C1 - Base Editing and Prime Editing
385: Systemic Delivery of LNP mRNA In Utero Permits Editing in a Mouse Model of Spinal Muscular Atrophy (SMA)
Type: Oral Abstract Session
Presentation Details
Session Title: Base Editing and Prime Editing II
Spinal muscular atrophy (SMA) is a leading heritable cause of infant mortality and is caused by a mutation of the SMN1 gene. Pathogenesis of the disease begins prenatally and is often irreversible. The fetus has unique properties that make it favorable for gene editing: cells are highly proliferative and amenable to mRNA delivery, the fetus is immunological immature and tolerant, and diseases with a high morbidity and mortality in the prenatal and perinatal period can be targeted. In this novel study, we used in utero delivery of CRISPR-Cas9 via lipid nanoparticles to target the SMN2 gene in severe SMA mice. We hypothesized that in utero LNP-assisted mRNA delivery permits efficient base editing at the SMN2 locus, thereby improving survival in a SMA mouse model. To test this hypothesis, severely diseased SMA mice were injected intravenously (IV) prenatally (E14) and postnatally (P0) via either the vitelline vein or facial vein, respectively, and compared to direct ICV injections. Survival and weight data were collected. Brains, spinal cords, and peripheral organs were harvested from mice and analyzed for editing efficiency, SMN protein levels, and mRNA splicing. Editing levels in intravenously injected mice at E14 were significantly higher than P0 injected mice. An increase in editing was correlated with enhanced survival, with improvement in mouse lifespan from P7 - P8 days to P15-19. Mice with the longest lifespan demonstrated the largest improvement in SMN protein levels. This study demonstrates that adenine base editing technology can be used to increase SMN2 exon splicing and produce a functional protein through IV in utero LNP assisted mRNA delivery in a severe mouse model of SMA. These results highlight the potential for further studies to improve brain and spinal cord targeting.
Plain Language Summary
Spinal muscular atrophy (SMA) is a leading heritable cause of infant mortality. It is caused by a mutation of the SMN1 gene which leads to a deficiency of SMN, a protein essential to cellular homeostasis. Pathology begins prenatally and is irreversible. Fetal gene editing provides a unique advantage to target diseases before irrevocable damage has been done. In this study, we used in utero gene editing with LNP assisted mRNA delivery to target SMA diseased mice. Mice were injected at varying stages of development, E14 (in utero) versus P0 (postnatal). Survival, editing levels, and SMN protein levels were collected. Edited mice demonstrated improved survival and increased SMN protein levels. With this study, we were able to demonstrate that adenine base editing can be used to increase SMN2 exon splicing and produce a functional protein through novel in utero delivery of LNPs.
Nicole Kus1, Marco Carpenter1, Rosa Choi1, Ana Maria Dumitru1, William Johnston1, Hooda Said1, Mohamad Gabriel Alameh2, William Peranteau3
1Children's Hospital of Philadelphia, Philadelphia, PA,2Ecole Polytechnique de Montreal, Montréal, QC, Canada,3The Children's Hospital of Philadelphia, Philadelphia, PA"
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