Assignment 1 of the Aquaporin-8 water channel gene (AQP8) to human chromosome 16p12

Aquaporins represent water channel proteins widely spread nature where they are responsible for the high water characterizing numerous plasma membranes (Agre, 1998). A number of aquaporins have been described in where their sites of expression predict roles in physiology disease (Agre et al., 1998). Some of these functions been already demonstrated (see Agre et al., 1998 for references). is triggered by the recent discovery of the Aquaporin- 8 water channel (AQP8) in rat (Ishibashi et al., 1997; et al., 1997), mouse (Ma et al., 1997) and human (Koyama et al., 1998) tissues where its distribution predicts in secretion of pancreatic juice, bile and primary saliva, dehydration, transport of fluid across placenta, and in the of water across the spermatozoa plasma membrane. involvement of AQP8 in clinical disorders of unknown origin is also expected. In agreement with phylogenetic , the genomic organization of the AQP8 gene a separate evolutionary pathway for AQP8 compared that of the other mammalian aquaporins (Koyama et al., 1998; Calamita et al., submitted for publication). This distinction be responsible for regulatory and functional features could still be unknown at the present. Uncertain is the that the mouse, rat and human AQP8 are orthologous each other. Here we report the fine mapping of the AQP8 gene to human chromosome 16p12, a region which is to the region where the mouse AQP8 gene maps (Calamita al., submitted for publication). This result demonstrates the mouse and human AQP8 genes are orthologous provides important insight into the phylogenesis of the .