Synthetically modified mRNA for efficient and fast human iPS cell generation and direct transdifferentiation to myoblasts.

Synthetic mRNA transfection enables efficient and controlled gene expression in human cells, without genome integrations. Further, modifications to the mRNA and transfection protocol now allow for repeated transfection and long-term gene expression of an otherwise short-lived mRNA expression. This is mainly achieved through introducing modified nucleosides and interferon suppression. In this study we provide an overview and details of the advanced synthesis and modifications of mRNA originally developed for reprogramming. This mRNA allows for very efficient transfection of fibroblasts enabling the generation of high quality human iPS cells with a six-factor mRNA cocktail in 9 days. Furthermore, we synthesised and transfected modified MYOD1 mRNA to transdifferentiate human fibroblasts into myoblast-like cells without a transgene footprint. This efficient and integration-free mRNA technology opens the door for safe and controlled gene expression to reverse or redirect cell fate.