AQP5 and chronic obstructive pulmonary disease: AQP5 is a single copy gene on human chromosome 12q13.[8] A single nucleotide polymorphism (SNP) in intron 3 (rs3736309) has been associated with the presence of COPD in a Chinese population, but not with cross-sectional measures of lung function or COPD severity.[9] Whether polymorphisms in AQP5 correlate with the decline of pulmonary function, a trait associated with the development and progression of COPD, is unknown.