AQP3 and keratoconus: In fact, in keratoconus, an eye disorder in which the cornea thins and gradually bulges outward, AQP5 was found in an RNA-sequencing analysis to be the most downregulated gene when comparing multiple diseased corneas to control corneas (AQP3 was also found to be downregulated in keratoconus but not to as great an extent as AQP5 [43]).