Species- and tissue-specific physiological regulation of vasopressin mRNA poly(A) tail length

Transgenic experiments can be used to test the extent to which genes from d ifferent species can be swapped around, but still retain function, and be a ppropriately regulated. A vector has been developed that directs the expres sion of foreign genes to specific groups of vasopressin (VP) hypothalamic n eurons in transgenic rats. Using this vector, we have expressed the bovine VP (bVP) RNA in the rat brain. In contrast to the situation in a mouse host , but like its endogenous rat counterpart, the mRNA encoded by the bVP tran sgene is subject to posttranscriptional physiological regulation in the hyp othalamus; its poly(A) tail dramatically lengthens as a consequence of 3 da ys of dehydration. Transgene expression is also seen in the adrenal cortex, but here, despite a marked increase in transgene RNA levels with dehydrati on, there is no change in poly(A) tail length. These data suggest that the mouse hypothalamus and the rat adrenal gland do not have the transcript rec ognition or enzymatic machinery required for the physiologically responsive poly(A) tail length modulation seen in the rat brain.