MAGIK: A rapid and efficient method to create lineage-specific reporters in human pluripotent stem cells

Precise insertion of fluorescent proteins into lineage -specific genes in human pluripotent stem cells (hPSCs) presents challenges due to low knockin efficiency and difficulties in isolating targeted cells. To overcome these hurdles, we present the modified mRNA (ModRNA)based Activation for Gene Insertion and Knockin (MAGIK) method. MAGIK operates in two steps: first, it uses a Cas9-2A-p53DD modRNA with a mini -donor plasmid (without a drug selection cassette) to significantly enhance efficiency. Second, a deactivated Cas9 activator modRNA and a 'dead' guide RNA are used to temporarily activate the targeted gene, allowing for live cell sorting of targeted cells. Consequently, MAGIK eliminates the need for drug selection cassettes or labor-intensive single -cell colony screening, expediting precise gene editing. We showed MAGIK can be utilized to insert fluorescent proteins into various genes, including SOX17 , NKX6.1 , NKX2.5 , and PDX1 , across multiple hPSC lines. This underscores its robust performance and offers a promising solution for achieving knockin in hPSCs within a significantly shortened time frame.