TRANSGENIC RATS REVEAL FUNCTIONAL CONSERVATION OF REGULATORY CONTROLSBETWEEN THE FUGU ISOTOCIN AND RAT OXYTOCIN GENES

We have asked whether comparative genome analysis and rat transgenesis can be used to identify functional regulatory domains in the gene loc us encoding the hypothalamic neuropeptides oxytocin (OT) and vasopress in. Isotocin (IT) and vasotocin (VT) are the teleost homologues of the se genes. A contiguous stretch of 46 kb spanning the Fugu IT-VT locus has been sequenced, and nine putative genes were found, Unlike the OT and vasopressin genes, which are closely linked in the mammalian genom e in a tail-to-tail orientation, Fugu IT and VT genes are linked head to tail and are separated by five genes. When a cosmid containing the Fugu IT-VT locus was introduced into the rat genome, we found that the Fugu IT gene was specifically expressed in rat hypothalamic oxytocine rgic neurons and mimicked the response of the endogenous OT gene to an osmotic stimulus, These data show that cis acting elements and trans- acting factors mediating the cell-specific and physiological regulatio n of the OT and IT genes are conserved between mammals and fish, The c ombination of Fugu genome analysis and transgenesis in a mammal is a p owerful tool for identifying and analyzing conserved vertebrate regula tory elements.