Cloning and characterization of murine Aqp5: evidence for a conserved aquaporin gene cluster

Aquaporin 5 (Aqp5), a member of the aquaporin family of membrane water chan nels, is thought to modulate the osmolality of fluids in the eye, lung, and salivary gland. Here, we report the cloning and genomic characterization o f murine Aqp5 and its expression in relevant mouse tissues. This gene, comp rised of four exons encoding 265 amino acids (121. 55, 28, and 61 amino aci ds respectively), is transcribed into an approximate 1.8-kb mRNA detected i n lung, parotid, submandibular, sublingual, and lacrimal tissues. Aqp5 enco des a protein that is 98% identical to rat Aqp5. An Aqp5 antibody detects a n approximately 27-kDa protein band in mouse lung, and an additional 29 kDa band in salivary gland. Cloning and physical mapping genomic fragments con tiguous with Aqp5 revealed two other members of the aquaporin family: Aqp2 and Aqp6, arrayed head to tail in the order Aqp2-Aqp5-Aqp6, and provides ev idence of a gene cluster conserved in order and orientation in both mice an d humans.