical for cellular functions and tissues homeostasis
The screening was based on double immunodetection of Survival motor neuron (SMN) and Cajal bodies (CBs)-marker coilin proteins (Fig. 1A)
Measurements of four dilutions (2 μg/ml, 200 ng/ml, 20 ng/ml and 2 ng/ml) in our immortalized spinal muscular atrophy (SMA) cell model showed a dose-dependent accumulation of SMN to CBs with flunarizine (B6) and gabapentine (F6; Fig. 1D)
Summary
Protein localization is critical for cellular functions and tissues homeostasis. Survival motor neuron (SMN) protein has a specific localization in the nucleus of eukaryotic cells[1,2,3,4,5]. One approach has shown that indole derivatives are potent splicing inhibitors with a selective action on splicing modulator SR proteins[32] Another group has reported that the central nervous system (CNS)-penetrant drug flunarizine causes in HeLa cells splicing changes of numerous genes including intron retention in SMN and coilin genes, but the mechanism is unknown[33]. Other screening assays have identified small molecules that modulate the splicing of transcripts from SMN2 gene to compensate for the lost SMN1 gene and improve the symptoms of SMA mouse models[35] Because some of these drugs are likely to have side effects with long-term usage, the combination of two or more molecules, which target distinct facets of SMA cell biology, at low dosage might be a more relevant therapy[36]. We found in vivo with flunarizine treatment the enrichment of SMN into CBs of spinal cord motor neurons and tissue-specific modulation of the splicing snRNA levels in SMA mice. We conclude that flunarizine represents a potential therapeutic strategy, alone or in combination, to reduce the disease severity of SMA
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
