Closely spaced tandem arrangement of AQP2, AQP5, and AQP6 genes in a 27-kilobase segment at chromosome locus 12q13.

The aquaporins (AQPs) are a family of water-transporting proteins that facilitate osmotically driven water movement across cell plasma membranes. Among the seven human aquaporins cloned to date (AQPs 0-6), genes encoding the four most closely related aquaporins (AQP0, AQP2, AQP5, and AQP6) have been mapped to chromosome band 12q13, suggesting an aquaporin family gene cluster at this locus. To construct a physical map and identify novel aquaporin gene members on this cluster, a human CEPH B yeast artificial chromosome (YAC) library was screened by PCR using primers derived from exon 4 of AQP2 and AQP0 genes. A YAC clone with 200 kb of human DNA was isolated and analyzed. Primary pulsed-field gel electrophoresis and Southern blot analysis indicated the presence of AQP2, AQP5, and AQP6 genes, but not AQP0. Restriction mapping and PCR analysis yielded a precise physical map in which the three aquaporin genes span only approximately 27 kb in the order, transcriptional orientation, and spacer length 5'-AQP2-5 kb spacer-AQP5-7 kb spacer-AQP6-3'.