The “iCre-FRT-Neo-FRT-IRES” cassette was inserted upstream of the ATG start codon of the mouse Epx gene and the IRES linker was inserted to precede the exons encoding the complete Epx. Cre recombinase is expressed under the regulatory control of Epx gene elements, without impacting the endogenous expression of the Epx gene. The FRT-Neo-FRT element is used to screen positive clones during the construction process, and the mice delivered to the customer have completed self-deletion of the Neo element.