The transgenic IG-DMR sequence of the mouse Dlk1-Dio3 domain acquired imprinted DNA methylation during the post-fertilization period.

"Declarations Ethics approval and consent to participateAnimal experiments were performed in a humane manner and approved by the Institutional Animal Experiment Committee of the University of Tsukuba. Experiments were conducted in accordance with the Regulation of Animal Experiments of the University of Tsukuba and the Fundamental Guidelines for Proper Conduct of Animal Experiments and Related Activities in Academic Research Institutions under the jurisdiction of the Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan. Consent for publicationNot applicable. Competing interestsThe authors declare that they have no competing interests. Competing interests The authors declare that they have no competing interests."

"Funding This work was supported in parts by JSPS (Japan Society for the Promotion of Science) KAKENHI grants (grant numbers JP19KK0384 to H.M., JP20K06481 to H.M., JP19H03134 to K.T., JP20K21360 to K.T., and JP22H00394 to K. T.), MEXT (Ministry of Education, Culture, Sports, Science and Technology) KAKENHI grants (grant number JP20H05379 to H.M.), and a research grant from the Takeda Science Foundation to K.T."