RML aggregates being much larger and more resistant to dissociation. Our analysis provides new molecular insight into an emerging puzzle in prion biology, the discrepancy between the infectious and neurotoxic properties of PrP.
We have asked whether comparative genome analysis and rat transgenesis can be used to identify functional regulatory domains in the gene locus encoding the hypothalamic neuropeptides oxytocin (OT) and vasopressin. Isotocin (IT) and vasotocin (VT) are the teleost homologues of these 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 genome 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 oxytocinergic 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 regulation of the OT and IT genes are conserved between mammals and fish. The combination of Fugu genome analysis and transgenesis in a mammal is a powerful tool for identifying and analyzing conserved vertebrate regulatory elements.The pufferfish, Fugu rubripes, has a 400-Mb genome that is about 7.5 times smaller than the human genome (1). We have been exploring the utility of this genome as a ''reference'' vertebrate genome, and we are interested in the extent to which gene structure, linkage, and regulatory function have been conserved over the 400 million years since fish and tetrapods diverged (2-4). To explore this concept further, we have studied the evolutionarily ancient vertebrate genes that encode the neuropeptide hormones oxytocin (OT) and vasopressin (VP). Mammalian OT primarily is involved in parturition and lactation, and VP is involved in the maintenance of salt and water balance. The genes encoding the OT and VP preprohormones are highly homologous at both the structural and sequence levels and are linked in the mammalian genome in a tail-to-tail manner with intergenic regions ranging from 3 kb (mouse, ref. 5) to 12 kb (human, ref. 6; rat, ref. 7). The two genes are expressed in distinct magnocellular neurons of the supraoptic nuclei (SON) and paraventricular nuclei (PVN) of the hypothalamus. In addition, VP is expressed in the parvocellular neurons of the PVN and suprachiasmatic nuclei. Because no neuronal cell lines express OT and VP, transgenesis that uses mice and rats as hosts has become the method of choice for the functional analysis of the OT (8-10) and VP (11-14) genes.In cyclostomes, the most primitive vertebrates, only the VP homologue called vasotocin (VT), is synthesized. However, teleosts contain two genes, VT and isotocin (IT), which probably have arisen by a duplication of the single parental gene. Teleost VT and IT are synthesized in separate neurons in the preoptic nuclei of the hypothalamus (15, 16). Although VT has been implicated in the maintenance of salt-water balance, the biological roles of VT and IT are ambigu...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.