Expression of a bovine β-casein/human lysozyme fusion gene in the mammary gland of transgenic mice

Abstract

Transgenic mice containing a bovine β-casein/human lysozyme fusion gene (pBZ) were generated in order to produce human lysozyme in their milk. The expression vector was a quadripartite fusion consisting of a 2 kb upstream DNA of the bovine β-casein gene, human lysozyme gene, intron II of the rabbit β-globin gene, and the polyadenylation/termination signals of SV40 DNA. Fertilized mouse zygotes were microinjected with pBZ, then transferred into the oviduct of foster mothers. Out of 20 mice born, 11 survived until post-weaning and three were identified as positive-transgenic by Southern blot analysis (one male and two females). The founder mice were mated to BCF1 mice to produce transgenic progeny. It was confirmed by RT-PCR and Northern blot analyses that the transgene was specifically expressed in the mammary gland of the founder mice. Furthermore, the artificial introns within the transgenic RNA was proven to be correctly spliced out as judged by RT-PCR analysis. These results indicated that transgenic mice generated in this study properly expressed the human lysozyme RNA in their mammary gland.