Poster #041, Sanford Burnham Prebys
Assessing self-amplifying RNA (saRNA) uptake into spinal muscular atrophy (SMA) patient-derived iPSCs as novel approach
Mentors: Kartik Sundaram, BA/BS; William Zeier, and Evan Y. Snyder MD, PhD
Background:
Spinal muscular atrophy (SMA) is an incurable neurodegenerative disease caused by the
genetic loss of spinal ventral horn motor neurons. Specifically, SMA is caused by a mutation in
Survivor Motor Neuron (SMN) genes 1 and 2. Mutations in SMN1 determine the disease, and
SMN2 copy number determines disease severity (more SMN2 copies can compensate for
decreased SMN1). Type 0 is the most severe as patients only have one copy of SMN2, yet Type
1 (Werdnig-Hoffman) is the most common form of SMA, where two copies of SMN2 delay
symptom onset by six months. Current antisense oligonucleotide (ASO) therapies modify
disease activity by promoting increased levels of SMN2, yet are only effective if patients already
have sufficient SMN2 copies. Current FDA-approved gene therapies have benefitted SMA
patients, yet possess harmful side-effects such as AAV-induced hepatotoxicity and
immunotoxicity.
Our Goal:
We propose another avenue for gene therapy: the use of self-amplifying RNA (saRNA) that can
both introduce and express the essential SMN1 gene independent of endogenous SMN2 copy
number and with comparatively less toxic side effects.
The Question We Need to Answer:
By testing a novel saRNA encoding for SMN1 (in a lipid nanoparticle [LNP]) on SMA
patient-derived human induced pluripotent stem cells (hiPSCs) during their differentiation into
motor neurons (MNs), we can examine MN number, health, and function. Also, the best time to
initiate this treatment in a patient is unknown: in utero or in infancy? To answer this question, we
are observing LNP-saRNA uptake in undifferentiated iPSCs before neural induction, modeling
the embryonic stage and the earliest possible time for treatment in a patient. We will measure
SMN protein levels in undifferentiated SMA-iPSCs. However, we will also examine SMN1
expression in embryoid bodies, which will tell us the degree of SMN expression in all potential
organ systems.