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The rat is an important laboratory animal for physiological,toxicological and pharmacological studies.CRISPR/Cas9 is a simple and efficient tool to generate precise genetic modifications in rats,which will promote the accumulation of rat genetic resources and enable more precise studies of gene function.To monitor Cre/loxP-mediated excision in vivo,we generated a Cre reporter rat strain(Rosa26-imCherry)by knockin of a Cre reporter cassette at Rosa26 locus using CRISPR/Cas9.Rosa26-imCherry rats exhibited inducible expression of the mCherry cassette(imCherry)using the Cre/loxP system,whereas normal rats exhibited ubiquitous expression of eGFP but not mCherry in the whole body.Injection of AAV9-Cre into the hippocampus and skeletal muscle resulted in mCherry expression in virus infected cells.Cre/loxP-mediated mCherry expression was then evaluated by crossing Rosa26-imCherry rats with transgenic rats ubiquitously expressing CAG-Cre,heart-specific a-MHC-Cre transgenic rats,and liver-specific Alb-Cre knockin rats.Finally,using the established system the expression pattern of Cre driven by two endogenous gene promoters(Wfs1-Cre knockin rat,Nestin-Cre knockin rat)was traced.In summary,we demonstrated excision of the loxP-flanked allele in Rosa26-imCherry rats via activation of mCherry expression in the presence of Cre recombinase.This newly established Rosa26-imCherry rat strain represents a useful tool to facilitate Cre-expression pattern determination and tracing experiments.