부산대학교 도서관

Differential expression of transgenes in transgenic animals is one of the main drawbacks of pronuclear injection. To overwhelm this issue, the genetic constructs are equipped with insulators. In this study, the consensus of exerting chicken hypersensitive site-4 (cHS4) insulator was examined on the shield of phosphoglycerate kinase-1 (Pgk-1) promoter from the surrounding chromatin in transgenic mice. The PGK-EGFP cassette was flanked by insertion of three copies of the cHS4insulators. Mouse zygotes’ microinjection by the constructed cassette was resulted in the birth of nine transgenic founders (F0). Copy-number-dependent expression of the EGFPwas investigated in the transgenic F1 offspring by fluorometry and real-time PCR. They showed no correlation between the expression level of transgene and gene copy number among the transgenic lines. Moreover, dissection of the EGFP-expressing mice revealed heterogeneous expression of the EGFPin the different organs. In conclusion, for the first time, these findings indicated that the cHS4sequence is not a perfect insulator to fully protect the Pgk-1promoter from the side effects of integration site in transgenic mice and it needs probably to some additional elements of the cHS4locus to reach this goal.