Expression of the rat arginine vasopressin gene in transgenic mice

A line of mice has been developed which are transgenic for an 8.2-kilobase (kb) genomic clone of the rat vasopressin (VP) gene. Using a polymerase chain reaction technique, the rat VP (rVP) transgene was shown to have tissue-specific mRNA expression in the hypothalamus, temporal lobe, parietal cerebral cortex, cerebellum, and posterior pituitary, similar to the tissue distribution of endogenous mouse and rat VP expression. Expression of transgenic rVP mRNA was also found in the lung and pancreas of the transgenic mice, sites of known ectopic expression of VP. Using two methods, Northern blot analysis with species-specific cRNA probes and a quantitative polymerase chain reaction technique, the quantity of rVP transgene mRNA was shown to regulate appropriately in response to an osmotic stimulus. After 72 h of water deprivation, the quantity of transgenic rVP mRNA increased 6.8 ± 3.0-fold. This was not significantly different than the fold increase in mouse VP mRNA quantity seen in nontransgenic mice (4.8 ± 1.5) but was significantly different (P < 0.05) than the 1.2 ± 0.03-fold increase in rat VP mRNA seen in normal rats after water deprivation. In the rat hypothalamus, VP mRNA poly(A) tail length increases with osmotic stimulation, while in the mouse it does not. The poly(A) tail of transgenic rVP mRNA expressed in mouse hypothalamus did not increase in length after osmotic stimulation. These findings suggest that: 1) this 8.2-kb rVP genomic clone contains information sufficient for proper tissue-specific and osmotic regulation of the rVP gene; and 2) mRNA poly(A) tail length regulation in vivo is dependent on trans-activating factors of the host cell. Mice transgenic for mutated constructs of this 8.2-kb rVP gene should be useful for whole animal studies to determine the role of cis-acting elements in the physiological regulation of VP gene expression in vivo.