RNAs encoded by a 3.5-kb bovine vasopressin gene construct are targeted to the neurohypophysis of transgenic mice

Recent studies have established that the RNA coding for the neuropeptide arginine-vasopressin (AVP) is expressed in the neurohypophyseal compartment of the hypothalamo-neurohypophyseal system. In order to determine the molecular mechanisms that direct this novel expression pattern we have now investigated whether an AVP transgene is similarly regulated. Using a reverse transcriptase-polymerase chain reaction (RT-PCR) approach that permits simultaneous analysis of both endogenous and transgene RNA levels, we have demonstrated that RNA derived from a 3.5-kb bovine vasopressin transgene is expressed in the neurohypophysis of transgenic mice, and is up-regulated by a physiological stimulus (salt-loading) in a similar manner to mouse AVP RNA. Sequences conserved between this region of the murine and bovine AVP genes are therefore sufficient to mediate neurohypophyseal expression. These lines of transgenic mice will serve as a model for the delineation of sequences that target expression beyond the neuronal perikaryon.