The TAG stop codon was replaced with the "3xFLAG tag-3xEAAAK-EGFP-IRES-iCre" cassette. Cre recombinase and enhanced green fluorescent protein (EGFP) are expressed under the regulatory control of Leng8 gene elements, without impacting the endogenous expression of the Leng8 gene. The 3xFLAG tag is a tag consisting of three tandem FLAG epitopes (DYKDDDDK). When inserted into a target gene, it allows for efficient detection, localization, or purification of the target protein using anti-FLAG antibodies. In addition to studies of Cre recombinase-mediated gene recombination, this model can also be used for EGFP fluorescent protein tracing studies.