Mouse myoblast cell line C2C12 cell line (ATCC, CRL-1772) was transfected with the piggyBac vector pPV-EF1a-EGxxFP (DMDex45_10)-iP-A containing a partial sequence of the human dystrophin gene exon 45 (deposited in Addgene, #204621), using the 4D-Nucleofector (Lonza). The vector induces single-strand annealing repair when genome editing is induced by the targeting gRNAs, and the split EGFP gene is repaired and emits EGFP fluorescence. After puromycin selection, EGFP-negative cells were sorted as one cell per well into 96-well plates and cultured in DMEM medium containing 10% FBS and puromycin, to establish subclones with minimum background EGFP signal. Thereafter, selected subclone was subjected to myogenic differentiation by using the DMEM medium supplemented with 2% horse serum for 9 days. LNP-CRISPR with or without ApoE3, prepared as described above, was added to the cells for 3 h on the day after seeding (undifferentiated) or day 9 of myotube formation (differentiated). The EGFP signals, as a readout of genome editing, were analyzed quantitatively using Opera Phenix (Cytiva) at 4 days after LNP-CRISPR treatment.