[Detection of Cre recombinase activity in Mx-Cre transgenic mice induced by INF in vitro]

The Cre recombinase and its activity in C57-TgN(Mx-Cre) transgenic mice is studied by polymerase chain reaction (PCR), Western blot, immunohistochemistry, immunogold electron microscopy and Southern blot. C57-TgN(Mx-Cre) transgenic mice harbouring cre gene in genomic DNA is demonstrated by PCR, and these mice which are induced by INF-alpha 1b could express Cre recombinase, which is confirmed by Western blot. With immunohistochemistry, we find that the Cre recombinase expresses in hepatocyte cytoplasm and nuclear of C57-TgN(Mx-Cre) transgenic mice. Cre recombinase expressed in hepatocyte cytoplasm and nuclear is further confirmed by immunogold electon microscopy. And it is supported that the Cre recombinase which is created from C57-TgN(Mx-Cre) transgenic mice induced by INF-alpha 1b can direct DNA recombination reaction in vitro. All evidence leads us supporting the view that the Cre recombinase expressed in C57-TgN(Mx-Cre) transgenic mice has activity. Thus we find a method to detect the activity of Cre recombinase in vitro.

[Generation of Mx-cre transgenic mice]

To generate the transgenic mice expressing cyclization recombination enzyme, the recombinant gene, in which the coding region of cre gene is derived by the promoter of mouse Mx gene, was microinjected into pronuclei of fertilized mouse eggs. Founders of transgenic mice harbouring the recombinant gene were screened by polymerase chain reaction (PCR) at genomic DNA level and confirmed by Southern blot. One line of Mx-cre transgenic mice was obtained. Then, the Mx-cre transgenic mouse line was cultured and propagated.