Abstract
To investigate the ability of 1.8 kb or 3.1 kb bovine β-casein promoter sequences for the expression regulation of transgene in vivo, transgenic mice were produced with human type II collagen gene fused to 1.8 kb and 3.1 kb of bovine β-casein promoter by DNA microinjection. Five and three transgenic founder mice were produced using transgene constructs with 1.8 kb and 3.1 kb of bovine β-casein promoters respectively. Founder mice were outbred with the wild type to produce F1 and F2 progenies. Total RNAs were extracted from four tissues (mammary gland, liver, kidney, and muscle) of female F1 transgenic mice of each transgenic line following parturition. RT-PCR and Northern blot analysis revealed that the expression level of transgene was variable among the transgenic lines, but transgenic mice containing 1.8 kb of promoter sequences exhibited more leaky expression of transgene in other tissues compared to those with 3.1 kb promoter. Moreover, Western blot analysis of transgenic mouse milk showed that human type II collagen proteins secreted into the milk of lactating transgenic mice contained 1.8 kb and 3.1 kb of bovine β-casein promoter. These results suggest that promoter sequences of 3.1 kb bovine β-casein gene can be used for induction of mammary gland-specific expression of transgenes in transgenic animals.
