[Expression of goat beta-casein gene targeting vector in mammary gland cell]

The study of mammary gland bioreactor is in the ascendant. In order to generate transgenic goats of well-controlled expression of exogenic genes, we constructed a human lactoferrin (hLF) gene targeting vector containing promoter, exon 1, intron1 and some of exon 2 (about 6.1 kb fragment) and exon 6 approximately 9 (about 3.3 kb fragment) of the goat beta-casein gene as well as hLF minigene, neo gene inserted into them and tk gene ligated to the 3' end of the construct. The 9.4 kb goat genomic sequences as homologous arms were initially amplified by PCR with local goat tissue DNA. The expression vector was named pBC-tk-neo-hlf. Then the recombinant plasmid pBC-tk-neo-hlf containing hLF minigene was transfected into mice mammary tumor cell line C127 by liposome, cell clones were selected with G418. After proliferating, the transfected cells were induced with insulin, luteotropic hormone and hydrocortisone. The result of Western-blotting analysis showed that the transfected cells can secrete hLF protein, and the recombinant protein expressed in cultured cell supernatant has the similar molecular weight as the native protein. The expression level detected by ELISA was 0.21 microg/mL. This result indicated that the targeting vector could efficiently direct the expression of hLF in mammary cells,and it confirmed the validity of the constructed vector. At the same time, C127 cell line proved to be useful for evaluating the regulation of a foreign gene expression in mammary gland specific expression vector.