Poster #061, Sanford Burnham Prebys Medical Discovery Institute
USING SELF-AMPLIFYING RNA TO REPLENISH SMN IN PATIENT SPECIFIC hiPSC- DERIVED NEUROECTODERM MODEL OF SPINAL MUSCULAR ATROPHY (SMA)
Mentors: Kartik S. Sundaram, BA, BS; William Zeier; Evan Y. Snyder, MD, PhD
Spinal Muscular Atrophy (SMA) is a genetic disease resulting in the death ofspinal ventral horn motor neurons and is caused by mutations in Survival Motor Neuron (SMN) genes one and two. Mutations in SMN1 determine whether or not patients have the disease, while SMN2 copy numbers correspond to severity of disease symptoms. Current antisense oligonucleotide (ASO) treatments aim to increase expression of functional SMN through increased SMN2. Existing gene therapies aim to provide functional SMN1. Successful ASO treatment is limited to patients with two or more copies of SMN2, while AAV9 can be administered only once due to immunogenicity and hepatotoxicity. A novel solution is offered through gene therapy employing self-amplifying RNA (saRNA) technology. SMN1-saRNA contains functional SMN1 and replicase RNA transcripts, which increase availability of SMN1 transcript for host ribosomes to translate into SMN proteins. These saRNAs are encased in LNPs which are endocytosed. We hypothesize that saRNA transducing SMN1 is a viable therapy for a broad population of SMA infants during and after neuroectoderm differentiation. To test this hypothesis, we have obtained human induced pluripotent stem cells (hiPSCs) from SMA patients. We are differentiating these hiPSCs into motor neurons (MNs) that have been treated with the SMN1-saRNA. We will determine whether the health and survival of these MNs is better than untreated SMA MNs and comparable to unaffected MNs including testing their ability to make functional neuromuscular junctions on hiPSC-derived isogenic myofibrils. Our goal is to test the viability of LNP-saRNA delivery as a possible treatment for SMA. We will measure the success of SMN protein production in neuroectoderm cells that have been treated at the hiPSC stage as well as in SMN1-saRNA treated multipotent neuroectoderm and motor neurons at each successive differentiation to determine the efficacy of gene therapy at each stage using this novel technology.