Aquaporins/major intrinsic protein (MIP) are a family of water-selective membrane channels. Aquaporin 7 has greater sequence similarity with AQP3 and AQP9 and they may be a subfamily. Aquaporin 7 and AQP3 are at the same chromosomal location suggesting that 9p13 may be a site of an aquaporin cluster. Aquaporin 7 facilitates water, glycerol and urea transport. It may play an important role in sperm function.