AQP7 (aquaporin 7)

The AQP7 gene shows a human lineage-specific (HLS) copy number increase in humans compared to great apes, monkeys, and prosimians. This copy number increase (at least 5 copies in humans vs. 1-3 in chimpanzees and other apes) was detected by cDNA array-based comparative genomic hybridization (Fortna et al. 2004). Aquaporins are thought to play a key role in water transport across membranes (Preston et al. 1992), and of the eight aquaporin family members assayed, the only one that showed an HLS copy number increase was AQP7 (Dumas et al. 2007; Fortna et al. 2004). AQP7 is also an aquaglyceroporin, and in addition to water, AQP7 is also capable of transporting glycerol, an energy storage molecule. Most of the AQP7 copies map to the pericentromeric region of chr 9, one of the most evolutionarily dynamic regions of the human genome and the location of the greatest concentration of HLS gene copy number increases (Dumas et al. 2007; Fortna et al. 2004). The HLS increase in copy number of AQP7 is a candidate to play a role in thermoregulation (sweating) and energy mobilization (via glycerol transport) from fat to muscle, adaptations that may have contributed to the enhanced capacity for endurance running found in humans (Dumas et al. 2007; Bramble and Lieberman 2004).