Molecular characterization of human Aquaporin-7 gene and its chromosomal mapping

The cDNA for the seventh mammalian aquaporin (AQP7) was isolated from rat testis, and its expression demonstrated at the tail of late spermatids (Ishibashi et al., J. Biol. Chem. 272 (1997) 20,782-20,786). Here we report the isolation of the mouse and the human AQP7 cDNA and the human AQP7 gene. The human AQP7 gene is identical with human adipose AQP (AQPap or AQP7L). The deduced amino acid sequences of human and mouse AQP7 were 68% and 79% identical to those of rat AQP7, respectively. The mouse AQP7 is 67% identical to the human AQP7. Such a lower conservation of AQP7 among species is unusual in the aquaporin family. The human AQP7 gene is composed of six exons distributing over 6.5 kb. The exon-intron boundaries are identical to those of the human AQP3 gene. The intron sizes are also similar. Moreover, chromosomal localization of AQP7 was assigned to 9p13 by fluorescent in situ hybridization, where AQP3 is also localized, suggesting that 9p13 may be another site of an aquaporin cluster.