Synthesis and Purification of modRNA

modRNA was synthesized and formulated as previously described [19 (link)]. T7 RNA polymerase-mediated transcription from a linearized DNA template, which incorporates generic 5′and 3′UTRs and a poly-A tail, was used for mRNA synthesis. The purification of RNA was performed using Ambion MEGA clear spin columns. RNA was then treated with Antarctic Phosphatase (New England Biolabs) at 37 °C for 30 min to remove residual 5′-phosphates. After re-purification and quantification by Nanodrop (Thermo Scientific), RNA was resuspended in 10 mM Tris HCl, 1 mM EDTA at 1 μg/μl for use. In mRNA, uridine was fully replaced by N1-methylpseudouridine. GFP and firefly luciferase ORF sequences were the same as previously described [14 (link)]. Open reading frame sequence for mouse IGF-1 modRNA was provided in the supplementary data (Additional file 1: Table S1).