Recombinase-mediated cassette exchange (RMCE) replaced the selection cassette in Gt(ROSA)26Sortm1(CAG-flpe)Arte with a 5' deleted neomycin resistance cassette, the chicken actin gene (CAG) promoter, loxP flanked strong transcriptional termination site (LSL), the human MYCN gene, IRES, and the firefly luciferase gene. Cre-mediated recombination can be utilized to remove the transcription termination site 5' to the MYCN allele to get MYCN expression.