SPDEF and chronic obstructive pulmonary disease: Song et al. (2017) had found hypermethylation of CPG-8 in the promoter of SPDEF and hypomethylation of CpG-14 and CpG-15 in FOXA2, was identified the abnormal methylation of SPDEF and FOXA2 during the differentiation of goblet cells is the basic factor of mucus hypersecretion in COPD, thus providing a new approach to understand mucus hypersecretion from the perspective of epigenetics.