Antisense oligonucleotide-mediated redirection of Igf1 alternative polyadenylation

Insulin-like growth factor-1 (IGF-1) has become an interesting potential therapeutic target for muscle wasting disorders, since it is known to modulate muscle growth and function. Alternative polyadenylation (APA) Igf1 gives rise to 3'UTR isoforms with different stability and translation efficiency due to their length and context-dependent miRNA binding sites. Igf1 transcripts with a shorter 3'UTRs are thought to be more stable and efficient during protein translation. Therefore, modulating the Igf1 polyadenylation site usage would be a potential approach to increase IGF-1 protein expression. In this study, we first investigated the Igf1 3'UTR isoforms in exercised mdx and WT mice by full-length isoform sequencing. We then redirected the APA of Igf1 from the distal to the proximal/middle polyadenylation sites to enhance the IGF-1 protein expression in mouse C2C12 myoblasts. Upon exercise, APA of Igf1 was redirected towards the proximal polyadenylation site in the WT mice only (P < 0.05). Transfection of C2C12 cells with this AON resulted in redirection of the APA towards the proximal site and increased IGF-1 expression/AKT phosphorylation levels. Strong enrichment was found for genes involved in sarcomere organization, muscle cell development and calcium homeostasis. Our study reports the effect of downhill running exercise on the Igf1 3'UTRs in mdx and WT mice and provides an in vitro proof of principle for redirecting the Igf1 poly(A) site usage as a strategy to increase protein expression without modifying the coding region of the gene, not only for IGF-1 but also for other targets with therapeutic potential in different conditions.