Spinal muscular atrophy (SMA) is the leading genetic cause of infant mortality. It is caused by mutations or deletions in the gene encoding the survival motor neuron protein (SMN). Increase the levels of full-length SMN protein originating from human endogenous SMN2 gene is a promising treatment strategy. Since motor neurons are selectively vulnerable to low levels of SMN, building a motor neuron-based reporter assay in vitro will provide a more promising platform for drug discovery. We have developed a robust method to produce large quantities of enriched functional motor neurons from SMA induced pluripotent cells (iPSCs), thus providing a consistent cell source for in vitro screening assay. The recently developed transcription activator-like effector nuclease (TALEN) technology makes it possible to establish reporter iPSC lines under the genetic background identical to a patient. By integrating the technological development and the unique vulnerability of spinal motor neurons to SMN mutations, we propose to establish a reporter assay based on SMA patient's motor neurons. We will first apply the TALEN technology to establish a reporter SMA iPSC line by inserting the NanoLuc (Nluc) luciferase reporter into the SMN2 gene locus. We will then generate large quantities of spinal motor neurons from this SMN2-luc iPSC line using our established protocol. We will examine whether the SMN2-Nluc motor neurons derived from SMA iPSCs respond to compounds that have been previously shown to increase SMN2 expression to validate the suitability of the SMN2-luc motor neurons for high-throughput screening (HTS). We will then conduct primary screening using available libraries followed by validation assays. This exploratory proposal, if successful, will establish a novel platform for identifying new therapeutic drugs for the devastating disease.
We propose to establish a drug screening platform using spinal motor neurons that are derived from SMA patients'iPSCs. This will likely facilitate the identification new therapeutics that will be effective for SMA.