[High expression of human FIX(hFIX) in transgenic mice directed by goat beta-casein gene promoter]

To probe the feasibility of efficient production of human clotting factor IX(hFIX) with the approach of mammary gland bioreactor of transgenic animals, we constructed hFIX mammary gland expression vector containing promoter, exon 1, intron 1 and exon 2 of the goat beta-casein gene about 6.7 kb fragment as well as full-length of hFIX cDNA and its modified intron 1 sequence. By using transgenic products and 12 transgenic founders (9 female, 3 male) were produced, and the integration rate thus was 11.2%. ELISA assay and Western blot showed that the milk of 8 female transgenic mice had hFIX expression with high clotting activities. The highest hFIX expression in the milk of one transgenic mouse reached 52.9 mg/L, and the highest clotting activity of the transgene milk was 279.2%. FISH experiments indicated that hFIX DNA was integrated in different chromosomes in different mice. This result indicated that the hFIX mammary gland expression vector based on the goat beta-casein promoter can efficiently direct high expression of hFIX gene in the milk of transgenic mice, which maintained high clotting activity.