The Sleeping Beauty (SB) transposon vectors used in this study. The SB transposon system consists of 2 components: the inverted repeat/direct repeats (IR/DR, indicated by arrowheads) flanking the gene of interest, and the expression cassette encoding the transposase. Caggs is a chimeric promoter derived from chicken β-actin and cytomegalovirus immediate-early promoter sequences. UbC indicates human ubiquitin C promoter; SB10, transposase; SB10ΔDDE, inactive transposase due to deletion of the catalytic domain; tNGFR/CD, truncated human nerve growth factor receptor and cytosine deaminase fusion gene; P2A and T2A, “self-cleaving” 2A peptides derived from porcine teschovirus-1 and Thosea asigna virus have been shown to express multiple genes. pT2/EGmCN and pT2/ENmCL were bidirectional SB vectors in which synthetic bidirectional promoters were used. mCMV indicates minimal CMV promoter; EF1α, human elongation factor 1α promoter; IRES, internal ribosomal entry sites; DsRed2, red fluorescent protein; Luciferase, bioluminescent reporter gene; and pA, polyadenylation signal.