Modeling the early phenotype at the neuromuscular junction of spinal muscular atrophy using patient-derived iPSCs.
Bottom Line: We generated NMJ-like structures using MNs derived from SMA patient-specific induced pluripotent stem cells (iPSCs), and found that the clustering of the acetylcholine receptor (AChR) is significantly impaired.Valproic acid and antisense oligonucleotide treatment ameliorated the AChR clustering defects, leading to an increase in the level of full-length SMN transcripts.Thus, the current in vitro model of AChR clustering using SMA patient-derived iPSCs is useful to dissect the pathophysiological mechanisms underlying the development of SMA, and to evaluate the efficacy of new therapeutic approaches.
Affiliation: Department of Clinical Application, Center for iPS Cell Research and Application (CiRA), Kyoto University, Kyoto 606-8507, Japan; Department of Pediatrics, Graduate School of Medical Science, Kyoto Prefectural University of Medicine, Kyoto 602-8566, Japan.Show MeSH
Related in: MedlinePlus
Mentions: Since the loss of NMJ formation is regarded to be an important hallmark preceding the motor neuronal loss, compounds that ameliorate the NMJ pathology may serve as promising therapeutic drug candidates. To evaluate whether the NMJ-LSs formation system used in our experiments can serve as a prototype for evaluating drug candidates, we assessed whether the SMN-inducing drug, valproic acid (VPA), could increase the AChR clustering in our co-culture system. VPA is known to increase the functional SMN protein by activating various promoters, including that of SMN2, and by correcting the abnormal splicing of SMN2 exon 7, mainly through the upregulation of splicing factors (Harahap et al., 2012). Co-culturing myotubes and SMA-iPSC-derived MNs treated with VPA significantly increased the AChR clustering (Figures 3A–3C and S3A), while the clustering was not induced when monocultured myotubes were treated with VPA (data not shown). NF accumulation was not rescued by VPA treatment (Figure 3A). We confirmed that VPA treatment increased both the SMN-Δ7 and SMN-FL mRNA levels in the SMA-iPSC-derived MNs (Figure 3D).
Affiliation: Department of Clinical Application, Center for iPS Cell Research and Application (CiRA), Kyoto University, Kyoto 606-8507, Japan; Department of Pediatrics, Graduate School of Medical Science, Kyoto Prefectural University of Medicine, Kyoto 602-8566, Japan.