RECEPTOR-MEDIATED TRANSFECTION OF MURINE AND OVINE MAMMARY-GLANDS IN-VIVO

Transfection of HC-11 murine epithelial mammary cells as well as murin e and sheep mammary glands were carried out using insulin-containing c onstructs that deliver DNA by receptor-mediated endocytosis to recepto r-expressing cells. In vivo transfection of mammary gland tissue with the luciferase gene was carried out by introducing the DNA constructs into the mammary ducts of both mice and sheep. The successful transfec tion of ewe mammary glands was demonstrated by the detection of lucife rase activity was demonstrated by the detection of luciferase activity in mammary gland biopsy material up to a month after a single adminis tration of the construct. To test whether products of expression of tr ansfected genes could be secreted into the milk in this system, the N- terminal secretory signal sequences of bovine beta-lactoglobulin or th e entire coding sequence of human alpha-lactalbumin were fused to the N terminus of the luciferases, both murine and sheep milk could be sho wn to contain luciferase activity, whereas mice, which had been transf ected with the nonmodified luciferase gene, did not secrete any activi ty in the milk. This approach demonstrates for the first time the poss ibility of gene transfer in vivo into mammary gland epithelial cells u sing constructs delivering DNA via receptor-mediated endocytosis.