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. Author manuscript; available in PMC: 2021 Jun 1.
Published in final edited form as: Nat Protoc. 2020 Oct 26;15(12):3777–3787. doi: 10.1038/s41596-020-00403-2

Figure 3. Schematics of COVID-19 GEMM designs, category 3: Knocking-in CRE-activatable cassettes into the mouse Ace2 locus.

Figure 3.

A CRE-invertible KI cassette is inserted in the opposite orientation to the mAce2 locus. Upon CRE-mediated inversion of the cassette through sequential recombinations of lox2272s and lox5171s, the transcript is spliced from exon1 to the inverted KI cassette and downstream transcription is terminated to prevent mAce2 function. This CRE-mediated inversion allows hACE2 expression in models #22 to #24 (not shown), or hACE2 and hTMPRRS2 expression in models #25 to #30. SA: splice acceptor. P2A: a self-cleavable viral peptide used for expressing two fusion proteins. IRES: Internal Ribosomal Entry Site.